Machining Supplementary Material PDF

Queen’s University Belfast Machining Supplementary Material Machining Operations and Part Geometry Dr Scott Millen Contents Machining Operations and Part Geometry........................................................................................... 2 Turning.................................

Queen’s University Belfast Machining Supplementary Material Machining Operations and Part Geometry Dr Scott Millen Contents Machining Operations and Part Geometry........................................................................................... 2 Turning.............................................................................................................................................. 3 Centre Lathe (Engine lathe)............................................................................................................... 5 Methods of Holding the Work in a Lathe...................................................................................... 5 Turret Lathe....................................................................................................................................... 6 Bar Machine...................................................................................................................................... 6 Automatic Screw Machine................................................................................................................ 6 Multiple Spindle Bar Machines......................................................................................................... 7 Boring............................................................................................................................................... 8 Drilling............................................................................................................................................... 8 Through Holes vs. Blind Holes....................................................................................................... 8 Reaming........................................................................................................................................ 9 Tapping.......................................................................................................................................... 9 Counterboring............................................................................................................................. 10 Drill types.................................................................................................................................... 10 Machining Operations and Machine Tools.......................................................................................... 11 Milling............................................................................................................................................. 11 Up-Cut Milling............................................................................................................................. 11 Down-Cut Milling........................................................................................................................ 11 Leadscrew Backlash.................................................................................................................... 12 Peripheral Milling vs. Face Milling............................................................................................... 12 Slab Milling.................................................................................................................................. 13 Slotting........................................................................................................................................ 13 Conventional Face Milling........................................................................................................... 13 End Milling.................................................................................................................................. 14 Profile Milling.............................................................................................................................. 14 Pocket Milling (Slot Drill)............................................................................................................. 14 Surface Contouring..................................................................................................................... 14 Machining Centres.............................................................................................................................. 15 Shaping and Planing........................................................................................................................ 15 Broaching........................................................................................................................................ 16 Internal Broaching....................................................................................................................... 16 Machining Operations and Part Geometry Each machining operation produces a characteristic part geometry due to two factors: 1. Relative motions between the tool and the workpart Generating – part geometry is determined by the feed trajectory of the cutting tool 2. Shape of the cutting tool Forming – part geometry is created by the shape of the cutting tool Figure 1 ‑ Generating shape: (a) straight turning, (b) taper turning, (c) contour turning, (d) plain milling, (e) profile milling Figure 2 ‑ Forming to create shape: (a) form turning, (b) drilling, and (c) broaching Figure 3 ‑ Combination of forming and generating to create shape: (a) thread cutting on a lathe, and (b) slot milling Turning A single point cutting tool removes material from a rotating workpiece to generate a cylindrical shape. Performed on a machine tool called a lathe Variations of turning that are performed on a lathe: o Facing o Contour turning o Chamfering o Parting o Threading Figure 4 ‑ Turning operation Facing - Tool is fed radially inward Contour Turning - Instead of feeding the tool parallel to the axis of rotation, tool follows a contour that is other than straight, thus creating a contoured form. Chamfering - Cutting edge cuts an angle on the corner of the cylinder, forming a "chamfer" Parting (Cutting Off) - Tool is fed radially into rotating work at some location to cut off end of part Threading - Pointed form tool is fed linearly across surface of rotating workpiece parallel to axis of rotation at a large feed rate, thus creating threads a) Facing b) Contour turning c) Chamfering d) Parting (Cutting Off) e) Threading Figure 5 - Variations of turning Centre Lathe (Engine lathe) a) Diagram of a centre lathe b) Photo of a centre lathe Figure 6 - Diagram and photo of a centre lathe, showing its principal components Methods of Holding the Work in a Lathe Holding the work between centers Chuck Collet Face plate a) Mounting the work between centres using a b) Three‑jaw (self-centring) chuck "dog” c) Four‑jaw (independent) chuck d) Collet e) Face plate for non-cylindrical workpieces Figure 7 - Methods of holding the work in a lathe Turret Lathe Tailstock replaced by “turret” that holds up to six tools, Tools rapidly brought into action by indexing the turret, Tool post replaced by six‑sided turret to index six tools, Applications: high production work that requires a sequence of cuts on the part. Figure 8 - Turret Lathe Bar Machine Like a centre lathe except collet replaces chuck, permitting long bar stock to be fed through headstock, At the end of the machining cycle, a cutoff operation separates the new part, Highly automated (the term automatic bar machine is often used), Applications: high production of rotational parts, Figure 9 - Bar Machine Automatic Screw Machine Same as automatic bar machine but smaller, Applications: high production of screws and similar small hardware items; hence, its name. Multiple Spindle Bar Machines More than one spindle, so multiple parts machined simultaneously by multiple tools, o Example: six spindle automatic bar machine works on six parts at a time, After each machining cycle, spindles (including collets and workbars) are indexed (rotated) to next position. Figure 10 - Multiple Spindle Bar Machine Figure 11 ‑ (a) Part produced on a six‑spindle automatic bar machine; and (b) sequence of operations to produce the part: (1) feed stock to stop, (2) turn main diameter, (3) form second diameter and spotface, (4) drill, (5) chamfer, and (6) cutoff Boring Difference between boring and turning: o Boring is performed on the inside diameter of an existing hole, o Turning is performed on the outside diameter of an existing cylinder, In effect, boring is an internal turning operation, Boring machines, o Horizontal or vertical - refers to the orientation of the axis of rotation of machine spindle. Figure 12 ‑ A vertical boring mill – for large, heavy workpieces Drilling Creates a round hole in a workpiece, Contrasts with boring which can only enlarge an existing hole, Cutting tool called a drill, twist drill or drill bit, Customarily performed on a drill press. Figure 13 - Drilling Through Holes vs. Blind Holes Through-holes - drill exits the opposite side of work  Blind-holes – drill does not exit work on opposite side Figure 14 - Two hole types: (a) through-hole, and (b) blind hole Reaming Used to slightly enlarge a hole, provide better tolerance on diameter, produce a round hole and improve surface finish. Figure 15 - Reaming Tapping Used to provide internal screw threads on an existing hole - Tool called a tap a) Tapping schematic b) Tap types c) Tapping process Figure 16 – Tapping Counterboring Provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the hole. Figure 17 - Counterboring Drill types Upright (Pillar) Drill - Stands on the floor, Bench Drill - Similar but smaller and mounted on a table or bench. a) Upright (Pillar) Drill b) Bench Drill Figure 18 - Drill types Work Holding for Drill Presses Workpiece can be clamped in a vice, fixture, or jig Vice - general purpose workholder with two jaws, Fixture - workholding device that is usually custom‑designed for the particular workpiece, Drill jig – similar to fixture but also provides a means of guiding the tool during drilling. Machining Operations and Machine Tools Milling, Machining Centers and Turning Centers, Other Machining Operations, High Speed Machining. Milling A machining operation in which work is fed past a rotating tool with multiple cutting edges, Axis of tool rotation is perpendicular to feed direction, Creates a planar surface; other geometries possible either by cutter path or shape, Other factors and terms: o Milling is an interrupted cutting operation, o Cutting tool called a milling cutter, cutting edges called "teeth", o Machine tool called a milling machine. Up-Cut Milling Using this method, the cutter teeth enter the work at the bottom of the cut and leave at the surface. As the chips are removed, they gather in front of the cutter which makes it difficult to see the operation. There is also a tendency for the work to be lifted away from the table. NOTE this method MUST always be used on machines without a backlash eliminator. Figure 19 - Up-Cut Milling Down-Cut Milling In this method the cutter makes contact with the work surface at the thickest point on the chip and leaves the work at the bottom of the cut. The major cutting force is downwards so the work is held firmly into the fixture. This enables the machine to take maximum cuts resulting in greater metal removal rates. The surface finish is also improved.  Figure 20 - Down-Cut Milling Leadscrew Backlash Backlash, sometimes called lash or play, is a clearance or lost motion in a mechanism caused by gaps between the parts. It can be defined as "the maximum distance or angle through which any part of a mechanical system may be moved in one direction without applying appreciable force or motion to the next part in mechanical sequence.” Peripheral Milling vs. Face Milling Peripheral milling o Cutter axis is parallel to surface being machined o Cutting edges on outside periphery of cutter Face milling o Cutter axis is perpendicular to surface being milled o Cutting edges on both the end and outside periphery of the cutter Figure 21 ‑ Two forms of milling: a) peripheral milling, and b) face milling Slab Milling The basic form of peripheral milling in which the cutter width extends beyond the workpiece on both sides Figure 22 - Slab Milling Slotting Width of cutter is less than workpiece width, creating a slot in the work Figure 23 - Slotting Conventional Face Milling Cutter overhangs work on both sides Figure 24 - Conventional Face Milling End Milling Cutter diameter is less than work width, so a slot is cut into part. Profile Milling Form of end milling in which the outside periphery of a flat part is cut. Pocket Milling (Slot Drill) Another form of end milling used to mill shallow pockets into flat parts is called a Slot Drill. Surface Contouring Ball-nose cutter is fed back and forth across the work along a curvilinear path at close intervals to create a three-dimensional surface form. a) End Milling b) Profile Milling c) Pocket Milling (Slot Drill) d) Surface Contouring Figure 25 - End, profile, pocket milling and surface contouring Machining Centres Highly automated machine tool capable of performing multiple machining operations under CNC control in one setup with minimal human attention Typical operations are milling and drilling, Three, four, or five axes. Other features: Automatic tool‑changing, Pallet shuttles, Automatic workpart positioning. Figure 26 - Operation of a mill-turn centre: (a) example part with turned, milled, and drilled surfaces; and (b) sequence of operations on a mill-turn center: (1) turn second diameter, (2) mill flat with part in programmed angular position, (3) drill hole with part in same programmed position, and (4) cutoff Shaping and Planing Similar operations Both use a single point cutting tool moved linearly relative to the workpart A straight, flat surface is created in both operations Interrupted cutting o Subjects tool to impact loading when entering work Low cutting speeds due to start-and-stop motion Usual tooling: single point high speed steel tools  Figure 27 - (a) Shaping, and (b) planning Broaching Moves a multiple tooth cutting tool linearly relative to work in direction of tool axis Figure 28 - The broaching operation Advantages: Good surface finish Close tolerances Variety of work shapes possible Cutting tool called a broach. Owing to complicated and often custom‑shaped geometry, tooling is expensive. Internal Broaching Performed on internal surface of a hole A starting hole must be present in the part to insert broach at beginning of stroke Figure 29 ‑ Work shapes that can be cut by internal broaching; cross‑hatching indicates the surfaces broached  METAL CUTTING & DRILLING Dr Scott Millen MEE2034: Manufacturing Technology 2 Week 1 LEARNING OUTCOMES AND OVERVIEW Outcomes You should understand the basic theory of metal cutting, You should understand the basic theory of drilling, You should understand different hole types, how they are made and why. Overview The mechanics and mathematics for metal cutting, Drilling, Hole types, Cutting fluid, The correct approach to drilling.  THE MECHANICS OF METAL CUTTING I To understand how metal cutting takes place we need to look at the tool/work interface, A cutting tool is best considered as a simple wedge, when forced into the material it causes it to "SHEAR“, As the tool penetrates the work material it shears in a zone extending from the tip of the tool to the original work surface, treated as a single plane, termed the "SHEAR PLANE" as illustrated. The idealized machining process Manufacturing and Design: Understanding the Principles of How Things Are Made by Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff  THE MECHANICS OF METAL CUTTING II Forces are required to propel the tool in the horizontal direction and push downwards in the vertical direction, Cutting depth Typically, the tangential force: 𝐹ℎ ≈ 1.5 𝑘 𝑡 Shear yield stress (~55% of the yield stress) Normally: 𝐹𝑣 ≈ 𝐹ℎൗ3 The resultant machining force: 𝐹𝑚 = 𝐹ℎ2 + 𝐹𝑣2 Manufacturing and Design: Understanding the Principles of How Things Are Made by Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff  THE MECHANICS OF METAL CUTTING III Chip formation Chips (cuttings or swarf) produced in metal cutting fall into three broad categories: Type 1 - Discontinuous Chip (Segmental) Type 2 - Continuous Chip Type 3 - Continuous Chip with Built-Up Edge Brittle material Ductile material Ductile material Large chip thickness Small chip thickness Low Cutting Speed Low cutting speed High cutting speed Inefficient cutting fluid Small rake angle on the tool Large rake angle on tool High pressure and friction at the Keen cutting edge Easily disposed of tool face The “ideal” chip under normal circumstances Poor surface finish Reduced tool life https://www.engineeringtribe.com/what-are-the-types-of-chips-in-metal-cutting/  DRILLING Creates a round hole in a workpiece, Contrasts with boring which can only enlarge an existing hole, Cutting tool called a drill, twist drill or drill bit, Normally performed on a drill press, A drill simultaneously performs rotating and feed motions. https://www.intechopen.com/chapters/32761  DRILLING II There are lots of different types of drills distinguished by; material, coating and geometry MATERIAL: High-Speed Steel (HSS) MATERIAL: HS Steel Cobalt MATERIAL: Carbide 1. Basic and inexpensive 1. More durable than HSS 1. Best heat/wear resistance 2. Forgiving in operation 2. More heat/wear resistance 2. Allows for through coolant 3. Can be resharpened 3. Can be resharpened 3. Can cost 10 x more Made from: Made from: Made from: Carbon, tungsten, chromium Steel alloy with 5-8% cobalt Tungsten carbide Used for: Used for: Used for: Soft materials like wood, plastic, Hardened materials and Hardest materials (all those in some metals, steel, brass abrasives including titanium, cobalt category and concrete, cast iron, bronze, and stone, and masonry stainless steel PRIMARY HOLE TYPES Through Hole Drawing symbol: Application: compatible with fasteners like bolts, screws, or pins that can completely pass through the material and secured with washers or nuts on the opposite side. PRIMARY HOLE TYPES Blind Hole Drawing symbol: Application: concealing fasteners (improved visual appearance) without the visible protrusion of traditional fastening elements, Advantages: prevent potential failure points (reduce stress concentration), optimise space, Disadvantages: potential trapped debris, more complex tapping. https://www.youtube.com/@ManufacturingET PRIMARY HOLE TYPES Counterbore Drawing symbol: Application: concealing fasteners (specifically socket-head screws), Pilot Hole Diameter, Pilot Hole Depth Counterbore Diameter Counterbore Depth https://www.youtube.com/@ManufacturingET PRIMARY HOLE TYPES Countersink Drawing symbol: Application: concealing fasteners (specifically countersunk screws). https://www.youtube.com/@ManufacturingET  PRIMARY HOLE TYPES Countersink vs Counterbore https://www.efunda.com/DesignStandards/plastic_design/csink.cfm  PRIMARY HOLE TYPES Tapped (or threaded) Holes Drawing symbol: For metric holes, the diameter symbol is replaced with an ‘M’. For example, a tapped hole for an M8 bolt would be ‘M8’. Application: Tapped holes are used to hold threaded components. Examples include screws, bolts and threaded rods. https://engineersbible.com/types-of-holes/ https://www.youtube.com/@ManufacturingET  PRIMARY HOLE TYPES Other types: Spotface - - a shallow counterbored hole Counterdrilled - - like a countersunk hole but there is a recess above it, Boring – enlarging an existing hole, Reaming – refining a hole to meet tight tolerances. https://engineersbible.com/types-of-holes/  CUTTING FLUID Cutting fluids are a type of lubricant and coolant specifically designed for metalworking, These fluids are applied in the machining zone to: Reduce friction levels between tool, chip, and workpiece, Help to remove chips that might otherwise interfere with the manufacturing process, Corrosion resistance and smoke suppression. Different types of CFs available can be classified: Non-water miscible - (oil-based) supplied as ready-to-use products, Water-miscible - supplied as a concentrate that must be diluted before application, Water-based - prepared by adding them to water. https://www.oil-store.co.uk/blog/top-advantages-and-functions-of-cutting-fluids-in-metal-machining/ SUMMARY Outcomes You should now understand the basic theory of metal cutting, Shearing effect and chip formation, You should be able to calculate cutting forces, You should understand the basic theory of drilling, Creates a round hole with a drill bit which can be made from different materials, You should understand different hole types, how they are made and why, Through hole, blind hole, counterbore, countersink, tapped (or threaded) holes.  LATHE TURNING AND CNC MACHINING Dr Scott Millen MEE2034: Manufacturing Technology LEARNING OUTCOMES AND OVERVIEW Outcomes You should be able to differentiate drilling, turning and milling, You should understand what numerical control is and how it relates to machining or manufacturing, You should understand the three metrics to determine how well the programme is doing, You should be aware of programming languages, You should be able to calculate speeds and feeds for a given process. Overview Lathe turning, CAD/CAM programming, CNC milling and tooling.  LATHE TURNING I A single point cutting tool removes material from a rotating workpiece to generate a cylindrical shape, Simple Turning Operation https://www.hubs.com/knowledge-base/cnc-machining-manufacturing-technology-explained/  LATHE TURNING II Variations of turning that are performed on a lathe: Facing, Step turning, Grooving, Chamfering, Parting, and more… https://msvs-dei.vlabs.ac.in/mem103/Unit5lesson4.html LATHE TURNING III Facing - Tool is fed radially inward to remove material from the front of the stock, Step Turning - creates two surfaces with an abrupt change in diameters between them. The final feature resembles a step. Chamfering - cuts an angle on the corner of the cylinder, forming a "chamfer" Grooving - creates a narrow cut, a "groove" in the workpiece. Multiple tool passes are necessary to machine wider grooves. Parting (Cutting Off) - results in a part cut-off at the end of the machining cycle. Others include: Taper turning, Contour Turning, Threading, Knurling, Drilling, Reaming, Boring and Tapping. https://turntechprecision.com/clueless-machinist/2020/8/25/10-machining-operations-performed-on-a-lathe https://www.youtube.com/@TomsTechniques https://www.youtube.com/@YorkIndustrialTech https://www.youtube.com/@SecoToolsAB  INTRODUCTION TO CNC MACHINING/MILLING CNC machining is the most common subtractive manufacturing technology today, Using CAD models, CNC machines precisely remove material from a solid block with a variety of cutting tools, High speed spindle (> 40,000 rpm), High feed rate drive ( > 15 m/min), High precision ( < 0.002 mm accuracy), Degrees of freedom (DOF) in milling. NB: rotation around the x- axis is the A-axis DOF; rotation around the y-axis is the B-axis DOF. Manufacturing and Design: Understanding the Principles of How Things Are Made by Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff CNC MACHINES Generally, CNC machines share a common layout: A flat working table, A milling cutter holding the cutting tool, The tool rotates at high speeds with considerable down force, There are also control and electronics involved.  CNC MACHINING - 3-AXIS vs 5-AXIS 3-Axis Machining - the workpiece is fixed in a single position – the spindle can move in X, Y and Z linear directions, Typically used for machining of 2D and 2.5D geometry. Machining of all 6 sides of a part is possible in 3-axis machining but a new fixturing set-up is required for each side, 5-Axis Machining – the spindle/workpiece can also rotate in the A-axis and C-axis, or in the B-axis and C-axis, Typically, capable of highly complex 3D shapes and surfaces. https://www.cloudnc.com/blog/cnc-best-practices-3-whats-the-difference-between-3-axis-4-axis-5-axis-milling CNC MACHINING - COORDINATE SYSTEMS CNC motion is based on the Cartesian coordinate system, Machine Coordinate System (MCS) - the XYZ position with respect to the home position (start position), Part Coordinate System (PCS) - establishes the Orientation, Alignment and Origin of your part, Fixture Coordinate System (FCS) - a previously measured coordinate system saved away for recall and used in repeated part programs. NC PROGRAMMING LANGUAGES There is no standard NC programming language, Every CNC machine manufacturer has a special language for programming their machines, The closest to a standard language are G/M codes, A G/M code CNC program is made up of a series of commands. Each command or block is made up of words, Each word is composed of a letter address (X,Y,Z,R, etc.) and a numerical value. Components of a G/M Code Program Sequence number (N-words) Spindle speed (S-words) Preparatory work (G-words) RPM -rev./min. Coordinates (x-, y-, z-words) Tool selection (T-words) Feed rate (F-words) Tool length offset (H-words) Feed rate - mm/min. Tool radius offset (D-words) Specifies Miscellaneous functions (M-words) G- and M- Words Miscellaneous function (M-words) Instructions to the controller (G-words) M00 Stop program G00 Point-to-point operation (rapid speed) M03 Start spindle on CW direction G01 Linear interpolation M04 Start spindle on CCW direction G02 Circular interpolation -clockwise M05 Stop spindle G03 Circular interpolation -counterclockwise M06 Tool change G04 Dwell (wait) for programmed duration M07 Turn coolant on (mist mode) G90 Absolute mode M08 Turn coolant on (flood mode) G91 Incremental mode M09 Turn coolant off M30 End of program G- and M- Words Example 1 N015 G00 X5.0Y5.0 Statement Number 15 (N015) G- and M- Words Example 2 N0027 G01 X175.25 Y325.00 Z136.50 F125 S800 T1712 M03 M08 ----------------- N0027 - Statement Number 27, G01 - a linear-interpolation motion to a position defined by: X175.25 Y325.00 Z136.50) F125 - with a feed rate of 125 mm/min, S800 - and a spindle speed of 800 rpm, T1712 - using a tool Number 1712, M03 - performing a clockwise turn of the spindle, M08 - and having the coolant on. ACCURACY IN NUMERICAL CONTROL ACCURACY, REPEATABILITY & RESOLUTION Accuracy = “correctness”. Closeness to required value, Repeatability = Ability to repeat the same result, Resolution = Smallest increment that can be read. LOW ACCURACY LOW ACCURACY HIGH ACCURACY HIGH ACCURACY LOW REPEATABILITY HIGH REPEATABILITY LOW REPEATABILITY HIGH REPEATABILITY CNC CAM PROGRAMMING Once the part has been designed using conventional mechanical design methods (structural analysis, FEA, fatigue study, etc.), the part is manufactured using the following method: 1. Create a solid 3D model of the part to be produced. Any standard CAD format is acceptable, 2. Import the solid model into the CAM (computer aided manufacturing) software, 3. Input the raw material stock size and set the part’s coordinate origin, 4. Input the necessary information for each tool used in machining the part features, 5. For each part feature, select the appropriate tool from the library and set the parameters necessary for machining that feature. Typical parameters include spindle speed, depth of cut, feed rate, number of passes, tool path pattern, etc. 6. Verify the programmed tool path(s) by running the CAM software’s virtual machining cycle.  CNC MILLING TOOLS Peripheral milling Cutter axis is parallel to surface being machined, Cutting edges on outside periphery of cutter, Face milling Cutter axis is perpendicular to surface being milled, Cutting edges on both the end and outside periphery of the cutter. Peripheral Milling Face Milling https://www.xometry.com/resources/machining/face-milling-vs-peripheral-milling/ *Supplementary material covering milling on Canvas  CNC MILLING TOOLS II End Mills https://www.xometry.com/resources/machining/types-of-milling-in-machining/ https://www.hubs.com/knowledge-base/cnc-machining-manufacturing-technology-explained/  CNC MILLING TOOLS Roughing and Finishing Roughing (or rough milling) The removal of larger amounts of material to quickly convert stock to the approximate final shape, Utilizes larger cutting tools, deeper and broader cuts, typically resulting in a coarser surface finish, Designed for efficiency and speed. Finishing Typically, the final stage of the machining process, Utilizes delicate, exact cuts using refined tools, Precise dimensions, stringent tolerances, and a superior surface finish can be achieved. https://www.youtube.com/watch?v=l1C34QmGuIA  MILL/TURN OR TURN MILLING Turn milling is defined as the milling of a curved surface while rotating the workpiece around its centre point, A mill/turn machine is a hybrid CNC machine that combines both milling (tool rotating) and turning (workpiece rotating) functions, Can complete complex operations faster and with potentially greater accuracy than traditional machining technologies, While other machines perform a single function, mill/turn machines can accomplish up to four operations at the same time. Representation of milling (a), turning (b) and turn-milling (c) operations https://www.mastercam.com/news/blog/milling-turning-and-mill-turn-what-are-the-differencesmilling-turning-and-mill-turn-what-are-the-differences/ https://www.sandvik.coromant.com/en-gb/knowledge/milling/turn-milling Comak, Alptunc. (2018). MECHANICS, DYNAMICS AND STABILITY OF TURN-MILLING OPERATIONS. 10.14288/1.0368954. THE MATHEMATICS OF METAL CUTTING I Speeds, feed rates and depth of cut are the three major variables that must be considered for successful and economic machining and must be established for any metal-cutting operation. A number of factors need to be considered when choosing the speeds, feed rates and depth of cut: The work material - may be too hard, the wrong size, or even the wrong material, Cutting tool material - may be too soft to complete the cut, Cutting tool geometry - the angles on the cutting tool may be incorrect for the desired cut, Cutting fluid (coolant) - may not be mixed correctly, or there may be too little, Condition of the machine – may be old, worn or damaged so cannot achieve the sizes or surface finish required.  THE MATHEMATICS OF METAL CUTTING II Speed Speed can refer to either cutting speed (Vc) or spindle speed (n), Spindle speed (n) is how fast our spindle/tool rotates and is measured in revolutions per minute (RPM), Cutting speed (Vc) is the tangent velocity on the cutting edge measured in meters per minute (m/min), Most cutting tool manufacturers supply a list of “recommended” cutting speeds for their cutting tools on a range of materials: Making Your CAM Journey Easier with Fusion 360 by Fabrizio Cimò  THE MATHEMATICS OF METAL CUTTING III Speed Equation Derivation 𝑉𝑐 = 𝑟 × 𝜔 S m/min mm rad/s n rev/min Vc m/min D mm 𝜋 3.14 𝑉𝑐 × 1000 𝑛= 𝐷 ×𝜋 Making Your CAM Journey Easier with Fusion 360 by Fabrizio Cimò THE MATHEMATICS OF METAL CUTTING IV Speed When programming a machine to cut material we typically specify the spindle speed, So, we need to get from cutting speed (Vc) to spindle speed (n): Cutting Speed n rev/min 𝑉𝑐 × 1000 Vc m/min 𝑛= D mm 𝐷 ×𝜋 𝜋 3.14 RPM Tool Diameter  THE MATHEMATICS OF METAL CUTTING V Task – Calculate the spindle speed for a high alloy steel material using a 20 mm SD99-200 end mill. ISO 513 Material Group Vc (m/min) 1 150 2 130 3 115 P 4 105 5 100 6 50 1 100 M 2 100 3 85 1 100 K 2 60 https://www.lfc.com.sg/products/detail/WIDIA-GP-Solid-Carbide-End-Mills https://www.youtube.com/watch?v=gTnkNHB7dss  THE MATHEMATICS OF METAL CUTTING VI Task – Calculate the spindle speed for a high alloy steel material using a 20 mm SD99-200 end mill. ISO 513 Material Group Vc (m/min) 1 150 𝑉𝑐 × 1000 2 130 𝑛= P 3 115 𝐷 ×𝜋 4 105 5 6 100 50 100 × 1000 1 100 𝑛= M 2 100 20 × 𝜋 3 85 1 100 𝑛 = 1592 𝑟𝑝𝑚 K 2 60 https://www.lfc.com.sg/products/detail/WIDIA-GP-Solid-Carbide-End-Mills  THE MATHEMATICS OF METAL CUTTING VII Feed Feed rate - how far the tool will travel in one minute (mm), For end mills, the feed rate can be calculated using: 𝑉𝑓 = 𝑓𝑍 × 𝑍𝑛 × 𝑛 𝑉𝑓 mm/min 𝑓𝑍 mm Speed 𝑍𝑛 - Feed rate Number of 𝑛 rev/min Feed per tooth teeth What is a tooth? What is the feed per tooth? Making Your CAM Journey Easier with Fusion 360 by Fabrizio Cimò  THE MATHEMATICS OF METAL CUTTING VIII Task – Calculate the finishing feed for the same material using a 20 mm SD99-200 end mill. Tool Part D (diameter) Zn (teeth) fz (mm/tooth) Number Roughing Finishing SD99-030 3.0 4 0.020 0.013 SD99-060 6.0 4 0.045 0.027 SD99-090 9.0 4 0.070 0.045 SD99-120 12.0 4 0.085 0.055 SD99-160 16.0 4 0.105 0.065 SD99-200 20.0 4 0.130 0.080 SD99-220 22.0 4 0.150 0.090 SD99-250 25.0 4 0.170 0.105 *these values are for teaching and should not be taken as exact 𝑉𝑓 = 𝑓𝑍 × 𝑍𝑛 × 𝑛 https://www.youtube.com/watch?v=gTnkNHB7dss  THE MATHEMATICS OF METAL CUTTING VIIII Task – Calculate the finishing feed for the same material using a 20 mm SD99-200 end mill. Tool Part D (diameter) Zn (teeth) fz (mm/tooth) Number Roughing Finishing SD99-030 3.0 4 0.020 0.013 SD99-060 6.0 4 0.045 0.027 SD99-090 9.0 4 0.070 0.045 SD99-120 12.0 4 0.085 0.055 SD99-160 16.0 4 0.105 0.065 SD99-200 20.0 4 0.130 0.080 SD99-220 22.0 4 0.150 0.090 SD99-250 25.0 4 0.170 0.105 *these values are for teaching and should not be taken as exact 𝑉𝑓 = 𝑓𝑍 × 𝑍𝑛 × 𝑛 = 0.08 × 4 × 1592 = 509.44 𝑚𝑚/𝑚𝑖𝑛 https://www.youtube.com/watch?v=gTnkNHB7dss THE MATHEMATICS OF METAL CUTTING X Depth of Cut (d) The depth of penetration of the cutting tool into the workpiece during cutting (millimetres), The depth of cut is dependent on: the required surface finish, the capacity and rigidity of both the machine tool and the workpiece, the horse power of the machine tool. Larger depth of cut - rough turning/milling, Smaller depth of cut - Finishing cuts, Higher depth of cut may break the cutting tool, It also influences chip thickness, type etc.  EXAMPLES Aerospace Mechanical www.youtube.com/watch?v=qgd5ta-zwXU https://www.prestigemoto.com/hardcore-tech/blog/cnc-engine-block-machining-service.html SUMMARY Outcomes You should now be able to differentiate drilling, turning and milling, Drilling – creating holes, Turning - generating a cylindrical shapes/profiles, Milling - precisely remove material from a solid block, You should understand what numerical control is and how it relates to machining or manufacturing, The language for programming machines and moving and completing actions, You should now understand the three metrics to determine how well the programme is doing, Accuracy, repeatability & resolution, You should now be aware of programming languages, G-Code (including G-, M-, S-, T- commands etc.) You should now be able to calculate speeds and feeds for a given process. An interesting turning video: https://www.youtube.com/watch?v=se1PsJwTpiY  SHEET METAL FORMING Dr Scott Millen MEE2034: Manufacturing Technology 2 LEARNING OUTCOMES AND OVERVIEW Outcomes You should understand what sheet metal working is, You should understand the different sheet metal processes, You should understand the application of different sheet metal joining processes. Overview The basics of sheet metal, Cutting processes, Bending processes and considerations, Rolling, drawing, spinning, and joining.  SHEET METAL INTRODUCTION Thickness of sheet metal = 0.4 mm to 6 mm, Thickness of plate stock > 6 mm, Operations usually performed as cold working, There is a general process flow: https://formlabs.com/uk/blog/sheet-metal-forming/ STRESS-STRAIN BEHAVIOUR  CUTTING PROCESSES There are three principal operations used to cut metal in pressworking: shearing, blanking, and punching, Shearing - Separating material into two parts, Blanking - Removing material to use for parts, Punching - Removing material as scrap. https://www.custompartnet.com/wu/sheet-metal-shearing  CUTTING PROCESSES - SHEARING A specific cutting process that produces straight line cuts to separate a piece of sheet metal, Normally used to cut a sheet parallel to an existing edge which is held square, Shearing has the following capabilities: Sheet thickness: 0.125 mm to 6.25 mm, Tolerance: ±2.54 mm, https://www.custompartnet.com/wu/sheet-metal-shearing  CUTTING PROCESSES - BLANKING A cutting process in which a piece of sheet metal is removed from a larger piece of stock by applying a great enough shearing force, In this process, the piece removed, called the blank, is not scrap but rather the desired part, Blanking can be used to cutout parts in almost any 2D shape, Blanked parts typically require secondary finishing to smooth out burrs along the bottom edge. https://www.custompartnet.com/wu/sheet-metal-shearing  CUTTING PROCESSES - PUNCHING Punching is a cutting process in which material is removed from a piece of sheet metal by applying a great enough shearing force, Similar to blanking except that the removed material, called the slug, is scrap, A CNC punch press can be hydraulically, pneumatically, or electrically powered and deliver around 600 punches per minute. https://www.custompartnet.com/wu/sheet-metal-shearing PUNCHING FORCE 𝜎 = 𝐹ൗ𝐴 L t 𝑑 𝐿 = 𝐶 = 𝜋𝑑  PANEL BEATING (HAMMERING) Traditionally, as far back as the 1920s, most automobile bodies had wooden frames with relatively heavy sheet-metal panels wrapped around them, These panels were beaten into shape by hand. A leather sandbag is used as A planishing hammer is used to support when using the smooth out a rear light housing. blocking hammer. https://www.uniquecarsandparts.com.au/how_it_works_panel_beating PRESS BRAKING - BENDING Bending can be done in two primary ways: V bending/Bottoming - bent between V-shaped punch and die, For low production, Performed on a press brake, V-dies are simple and inexpensive, *air bending produces a shallow V-shape. Wipe/Edge bending - involves cantilever loading of sheet metal, Pressure pad required, For high production, Dies are more complicated and costly.  PRESS BRAKING - BENDING Step Bending (Bump Bending): Repetitive V-bending, Uses many V-bends in succession to get a large radius for your workpiece, The final quality depends on the number of bends and the step between them, The more you have them, the smoother the outcome. https://youtu.be/l43i4ok1RLc?si=HCqk_6HWrIbABjlL  BENDING - THE MINIMUM BENDING RADIUS A flat blank of constant thickness t is bent over an angle α with a radius R, How small can R be, as a function of t, a, and the material’s formability? To answer this question, we draw up a simple model by making these five assumptions: 1. All deformation that takes place in a bending zone defined by a and R. Outside this zone, no deformation occurs. 2. The metal elongates in tension in the same manner as in compression. 3. At mid-thickness of the sheet, at the radius equal to R, there is a “neutral axis” that does not change in length. 4. The metal outside the neutral axis elongates and becomes thinner, and the metal inside the neutral axis compresses and becomes thicker. 5. The metal is isotropic and homogenous, meaning that is has the same behaviour in all directions and at all locations. Manufacturing and Design: Understanding the Principles of How Things Are Made, Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff Butterworth-Heinemann/Elsevier, 2014, First edition. BENDING - SPRINGBACK Defined as: a change in shape of the part as the load is removed, After the punch is removed, the angle increases due to elastic deformation. The increase in the angle is called springback. BEND TYPES Standard bend (flange): Bend relief notches: Joggle: BEND TYPES Hems: Gusset:  ROLLING Roll bending is ideal if we want to make larger radii bends, This method allows us to make a cylindrical product, The forces required to do this are relatively modest, especially because the deformation is usually obtained gradually, (a) Schematic of roll bending; (b) curved strip and rolled product (pedal bin). Manufacturing and Design: Understanding the Principles of How Things Are Made, Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff Butterworth-Heinemann/Elsevier, 2014, First edition.  ROLL FORMING A long strip of metal is fed through a series of rollers at considerable speed (≥1 m/s) to produce a profile, The rollers progressively generate the desired cross-section, Product-specific investments are high, therefore only suitable for high volumes, Roll forming is mostly done with low to medium carbon steels, certain low alloy steels, and stainless steels. Manufacturing and Design: Understanding the Principles of How Things Are Made, Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff Butterworth-Heinemann/Elsevier, 2014, First edition.  SUPERFORMING A metal blank is heated to softening point and formed onto a single-sided tool using air pressure, Temperatures between 450-500oC, Thompson, R. (2007) Manufacturing Processes for Design Professionals. London: Thames & Hudson, Limited.  DEEP DRAWING Sheet metal forming to make cup-shaped, box-shaped, or other complex-curved, hollow-shaped parts, Sheet metal blank is positioned over die cavity and then a punch pushes the metal into opening, (1) before punch contacts work, (2) near end of stroke. Schematic for (a) deep drawing and (b) typical application. Manufacturing and Design: Understanding the Principles of How Things Are Made, Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff Butterworth-Heinemann/Elsevier, 2014, First edition. STAMPING Used to form shallow sheet and bend profiles in sheet metal, The tooling cost is high so is most appropriate for mass production. Embossing - creates indentations in sheet, such as raised lettering or strengthening ribs.  METAL SPINNING Metal spinning, or spin forming, transforms a flat circular blank or disc shaped workpiece into axially symmetrical round shapes, Made possible with the use of a lathe and a roller, Mandrel - a forming die that gives volume or shape to the metal disc and supports the workpiece as it is rapidly spun, Roller - a rigid tool that applies localized force which causes the workpiece to flow over the mandrel in order to transform it to the desired shape. https://www.iqsdirectory.com/articles/metal-spinning.html https://www.youtube.com/watch?v=4DKN1qAMQig SHEET METAL JOINING Riveting A rivet is a nonthreaded mechanical fastener which has the appearance of a metal pin, The rivet is either drilled, placed or punched into a hole, This process deforms the tail, holding the rivet in place, Rivets tend to be much cheaper to install than bolts, Childs, Peter R. N. Mechanical Design Engineering Handbook. Second edition. Oxford, England ; Butterworth-Heinemann, 2019. Print. https://www.youtube.com/watch?v=u9EnPAgo8p4  SHEET METAL JOINING Clinching Sheets of 0.5 to 3mm thick, up to a total joint thickness of about 6mm, Joining process drawing a circular button through two sheets, forming a mushroom shape, interlocking them together, As the joint is made by local plastic deformation of the sheets, it is essential that the materials have sufficient ductility to avoid cracking, Clinching provides a cleaner alternative to riveting and spot welding, No sparking or burning, No pre-punched hole, No extra component. Manufacturing and Design: Understanding the Principles of How Things Are Made, Bruno Ninaber van Eyben, Erik Tempelman, and Hugh Shercliff https://www.youtube.com/watch?v=P1iMcCI70R0  SHEET METAL WORKING EXAMPLES Sheet metal parts for consumer and industrial products such as Automobiles and trucks, Airplanes, Railway cars and locomotives, Farm and construction equipment, Small and large appliances, Office furniture, Computers and office equipment.NR212-Lecture 7-Slide No. 3 https://www.goebelfasteners.com/why-are-airplanes-manufactured-with-riveted-joints-instead-of-welded/ LEARNING OUTCOMES AND OVERVIEW Outcomes You should understand what sheet metal working is, Sheet metal work covers the manufacture of products from a sheet of metal of typical thickness 0.4 mm to 6 mm, You should understand the different sheet metal processes, Cutting, bending, rolling, deep drawing, stamping, spinning, You should understand the application of different sheet metal joining processes, Riveting or Clinching.  3D PRINTING LASER CUTTING Dr Scott Millen MEE2034: Manufacturing Technology LEARNING OUTCOMES AND OVERVIEW Outcomes You should understand the basic theory of 3D printing, You should understand the purpose of support material, infill density and layer height, You should understand how prints can be stabilised, You should understand the benefits of 3D printing over other technologies in prototyping, You should be aware of what a laser is and how it relates to cutting in manufacturing, You should be able to account for Kerf and Heat Affected Zone in your designs. Overview 3D printing introduction, Components of a printer and resulting prints, Laser and laser cutting overview, Kerf and Heat Affected Zone (HAZ).  ADDITIVE MANUFACTURING Additive Manufacturing (AM) is a manufacturing technology that builds 3D objects by adding layer- upon-layer of material, The printing material can be plastic, metal or even concrete, Subtractive manufacturing is a manufacturing technology that creates objects by removing material from solid blocks, bars or rods through cutting, boring, drilling, and grinding. https://pubs.rsc.org/image/article/2016/CS/c5cs00714c/c5cs00714c-f1_hi-res.gif  3D PRINTING The first 3D printer was invented in 1987, which used the stereolithography process, Three broad types of 3D printing technology; sintering, melting, and stereolithography. Sintering - the material is heated, but not to the point of melting, to create high resolution items, Melting methods - use lasers, electric arcs or electron beams to print objects by melting the materials together at high temperatures, Stereolithography - uses a light source/laser to interact with the material in a selective manner to cure and solidify a cross section of the object in thin layers. https://www.youtube.com/watch?v=yW4EbCWaJHE https://www.rankred.com/what-is-3d-printing-working-principle-types-applications/  Print head cable and PRINTER Bowden tube Print head (hot end) Feeder Build plate USB port Spool holder and spools Control panel MATERIALS Many filament types are available: Polylactic acid (PLA), Acrylonitrile butadiene styrene (ABS), Nylon, Carbon fibre, Thermoplastic Polyurethane (TPU), Polyethylene terephthalate (PET). EXTRUDERS The extruder is the part of the 3D printer that does the printing, Extruders can be single- or dual-extrusion, This translates to the number of print heads, A dual-extrusion system allows users to mix and match materials and colours. A print core is a compact hot end containing the nozzle, heater block, heater and sensor, AA for non-abrasive materials, BB for support material. SUPPORT MATERIAL, INFILL AND LAYER HEIGHT Support materials allow for complex geometries and internal features that, would otherwise deform before they hardened, Breakaway vs soluble support materials, Infill refers to the internal structure of a 3D printed part, Optimize part weight, strength, and printing time, Typical infill density is 20 - 50%. Layer height is a measurement of how much material the printer’s nozzle extrudes for each layer of your part, Number of layers = total height / layer height. 3D PRINTING PROCESS 1. 3D CAD File in.STL format  3D PRINTING PROCESS 1. 3D CAD File in 2. SLICING.STL format.GCODE file Brim http://my3dconcepts.com/wp-content/uploads/2017/04/How-3D-Printing-Works--1030x309.png  3D PRINTING PROCESS 1. 3D CAD File in 2. SLICING 3. PRINTING.STL format.GCODE file Brim 4. FINAL OBJECT http://my3dconcepts.com/wp-content/uploads/2017/04/How-3D-Printing-Works--1030x309.png G-CODE G-code is the most widely used computer numerical control (CNC) and 3D Printing programming language, ;Generated with Cura_SteamEngine 5.3.1 G92 E0: Resets the extruder and prepares the printer for a new print, G92 E0 M109 S250 G280 S1 M109: Wait until extruder reaches T0, G0 Z20.001 G1 F2700 E-8 G280 S1: the printer should not prime, ;LAYER_COUNT:46 ;LAYER:0 M106 S102 M106 S[x]: Sets the cooling fan speed to cool down the hot end or M204 S1000 M205 X20 Y20 turn off the cooling fan after a print finishes, G1 F600 Z2.2 G0 F9000 X179.758 Y122.351 Z2.2 ;TYPE:SKIRT G1 F[x] E[-x]: Instructs the printer to retract or pull back filament G1 F600 Z0.2 G1 F2700 E0 using the extruder. G1 F900 X178.893 Y123.553 E0.01857 G1 X177.124 Y125.533 E0.05187 G28: Homes all axis; this puts your printer into its home position,.. G1 F1800 X172.45 Y117.18 E272.72539 G1 X[x] Y[x] Z[x] F[x] E[x]: Moves the printhead and sets the feed rate, ;TIME_ELAPSED:1390.752763 G1 F2700 E264.72539 Typically, this command is followed by a variation of the same command and M204 S3000 M107 used for printing a test line, M82 ;absolute extrusion mode M104 S0 M104 T1 S0 G1 Z[x]: Moves the Z-axis, ;End of Gcode  RAFT VS BRIM VS SKIRT Raft - a horizontal latticework of filament located underneath the part, The part will be printed on top of this raft, instead of directly on the build platform surface, Primarily used with ABS to help with warping and bed adhesion, Once the print is complete, the raft effortlessly peels away from the print and can be discarded. Raft https://www.simplify3d.com/resources/articles/rafts-skirts-and-brims/  RAFT VS BRIM VS SKIRT Skirt - an outline that surrounds the part but does not touch it, It is extruded on the print bed before starting to print the actual model, Main purpose is to help prime the print head and establish a smooth flow of filament, Brim - a type of skirt that is attached to the edges of the model, Main purpose is to to hold down the edges of the part, which can prevent warping and help with bed adhesion, The thin brim can be separated from the solid model and discarded after printing. Raft Skirt Brim https://www.simplify3d.com/resources/articles/rafts-skirts-and-brims/ PAUSE-AT-HEIGHT Pause-at-height is a unique function in additive manufacturing processes, It allows components to be enclosed within the print. 1. Print pauses at chosen height 2. Enclosed component is inserted 3. Print completes RAPID PROTOTYPING Rapid prototyping is the fast fabrication of a physical part, model or assembly using 3D computer aided design (CAD), The creation of the part is usually completed using additive manufacturing, or 3D printing, Rapid prototyping traditionally creates pre-production, 3D parts in materials that are different to the intended production material or with different physical properties. PROTOTYPE DELIVER REFINE & REVIEW ITERATE  3D PRINTING OF CONTINUOUS CARBON FIBRE Continuous fibres are strongest when loaded in tension, Understanding where the fibres are loaded in tension, And how a given load can distribute amongst the local fibres, The choice of fibre influences the behaviour of the part: Carbon fibre – very high strength to weight properties, Fiberglass - intermittent loading conditions, cost-effective, Carbon Matrix Carbon Fibre + = Fibres Material Composite Kevlar – shock and impact resistant material. https://www.darkaero.com/knowledge/composites/what-is-a-composite/ https://markforged.com/resources/learn/design-for-additive-manufacturing-plastics-composites/3d-printing-strategies-for-composites/fiber-reinforced-3d-printing-what-you-need-to-know  3D PRINTING OF CONTINUOUS CARBON FIBRE II Reinforcing For Different Loading Conditions Tension - Align the fibres with the tensile force, Bending - Place fibre planes on the extreme faces experiencing bending, Compression - Build a scaffold of fibre to reinforce against compressive forces. https://markforged.com/resources/learn/design-for-additive-manufacturing-plastics-composites/3d-printing-strategies-for-composites/fiber-reinforced-3d-printing-what-you-need-to-know  3D PRINTING OF CONTINUOUS CARBON FIBRE III Mei, H. et al. Tailoring strength and modulus by 3D printing different continuous fibers and filled structures into composites. Adv Compos Hybrid Mater 2, 312–319 (2019). https://doi.org/10.1007/s42114-019-00087-7 https://www.youtube.com/watch?v=46MyMgrGhho  LASER CUTTING Dr Scott Millen MEE2034: Manufacturing Technology 2 LASERS LASER - an acronym for Light Amplification by Stimulated Emission of Radiation, The conversion of electric energy into light energy and into thermal energy, Laser light is monochromatic - of one wavelength, Laser light is also coherent – all light waves vibrate at the same frequency and are in phase, Therefore…laser light can be transmitted in a near perfectly parallel beam.  LASER CUTTER STRUCTURE Laser cutters generally consist of the following main parts: Power Supply: A high voltage power system is used in laser beam machining, Capacitor: A capacitor bank charges and releases the energy during the flashing process, Flash Lamps: An electric arc lamp that produces an extremely intense, coherent, high-intensity beam, Reflecting Mirror: maintains and amplifies the laser beam and directs the laser beam towards the workpiece. Laser Light Beam: The beam of radiation produced by the laser, Lens: used to focus the laser beam onto the workpiece (designed to focus the energy at one particular distance which is optimal for that set up), Workpiece: The workpiece can be metallic or non-metallic. In this machining process, any material can be machined. https://themechanicalengineering.com/laser-beam-machining/  LASER CUTTING APPLICATIONS Laser light is focused on a small spot, The concentrated energy causes local melting, evaporation and ablation, Most cutting lasers use assisting gas to increase efficiency, Assisting gases cool and clean the cutting area of molten material, Laser cutting can be used on metals, ceramics, plastics, glass and cloth. Manufacturing Technology by R.L. Timings (Author), Steve Wilkinson LASER CUTTING APPLICATIONS II Fusion cutting - an inert gas (typically nitrogen) is used to expel molten material out of the kerf, the laser beam must supply all of the energy needed for cutting, Flame cutting - oxygen is used as the cutting gas and chemical reactions support the laser beam, Remote/Sublimation cutting - primarily used for precision cutting tasks which require very high- quality cutting edges, The laser vaporises the material - minimised melting, The assist gas shields the cutting areas from the environment and oxidation. Note – The QUB laser cutter uses compressed air due to being relatively low energy at 50w. Metal cutting has to be inert. LASER CUTTING APPLICATIONS III General Advantages General Disadvantages High cutting speed High capital equipment cost Small heat-affected zone Higher operating costs (consumable gases) Good profiling accuracy Potential safety hazard of laser and vaporised material Smooth cutting finish No cutting forces on work piece LASER CUTTING PROCESS Sheet material is placed on the cutting bed and accurately positioned, The laser head moves to the initial start point and begins heating the material, The material reaches a molten state throughout its thickness, Once molten, a high-pressure stream of inert gas is directed at the molten material and begins blowing it out of the kerf, The laser head then follows the cutting path, Continuously heating the material to its molten point and blowing the molten material from the cut, Parts are then removed from the bed. KERF Kerf is the width of material that is removed by a cutting process, Almost all cutting mechanisms leave a cutting kerf, e.g., laser cutting, plasma cutting, CNC Milling and others, Each cutting process produces a different width. The following demonstrates the smallest kerf a process may produce: Cutting mechanism Smallest kerf CNC cutting Range depending on the tooling Mechanical and Hand Saws 3.175 mm Laser cutting 0.2 mm Plasma cutting 3.8 mm Waterjet cutting 0.9 mm Oxy-fuel cutting (flame) 1.1 mm KERF II Laser cutter kerf is challenging to account for, Different factors can effect the kerf width of a laser cutting machine: Quality of the laser beam, Beam width - determined by the focal length (distance from lens to part), but beam width can change depending on the thickness of your material, Different cutting materials - Wood gets burnt away by the laser, but plastics may shrink away as they are not only cut but melted. Thickness of material, Cutting speed.  KERF III The kerf needs to be accounted for to produce accurate parts, KERF = INTENDED CUT – ACTUAL CUT If you want to cut a 150 mm x 150 mm square and the laser removes 0.2 mm of material the resulting part will be: 150 mm 149.9 mm 149.9 mm 150 mm https://parts-badger.com/whats-a-kerf/ https://cutlasercut.com/drawing-resources/expert-tips/laser-kerf/ https://makezine.com/article/workshop/accounting-for-kerf-how-much-material-is-really-removed-by-your-cutter/ HEAT AFFECTED ZONE (HAZ) Heat Affected Zone (HAZ) is the area of the base material which has not melted but whose microstructure and mechanical properties were affected by the heat, During thermal cutting the material quickly heats up to its melting point in a local area and is then rapidly cooled down due to surrounding colder materials, Laser cutting generates the smallest HAZ among all thermal cutting techniques, The extent of the HAZ effect is mainly based on cutting temperature, heated area and cutting speed.  DIRECTED ENERGY DEPOSITION (DED) DED is an AM process that adds material alongside the heat input simultaneously, DED uses a heat source to melt a powder or wire as it is deposited onto the surface of an object, Powder provides greater accuracy in deposition but wire is more efficient with regards to material use, Layers are typically 0.25mm to 0.5mm thick, DED can be used for repairs. Schematics of two DED systems (A) uses laser together with powder feedstock and (B) uses electron beam and wire feedstock. Alojaly et al., Review of recent developments on metal matrix composites with particulate reinforcement, Reference Module in Materials Science and Materials Engineering https://www.youtube.com/watch?v=oL7bMhPTtDI SUMMARY Outcomes You should understand the basic theory of 3D printing, Builds 3D objects by adding layer-upon-layer of material, You should understand the purpose of support material, infill density and layer height, Support materials allow for complex geometries, Infill refers to the internal structure, Layer height is a measurement of how much material is extruded in each pass, You should understand how prints can be stabilised, Brim, Raft and Skirt options You should understand the benefits of 3D printing over other technologies in prototyping, Pause-at-height, enclosing components, You should be aware of what a laser is and how it relates to cutting in manufacturing, Light Amplification by Stimulated Emission of Radiation You should be able to account for Kerf and Heat Affected Zone in your designs.  CASTING Dr Scott Millen MEE2034: Manufacturing Technology 2 LEARNING OUTCOMES AND OVERVIEW Outcomes You should understand the basic theory of casting, You should be able to differentiate the casting processes and their applications, You should be able to identify common casting defects. Overview Casting overview, Investment Casting, Sand Casting, Die Casting, Conclusions, Feedback Poll.  CASTING Casting is a manufacturing process that converts a liquid to a solid, through solidification, using a mould, The liquid is poured into the mould, The liquid and mould are then cooled, and the solid part (the casting) is extracted. https://www.instructables.com/Introduction-to-Mold-Making-Casting/ PRINCIPAL ADVANTAGE OF CASTING Casting allows Engineers and Artists to create complex shapes in a cost effective manner. Bronze Plaque for Titanic Commemorations CASTING PROCESSES Different casting processes: 1. Investment casting - a wax pattern is used to shape a disposable ceramic mould, 2. Sand casting - metal casting process, sand as the mould material, 3. Plaster Casting - similar to sand casting but with plaster of Paris mold, 4. Die casting - molten metal is poured or forced into steel molds. Image credit: Funtay/Shutterstock.com INVESTMENT CASTING Liquid metals are formed into complex and intricate shapes in this process, It uses non-permanent ceramic moulds, https://www.youtube.com/watch?v=ksojUEgrvtM  SAND CASTING In sand casting molten metal is poured into a sand mold containing a hollow cavity of the desired shape (negative impression), After cooling the sand is broken away and shaken out, Casting materials for sand casting include metal, concrete, epoxy, plaster, and clay. Properties and Applications of Sand Casting Wide range of metals, sizes and shapes, Mostly for cast iron, Low cost process for mass production, Poor finish, wide tolerance of dimensions https://www.iqsdirectory.com/articles/die-casting/sand-casting.html  SAND CASTING II Sand casting process involves the following sequence of operations: 1. Pattern manufacture, 2. Creating a mould using the pattern and moulding sand, 3. Mould clamping – to prevent the parts of the mould splitting during metal pouring, 4. Melting and treating the metal before pouring, 5. Cooling and removal of solidified form, 6. Fettling of the casting, 7. Inspection and testing (if applicable) https://www.youtube.com/watch?v=fCyaJ8Q76U8  SAND CASTING III Pattern - a replica of the original object to be cast, This pattern is used to make a negative cavity in the mould into which molten metal is poured during the casting process, Pattern must be made from a rigid material that is easily shaped and will not deform during the sand moulding process, During sand casting the pattern is removed from the sand mould as a solid, Taper of the pattern vertical edges is required to avoid mould breakage, https://www.iqsdirectory.com/articles/die-casting/sand-casting.html  SAND CASTING IV When molten metal cools it contracts, the pattern should therefore be made slightly larger to accommodate this contraction, The magnitude of the contraction allowance depends on two factors, the size of the casting and the material type: For aluminium the contraction allowance is 1.3%, For cast iron the contraction allowance is 1.0%, For steel the contraction allowance is 2.0%, For leaded gunmetal the contraction allowance is 1.5%. Manufacturing and Design: Understanding the principles of how things are made, Tempelman, Shercliff and Ninaber van Eyben, https://doi.org/10.1016/C2011-0-08438-7 SAND CASTING V Pattern Design Features Most castings require machining to improve their dimensional accuracy, Fettling describes the processes by which crude casting is turned into a quality component - the removal of unwanted elements produced in the cast. To provide material for machining the pattern is made slightly bigger, This increase in the pattern dimensions is referred to as the machining allowance. 2-10 mm machining allowance Total dimension of Exterior surface rough casting after machining SAND CASTING VI Pattern Design Considerations Avoid thin pattern cross sections - too thin = cools too quickly, solidifies before mould cavity full – “Non filling” or “Misrun”, Avoid sharp corners / abrupt changes of section - use fillet radii, gradual change from thick section to thin section Click on link below to view a video on Sand Mould Manufacture at BMC Foundry (22 mins): https://youtu.be/vl7cL4mYLGU DIE CASTING In die casting a permanent mould or die is made from steel, Molten metal is then poured into the die to form the casting, There are three types of die casting, gravity die casting, low pressure die casting, high pressure die casting. DIE CASTING II GRAVITY DIE CASTING (GDC) A repeatable casting process used for non-ferrous alloy parts, typically Aluminium, Zinc and Copper Base alloys, Gravity is used to fill the mould with the liquid alloy, GDC is suited to medium - high volume products. Die parts assembled and clamped Metal poured into runner Die opened and casting ejected DIE CASTING III GRAVITY DIE CASTING (GDC) Advantages Disadvantages Good dimensional accuracy Limited Design Flexibility Smoother cast surface finish than sand casting High Initial Investment Improved mechanical properties compared to Longer Lead Times sand casting Thinner walls are achievable Relatively fast production times  DIE CASTING IV LOW PRESSURE DIE CASTING Low-pressure die casting is a method of production that uses pressure (typically 2 to 5 bar) – rather than gravity – to fill moulds with molten metal, Typically, molten metal is introduced into the mould from below, Gas pressure holds the metal in the die until it solidifies, Production rates are fair, Minimum wall thickness' are as little as 2-3mm, Reduced fettling and trimming required, Surface finish better than gravity die casting https://www.open.edu/openlearn/science-maths-technology/engineering- technology/manupedia/low-pressure-die-casting-counter-pressure-casting  DIE CASTING V HIGH PRESSURE DIE CASTING The shortest route from molten metal to completed component, Molten metal is injected into a hardened steel mould and solidifies under pressure (up to 2,000 bar) before ejection, Ideally suited to high production rates, Minimum wall thickness' are as little as 1-2mm, Provides the best surface finish of casting processes, High startup costs are only reduced by long casting runs. https://midlandpressurediecasting.co.uk/pressure-die-casting/  EJECTOR PINS AND DRAFT Direction DRAFT of Part Large flat Exaggerated draft Removal Tool area angle Part Good Design Mediocre Design Any flat areas of a mould require draft or taper, This draft will vary with the alloy used and with the depth of the wall, Specify a large draft angle wherever practical (but ≤1o is tolerable). EJECTOR PINS Used to apply a force to eject the part from the mould, Ejector pin marks on most die castings may be ±0.38mm, Avoiding pin marks: reduce pressure, control temperature, more draft. https://www.cavitymold.com/how-to-fix-ejector-pin-marks-in-injection-molding/ CASTING DEFECTS Rough Surface Finish Inadequate compaction of moulding sand Satisfactory compaction of moulding sand A PDF summarizing further defects is available on Canvas SUMMARY Outcomes You should understand the basic theory of casting, A manufacturing process that converts a liquid to a solid, through solidification, using a mould, You should be able to differentiate the casting processes and their applications, High-Pressure Die Casting (high pressure to fill hardened steel mould), Low Pressure Die Casting (low pressure to fill mould), Gravity Die Casting (gravity to fill the mould), Investment (wax and ceramic), Sand. You should be able to identify common casting defects – surface finish, misrun etc. Examples of Casting Defects Casting Defects – Rough Surface Finish Flywheel casting with rough Flywheel casting with good surface finish due to inadequate surface finish due to satisfactory compaction of moulding sand compaction of moulding sand Casting Defects – Porosity Causes of Casting Porosity - Moisture content of greensand too high - Inadequate sand mould venting - Sand mould permeability too low Casting Defects – Non-Filling Causes of Casting Non Filling Defects - Pattern thickness too small - Poor molten metal pouring technique - Molten metal pouring temperature too low Casting Defects – Sand Inclusions Causes of Casting Sand Inclusions - Sand mould breakage - Poor cleaning of sand mould Casting Defects – Fins Causes of Casting Fins - Soft compaction of the sand mould causing the mould to crack during molten metal pouring - Improper clamping of cope to drag Casting Defects – Mismatch Cause of mismatch - Poor alignment between drag and cope mould  ABRASIVE MACHINING PROCESSES Dr Scott Millen MEE2034: Manufacturing Technology 2  ABRASIVE PRINCIPLE Abrasive machining is a material-removal machining process that involves the use of abrasive, The primary objective of abrasive machining is to achieve a desired surface finish or to bring the workpiece to a defined shape, Material is removed from the desired workpiece by the multitude of hard abrasive particles applied using external energy, The particles are quasi-wedge shaped so have the same working principle as metal cutting. Pandiyan et al., Modelling and monitoring of abrasive finishing processes using artificial intelligence techniques: A review, Journal of Manufacturing Processes, 2020 https://doi.org/10.1016/j.jmapro.2020.06.013. CHARACTERISTICS OF ABRASIVES Hardness - the material's ability to resist deformation and wear, allowing it to efficiently remove material from the workpiece., Toughness - the ability to withstand stress and impacts without fracturing, Friability – a measure of an abrasive's ability to break down into smaller particles during use, ensuring a continuous supply of fresh cutting edges, Grit Size - refers to the size of abrasive particles, usually measured in microns or mesh sizes, Coarser grits are effective for heavy material removal, while finer grits are ideal for achieving smooth finishes, Particle Shape - Irregular shapes (sharp-edged particles) provide aggressive cutting, whereas rounded or spherical particles tend to produce finer finishes. ABRASIVE TYPES Conventional abrasives - such as aluminium oxide and silicon carbide, among the most frequently used, Superabrasives - Diamond and Cubic Boron Nitride have superior hardness/heat resistance, particularly when processing hard and challenging workpiece materials, Natural Abrasives - diamond and garnet. Limited but specialised applications, Synthetic Abrasives - consistent size and quality for precision grinding operations, Bonded Abrasives - the combination of abrasive grains held together by a bonding material, Coated Abrasives - abrasive grains are fixed to a backing material, e.g. sandpaper, Loose Abrasives - free grains employed in operations such as abrasive waterjet cutting and blasting.  ABRASIVE MACHINING Abrasive grain acts as the cutting tool insert, However, the grains have undefined geometry and are distributed randomly with different orientations, Machining processes which use abrasives to remove material are otherwise called finishing or polishing, Common abrasive processes are Grinding, Honing, Sanding, Polishing, Buffing, Lapping, Abrasive Waterjetting, Sand Blasting and Glass Blasting, Kibria et al. Introduction to Abrasive Based Machining and Finishing. Springer, Cham. https://doi.org/10.1007/978-3-030-43312-3_1 Ratnasingam, J. (2022). Sanding Process. In: Furniture Manufacturing. Design Science and Innovation. Springer, Singapore. https://doi.org/10.1007/978-981-16-9412-7_7  ABRASIVE MACHINING PROCESSES Grinding - the most common abrasive machine process done using a grinding wheel or abrasive belt on a grinding machine, The hardness of the grinding wheel / disc is measured by grit, Normal range between 24 and 100 grit. Honing - used to control the size and form of an ID surface, Similar principle to a reamer, Slower process than grinding with lower heat and pressures, Kibria et al. Introduction to Abrasive Based Machining and Finishing. Springer, Cham. https://doi.org/10.1007/978-3-030-43312-3_1 https://waykenrm.com/blogs/honing-process/  ABRASIVE MACHINING PROCESSES Sanding - to make the surface look uniform and remove any imperfections, Performed by high-speed sanding discs. Polishing - a finishing process where material removal is very minimal, Multiple applications of finer and higher grit abrasives along with a suitable polishing compound, Buffing - performed to remove burrs and enhance surface finishes, Normally uses stationary polishers and die grinders, Lapping - used for flat parts - two surfaces having an abrasive between them, The part is ‘sandwiched’ between two abrasive wheels, allowing both sides of the workpiece to be addressed, Lapping uses loose abrasive instead of bonded abrasives Can generate mirror-like surface finishes. Kibria et al. Introduction to Abrasive Based Machining and Finishing. Springer, Cham. https://doi.org/10.1007/978-3-030-43312-3_1 https://waykenrm.com/blogs/honing-process/  ABRASIVE WATER JET Uses high pressure jets of water provided by pressurising pumps that deliver a very high-powered stream of water to cut and shape various types of materials, The water is pressurised to ~392 MPa and projected using a small precision nozzle, Pure water jet cutting is designed for soft materials such as wood, plastics, foam, paper, and rubber, An abrasive is added to the water stream for titanium, stainless steel, aluminum etc. Pandiyan et al., Modelling and monitoring of abrasive finishing processes using artificial intelligence techniques: A review, Journal of Manufacturing Processes, 2020 https://doi.org/10.1016/j.jmapro.2020.06.013. ABRASIVE WATER JET II Initial Water Jet Piercing The first cut made by a water jet cutter is referred to as the pierce, The pierce is wider than the normal kerf, Different piercing methods can be used depending on the material to be cut, Pierce Stationary, linear, circular, and low pressure methods. 1.27 mm 1.07 mm  ABRASIVE WATER JET III Initial Water Jet Piercing There is no spinning spiral cutter to remove the debris, Debris has to come back out of the same hole that the jet goes in, If the jet is 1.0 mm, theoretically the hole will be that diameter, However, water and abrasive material have to leave the hole, Therefore, a 1.0 mm hole might become 1.25 mm as the water escapes eroding the hole more. Orbanic H, Junkar M. An experimental study of drilling small and deep blind holes with an abrasive water jet. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2004 ABRASIVE WATER JET IV Initial Water Jet Piercing Stationary - the cutting head remains in a fixed position while the cutting stream works its way through the material, Good for cutting thin materials (