CNC Milling Lab Practical Session Theory PDF

## Official (Open) ME2016 Computer-Aided Machining ### CNC Milling Lab Practical Session 2 (Group) **Class:** DME/2A/27 **Group:** 2 **Date:** 15 Jan 2025 | Name | Adm. No. | |---|---| | Ahilan | 23/6875 | | Joei | 2317 12-8 | | Eldrick | 2316213 | | Snigdha | 2316790 | | Merlin | 2816960 | 1....

## Official (Open) ME2016 Computer-Aided Machining ### CNC Milling Lab Practical Session 2 (Group) **Class:** DME/2A/27 **Group:** 2 **Date:** 15 Jan 2025 | Name | Adm. No. | |---|---| | Ahilan | 23/6875 | | Joei | 2317 12-8 | | Eldrick | 2316213 | | Snigdha | 2316790 | | Merlin | 2816960 | 1. **(a) Explain the two main purposes of using parallel bars in this lab exercise.** - Lifts the workpiece so that the cutter does not hit the vice or the table. - Ensure that the work piece is parallel to the working table. **(b) What is the height of the parallel bars you used in this setup?** 35mm **(c) Do a measurement of 'B' on the machine vise. If the min clamping depth of 5 mm required to provide a firm workholding, and min clearance 1 mm to provide safe cutting. Determine the range of the parallel bars height 'A' that can be used in this exercise. Show your working below.** **RAW STOCK SURFACE**  40 - 8.5 = 頭 + 1 mm clearance = 32.5 : range: 32.0 33.0, 34.0 35.0 ### CNC Milling Lab Practical Session 3 (Group) **Class:** DME/2A/27 **Group:** 2 **Date:** 22 Jan 2025 | Name | Adm. No. | |---|---| | Ahilan | 2316175 | | Merlin Jerwing | 2316961 | | Snigdha | 2316990 | 1. **Explain how you obtained the overall thickness of the Caster Base of 16mm with the general tolerance ±0.1mm. (State the detailed steps in point form)** - Touch the // bar using the probe to get the workpiece thickness for the work origin. - Enter +16mm for G55 @ 2-axis. 2. **(a) It is difficult to establish the Work Zero of the part after the stock flip because the raw stock is obstructed the 3D measuring probe. Explain the necessary steps on how you determined the G55 Work Offset (X, Y) for the 2nd side machining. (State the detailed steps in point form)** - Find the center (x, y) roughly of the workpiece. - To find the center, we measured the sides of the workpiece using a probe and divided it by 2 to find the center. - Use dynamic cutting to face away the raw material. - We input (x, y) + G55. - To attain symmetry the process touches both left and right sides. - X-axis is fixed at the center **(b) What would be the consequences if a student forgot to re-establish the Work Offset G55 after the facing operation?** The workpiece would be over cut and the measurement will not be accurate. The slot will be misaligned from the center. **(c) There is no tool wear compensation conducted in this practical. Explain why you do not need this step.** The 75mm slot is open tolerance. **(d) When machining the 2nd side of the Caster Base, you realised that you obtained 12.2mm instead of 12mm. What is the feasible method you can use to achieve 12mm as per required?** G55 Z-offset. Offset the workpiece by -0.2mm and do another cut. ### CNC Milling Lab Practical Session 4 (Group) **Class:** DME/2A/27 **Group:** 2 **Date:** 22 Jan 2025 | Name | Adm. No. | |---|---| | Ahian | 23/6875 | | Merlin Jerwing | 2316961 | | Snigdha | 2316990 | 1. **The part could be machined in the two different orientations shown below.**  **(a) Which orientation was selected when machining the Bracket?** Diagram A **(b) Explain why it was chosen.** The workpiece has lesser chances of sliding and getting offset because the cutting force is in the direction of the clamping jaw. 2. **Dynamic milling is applied to rough out the bracket. Do a close observation of the cutter movement during machining.** **(a) How much time (min) is required to rough out the bracket?** 1 min 5 sec **(b) What is your observation on the machining technique?** - Depth of cut (mm): 28mm - Feed rate (mm/min): 2500 - Chip thickness (mm): 0.24 **(c) What is the diameter you obtained for Ø22.03 ± 0.01mm bore hole on the Caster Bracket?** Measured Ø22.03mm: 22.035mm **(d) Explain why it is necessary to pre-drill a hole on Ø22.03 ± 0.01mm bore hole. Name another approach that could be used to machine the bore hole.** Endmills do not come with center cutting, so to avoid center cutting, first call to pre-drill hole is made. A Helical ramping could be used instead to machine the bore hole as well. 4. **Ø22.03 ± 0.01mm bore hole has been machined in 1st setup. Explain why we should not leave it to the 2nd setup and machine it from the opposite side as shown in figure below instead.**  X, Y, Z datum cannot be achieved and thus cannot achieve the required return to its true position. This is to ensure assembly can be done properly. ### CNC Milling Lab Practical Session 5 (Group) **Class:** DME/FT/24/27 **Group:** 2 **Date:** 5 Feb 2025 | Name | Adm. No. | |---|---| | Ahilan | 23/6875 | | Joei | 2317 128 | | Merlin | 2316961 | | Snigdha | 2316990 | 1. **(a) In 2nd setup machining, explain how the G55 Y-Coord Work Offset is determined.** The jaw is set on the fixed jaw of the vice. **(b) The bracket is secured on the vise with a V-shaped moving jaw. Evaluate the alternative method of holding the Bracket directly on the standard vise as shown in figure below. (state the advantages and limitations)** **Advantage:** Don't need to machine v-shape moving jaw. **Disadvantage:** There is hangover, which causes vibrations which will cause a rough surface finish. 2. **Give a sketch of the existing setup on the machine for the 2nd side. Indicate the datum face that you used to establish the Work Offset G55 for Z direction.**  3. **The figure below shows the setup for the 3rd side machining. The 3D Taster is contacted the screw tip (stopper) that fixed on the vice. It is to establish the X axis Work Offset G56. You are to note down the following:**  - (a) Machine position when it touch the stopper: -469.1453 - (b) Work Origin X-axis after setting up: -428.1453 - (c) Explain why the difference of (b) - (a) above is always 41mm: The bar stopper and the machine position when it touches the stopper creates a fitting datum. The work origin x-axis after setting up will decrease by 41.0mm as the position xaw always be in always be in the middle... 8 + 81/2 = 41.0mm 4. **For 3rd setup, the counterbore Ø20 x 2 is done with Ø16 HSS endmill using pocketing operation. However, Ø20 endmill could also be used to produce it with a simple drilling cycle. Explain why such a practice is not recommended here.**  Since, the Ø20 End mill has a corner, the corner cannot be cut. Therefore, it will leave the piece with unnecessary extra material. Sizing down to Ø16 HSS will ensure that there is no extra material left near the drill hole. It is better to have flat counterbore.