Injection Moulding PDF

INJECTION MOULDING CORPORATE TRAINING AND PLANNING CORPORATE TRAINING AND PLANNING  Type of Injection Moulding Machine Hand Injection Moulding M/C Plunger type Injection Moulding M/C Reciprocating Screw Type Injection Moulding M/C  Hand Injection Moulding Ma...

INJECTION MOULDING CORPORATE TRAINING AND PLANNING CORPORATE TRAINING AND PLANNING  Type of Injection Moulding Machine Hand Injection Moulding M/C Plunger type Injection Moulding M/C Reciprocating Screw Type Injection Moulding M/C  Hand Injection Moulding Machine vertical machine consists of Barrel, Plunger, Band Heaters along with energy regulator, Rack & Pinion system for Injecting the material by the plunger, a torpedo and nozzle.  Plunger Type Injection Moulding Machine Vertical & Horizontal Plunger Type Injection Moulding Machine The Reciprocating Screw Type Machine components  The Injection Process Plasticises the material by reciprocating Screw. Injects the molten material to a closed mould – via a channel system of gates and runners. Cools the Mould. Refills the material for the next shot. Ejects the Product. Closes the Mould for further cycle. Injection Moulded Items Injection Moulded Items Injection Moulded Items  Advantages of Injection Moulding Process Parts can be produced at high production rates. Large volume production is possible. Relatively low labour cost per unit is obtainable. Process is highly susceptible to automation. Parts require little or no finishing. Many different surfaces, colours, and finishes are available. Good decoration is possible. For many shapes this process is the most economical way to fabricate. Process permits the manufacture of very small parts which are almost impossible to fabricate in quantities by other methods.  Advantages of Injection Moulding Process Minimal scrap loss result as runners, gates, and rejects can be reground and reused. Same items can be moulded in different materials, without changing the machine or mould in some cases. Close dimensional tolerances can be maintained. Parts can be moulded with metallic and non-metallic inserts. Parts can be moulded in a combination of plastic and such fillers as glass, asbestos, talc and carbon. The inherent properties of the material give many advantages such as high strength-weight rates, corrosion resistance, strength and clarity. Limitations of Injection Moulding Intense industry competition often results in low profit margins. Mould costs are high. Moulding machinery and auxiliary equipment costs are high. Lack of knowledge about the fundamentals of the process causes problems. Lack of knowledge about the long term properties of the materials may result in long-term failures.  Machine operation sequence The mould closes and the screw begins moving forward for injection. The cavity fills as the reciprocating screw moves forward, as a plunger.  Machine operation sequence The cavity is packed as the screw continuously moves forward. The cavity cools as the gate freezes off and the screw begins to retract to plasticize material for the next shot.  Machine operation sequence The mould opens for part ejection The mould closes and the next cycle begins Injection Mould  A two-plate mould. A three-plate mould. The moulded system includes a delivery system and moulded parts.  Machine operation sequence/Processing Step 1.Mould close 2.Tonnage build up/Locking 3.Injection 4.Holding(Packing) 5.Refilling(Dosing/Charging) / Cooling 6.Suck back 7.Mould open 8.Ejection CORPORATE TRAINING AND PLANNING Cycle time in injection moulding  Process Controls Injection Moulding cycle can be broken down into four phases: Fill, Pack, Hold, and Cooling/plastication These phases can be controlled by following variables: Injection Speed, Plastic Temperature, Plastic Pressure, Cooling Time and Temperature.  Back Pressure (Kg/Cm2 or bar) Back pressure is the amount of pressure exerted by the material ahead of the screw, as the screw is pushed back in preparation for the next shot. Effect of Back Pressure More Homogeneous Mix Proper Melting More compact Sometime leads degradation  Injection Speed (cm/Sec) The injection speed is the forward speed of the screw during its injection operation per unit time. Effect of Injection Speed Easy Injection of Material Avoid Short-Shot Some times leads more orientation & burn marks  Screw Rotation Speed The screw rotation speed (RPM) is the rate at which the plasticizing screw rotates. The faster the screw rotation result the following.. Faster the material is compressed by the screw flights Increasing the amount of shear heating Low residence time, some less melting CLAMPING SYSTEM CORPORATE TRAINING AND PLANNING  TOGGLE TYPE CLAMPING A toggle is mechanically device to amplify force. In a moulding machine, which consists of two bars joined, together end to end with a pivot. The end of one bar is attached to a stationary platen, and the other end of a second bar is attached to the movable platen. When the mould is open, the toggle is in the shape of a V. When pressure is applied to the pivot, the two bars form a straight line. TOGGLE TYPE CLAMPING  TOGGLE TYPE CLAMPING ADVANTAGE Low cost and lower horsepower needed to run. Positive clamp of the mould DISADVANTAGE Do not read the clamp force. Clamping is more difficult. Higher maintenance as lubricant is provided.  HYDRAULIC CLAMPING A clamping unit actuated by hydraulic cylinder, which is directly connected to the moving, closed the mould. In this case ram of hydraulic system is attached to moving platen. There are two halves in hydraulic cylinder, which is actually inlet and outlet of oil. When oil goes to the cylinder with pressure oil pushes the ram to forward direction by which moving platen moves and mould closed and when oil comes from the cylinder the ram come back and mould is open. HYDRAULIC CLAMPING  HYDRAULIC CLAMPING ADVANTAGE Clamp speed easily controlled and stopped at any point. Direct a read out of clamp force. Easy adjustment of clamped force and easy mould set up. Low maintenance as part is self lubricated. DISADVANTAGE It is higher cost and more expensive than toggle system. None positive clamp.  TIE-BAR LESS CLAMPING Tie-Bar less clamping system is basically Hydraulic clamping system without any tie bar. The platen is moved on a rail system. The main advantage of this system there is no limitation of mould platen size. As there is no tie bar so the mould dimension is not so important. Also mounting of the mould is easy and it is very useful when products eject from the mould is manual. TIE-BAR LESS CLAMPING  TIE-BAR LESS CLAMPING Much larger mould mounting area. Larger stroke compared to the toggle type machines. Full machine capacity can be utilised. Smaller machines can mould larger components. Saves floor space. Saves electrical energy because of reduction in the size of machine. Has the capacity to reduce weight of the moulded component because tie- bar stretching is not there. Machine becomes very flexible for future modification. Easy access to mould cavity's because of the absence of the tie bars. Robotic arm movement becomes easy. Fewer moving parts so lesser wear and tear so longer life for machines. Lower lubrication required. Removal of mould plates much simple. Greater stability. THANK YOU