12 Injection Molding

Injection Molding

MFG 355

15 Ton Injection Molding Machine

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77 Ton Injection Molding Machine

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150 Ton Injection Molding Machine

Equipment

• Injection Unit

Screw drive arrangement

Feed hopper

Barrel heaters Nozzle

Tool

Screw Check valve Screw tip

Equipment

• Injection Unit

Injection

• Parts of the injection screw– Screw– Head and check ring

Equipment

• Molds

Molds

Mold Materials

• Aluminum filled epoxy

• Aluminum

• Tool steel

• Stainless steel

• Hotwork die steel

• Beryllium-copper

Mold Materials

• Choice based on critical properties– Machinability– Coefficient of thermal expansion– Specific heat capacity– Thermal conductivity– Density– Hardness (abrasion resistance)– Yield strength– Weldability

Mold Parts

• Bases– Standard sizes– Hold mold inserts– Can decrease overall mold costs

Mold Parts

• Guide pins– Align mold cavities

Guide pins

Mold Parts

• Sprue Bushing– Hot sprue– Cold sprue

Mold Parts

• Sprue Bushing– Hot sprue

Mold Parts

• Sprue Bushing– Cold sprue– Sprue puller

Mold Parts

• Sprue Bushing– Cold sprue– Sprue puller

Mold Parts

• Runner

Mold Parts

• Runner– Layout

Conventional Improved Balanced “H” Circular

Mold Parts

• Runner– Layout

Conventional Improved Balanced “H” Circular

Mold Parts

• Runner– Cold well

Mold Parts

• Runner

Mold Parts

• Gates

Submarine Gate

Pinpoint Gate

Fan or Edge Gate

Mold Parts

• Gates

Sprue Gate

Tab Gate

Flash Gate

Mold Parts

• Gates

Internal Ring GateExternal Ring Gate

Mold Parts

• Gate

Mold Parts

• Gate

Mold Parts

• Gate

Mold Parts

• Cavity– Where the part is made– Layout is critical to material flow

Mold Parts

• Cavity– Knit/weld lines

This shows where the weld lines (shown in red) will most likely occur withthe part gated in the center (yellow cone).

Mold Parts

• Cooling– Reduce cycle time– Control formation of crystalline areas – Freeze part

Mold cavity

Cooling lines

Mold Parts

• Ejector system

Ejector Plate

Ejector pins

Return Springs

Equipment

• Clamping Unit

Equipment

• Clamping Unit– Toggle clamping– Hydraulic clamping– Hybrid hydraulic-toggle clamping

Equipment

• Clamping Unit

Equipment

• Clamping Unit– Toggle system

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Plant Concepts

Safety

• High clamping forces

• High pressure lines

• High voltage

• High temperatures

Safety

• Position switches– Mechanical, hydraulic and electrical

• Shields

• Lock out/tag out

Material and Product Considerations

• Shapes– Possible to do very complex shapes

• Structural features– Pins, ribs, bosses, threads, holes

– Deep parts are possible– Internal or external threads– Undercuts require sliding mold sections

Sliding Mechanism

Material and Product Considerations

• Part design– Uniform wall thickness

• Helps reduce dimples, shrink marks and distortion

– Ribs• Save weight at given strength

– No sharp bends• Helps to fill the mold cavity easier

– Oversize the mold• Shrinkage amount is dependant on material and

additives/fillers

Operations and Control

• Temperature of melt

• Temperature of mold

• Pressure of injection and hold

• Injection or fill rate and time

• Dwell time

• Freeze time

• Ejection (dead time)

Special Injection Molding Processes

• Coinjection molding– Two separate screws– Two different material selections

• Color, strength, flexibility

Special Injection Molding Processes

• Coinjection molding

1 2 3

Special Injection Molding Processes

• Coinjection molding

Part 1

Part 2

Special Injection Molding Processes

• Flow-controlled injection processes– Sometimes called Scorim

Special Injection Molding Processes

• Flow-controlled injection processes– Sometimes called Scorim

Special Injection Molding Processes

• Gas injection molding– Employs gas to create hollow parts

Special Injection Molding Processes

• Injection-compression molding

Injection-CompressionMolding

Injection Molding

Parts were made with the same mold. The only difference between the two parts is the use of the compression cycle

Modeling and Computer-Aided Mold-Flow Analysis

• Used to help identify potential problems with the mold/part design

• Models based on the CAD part

• Adjusted by resin

Thank You