What is injection moulding?

Injection moulding is an established process for manufacturing plastic and rubber parts. The raw material is plasticised and injected under pressure into a mould, where it is cured or hardened. vulcanised.

 

Sequence of the injection moulding process for rubber

  1. Feeding the raw material: Raw material is fed in as granulate (e.g. TPE), strand material (usually for Rubbers) or liquid (e.g. LSR)
  2. Plasticising: The raw material is plasticised and homogenised in the plasticising unit, usually equipped with a screw, by means of temperature and shear stress. With Rubber or LSR only little or no temperature is applied to prevent premature vulcanisation.
  3. Closing the mould and injection: The plasticised material is injected into the closed mould under high pressure and injected into the mould via the channel system. Cavities managed
  4. Press on and VulcanisingDepending on the material and the desired degree of cross-linking, the material is heated to 120-220°C, held for a defined time and vulcanised. The pressure is maintained in order to
  5. to prevent shrinkage and air pockets.
  6. Opening, demoulding and post-processing: The component is removed from the mould and generally post-processed, e.g. Deburred or coated

 

Advantages:

  • Short Cycle times through automated cycle sequences and parallel pre-plasticising
  • Efficient operation thanks to a high degree of automation
  • Very good dimensional accuracy and reproducibility, even with complex components
  • Very little material loss, especially when using a cold runner system

 

Disadvantages:

  • Processable material variety more limited than with compression moulding
  • Comparatively high tool costs
  • Difficult handling of inserts

 

Processed materials:

  • Thermoplastic elastomers (TPEs): Plastics that are flexible and elastic at room temperature, but can be deformed like thermoplastics when heated
  • Rubbers incl. solid silicone rubber: Particularly suitable are EPDM, NBR, SBR, VMQ, CR or FKM. Less suitable, however, are NR, BR, HNBR, IR or IIR
  • Liquid silicone (LSR): Liquid raw material that no longer needs to be plasticised, but is merely homogenised before injection

 

Typical applications:

  • Injection moulding is a standard process in rubber production. It is the right strategic choice especially for
  • large series in which short Cycle times and high efficiency are important
  • particularly high demands on dimensional accuracy and reproducibility
  • Materials used in the Moulding presses are not (economically) processable, such as TPE or LSR