31.[Medical Mould] What are the key points to note in the insert injection process?

Insert injection process technology is widely used. I hope this article can give some inspiration to friends who want to understand this knowledge.——-Vito.

[Medical Mould] What are the key points to note in the insert injection process?

Medical Mould

Insert Molding is a process in which the insert is prefixed in a suitable position in the mould and then injected into the thermoplastic or thermosetting material to form the insert, which is then wrapped tightly by the cured material to obtain a product with the insert. Widely used in automotive, medical, electronic, etc., common inserts are metal and plastic.

1. What are the key points to note in the insert injection process?
1. whether the performance of the insert itself can be suitable for the second package (e.g. the insert is not temperature resistant, etc.)
Solution direction.
(1) In the early stages of the project to assess the material properties of the insert and plastic parts, the structure, whether it is suitable for insert injection, full research on the demand, combined with the process material experience to fully assess.
(2) Where primers are involved, attention should be paid to analysing the bonding effect of the primer on the two materials.

2. The insert is easily affected by the second injection glue after injection to produce shrinkage and deformation.
Solution direction.
(1) The shrinkage rate and thermal expansion coefficient of the insert and the plastic part are not consistent after moulding and are prone to deformation. The structure of the insert and the plastic part needs to be evaluated at the DFM stage, especially whether the meat thickness is reasonable.
(2) Stress deformation caused by poor demoulding, which can be solved by increasing the number of pushers, setting the demoulding slope and other methods.
(3) Deformation due to residual stress caused by moulding conditions, to be noted.
(4) Deformation caused by uneven cooling or insufficient time during injection moulding.

3. The amount of pre-pressure on the surface of the insert and the selection of the pre-pressure method are difficult, reflected in the indentation and injection sealing glue to produce a burr.
Direction of solution.
(1) The DFM stage needs to assess whether the structure at the sealing glue is conducive to the sealing of plastic parts.
(2) The mould design needs to design a reasonable pre-pressure value at the sealing place according to the insert material and the plastic material, too large insert is easy to crush, too small is easy to produce burrs. According to the material of the insert, the amount of pre-pressure can be appropriately left and gradually adjusted and optimised in the process of test mould verification.
(3) Reasonable precision should be ensured at the sealer during mould processing. Avoid uneven pre-pressure leading to local bruising and burrs.


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