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How do I narrow down specific values when selecting a plastic for injection moulding?

My part is uniform in wall thickness and thins out where a hinge a present.

Properties:

  • Will not go under many cycles in its lifetime, however, needs to be rated for thousands of cycles
  • The entire part is about as long as a finger and the hinge will displace minor distances (2-3 mm)
  • Will have to operate in temperatures from -20 to 60 Celsius
  • Applied forces are minor and not sudden

I have designed the hinge as follows:

Right Angle Hinge

I have the model in CAD and have run FEA to figure out stresses (ie. Von Mises). I have also 3D printed it in ABS, and it has passed vibration testing and performs as designed.

The criteria I have narrowed down based on matweb is:

  1. I need the hinge to bend easily, so it does not affect the entire product- a low flexural modulus
  2. As the plastic part is supported in one area, I need it to be able to withstand vibration testing. Therefore, sorting by the lowest density so that it does not collapse underneath its own weight
  3. Shore Hardness D of around 60 to 80, as I need the part to not be flimsy yet not too rigid
  4. Despite the hinge being able to bent easily, I need it to also return to its original form when it is not stressed- a high resilience

How do I go about determining specific values for the criteria? Are there other mechanical values I am neglecting?

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  • $\begingroup$ One approach would be to look at what materials are available from your vendor and work backwards from there. Also, point 4 I think you could interchange resilience with yield stress. $\endgroup$ – jko May 4 at 12:00

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