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22nd November 2014, 12:00 PM
#1
material for no sink mark product
Hi There,
I am a design engineer and I have just started to design the plastic parts but before starting it, I have seen some earlier designs and parts with wall thickness 2-3 mm and with a provision of bosses to accomodate the inserts for attaching it to other parts.
But due to design requirements the earlier designs had boss root thickness>1.25 thickness of the material and resulting in sink marks. When I have asked to reduce the boss thickness as this is one of the reasons for the sink mark, they informed me that we cannot reduce the thickness as it is the design requirement.
So, Now I am in search of materials which do not produce any sink mark if the boss thickness>1.25 thickness of material.
It would be great if you can share any.
Thanks,
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22nd November 2014, 02:19 PM
#2
Re: material for no sink mark product
The plastic design rules of thumb are for all thermoplastics with there being slight adjustments for semi-crystalline or amorphous. At 1.25% of the nominal wall thickness, you are going to have sinks!! Did they ever answer you as to why they want that much material there?
Depending on the resin and end use requirements you MIGHT be able to use a chemical foaming agent (CFA) to foam the thicker areas and remove or at least reduce the amount of sink. A blowing agent works similarly BUT the cells are not smaller or more consistent in shape not to mention the part cosmetics suffer with streaks and blooming on the surface.
Rick.
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25th November 2014, 06:06 PM
#3
Re: material for no sink mark product
Dear Sir,
Thank you very much for the reply.
The 1.25 thickness is required to put the inserts as this part will be mating other parts. Therefore we have go> 1.25 thickness.
Also, As you mention about the foam, I think I need to study about it to understand what exactly you mean. (Any reference link would be highly appreciated).
Will get back to you soon!!
Thank you very much.
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25th November 2014, 10:43 PM
#4
Re: material for no sink mark product
Just search for chemical foaming agents and you will find what you need. Clariant is one supplier. They have info on their website.
Rick.
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20th December 2014, 01:38 PM
#5
Re: material for no sink mark product
Hello,
The material included glass fiber will be met your requests, such as PC/ABS+GF, PA66+GF...too many
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