effect on part quality when using recycle material
effect on part quality when using recycle material
(OP)
Hi there, can anyone tell me what would be the possible effect on plastic parts when they are run with 50% mixture of regrind/shredded material.
Any common defects that can be linked to this?
Thanks a lot.
Any common defects that can be linked to this?
Thanks a lot.
Best regards,
ct





RE: effect on part quality when using recycle material
RE: effect on part quality when using recycle material
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: effect on part quality when using recycle material
Best regards,
ct
RE: effect on part quality when using recycle material
Frank M.
Tradewind Resources
http://www.tr-usa.com
RE: effect on part quality when using recycle material
Do you really want to know what is causing your problem or are you looking for someone to agree with the opinion you have already formed?
Give us details like polymer type, filler and reinforcements if used, colour, a quick description of the part, including size, section thickness, gate position and gate size.
Also an indication of moulding conditions would help, as would some indication of the machine age, control system, condition and size.
Where, when and how you measure the part would also help as some materials shrink and or expand for a considerable time after moulding
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: effect on part quality when using recycle material
The readings obtained are 35 and 34.8
Wall thickness is 1.5mm
Best regards,
ct
RE: effect on part quality when using recycle material
Now we are talking.
Unfilled ABS is normally a very dimensionally stable material and fairly forgiving of most things that vary shrinkage.
My thoughts are it could be any one of the following
1) There was a change to the colour formulation
2) There was a change in the base resin (different supplier or change in spec from the same supplier).
3) The ring check valve on the machine was worn and not holding pack.
4) Dare I say it, regrind material might be used and is not consistently charging the barrel of the moulding machine.
5) The melt viscosity of the material is varying due to use of regrind or due to suppliers variation and this is affecting the pack of the moulding.
6) The gate might be to small, giving less than optimum pack.
My main suspicion is that the mould is not fully packed, as other variables such as degree of crystallisation do not have much effect on ABS, and there are no fillers to complicate the situation.
If you are normally getting optimum pack plus a safety margin, you have a repeatable process, but if you are getting less than optimum, normal variations within the process can have a large effect.
Try weighing the parts to see if the smaller parts are also lighter. Make sure you always weigh parts from the same cavity if the mould is multi cavity.
If it is multi cavity, are all cavities the same, or does one cavity vary more than another?
You say the parameters are no change. While the parameters might be set the same, this can only be done within the accuracy of the controls of the parameters, and some parameters are often not controlled, like cooling water flow and temperature, or electrical supply voltage variations etc etc.
It is not that uncommon for two different die setters to get a different result with the same mould in the same machine with the same set up sheet, as they might set things differently when those things are not specified in the set up sheet.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: effect on part quality when using recycle material
The job was pulled, and it was no surprise.