we have cought in very critical condition .We have manufactured tool for PA66 (Unfilled) long part . Approx size of part is 500 X 60 mm .
The material is having different shrinkage factor in Parrallel & perpandicular direction ( 1.5 & 0.5% resp). While building mold part got scaled in 0.5 % in parallel & 1.5% in parpandicular direction. After trial we come to know the actual condition . The actual part size coming is bigger than required.
The part is feed with single cashew gate. First we are trying not to change tooling of core & cavity.
Kindly give your opinion about how can I help it out by doing analysis in moldflow.
Currently I am doing below iterations for improvement
1.Adding one more gate ,also looking for different type of gate system.
2.Cooling time is reduction .
3.Material change from unfilled to glass filled materail thus can think of reduction in size.
Unfortunately, there's probably not too much you can do to fix the problem. To make a part smaller, you can underpack the part, but that will probably not give you enough of an improvement on a part that size.
Adding a gate will probably only help pack the part better, which can result in a larger part.
Cooling time should be set by when the material is able to be removed from the tool. Altering that has little effect on size. Actually making the tool hotter, with a longer cooling time can help the material to create more crystal structures, which will help to shrink your part more.
Switching to a glass filled material will reduce the amount of shrinkage, which means your part will come out longer. You could look for a material that has higher shirnk rates. But I'm guessing that most materials within the current product range will have similar shrink.
Finally, without actually fixing the problem (recutting steel), all other changes will reduce your processing window making it hard to get good parts and increasing scrap. If possible it's best to change the steel. But there is seldom time or money for doing that.
Best of Luck,
Thanks for sharing your opinion.
We are doing same (Cutting steel once again).
In further to this can you please share your opinion for below doubt
Actually if you see problem arise due to wrong consideration of shrinkage factor by mold designer .
Mold designer gave shrinkage differently in parallel & perpandicular direction .
My doubt is .......... for longer part whether shrinkage should be added differently for parallel & perpandicular directions ?
or mean (Uniform ) shrinkage should be assigned in mold design ?
Please share your valuable opinion .
Also Requesting all viewers kindly share their experience whether in mold design Shrinkage can be assigned to mold in parallel & perpandicular direction or it should be assigned uniformly?
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