PVC Issue
PVC Issue
(OP)
We have been manufacturing a sample block housing that is machined from PVC for many years (volume = 10K).
All of the sudden we recently have been getting cracks in the PVC when the housing is placed under internal hydrostatic pressure. The pressure is pretty nominal and the walls are plenty thick. We have been doing this test (100%) since the product was introduced.
Our machine shop says that they have not changed their process at all (the part is machined on a CNC). Could the wrong cutting fluids cause this? The cracks are not jagged and are perfectly straight along the part.
Are there certain types of PVC that are more brittle?
All of the sudden we recently have been getting cracks in the PVC when the housing is placed under internal hydrostatic pressure. The pressure is pretty nominal and the walls are plenty thick. We have been doing this test (100%) since the product was introduced.
Our machine shop says that they have not changed their process at all (the part is machined on a CNC). Could the wrong cutting fluids cause this? The cracks are not jagged and are perfectly straight along the part.
Are there certain types of PVC that are more brittle?





RE: PVC Issue
Solvents in cutting oil can cause stress cracks in PVC.
There are many grades of PVC and several aspects of the polymer formulation will effect the performance re stress crack. The most likely cause is the "K" factor of the polymer, but it can also be effected by additive packages.
The processing conditions when manufacturing the block can also have an effect.
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RE: PVC Issue
RE: PVC Issue
What cutting fluids should I advise our machine shop to avoid?
Also does anyone have a link that describes the different types of PVC?
We have not seen this problem on the first 10K of the products we assembled and tested so I am comforatable with the material choice.
RE: PVC Issue
RE: PVC Issue
Many people machine parts from PVC. I don't know that you need to do all the testing of different cutting oils. I would ask your material supplier. They may have some ideas for you.
Also, make sure somebody hasn't tried to speed up the machining time. I've seen some problems with cutting too fast.
RE: PVC Issue