Extruded PVC material issues....

[PlantationPete]

A supplier is sending PVC extrusions with a wide range of wall thickness variations, up to 0.030" in extreme cases but more so around 0.020". These variations occur in a single 12' length along with wavy and distorted sections along the length. Another supplier is golden, no appreciable variation. They aren't giving us any info to go on but the punch we use on this part won't fit the varying thicknesses and our good supplier cant provide enough of what we need. Is this a common issue or can anyone offer any insight on why this is occurring? I'm thinking uneven heating of the material being extruded or perhaps uneven cooling post extrusion. This is not my area so I'm hoping someone can shed some light on this. Thanks in advance and have a great day.

 

[boslab]

I can comment on Ali extrusion, the water bath being excessive or inadequate, speed changes, end defect, stop marks, excessive straightening ( stretching) inadequate straightening , puller not set properly ( usually a roller set up on plastics I read)
All this boils down to variable production. Without being there hard to quantify, but it would seem your dodgy stuff needs 100% goods inward inspection for that supplier, I suppose that’s going to be visual in the first instance as if wall thickness is variable doing metrology
Might be difficult.
I’ve only seen one CMM with a 5m long travel, I bet that cost but it was for aircraft bits so cost no object.
If it’s your custom die then it can be retrieved and sent to another extruder I suppose.
Mark

 

[technocrat]

What does the supplier say?

 

[PlantationPete]

What does the supplier say?

They say there's nothing wrong and won't give out their spec range on the material.