Roller - Die // Deformation issue

[Skirmish]

Hi, we are having issues with our new roller-die machinery. It is a cold feed extruder with a two rolled calender. Like this image: (with a chiller, and a wind up system)

It uses contoured rolls (shells) to produce contoured innerliners:

We are having problems with the "trapezoid form" shaped on the cilinder, mainly because produced innerliners minor and major bases, are much smaller than we predicted (months ago, we could achieve those dimensions, but nowadays... something changed). The weird thing is that product's trapezoid height is ok, the problem is only on the bases width. Process parameters were not changed in this lapse.

So... It can be something related to compound swelling, head preassures,Rolls profile or maybe speed factors?... we are really lost. And the machine was really expensive. Really.

If you can give us some light We'll thank you forever, seriously.

Please ask me if you need more information.

 

[ornerynorsk]

"something changed" . . . . "months ago, we could achieve those dimensions"

Do you have adequate process and material records from when things were OK so that a meaningful comparison can be made? I have no experience in calendaring or sheet extrusion, but troubleshooting principles are similar across many methods of manufacture. Speed, temperature, formulation, etc, etc.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Skirmish]

Hi, thanks for answering.

Process parameters are the same, the only thing that changed slightly was the compound.

 

[Compositepro]

If the height is correct but the width is wrong then you are not feeding the correct amount of material into the rollers.

 

[Skirmish]

Compositepro, Hi.

Total width is ok (of the complete profile), the problem is only on the bases of the smaller trapezoid. Feed is ok, I mean flow is abundant.

Can be it an improper swelling? But its weird because height is ok.

 

[JDLSHF]

Hi there.

Well, my contribution is the following: it seems, if i'm correct in what i read, that you already have the answser. If you are having problems with the calendered material's geometry, but in width, would mean you are not having enough swelling. The calendered does not control your geometry in full. You system probably is ajusted to get those measures and geometry for a certain swell and calender role distance. If one of those fails, you will not get that result.

The second part of the answer that you already have, that might strongly be responsible for the swelling effect, is the compound (that is if the service conditions are the same as you say they are).
Those slight changes, sometimes, can mean big problems. A slight change in viscosity, for example, might be the difference between injection or not a compound. And it's only slightly.

Make sure that those service parameters haven't changed (sometimes we take it for granted) and what as been done to the compound. You control your geometry and measures indirectly, bare that in mind. And flow being abundant, will not necessary mean that the swell is enough for you to have your result.