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What is happening to my HDPE?

This topic contains 4 replies, has 2 voices, and was last updated by  Anonymous 4 weeks ago.

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Phil S. wildplastic

What is happening to my HDPE?

16/11/2019 at 03:48

Hi guys, can anyone tell me what is happening to my HDPE upon extruding? It looks chafed or scaly? Sometimes It only happens in the beginning of extruding, then it goes away, then comes back, very inconsistent.

I have 160º on nozzle and 170º on barrel.

My first guess is that it is getting burned but I have experimented by lowering the temperature with no change.

It appears to happen more when color is being changed and mixed or if it is left in the barrel too long. On certain colors there is no issue but with sometimes with certain colors it happens.

Has anyone experienced this before?

Thanks!

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starter
16/11/2019 at 03:50
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Pic:

new
16/11/2019 at 12:42
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hi,
normally this can be solved by lowering the motor speed. If you’re are already at the lowest speed – you can tweak the VFD to allow lower or higher speeds speeds (max. +/- 50%). That are standard settings on most VFDs – called ‘Minimum Frequency’. Or post the model/brand of the VFD & motor – possible somebody can figure this out here 🙂

Other than that, assume that the measured temperature is about 15% off the real one in the barrel – depends on your setup (picture ?).

starter
16/11/2019 at 23:40
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Thanks for the reply

I’ll try lowering it on my VFD. Right now it’s running on average 35hz, but will test at 20hz and see if that solves it.

How’s my temp? Should I increase to 180°?

Im running a 3HP SEW with reducer and VFD. It powers my shredder and extruder simultaneously.

Thanks again!

new
17/11/2019 at 11:51
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Hi,
going too low may harm the motor – as thumb rule – I wouldn’t go more than 50% below of the designed operating frequency – it can get really hot there.

And yup, increase temperature just 🙂 I would also check that the heatbands are actually well distributed over the barrel. Insulation makes also it’s magic 🙂

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