weird extruder problem,help

[rcvinyl]

Hi Trolls!
Recently, our extruder has a very strange problem.
When it extrudes PVC, it will produce a pungent sour smell.
our tempature setting is 135
The extruded pvc cake has very rough edges and is very soft, as if there is a lot of air in it. Has anyone encountered this problem? Could it be the problem of the extruder screw?

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Many Thanks
Roger

[martinstamper]

The sour smell you mentioned is Chlorine gas. Not very good for you. The texture, softness and smell all mean that the PVC is burning. Perhaps your thermometer is broken? I would suggest getting a meat thermometer that you can stick in the middle of the puck. They're always handy to have around the plant anyway.

[Aussie0zborn]

You have burned the vinyl. Is this new or 100% recycled? Follow Martin’s advice above. The extruded vinyl should be shiny and you should be able to leave a fingerprint on it.

[rcvinyl]

Martin and Aussie0zborn,thanks for your help!
my pvc is new.
we lower the temperature to 125(both heating unit)，the smell is gone and it looks much shiny and smooth now。
we extruded all the black compound out and put some new clear compound in it,
it seems we have a new problem, the cake have some mark, like watermark on the surface, and cake's up side and down side looks slightly different, I guess this is not good?

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[rcvinyl]

it seems thing getting worse... we lower the temperature to 115 and 95 the cake surface still have burn mark

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[Aussie0zborn]

Is that clear vinyl compound?

[rcvinyl]

Is that clear vinyl compound?

yes it is

[Aussie0zborn]

The burned black viinyl compound is stuck to the inside of the barrel and on the screw of the extruder and some of it is coming out. You will see it better with white vinyl. These burned pieces will give you noisy records.

The vinyl cake should ideally be about 10 degrees C lower than the mould temperature but this depends on the particular compound as some have a different melting point.

The supplier of the vinyl compound should be able to give you a “temperature profile” for their particular compound. Where you might have an extruder with three heat zones, the profile will tell you the recommended temperature for each zone.

The “watermarks” you mentioned earlier are normal.