Posts: 5
From:Sydney , NSW , Australia
Registered: Apr 2003

posted April 14, 2003 05:49 PM               

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Hi ALL,
I will appreciate if I can get an answer for the following:

I understand the main difference for the selection of twin screw extruders is the extrusion production output rate.Say, if one is trying to produce rigid-pvc profile extrusion(190mm,160mm rectangular box with a middle divider wall at 190mm dimension,all wall thicknesses are 1.5mm)at the rate of 400 to 450 kg/h(3 to 3.5 meters/minute speed), would obvious answer be parallel twin screw?
Also I am led to believe that conical twin screw extruders would be more suitable for variable rates between 125 to 350 kg/h,however; the parallel twin extruder is more suitable constant and rather higher(in excess of 350 kg/h) profile extrusion rates.
The other issue for preferences could be practicality and replacement cost of screws.
Can anyone answer to these questions without being bias? I am confused ,I am getting different answers.HELP please.
many thanks - Burak

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Posts: 41
From:Silver City, NM, USA
Registered: Jun 2001

posted April 15, 2003 01:08 AM               

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Burak,
Both parallel and conical twin screw extruders will deliver good quality profiles
at the required out put rates you want. I happen to feel that conicals are a little more "forgiving" in terms of minor formulation errors--i.e. lubricant or other additive mistakes. Both types work well with rigid PVC powder blends, assuming full screws
and a temp. profile to allow maximum RPMS for
maximum output rates!!

Skip

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Posts: 5
From:Sydney , NSW , Australia
Registered: Apr 2003

posted April 15, 2003 06:48 AM               

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Skip
thank you for your comment.I understand that your comment is for rigid pvc dry blend(ie,powder).What about pelletised compound ,would your comment be the same?
Regards -Burak

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Posts: 41
From:Silver City, NM, USA
Registered: Jun 2001

posted April 15, 2003 10:44 AM               

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Burak,
Yes, both types of twins can run pellets (they run 100% regrind), provided the starve
feeder monitors the amount of material entering the feed zone, to control amps and torque. 1/3 to 1/2 filled screws, at a higher RPM should give your desired output rates.

Skip

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