posted September 14, 2006 08:36 AM               

This is a very simple question with a very complex answer, which is "it depends".

Mostly the temperature setting will depend on the viscosity of the material you are using. Typically sheet will use a high viscosity resin. Higher viscosity resins will typically use higher temperatures than lower viscosity resins becuae low temperatures require too much motor power. Low temperatures would be nice because they increase melting, improve pumping and lower the melt temperature.

One reference suggests 375-400F for 0.6MI

SPR Extrud Simulation program suggests 260F as optimum for melting at 0.6MI, but that would require a 1000HP motor be installed at 100RPM maximum gearing.

Other issues that may affect temperature selection are the screw type, heater/cooler type, RPMs, vent ports, die restriction and more.

As a practical approach some suggest starting with a stable extrusion process and make a 30-50F change in a single zone. Start with the rear zones and work forward. I would wait 3-4 hours on a 6" machine for the temperature change to stabilize. Check the before and after condition of the process and decide if you went in the right or wrong direction or neutral. Make your next move based on the result.

I have many tools available to help speed up this process and offer them on a professional basis. Please send an email if you are interested in more information.

Good luck.

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Best Regards,

Tom Cunningham

posted September 19, 2006 04:56 PM               

Once you get the solids conveying temperature so the flow is stable, you will not want to meddle with that. The temperature in the melting section must be enough to get the material melted, then left alone. The metering temperature will be set by what you want for a product temperature.

My advice is that once you find a stable temperature profile, you will not want to change it to try to increase rate.

If you want to get an indication of the product temperature you can expect, try the spread sheet for the metering section at http://www.extrudertech.com/METERINGTEMP.XLS
You will need to assume that the polymer enters the metering at the melt temperature. Then you can get an idea of how to set the barrel zone. The flow in spread sheet is not affected by the temperature, but is set constant rate/rev.