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dynisco controller/pid settings

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Author	Topic: dynisco controller/pid settings
paddy66 Member Posts: 4 From:ireland Registered: Feb 2007	posted December 02, 2007 08:10 PM hi guys, we use closed loop melt pressure control on two extrusion lines and find sometimes that tinkering with pid settings on these can improve process stability, but at the minute it is only a shot in the dark and not very scientific. I was wondering if any of you guys have experience of this and know what settings work best with diferent materials e.g nylon 11,12, pebax etc or is it all just trial and error. Your thoughts would be appreciated. IP: Logged
Tom C Moderator Posts: 904 From:Brodheadsville, PA USA Registered: Jun 2001	posted December 02, 2007 09:50 PM You might first look at the type of control action you are getting. Are the extruder RPMs cycling, or is there a long term drift, or is it random? Ideally the extruder should deliver constant pressure. If there is no error, then no correction is required. This never happens in real life, but improvements can be made. Tuning may be dependent on the extruder issue you are trying to correct. A better effort may be towards controling other aspects of the process or a better screw design. IP: Logged
Stephen J. Derezinski Senior Member Posts: 86 From:Penfield, NY, 14526, USA Registered: Apr 2003	posted December 03, 2007 04:21 PM Paddy- As usual, first place to look for flow instability is the solids conveying. Instability can exist at many frequencies and be very dependent on process temperatures. So, you may want to try some solids zone temperature tweeking. For some background, see www.extrudertech.com/antec2001.pdf ------------------ Steve Derezinski, Ph.D. Extruder Tech, Inc. steve@extrudertech.com www.extrudertech.com IP: Logged
alpertl Senior Member Posts: 57 From:Dayville, CT USA Registered: May 2002	posted February 06, 2008 07:35 PM quote: Originally posted by paddy66: hi guys, we use closed loop melt pressure control on two extrusion lines and find sometimes that tinkering with pid settings on these can improve process stability, but at the minute it is only a shot in the dark and not very scientific. I was wondering if any of you guys have experience of this and know what settings work best with diferent materials e.g nylon 11,12, pebax etc or is it all just trial and error. Your thoughts would be appreciated. http://en.wikipedia.org/wiki/PID_controller IP: Logged
Tom C Moderator Posts: 904 From:Brodheadsville, PA USA Registered: Jun 2001	posted February 06, 2008 07:46 PM Nice link. ------------------ Best Regards, Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged

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