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Need help with MOOG Dual PWM Amplifier G123-814-001 controlling a Weing Moulder Speed via a Linde hydraulic pump and valve

Have just upgraded a Allen-Bradley Compactlogix PLC from L30 to L31 which is controlling a Weinig Moulder speed. We have an Analogue card sending a signal to a MOOG Dual PWM Amplifier G123-814-001 and this then drives a forward and reverse valve on a Linde pump. The feedback is via an 1000pulse encoder and the problem is that we can't control the speed properly, when you start the feed or change speed, the speed fluctuates for about 30-60 seconds before settling down to the required speed (ie: if speed set to 65m/m, when started it will jump to 100mpm, then go down to 20m/m then it will go to about 40-45m/m and then slowly work its way to 65m/m). Inside the program we are using a Speed PIDE to control this and have the "P" set to about 1 and the "I" set to about 12. This was done using tuning software and the figures seemed wrong to me as normally the "I" is about a tenth of "P".

Could anyone please give some advice as I have never worked with these before.