Some of the unique requirements of applying servodrives for Parison and Blow Pin applications in blow moulding machines include the need for protection against incorrect commands or wiring failures, easy set tuning and troubleshooting for users, and an interface for analogue feedback to help retrofit old machines.
Moog was able to integrate its DS2000 Servodrive with its Modular Parison Controller by adapting the software to allow digital position loop closure and implementation of special functions useful on blow moulding machines. There were no hardware changes to the standard DS2000 Servodrive. This solution is called the PDS2000 and it can be used for any application requiring analogue position reference and/or analogue feedback. It is optimised for Moog’s Fastact G, Fastact T and Fastact Y Servomotors.
Description of the PDS2000 Servodrive Solution
Using two parameters (CW and CCW Override SW) it is possible to program the servodrive to add or subtract an extra stroke to the measured one in order to get specific application functions:
- Blow Pin Application: The effective stroke is set wider than the measured one so the actuator can push against a mechanical limit to cut the bottle top (Positive Value)
- Parison Control Application: The effective stroke is set less than the measured one so the actuator cannot hit any mechanical limit, thereby avoiding damage to the machine head and/or parison actuator (Negative Value)
- 4ms Serial Link refresh time; position loop closure via serial link in 8 ms
- Speed and position gains fully programmable
- Auto run of homing sequence at every drive power on; repeatable upon command after a drive reset
- Consistency check/limitation of reference command against the detected stroke
- Feedback transducer open circuit monitor
- The position feedback can be either the motor resolver or an absolute analogue transducer (usually a potentiometer), applied on the “AN FEED” differential input
- The position set point can be analogue (-10 to +10 V), applied on the “P REF” differential input, or digital through Serial Link Position Command on RS 485/422 interface
- Analogue position command programmable within ± 10 Volt range
- Analogue feedback output range within ± 15 Volt
- Feedback transducer power supply got from J2B connector (+15 V dc, 100 mA max)
- Incremental feedback achieved through the motor resolver
- 10 bit resolution of analogue inputs:
- for ± 10 Volt, the LSB weight is 20 mV
- for ± 15 Volt, the LSB weight is 30 mV
- 12 bit resolution for resolver pole pair:
- for two poles resolvers, the LSB weight is 0.09°, 5 sterad
Franco Talpone is responsible for training and new applications for Moog in Italy. He has been working at the Casella location since 1994 and prior to this he taught in Public Schools and University. He has a Ph.D in Physics.
Ugo Di Lalla is the Systems Engineering Manager for Moog in Italy - Malnate site. He joined Moog in 1990 and he has been working on aerospace and industrial control systems since 1978. He has a University degree in Mechanical Engineering.