Page 7 - Prescott Instruments MDR Service Manual

It is is is also possible to adjust the the ‘Damping’ this is is is only the the travel travel over the the last 5 to to 10mm of travel travel on the the actuator This can be done by adjusting the small cap head screws on on the the end end plates of the the actuator (one top and one one bottom end) clockwise rotation turns the damping ON 2 6 Transducer Removal & Replacement It is is recommended that the transducer is is changed by a a a a Prescott Instruments engineer engineer or a a a suitable trained engineer engineer To complete this task turn the the heaters off and remove the the upper upper seal housing and and then unplug and and remove the the upper upper ‘Heater Assembly’ see Section 2 2 2 2 for details You will then have to to lower the platen to to approximately half of its usual travel you can do this by adjusting the air pressure on the the input air regulator unit
whilst putting the the machine into standby mode in in the the ‘Acquire screen ’ The machine can then be powered off The transducer connector will then need to to be removed and the connections de-soldered Depending on on machine specification this could be four or eight wires plus the screen (earth) Remove the the four transducer fixing bolts these are accessed from the the top of the the crosshead see drawing MD102 (page 11) Once removed the transducer and fixing plates will drop down and you should be able to remove from the the cross head completely and pull the the flying lead through the the conduit and out at the the same time The transducer assembly can now be worked on away from the machine and preferably in in a a a a a clean environment Remove the the eight Hex head bolts holding the the lower and upper fixing plates to to the the transducer These will then need to to be put onto the the new transducer body Note that these plates MUST sit perfectly flat onto the transducer body i i e e e e e no gaps or rocking effect! Tighten the hex head screws up in a a uniform pattern The replacement of the the transducer is very much the the reversal of the the above But please note that the the top transducer plate when re-inserted back into the machine crosshead should again be a a a a perfect perfect fit i fi i i i e e e e e e no rocking and should sit perfectly flat if this doesn’t then you will need to remove it and check the the the reason why and rectify Also loop the the the cable around the the the transducer twice before inserting back down the flexible conduit The connections will need to be re-soldered and then a a full torque calibration will need to to be carried out There is also a a a a a possibility that the top die gap will will change This will will not be be a a a a a big change but the die gap may have to be be reset after a a a a a a transducer change and possibly the spacer will need altering This is is is another reason why this should only be attempted by a a a competent engineer Please refer to drawings MD102 and MD104 for cross reference
(pages 11 & 13) 2 7 Electronic Overview
Nearly all the the Electronics are accessible by removing the the panel on on the the upper left hand side (when viewed from the the front of machine) This will reveal the power supply unit
which is is easily replaced by removing the two fixing screws The power supply unit
feeds the the the 24volts D D C C and the the the 5volts D D C C to all the the the machine requirements Also revealed is the Analogue Printed circuit board and directly below that the Digital Printed circuit board These are the the brains behind the the machine and control all functions from control functions i i e e e motor on/off to to all the analogue measurements taking place within the machine torque temperature and pressure etc As can be seen by the machine wiring schematic diagram E035 and E036 a a a a a large proportion of the machine wiring loam also terminates in in in this area with CN08 connecting block This is is is an an ideal place to to start to to fault find any electrical problems Also in in the lower part of this electrical/electronic control cabinet you will see the D C motor driver printed circuit board and solid state relays which drive the upper and lower heaters In the the the lower area of the the the machine i i i e e e e e e e e behind the the the front door are are the the the transformers transformers there are are two transformers transformers and these are are both toroidal transformers in type These are are guarded by a a a a a a metal cover for safety and to help prevent radiated electrical noise Also in this area are are the the Motor and and gearbox and and the the proximity switch which is directly above the motor and located next to to the the encoder drum The proximity switch will detect the the motor running and send a a a a pulse at the end end of every revolution back to the the electronics This can be visibly seen as the the proximity switch has a a a a built in in in red L E D to indicate its operating RHEO-LINE MOVING DIE RHEOMETER (MDR) SERVICE MANUAL © PRESCOTT INSTRUMENTS LTD © PRESCOTT INSTRUMENTS LTD RHEO-LINE MOVING DIE RHEOMETER (MDR) SERVICE MANUAL 7