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Old May 3rd, 2018, 02:11 PM   #1
United Kingdom

aPLCable is offline
Join Date: May 2018
Location: NI
Posts: 3
Hydraulic Help

Having problems retrofitting plc to an OEM textile machine, the hydraulics involved are beyond my level of understanding and i need a little help

The jigger machine in question has one heavy roll on either side driven by hydraulic motors. The material is threaded through/around 3 other free running rollers, when the machine runs material is wound onto one roll from the other, when the direction is reversed the material is wound onto the opposing roll. One roll seems to drive and the other brakes to stop material unwinding itself and maintain good even tension as it is wound from left side to right side and vice versa. It is wound side to side to pass the material through a dyeing process.

At this stage the original plc has been replaced
I will attach/follow with a hydraulic schematic, it is the understanding of this which is my main problem

From translating the manual and speaking to operators, the original control panel had 6 buttons as follows

Speed Manual/Auto- toggles on/off speed control
Weight Manual/Auto- toggles on/off weight control
Speed up button- increments speed setpoint
Speed down button- decrements speed setpoint
Weight up button- increments weight setting
Weight down button- decrements weight setting

I/O as follows

1 An. Out 0-10v to proportional valve card for speed (this valve has feedback back to card, however im only required to give the card 0-10v signal for position, speed in m/min)
1 An. Out 0-10v to proportional valve for weight (no feedback from this valve, appears to be pressure reducing valve, referred to as weight in documentation, previous units were kg or bar, setting from 0-50kg)
1 Encoder Input, counts pulses from magnetic encoder on one of the free running rolls, feedback of speed cloth is running through at, also gives indication of meter count
3 Dig. in from another plc (marcia(scheda elett.), marcia lenta, marcia pendolomata). Cant find any indication of what these are, also cant get them to activate...
1 Dig. in "prop card healthy"
1 Dig. in "allow meter count"
1 Dig. out "PLC Healthy signal" goes to another plc

At this stage i havent programmed any of the automatic control using the encoder feedback to maintain speed setpoint and weight.
i have setup basic system wherby on the screen i can output a manual speed and manual weight setting to the valves, i can also see the speed in m/min the cloth is coming through at. It works to an extent as when i increase speed it speeds up roll, and when i increase brake

i need help to understand the hydraulic schematic and devise automatic control system.
I also have a number of issues which i cant get understand atm

* manual refers to max speed as 150m/min, i can only get up to 75m/min with minimal brake , operator also reckons it ran far quicker in past
* when applying brake cant get enough tension on roll to wind material nice, tight and so smooth.
often increasing weight setting will reduce speed to a stop before it keeps proper tension on material, sometimes in this case driving roll will stop and rear or braking roll will continue to drive on unwinding lots of material.

Could someone please help me understand hydraulic schematic, what i need to do to gain proper control of the system and ways to check if the hydraulic set is working properly or anything which will point me in the right direction?

From the hyd. dia i understand the two valves which switch direction by switching lines of motor, i dont understand the effect increasing/decreasing signal to prop prv has on system. i dont understand what the valves marked s1 and s4 are doing to the system.

Hope you can help, request any additional info if necessary...
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