Need Some Help for Hydraulic Control System


Thread Starter


An obsolete oem plc/hmi for a textile machine died and a replacement unit must be programmed based on info from operators and manual in OEM's native Italian.

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.

<b>Moderator's Note:</b> At this time does not accept attachments. We recommend you up load the schematic to a site like Google docs or other download site and post the URL in a follow on message.

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 I'm 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). Can't 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 haven't programmed any of the automatic control using the encoder feedback to maintain speed setpoint and weight.

I have setup basic system whereby 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 can't 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 can't 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 don't understand the effect increasing/decreasing signal to prop prv has on system. I don't understand what the valves marked s1 and s4 are doing to the system.

Hope you can help, request any additional info if necessary...
From what you have described and without seeing a hydraulic schematic, it appears the hydraulics is working at low pressure.

Generally starting a hydraulic pump without energising valves goes into re-circulate mode - that is pumping fluid back into the tank, merely to be on standby/warming the fluid to working temperature. This may explain the low pressure if you are attempting to run the motors at the same time.

Energising a valve to stop re-circulation and operating a proportional valve simultaneously suggests the way forward. There should be a pressure gauge on the hydraulic power pack to give you a guide as to working pressure.

As stated by editorial, post your hydraulic schematic on the 'net and give us the URL.
Clearly the hydraulic circuit hasn't re-circulate mode; S1 appears to be the 'run' valve although to me is working upside down - energise to stop.

S4 appears to regulate tension but couldn't state how without fully understanding valve symbols and not seeing the machine layout. In short you need someone from maintenance to describe how they see how the hydraulics function.