Durma Rolls going wrong - can't diagnose where the fault is

[Addyboon]

Hello All,
We have a set of Durma Rolls HRB-4 hydraulic 4 cylinder roller with an ESA controller. It is having a couple of problems and we are not sure where the fault is - I am hoping someone could help point us in the right direction for fault finding.
fault 1 - as we roll a sheet and use the forward and back buttons to feed the sheet through the rollers, the forward button occasionally does not go forward but goes back instead. When this happens we reset the machine and then start again and it works fine until it goes wrong again.
We changed the relay in the circuit because it was slightly blackened but this did not solve the problem.

Fault 2 - in the middle of rolling one of the rolls moved upwards without being asked to do so. The numbers set in the machine just completed changed on their own with no input from us.

We have had an engineer come and look at the machine but because the faults are intermittent and are not always there he can't trace them.

He doesn't suspect the valves because they do seem to be working properly - i.e. when both buttons are pressed together the valve locks as it should do.

He does suspect the controller and thinks it might need replacing. I am wondering if we can just do a hard reset first if such a thing exists. I do have the manual but it's not the easiset to understand (turkish translation) but I will keep looking.

Any advice would be much appreciated.
Thank you,
Adelaide

 

[Addyboon]

Thank you Milland - for the advice (safety and and electrical) and the link (we’re not in America but we have similar here). I will contact them and hope they talk at the same knowledgeable level as you do. A new control unit is 6000 ish so we do need someone who knows these machines. I’ll report back with the next set of findings when we have them.

 

[sfriedberg]

Among the other things to suspect would be missing or intermittent connections. We had a DRO which would spontaneously jump large distances (e.g., more than an inch). We finally tracked this to a poor ground connection on the DRO box itself. The cables to the read heads were all fine; the problem was the equipment grounding conductor. (And no, we don't have an explanation for how a flaky EGC could cause the readout to shift.)

 

[Addyboon]

Thank you sfriedberg - this is very useful information too. A bit of an update - we disconnected the numeric control unit from the rolls which was just a matter of uncoupling two large male/female pin/socket connectors. We blew them out with compressed air. One of the sockets was brown with rust and there was a strip of paint which was laying across the pins. I’m not sure if the paint is metallic. We sprayed it with contact cleaner. Reconnected it and, touch wood, it hasn’t put a foot wrong. Thank you though for helping.