Poor Shilin Memory?

[Guest]

Hi guys,

There is a traverse machine in my place now not working properly. The machine carry items automatically from one tank to another. There are several tanks and the machine would work by considering the setting time at each tank. This machine was built a year ago by our vendor. In the early few months the machine works perfectly. But later the machine would start having problems by 'not moving to the tank it supposed to go' or 'move to the tank it is not supposed to go'.

Thing get worse recently where the machine made those kind of error few times in a day. We asked the vendor about this problem. The feedback we'd got is that our machine is using a Shilin PLC and it has a poor device memory. I had gone through the program which is written by a very experience programmer and it seems to be comprehensive and well written. I will try to write my own program to resurrect the problems of this machine. However, i just curious if the reason we were told would make sense, that Shilin has poor memory? That it's not the problem occur in the program?

Thanks.

 

[Alan Case]

The function a program performs DOES NOT change. The program might change (rarely) if there has been a spike etc but the change is usually to wipe part or all of the code. If you have the original code then reload it. Now you know the PLC was as it was when it first arrived and it did work then. What changes is items connected to the PLC. This will be where you problem lies. Regards Alan Case

 

[Tom Jenkins]

I agree with Allan, programs rarely change spontaneously. Most often a setpoint or tuning parameter has been modified. Second most often is a senor or other field device fails or the wiring gets loose. Third most common problem is an I/O card fails.

 

[mnehez]

I agree with both

If you reload memory to a machine that hasnt been modified then you should get as new results. Also is there an eprom? Has the machine or rather has the plc ever been shut down and rebooted? And prier to that ensure that there isnt a battery problem first.
I would tend to belive that an outside problem exist's. You might have a 5 star plc but in order
to make money the vendor could have used cheap valves or other.

 

[reachasp]

Hi

I agree with Alan & Tom. Reloading of the program will help
in finding the cause of problem. Also the PLC programs do not get
corrupted that easily.

Besides reloading the program in PLC can you check following things

- Check the physical conditions of the feedback devices. Sticky
limit s/w , relay contacts.
- Pl. go thru the ladder. Find if any time based motion is there ?
By the way it is not very clear what kind of drive & feedback is
used to control the motion.Pl. check if any stepper motor is used
which is missing steps OR faulty encoder giving absurd results.
Regards
asp

 

[Asari]

Years ago I have similar problem on traveling head die cutting machine. It can't lift up, actually the lowest level limit switch has been touched.

The output led was off, but there was voltage that energized the solenoid valve because of sticky relay. Solution to that problem we add the higher current capacity of relay to anticipate the spark and sticky relay contact.

The problem is gone.

Note
Shihlin(AXn) is similar with Mitsubishi(FXn) if you are willing to change the PLC and use the original program.

Arie

 

[JesperMP]

I dont know about Shilin or Mitsubishi PLC's, but all other PLC's I know of have CRC checksum test of the program memory. If the test fails the PLC will fault.

I think that the response from your vendor is unprofessional.
Anyhow, the vendor is under normal circumstances responsible for the proper function of the delivered machinery. So he shouldn't snub you off with a "bad component" reason (and certainly not an unlikely one).

 

[stevecase]

If you use a shilin then you get a PLC clone for the Asian market that are imported by small companies, what do you expect money back guarantee?