lotem 800V drum speed deceleration

[ansoft]

Hello ,
I have the following problem- on Lotem 800V the drum speed decelerate from time to time. From 900rpm, it slows to 570rpm for example. The speed decelerates and if the Lotem "decides" increases the drum speed to the normal value. I have checked the wall voltage-it is OK, the diagnostics does not show any problems. I have checked the fuses and they are OK. Everything seems to be OK, but from time to time the drum decelerates.
It is interesting that the syncronization between the carriage motor and the drum motor remains, because if the deceleration starts when the plate is exposed on 90%, there are no artefacts on the plate- skew image or something like that.

I appreciate any suggestions.

 

[PACH]

Hello ,
I have the following problem- on Lotem 800V the drum speed decelerate from time to time. From 900rpm, it slows to 570rpm for example. The speed decelerates and if the Lotem "decides" increases the drum speed to the normal value. I have checked the wall voltage-it is OK, the diagnostics does not show any problems. I have checked the fuses and they are OK. Everything seems to be OK, but from time to time the drum decelerates.
It is interesting that the syncronization between the carriage motor and the drum motor remains, because if the deceleration starts when the plate is exposed on 90%, there are no artefacts on the plate- skew image or something like that.

I appreciate any suggestions.

Hi,
Do you get any error messages when you have the problem?

 

[gig0]

Just a guess but is it possible the compressor has something to do with it? Does the psi gauge fluctuate when the drum is spinning?

 

[PACH]

Just a guess but is it possible the compressor has something to do with it? Does the psi gauge fluctuate when the drum is spinning?

NO. The drum rotation has nothing to do with the vacuum in the drum. You will see a slight change in the compressed air gauge when a plate is loaded or unloaded from the drum.
Do you get an error message when the drum decelarates? Does the exposure gets aborted?

 

[ansoft]

The Lotem decelerates, but the exposure does not stop, even the drum speed is low. I have checked the fly-off sensors and they work OK. The air pressure is 6 atmospheres, stable. After the exposure is "complete", the error is "Drum go to position timeout" and the plate is on the drum. After "Force plate on drum" and Unload, the plate is unloaded. Next job is possible only if the Lotem software is restarted.
Regards!

 

[PACH]

The Lotem decelerates, but the exposure does not stop, even the drum speed is low. I have checked the fly-off sensors and they work OK. The air pressure is 6 atmospheres, stable. After the exposure is "complete", the error is "Drum go to position timeout" and the plate is on the drum. After "Force plate on drum" and Unload, the plate is unloaded. Next job is possible only if the Lotem software is restarted.
Regards!

Hi Ansoft,

The following could give you the problem with the drum:

Wall voltage is too high.
Interlock key and/or interlock is incorrectly postioned
Distribution board may need replacing.
Drum driver is not comp level P.
MCF board may need replacing.
Drum encoder may need replacing.

Good luck.

 

[ansoft]

Hi PACH,
You read the planet, but I must tell you that the wall voltage is good, the drum driver works according to the spec, only green LED is ON, the interlocks work fine. I am looking for a solution that is sure, because either of the boards- distribution, MCF or drum driver are quite expensive. I must be sure....Regards

 

[PACH]

Hi PACH,
You read the planet, but I must tell you that the wall voltage is good, the drum driver works according to the spec, only green LED is ON, the interlocks work fine. I am looking for a solution that is sure, because either of the boards- distribution, MCF or drum driver are quite expensive. I must be sure....Regards

i DID READ YOUR MESSAGE. I am afraid it could be any of the parts that I told you about. There is never a simple and straight solution to this problem. Start with the Drum driver (ELMO).
Sorry, but this is the best advise I can give you re. your problem.

 

[spapa]

It's really a difficult problem to solve.
About the drum driver pcb. I have noticed in a machine witch suddenly rotated with full revolution for some moments (and acted like 7 Richter earthquake) that the 5V voltage on the PCB was 4,6V actually. This can be measured with a digital volt meter.

This can be adjusted by power supply, if measured below than 5V (I cannot advice to do it yourself).

The low voltage makes logic electronics on drum driver pcb to reset

 

[ansoft]

Dear SPAPA,
The very first thing I did, was to measure the voltage in the E-box. The 5V was 4.75V and I adjusted it. It is easy with one potentiometer. PACH is right about the the drum driver(ELMO), but what confuses me is that the LED indication of the drum driver shows correct performance. A sudden drop of the voltage of the E-box may be?
Regards!

 

[PACH]

Dear SPAPA,
The very first thing I did, was to measure the voltage in the E-box. The 5V was 4.75V and I adjusted it. It is easy with one potentiometer. PACH is right about the the drum driver(ELMO), but what confuses me is that the LED indication of the drum driver shows correct performance. A sudden drop of the voltage of the E-box may be?
Regards!

Ansoft.

Try and measure the 5V on the MCF card. It should be 5.1v. The PSU that you need to adjust is at the bottom of the E box and you can see this pot. if you go on your knees and look from the rear side of the Lotem. It is not easy to see and adjust as you have to look through the ventilation holes of the E box and the trapezoidal lower pannel of the Lotem.
As far as the ELMO goes try and get the latest revision one.
Good luck.

 

[ansoft]

Dear PACH,
I adjusted the pot you described and confirmed the 5V on the TP on MCF. I did this first when I stood up this problem. The voltage is OK. I forced the drum to rotate with 20rpm with open covers and cheeters and examined the drum driver LED indication. Only the green LED was flashing.
I am tired from this problem I would like to scream very loudly....

Regards!