GTOZ Second Unit Registration Shifts while Printing?

[Piyath Pamuditha]

I’m running a Heidelberg GTOZ 52 and have been facing this issue since last week.

I can register both printing units perfectly at the start, but after printing around 100 sheets, the second unit registration shifts about 2 mm toward the operator side. After running for a while, it gradually returns to the correct position on its own.

The registration only moves toward the operator side and then comes back to its original position.

I should also mention that the lateral adjustment feels much looser when the machine is running on impression. When the machine is stopped, it feels normal, although still slightly loose.


I’ve attached a few images showing the misregistration, as well as the slur/doubling bars when the registration is correct and when it is out of register.


Has anyone experienced a similar issue before or have any idea what could be causing it? Any suggestions would be greatly appreciated.

 

[junker1984]

Pull OS side cover, check for thrust bearing failure at plate cylinder. I see in your pics a clean image movement laterally, don't see slur in pics. Unless I'm not getting clean pictures over internet, it appears you have unstable plate cylinder. Keep in mind, instability on GS of plate cylinder would normally cause circumferential variances without doubling, instability on OS would cause lateral deviation without doubling (slurring).

 

[Piyath Pamuditha]

Pull OS side cover, check for thrust bearing failure at plate cylinder. I see in your pics a clean image movement laterally, don't see slur in pics. Unless I'm not getting clean pictures over internet, it appears you have unstable plate cylinder. Keep in mind, instability on GS of plate cylinder would normally cause circumferential variances without doubling, instability on OS would cause lateral deviation without doubling (slurring).

Hello Junker1984! I have waited for your reply and thank you for your quick response.
We have already checked the OS Thrust Bearings, Tbh there was a disorder of first thrust bearing when someone who trying to fix the bearings previously but this issue was not there when we purchased the machine. So we cleaned the housings and rearrange the thrust bearings correctly and fixed again. I’ll attach some photos of the photos I took. And I was wondering what cause the loosening of the lateral adjustment key when it’s on the impression while machine is running?

 

[junker1984]

Often times, I saw that due to the limiting bolt coming loose and falling out in the lateral adjustment assembly, the threaded flange ends up turning out too far, and even becoming disengaged. Look at bottom side of adjusting mechanism, is the 5mm movement limiting bolt in place?

 

[Piyath Pamuditha]

Often times, I saw that due to the limiting bolt coming loose and falling out in the lateral adjustment assembly, the threaded flange ends up turning out too far, and even becoming disengaged. Look at bottom side of adjusting mechanism, is the 5mm movement limiting bolt in place?

Yes it’s in place, we have even add a spring load with a little washer to make it more tighter. Now we have checked the both Plate cylinders using a dial gauge and the first unit plate cylinder is correctly in place and second unit is moving.

 

[junker1984]

I wonder if one of the cylinder bearings has failed, but not catastrophically, causing the cylinder to to walk laterally?

 

[Piyath Pamuditha]

I wonder if one of the cylinder bearings has failed, but not catastrophically, causing the cylinder to to walk laterally?

I don’t think so, these are some photos I took when we checked the bearings, today we have switched the first unit Thrust bearing to the second unit but the issue is still same and 1st unit is rock steady.

 

[junker1984]

Have you looked at the alignment pin in the plate cylinder double gear assembly (gear side)? I I would think that if there was an issue there, the image would be out circumferentially, but it may be worth a look. I’ve been retired many years, but something tickles my brain that I had seen a major failure in that assembly which caused the cylinder to hang up.

 

[Piyath Pamuditha]

Is this one? Our technician suspects the it would be a problem too, then we checked it and there’s a very slight wear like . That’s why it’s still on with two screws.

Have you looked at the alignment pin in the plate cylinder double gear assembly (gear side)? I I would think that if there was an issue there, the image would be out circumferentially, but it may be worth a look. I’ve been retired many years, but something tickles my brain that I had seen a major failure in that assembly which caused the cylinder to hang up.

 

[junker1984]

Yes, but as I'd mentioned, slight wear on that pin would typically influence only slight changes in circumferential register. The instance I'd recalled involved extreme wear of pin and elongation of the bore it rides in on the inner gear. Still worth a look, though.

 

[Beguin]

Good evening, did you check the roller on the printing cylinder?

 

[Piyath Pamuditha]

The thing is, the Misregistration corrects by itself. Is it beacause the Spring Load?

Yes, but as I'd mentioned, slight wear on that pin would typically influence only slight changes in circumferential register. The instance I'd recalled involved extreme wear of pin and elongation of the bore it rides in on the inner gear. Still worth a look, though.

 

[Piyath Pamuditha]

Hello Thanks for your kind reply!
Sorry I didn’t quite understand what you said, which roller are you referring to?

Good evening, did you check the roller on the printing cylinder?

 

[junker1984]

The thing is, the Misregistration corrects by itself. Is it beacause the Spring

 

[junker1984]

That would be the approach I would take. I'd be prone to examining what is causing the cylinder to hang up, keeping in mind the heavy spring load is eventually restoring nominal position. I must say, after repairing GTO presses for decades, I don't recall ever seeing this. Most issues I recall involved mainly circumferential issues.

 

[Piyath Pamuditha]

That would be the approach I would take. I'd be prone to examining what is causing the cylinder to hang up, keeping in mind the heavy spring load is eventually restoring nominal position. I must say, after repairing GTO presses for decades, I don't recall ever seeing this. Most issues I recall involved mainly circumferential issues.

Another Fascinating thing is when we are running at 6000 it’s starts move towards OS but if we start production at the top speed of 8000 the misregistration movement is very much minimal. I’m wondering what cause this issue, Are the Needle Bearings and Thrust bearings look ok for you in my recently uploaded photos?

 

[junker1984]

They do appear to be OK, thrust washers will be obviously scraped away if thrust bearings fail, and cylinder bearing races would show same scraping and in extreme cases, the cases of the bearings would twist. I see no indication of that. Did you recently install this? Is it possible with came from a refurbishing company that installed incorrect cylinder bearings? I don't recall how many sizes are available for GTO, but the factory bearing kit for re-fitting bearings on a Speedmaster/S-line press contains up to 20 different sizes, in microns.