Heidelberg 2005 Heidelberg 74- 2 colour

[Alistair Tinsley]

Hello all members
I Have a problem with my Heidelberg 2 colour 74. I set print perfect but as I run few hundred sheets the print moves.I reset and go but again after few hundred sheets same problem. Is the sheet likely to be moving slightly from cylinder to cylinder as it is being transferred or could it be more the register at lift end..
Any ideas on this guys.
Thanks in advance
A

 

[junker1984]

Because it seems to be that the movement is circumferential only (as is seen in the picture you posted), and if the image issue is consistent across the whole sheet, I would focus on the alignment pins of the plate cylinder.

 

[Alistair Tinsley]

Hello junker
Thanks for replying.
But I set perfect .Then you would think something is moving slightly.
I have keep aligning as I go through the run.
Cannot take my eye of it.
It's not intermittent it seems to be a gradual movement
Thanks
A

 

[junker1984]

Is the movement consistent across the whole sheet? If so, I stand by my recommendation.

 

[junker1984]

My apologies for not being more specific in my suggestion, by "alignment pins", I'm referring to the pin/bushing configuration on the plate cylinder gearing, under gear side cover.

 

[Alistair Tinsley]

Yes it is across the sheet
Funny I was thinking that could be something in there.
Would you have pics on the general direction of gearing and I will take a look Monday.
Finished now for the weekend.
Thank you for the reply.
It's much appreciated
A

 

[junker1984]

Look at the face of the cylinder double gear configuration, you’ll see a bushing bolted to the outer gear and a pin that’s bolted to the inner gear inside the bushing. You may not notice any indication that there is wear between the two, but sometimes there is a rusty in appearance residue coming from within. You may also notice a greasing nipple near the assembly, not sure if the 74 had it. Along with wear of the pin bushing, there could also be wear in the brass bushing of the outer gear that rides on the journals of the inner gear. Much of this is not really in the scope of a pressman’s knowledge, as the assessment and diagnosis of the issue requires disassembly of the complete gearing configuration.

 

[Alistair Tinsley]

Okay..
Thank you for the details.
Your a gentleman
Regards
Alistair

 

[junker1984]

Me? A gentleman?

 

[Alistair Tinsley]

Good morning Junker.
Am I looking in correct direction for what you tell me as regards movement.
I am quite new to the press having work on Cylinders this padt 30yrs.
I am not afraid to strip a machine as I do it regularly but need to know the workings of it to understand wete the problem is originating.
The operator has run it this morning and has even run out of adjustment on the digital movement.Its is always moving in one direction which is up the sheet.
Sorry for troubling you .
What do you think ?
Thanks
A

 

[junker1984]

You are looking in correct area. I never had occasion to dismantle the configuration on a 74 press, but many in all other lines (102, 72 and S presses). The pin/bushing should be visible as you rotate machine, under the removable shroud.

 

[Alistair Tinsley]

Hi Junker.
Okay will take closer look
How does the fine movement work.
Is it small drive on a motor or pneumatic movement
A

 

[junker1984]

First, is it possible the plate is slipping out of the clamps? Look at plate to see if "skid marks" are visible. Movement of image is controlled by the servo which drives the outer gear laterally, and in turn, due to the helical cut of gears, changes the image circumferential positioning.

 

[junker1984]

A note, if you decide to explore this possibility yourself, keep in mind that the yoke which retains the gearing is under heavy spring load. I'd not recommend doing this without experience.

 

[Alistair Tinsley]

Okay .
Will keep that in mind.
Will do some more research.
Is this likely to be the cause of the movement though.Have you experienced this?

 

[junker1984]

Not as extreme as you’ve mentioned in previous posts, and usually only after going from make ready to production and after stopping and starting after a feeder trip or similar.

 

[junker1984]

Does this have CPC? Principle remains the same, but no servo without CPC.

 

[Alistair Tinsley]

Excuse my ignorants but what is a cpc?
We found a movement of 1mm over a run of 5000 sheets.
Why movement always the same direction?You would imagine that there would be certain amount of movement within the scope of the wear then it would halt,but this does not seem to be the case.
I am trying to understand how the mechanical movement is made in the cylinder by pressing the buttons on the screen.
I also would need to find which unit has the problem.
Bit of a pain

 

[junker1984]

I follow now, you have Compact CPTronics, and you make your register moves on the panel at unit two, yes? Compact came out as I was exiting the industry, and I have little knowledge regarding such. However, as I have previously mentioned, the principle is the same…when you push a button to make a circumferential register move, a servo drives the outer spring loaded gear laterally on the inner gear journal, and as the gear travels laterally, it rotates the cylinder positioning relative to the travel on the helical gearing. Movement is kept ever consistent by the pin/bushing configuration I mentioned earlier. If they are worn, the gear hangs up until you hit run, and at that point, it may jump padt the position you selected, or slowly work its way over in steps. When you made ready, you thought you had set positioning spot on, but due to the wear, you went farther than desired. This is difficult to explain in this medium, and this may not even be the problem your experiencing…but from your posts, it sounds like the issue I ran across throughout many Heidelberg press lines.

 

[Alistair Tinsley]

Yes it is cptronics.
I am with you now as regards how it moves.
Thank you for taking the time to explain to me.
I appreciate it.
Quite a job to put right if I've never done it before .No way round it I take it