I’ve notice I have been getting inconsistent pressure from my Heidelberg SBG. Looked up some scores today and pressure was changing as I was running. Any ideas?
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Little more info, scoring to typan, to jacket.
Scoring with matrix?
Around cylinder or across?
Paper type and weight?
Place type high rule in Bed, 5 inch inward from cylinder edge left and right, of setup score line ditto. Run - ink or score and check if variance from sheet to sheet (just run a handfull sheets). If variance, Bearing - if stable you’re ok but othe sources of the Problem. walking makeready, bed not running horizontal etc etc.
Running 4 scores around the cylinder -not across.
.918 rule using matrix on top of die cut jacket. Placed a few sheets under steel beneath form to get score folding as preferred. Scores ran 21”
Stock is 140# index. size was 22” x 28”
Pressure varied through run. Light, then heavy, then light.
You are probably hitting too hard. do some research on creasing and use of matrix. Look to the matrix manufacturer for the technical details. Part of the problem is the use of the word score instead of crease.
Mike, you are correct. I was creasing, not scoring. Old habits of language are tough to change. I’ve been using creasing matrix for 20+ years and running letterpresses and various offset equipment for the last 30+years.
Haven’t encountered pressure varying during the run as much as what happened yesterday. Machine was purchased 12 years ago and had 2 Heidelberg cylinder people check before purchasing - they offered to buy the machine.
I’ll get in touch with them to go over the machine. Gut feeling is the bed is not horizontal.
Are the bearers and gears for both the bed and cylinder clean? Just a thought.
When I have to run a heavy amount of packing my press will back off impression at times. It never goes back on on it’s own. It’s almost as if you don’t put it on impression at just the right time it doesn’t “lock” into place.
Bearers and gears are clean. Checked main rack gear and clean also. Unfortunately, job was too big for our Miehle V-50 and our clamshell die cutter was busy.
Thought I’d check with the people here to make sure I’m not missing something.
One speculation, (the author is only the messenger) !! A good Buddy from way back, lifelong H/berg cylinder Minder, and still sub-contracting on H/berg cylinders had the same kind of problem, long time ago.
He was creasing with matrix, several creases, across the cylinder.
The eventual cause was found to be because He was working very close to the grip edge, the jacket although cranked up very tight with the Canvas Tail end, was as tight as possible.
The (assumed) perfect 90 degree fold on the jacket where it leaves the Pinch Bar in the cylinder was NOT hugging the first 1/2” to 3/4 ” of the cylinder, causing the jacket to deform, just enough to give the conditions as above.
May be completely irrelevant, sincere apologies if so.
Sounds like you have too high a rule and the cylinder is “jumping” and not settling down. You might set the impression lever to heavy (which increases the the cylinders resistance to rising during impression.
Presuming your bed was cut to .937? If the press had been rebuilt by one particular rebuilder, I’d look and see if the bearers were high enough—but that’s another story for another day.
Just a thought but is the rack under the bed that drives the bed nice and clean if you’ve dropped a sheet or two it will lift the bed a tad then you’ll run into bearer shear problems.
The bed will rumble along the rack and mash the paper but it has nowhere to go?
Response for Mick: Die cut jacket is very firmly in place. Also I purposely started the rules 1.5” from the gripper edge to avoid this issue.
MikefromMontana: Impression lever was set to medium. I’ll try increasing to heavy.
Elrodandy: Center rack is clean of any debris.
Thanks for the responses. I think it may be the bed is rocking since pressure is changing during the run. Too light, too heavy etc.
Mikedprinter, Thank you for the *nod*
I was only the messenger, as I am for the next one, follows:- thus, and only gleaned from chatting to visiting engineers, H/berg, usually! When one Heidelberg got severely smashed up, (maybe several sheets between the cylinder and the bed), (author) heard the bang in the Monotype dept.
It appears that the Cylinder is lifted off Impression, via 2 massively powerful >Jack,s< but retained in the correct orientation with 4 massive bolts.
But because the *Pile Up* was so severe it smashed the stanchions that carry the cylinder and ripped the bolts from the base, ending in a repair bill running into thousands of £/$.
Is it remotely possible that Your Cylinder Jacks are just a little suspect.? Having seen the weight of the bed(s) and the size of the Rollers that the bed runs on, ROCKING would seem to be the least likely.
Perhaps, as far as possible close examination of the Tracks that the massive ROLLER bearings run in, minute inspection of the channels, beyond the width of the actual roller,s, i.e. normally seen as the run off for the track lubrication - minute particals of metal, etc.
Is it possible to call up Your own *Wittenburg* or even Contact our U.K. Senior Graphics,
Given the request, I would be happy to speak with our S.G. on your behalf, and then relay their suggestions, on the Forum or On line… Mick
make sure the impression lever goes to the same spot each time. on some machines they tend to “creep”. there should be a stop inside the cover that the lever is to rest against when on impressions. many of these are broken off. it is imperative that the lever go to the point it completely locks. impression should be adjusted with make ready.