Roller Height Nightmare

I think you have the new comers belief in trying rollers without ink and trying to have everything workout. First, your press is worn after all these years. And each side of the press may be worn differently. At best you will reach a compromise that will work for most setups. Then rollers may be old and worn, especially if you’re taking over an existing press, and seldom do you get decent rollers with with the purchase of a press. Even with the newer synthetic rollers have a useable life span that may be a year long or maybe up to 7 or 8 years. But before you go nuts, ink up your press and see what happens.

If you’re not getting even contact of the rollers with the (type-high?) type or block you want to print, one quick and easy solution is to scotch-tape a sheet of cover-weight paper to the back side of the forme or block (being sure that the tape itself is not overlapping onto the back of the type or block) to add a little to the height of the type and see what effect that has; of course it will add impression as well and if that is undesirable you can remove the equivalent thickness from your platen packing. You may find that indeed the bed or platen are slightly “dished” from excessive pressure or wear, so that such ”makeready” will be necessary for every job to level things up. If you have a roller height gauge (which should be very slightly under .918 inches) you can tell if the bed or the platen of the rollers are at fault. “New” rollers that have been stored a long time can deform due to “plastic flow” from gravity, so using a type-high gauge under the rollers, mounted on the press, between the rollers and the bed, and sliding the type-high gauge under the rollers at different points, then rotate the rollers 90 degrees over the same place on the bed and checking again, can reveal any distortion of the cylindrical and concentric state of the rollers.

From the video you sent, the core of the roller seems bent. So you will get ink, then no ink, just like pictured in your example.
The best would be to get new rollers with a straight shaft/core.

That would eliminate some variables, and then you can trouble-shoot the rails and ink itself.

Thank you for the inputs.

I have two brand new sets of rollers and it’s hard for me to believe all 6 of them would be defective.

I noticed yesterday while rolling the rollers on a flat surface that the trucks have a “rising and falling” movement. I can see a clear gap showing up during a full rotation. The sound also points to that same conclusion. I can hear the truck rolling on the table, then nothing, then rolling sound again.

I’m not sure whether this is considered normal tolerance for trucks, but it would explain the roller behavior I’m seeing. The trucks are brand new. I’m tempted to order another set, but it feels a bit like gambling.

Do you have a workbench vise you can access? Try clamping the roller shaft (with scraps of wood between shaft and vise jaws to prevent damaging the core) and then rotating all the trucks on the other end of the core - that should reveal whether the trucks are “concentric” or not. Similarly, you could clamp one of the trucks in the vise, similarly protected, and put one end of the roller core in it and then rotate the roller in the truck, and observe carefully the roller surface for evidence of eccentricity, or of wobble of the other end of the roller. It would also be possible that the core ends are slightly bent, if they are used cores, and that would be visible while rotating the roller in the truck with first one and then the other core end inserted. It is very difficult to see such variations when “eyeballing” the rollers just in your hands.

Simon, you don’t mention what kind of trucks you have in this question. If you have Morgan expansion trucks, it is very possible and very likely that they are not set properly.
You would probably be better off getting a set of new Delrin (plastic trucks) from someone like NA Graphics or Todd’s Press Time.

You can see the Delrin rollers on my 8x12 C&P in this pix, as my wife Beddy prints.
Then you can put the trucks and rollers on a flat surface to truly determine whether the rollers are true and/or whether the cores are bent.
Another problem you could run into is if the trucks are slipping on the nibs on the cores, you will have a slur that wipes the type/plate clean as they speed past at different speeds, trying to make up for the slack between the core and the truck itself.
If none of this makes sense to you, email me at [email protected]

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Simon,

If you roll your rollers (with NO TRUCKS ON THEM, RUBBER ONLY) across a tabletop (with a bright light behind them) and you can’t see light passing under them then the rollers themselves would appear to be straight.

(If the rollers were bent you’d see light between the table top and the sides of the rollers at one point and then light between the table top and the mddle of the roller at the opposite side.)

If the above test says the roller is flat, then roll your rollers across a table and see if the “height” of the shaft seems to get closer and further from the table as it rolls, then:

A. Again, give them a gentle roll on a flat and level table top. If, as they’re rolling, they speed up, slow down, speed up, slow down, then your rollers might be oval, not round. Otherwise,
B. If the rollers don’t speed up and slow down, but the shaft still goes up and down you likely either have a non-concentric shaft (so it’s parallel to the roller, but not in the centre) or you have a bent shaft cast in to the roller

If everything above seems ok the maybe the trucks are actually non circular.

From what you’ve said (distance from the height guage being different in the middle than the sides) I suspect a bent roller.

Where it gets confusing:
“during a whole rotation, the gauge is off contact, then touches slightly”

Maybe there’s two things a little off. Maybe the trucks are a bit off and the rollers are a bit off. Check them both.

But also, do with Fritz suggested - hand ink the type and see how it prints.

Occams razor would say there’s not chance the bed’s off but run a print and see.

Thank you for taking the time to help me with this. I really appreciate it!

I have Delrin trucks; they are brand new as well. I bought them at the same time as the rollers.

I checked the rollers on a granite countertop with a light behind them, and they appear flat. I also checked the bed with a straightedge (…and light), and it appears flat also. I will check for the roller cores.

I originally noticed this issue while inking a plate for the first time. A whole horizontal section wasn’t receiving ink. After some troubleshooting, I tried to rotate a roller manually. That blank section got inked properly, but then another one got neglected. So the issue follows the rollers.

From the beginning, my assumption has been “Rollers and trucks are brand new, so there cannot be anything wrong with them; it must come from the press instead”. But after all the troubleshooting I have done so far, the press doesn’t seem to be responsible. Unless I am really missing something…
The trucks seem off to me, but again, I don’t know what a proper truck is supposed to look/feel like.

I’m having a hard time wrapping my head around the idea that new rollers or trucks could be the issue. Is it actually common for brand new rollers to be slightly out of concentric, or for cores to be off just enough to cause this kind of behavior? Would this be something a manufacturer might miss, or is there another explanation I should be looking at?

Simon,
Here are a few other things you can check. I already asked about if the trucks have anyplay on the nibs on the cores. If there is any play, the rollers will not be driven properly and will drag and squee-gee (sp?) ink and wipe the plate clean in certain areas.
You should try turning the artwork 90 degrees and see if the issue follows the artwork, ie. laterally rather than horizontally.
Presumably, if it is roller-related, it will remain a horizontal problem. If it goes vertical, it’s in your plate/artwork.

You should also check for any play between the small gear on the drive crank and the big gear. Any play there will cause a slur, similar to the squee-gee effect mentioned above. If there is play, hammering in the key on the gear should tighten up the slop.

You should also try putting the rollers in different positions, left to right and top to bottom.
Typically, out-of-round rollers, trucks, or cores will make any one of them travel at a different speed over your plate.
These issues also cause a “traveling” issue, that is, you may get some perfect prints and then the issue will drift up or down the page, then disappear, and come back at the top and and work its way down again. This is a sure sign something is out of round.

In all cases, use the scientific method, one change at a time.
good luck,
Steve

What is the material of the roller covering, how old is it, and how has it been stored? Some materials used for small press ink rollers will “cold-flow” or sag under their own weight, during extended storage in the same position, and the condition can be made worse by heat or high humidity in some cases; composition and some other soft flexible materials will do this. If the rollers sat in their packing box for an extended time that could well have happened and it would cause the symptoms you are experiencing. The change is a result of time and environment and not use wear. Urethane is one of the more frequent victims.

So I guess there’s a couple of things to try.

Steve’s suggestion about rotating 90 degrees is a good one.

Also check the bearers (that the trucks run on) if 90 degrees doesn’t help.

The slurring issue shouldn’t really be an issue, but if the trucks are loose you can “tighten” them on the shaft by slipping a bit of paper in between the shaft hole in the truck and the shaft so that the truck becomes tight on the shaft.

In my (albiet limited) experience the slurring most often still inks the type, just not very well.

If you hand in the forme, does it print, and print evenly?
If not, maybe that plate’s not 100% flat.