SP15 roller height changes erratically

I’ve been experiencing an issue with the roller height on an SP15.

I calibrate the rollers, and after pulling a few proofs, I can tell something isn’t right. I check the rollers again, and find they’ve shifted, drastically — sometimes after just two or three impressions.

It isn’t happening all the time. On Saturday I tried to catch it in the act, locking up a basic form and pulling a number of impressions, switching between trip and print modes. But the roller height held steady through a dozen or more impressions.

Then the next day I locked up a different form, and I got several satisfactory impressions before something had clearly shifted. I cleared the bed, and checked the height at several different points along the length of the bed, advancing the carriage a few inches at a time, and getting wildly different results.

  1. With the crank in the 8 o’clock position, both rollers are just over the bed. The geared roller is okay while the forward one is too low.
  2. With the crank at 10 o’clock, the geared roller is high and now the forward roller is okay.
  3. In the 12 o’clock position (the carriage at the halfway point), the geared roller clears the roller gauge completely, and the forward roller is now a touch too high. And so on.

I repeated the test in print mode and in trip and got the same result. Although I can’t assert that the measurements are identical each time, they at least conform to the pattern described above (okay; high; very high, etc).

Seeing the thread from August 2024, “SP20 roller height changing as carriage travels end-to-end,” that required a bearing adjustment, I suspect my issue is related. One thing that mystifies me is that the issue appears to resolve itself (as it did a few days ago), but always crops up again.

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Ernst Schaefer
4 days ago

bravo tim, thats a good idea with the dial caliper. it would be helpful to know if the front of the carriage goes up or down. are you getting a higher reading or a lower reading? that will tell you where to look for the mistake in your bearings adjustment. and yes .062 is a lot thats 15 sheet of copy paper.
please understand that not standing in front of the press makes every idea i have kind a shoot in the dark.
you need to find out what could the carriage make rocking, a bearing with a flat spot, some dirty or totally worn bearers?

Last edited 4 days ago by Ernst Schaefer
Ernst Schaefer
22 days ago

i put my indicator here

IMG_1487
Ernst Schaefer
22 days ago

ha, that is really strange. it seems your carriage is “wobbling” this can have a few reasons: the bearers are dirty, or the bearing are dirty or worn, not right adjusted or the bearing holders are loose.
first i would put a indicator with a magnetic base on the carriage and find out how big the movement up and down of the carriage is. see picture.
than i would loosen up all the eccentric bearings and start adjusting the carriage from scratch. in the new release of pauls book there is a great description how to do it on the sp-15. 

IMG_1486
Paul Moxon, Moderator
Admin
28 days ago

Extending what the Arm explained, the form roller gear has a press-fitted hub. This is the part that projects from the side with two set screws to tighten the gear against the roller core. The bore or inner diameter of the hub could be reamed out causing the core to be off center to the gear. The hub can be knocked out and the hub replaced or purchase a replacement gear.

Last edited 28 days ago by Paul Moxon, Moderator
The Arm
29 days ago

Two more things to check, after looking at what Ernst has already said-

Paper dust and oil can build up in the teeth of the rack upon which the gear of the rear roller meshes and this can cause the gear to unpredictably lift the roller as you make a pass down the bed.

Also be sure that the gear sits centered on the roller core. If you raise the rollers and spin that rear roller, you should be able to see any off-centeredness or wobble with the naked eye. It is not uncommon for a sloppy roller maker to cut away the face of the core where the roller should mount thereby making the gear seat poorly.

DGM

Ernst Schaefer
30 days ago

i guess your rollers are not round. here is how to test it: put the press in print mode (later you repeat the test in trip) roll the carriage in the middle of the bed and block it with some tapered woodblocks or clamp some wood blocks on the bearers. you dont need to ink the press up. the resistance to pull out the lollipop will tell you whats going on. start with the front roller, the one without gear. with the oscillator roller down mark the top of the formroller and test the resistance with the lollipop at the ends and the middle. now lift the rollers up and turn the front roller a 1/8 turn. check again. repeat this till you are back where you started. if the rollers are correct at all test position than they are round. if the resistance for pulling the lollipop changes, they are not. always test with the oscillator roller down. ddo the same with the roller in the back. than do the same test in trip mode.let us know what you found out.

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