Inconsistent Inking - Key Cores to Trucks?
I have a Sigwalt #5 press and am running into issues with inconsistent inking on the photopolymer plate. I am trying to print 7 lines of 11 pt type. Sometimes the plate gets fully inked, then after about 10 successful prints one of the lines isn’t getting inked. Usually I can spin the rollers and try again and it works for another handful of prints, until one of the other lines isn’t being inked. Sometimes it is only half of a line, it is very inconsistent.
The plate is on a boxcar base and is locked into a (new to me) original chase. I have metal trucks and brand new rubber rollers. The roller cores are not keyed to the trucks. I’m using Van Son rubber based ink.
I’ve re-locked the chase to make sure it isn’t too tight. The rails are clean and aren’t taped at all.
I’m thinking that my issue could be related to the fact that the roller cores aren’t keyed to the trucks. Are there any workarounds to keying the cores to the trucks? Or, where could I go to get this done (I’m in the Boston area)? What does it look like when this is done?
Another thing that I noticed, one of my roller hooks is about a quarter of an inch shorter than the other 3. I believe all of the springs are about the same size. Could this be adversely affecting the pressure of the rollers?
Thank you!
Keys and keyways on those rollers would be difficult. You could get a machinist to drill and tap radial holes in the large diameter of the trucks for 6/32 allen set screws to bear on the cores, and file small flats on the cores (though that probably isn’t necessary). If the holes align with the rails and the setscrews are below the surface there won’t be a bump. Check before doing that, though, that there is no play between the trucks and cores — if the trucks are able to move perpendicular to the cores even a very small amount that will cause the problem you’re seeing. If that’s the case shimming the trucks true will be nearly impossible. Better to go for a small amount of extra roller contact. You could put a shim of a piece of thin paper behind the base to see if that helps the problem.
Bob
Is it possible that you have envisaged a problem that is actually located elsewhere in the system, even with the size of the machine taken into account, but with the comparitively small number of (stated) image/lines of type, being printed, there must surely be so little drag/friction as to make it impossible for the cores/compound to skid or go out of sync, exactly together (x2).
Possible *proving* experiment,with all 4 trucks & cores marked, with felt tip (spirit) pen or bright coloured ink etc etc, do several passes/impressions under actual print conditions!!!
If after 20/30 (for example) passes all are still in sync, back to the drawing board???
If proved, and all are out of sync, & *skidding* , , Plan *B* . Drill & Tap the trucks, for *Allen* Grub screws.
As the profile & previous entries, and your resume above, implies that you have mastered the intracisies of lock up, make ready, register, impression, ink distribution, etc etc, drilling and tapping 4 grub screw holes should be a cynch!!!
I.E. with 4 grub screws from local hardware store + 2 thread taps, 2nd & plug, (set of 3 is usual, fine taper, 2nd and plug) the trucks do not need a *blind* hole tapped!!!
With just the use of a simple, D.I.Y. style drill press, and just one 1/8” or 3/16” drill bit, (lowest common denominator of 6/32”?) with grub screws to suit, grip the truck(s) with soft jaw vice, under the drill press, drill with care.!! put the truck back onto the core, position exactly for bearer width, same drill through original hole (before tapping the thread) small recess drilled into the stock, of less than 1/16”, depth, rather than hit & miss flat? . . the rake /angle, of the point of the drill will usually match the rake/angle of the point of the grub screw = positive positioning!!!
The above offered only on the basis of having (up to a point) mastered the vagaries of successful letterpress reproduction. or Apologies.
Please make sure your press rollers are keyed to the roller runners (or trucks). This means that the rollers turn as they pass over the forme and do not skid or slide. Also just enough pressure on the quoins to hold the forme together.
A roller setting gauge,
(from ebay?), I think, is essential equipment for every small printer.
To test the theory of ink rollers slurring, you can cut a piece of scrap plate material with an image next to the one you are using as a “bearer”. Make certain the bearer extends beyond the image each way as the rollers move up and down, so it will start the rollers moving prior to contacting the image plate. If this doesn’t improve the image inking, the loose rollers are not at fault.
I have an old Kelsey with unkeyed rollers, and I regularly lock up a piece of type-high wide rule at the edge of the chase to keep the rollers turning prior to hitting the image, eliminating the slurring.
John Henry
Apologies for the delay but I wanted to give an update - Upon DickG’s suggestion I put a piece of thread or two between my roller cores and trucks. This helped tremendously with my rollers slurring. But, as expected by some, this was not resolving all of my issues. Next I cut a manilla folder to the size of of the chase bed and taped two sheets to the bed. I then taped up my rails. My printing is now consistently even!! In the future, I will remember to also try putting scrap plate material near the edge of the chase to help with an slurring.
Thank you all for your time and guidance!! I appreciate it!