SP15 mis-registration

Dear Paul,

I shouldn’t think you remember me as it must be over 15 years ago I sought your advice with regards to my Vandercook SP15 serial #22245 – there was a suspected broken spring. I dismantled the carriage, cleaned it up, re-greased it and put the press back together again! I obviously set up the carriage bearings, and I have been using it ever since. However, I now have a problem with mis-registration.

I make relief engravings in small editions. I don’t use the inking mechanism as its hand cranked and I only do runs of 25-50 so it just seems easier to ink with a hand roller. The work I make is off hand engraved blocks which are glued down to 18 mm MDF (or plywood) to give a block height of about 20 mm. I make the blocks up to type high with under-packing which is always over ‘type high’ although the pressure from printing is never too excessive, and it is always fairly easy to take the carriage across the block.

I am getting in touch as I have the problem of inconsistent registration which seems to come and go but can be as bad as up to 1.5 mm out. Then it will be fine for a few prints, then back out again. I’ve put this down to extremes of humidity, temperature fluctuation, blocks moving, and human error. However, after printing today I think I can rule this out. I’m very careful with feeding in the paper to the grippers, the paper has a guillotined edge and I tend to gently let the paper slide under my fingertips against the cylinder whilst taking the impression, so I’m pretty sure it’s not me causing the problem. The engravings are quite fine, take ages and can be easily ruined by mis-registration as they are printed in colour reduction so the registration needed is down to a very fine line.

Have you got any idea what this could be and where I should start to try and sort this out?

My plan is to check the evenness of pressure with type high rule and a blind print, check the packing, and adjust the carriage bearings following the guidelines in the article “Aligning the carriage bearings”. I remember doing this before, but it’s 16 years since I got the press and they’re supposed to be done periodically. I keep the press covered and clean it and oil it before I use it.

When I set the carriage bearings before I think I may have used bits of paper, I can’t quite remember, but I know I had to readjust as when I used the press and moved the carriage from the middle of the bed, where I set the bearings up, it was too tight by the paper feed to click in to place nicely.

Any thoughts and advice would be much appreciated before I start. Thank you in anticipation!

Best wishes, Neil

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Paul Moxon, Moderator
Admin
6 months ago

Hello Neil.

It sounds like you have been thoughtful in trying the determine the cause of misregistration. I will be interested to learn the results of your blind inpression test.

There are other factors to consider:
I trust that your lockup is sound, and while you say that your impression is light, I wonder if your packing as tight as it can be. Might there be a bagginess (looseness) that causes the end of your sheet to fishtail or bounce? Are your gripper bar screws tight. The shanks can become bent over time.

For those curious why Neil had previously disassembled the carriage, the reason is that SP15s with a serial number before 23925 have a coil spring and shaft that regulate the cylinder eccentric which can only be accessed in that manner as opposed to later models that have a leaf spring.

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