I just replaced the rollers on my SP-15 and am having trouble printing the first time out. The rollers were purchased from another press owner, but were new and unused, still in original NA Graphics packing and boxes. This was the first time I’d changed the rollers but didn’t encounter any difficulties with changing over the bearing blocks, gear, etc. I’m using a boxcar base and photopolymer plate which I’ve printed from successfully before. The problems I’m having are–
a. The image has a fine darker line of ink around most of the outer edges. I’ve tried 3 different paper stocks and all show the same problem.
b.The front roller has a consistent pattern of blotchy, darker areas of ink, looks sort of like skid marks. The back roller looks normal.
c. After I adjust the rollers to proper height and run just one or two impressions, then recheck roller height, both rollers have shifted. Usually back roller moving up and front roller moving down, both consistent from side to side. I’ve made sure the screws on the blocks are made tight with allen wrench each time.
I never encountered this particular problem with the old rollers. All the oscillation and roller movements look normal to me, but apparently something is off. Any ideas would be most appreciated, thank you!
Also, I’ve posted photos of the rollers showing the unusual ink coverage here:
http://www.scdesign.net/press_images.htm
Today I finally had time to switch the rollers as Fritz suggested, and I tried printing the same plate again. There was quite a bit of improvement, the darker outline around the edge of the image was barely noticeable, and on some parts not there at all (there is more image to the plate than what I posted). The rollers held their positions. However, the back roller (previously in the front position with the odd dark splotches in the above photo) still shows a slightly overall mottled appearance, the ink doesn’t look smooth and even, but sort of “tacky”.
Also, when I test the roller height with the gauge, the stripe from the back roller is more diffused, less sharp, than the stripes from the front roller, even when all are the same width. This happened before also, on the front roller (which is now in the back) but I wasn’t sure it was significant. Now I think it must be since the “diffused” stripe is particular to the blotchy roller regardless of the roller’s position front or back.
Unfortunately my day job keeps me from being able to use the press every day, but I plan to try a different plate this coming weekend. Any further suggestions most appreciated, thank you!
Remember also that only the second half of the hole that the lock screw passes through is threaded. This is what allows the split sections to squeeze together without stripping the threads.
Eric,
I do have to apply some strength to tighten the locking screws, but if I get them securely tight the knobs stay put. Someone did put marks on the knobs prior to my owning the press, so I do keep an eye on them to check for possible movement. Is there anything else that could cause the rollers to change position?
Loose roller adjustments are pretty common on the SP-15.
Can you still turn the adjusting knobs when the locking screws are tightened? Cleaning the threads of both the knob and block may help (especially if oil has gotten in there), and you might try some teflon plumbers tape around the threads. At SFCB they put marks on the knobs to indicate whenever there is movement.
It has also been suggested that widening the slot mightd allow a tighter grip on the adjusting mechanism.
Hi Fritz,
Thanks for replying. The original rollers came with the press (serial #25838) and I have no way of knowing their age. They worked OK at first, but as I’d begun having inconsistent and less successful results, and had posted previously about them as you mention, I finally decided to switch to the new rollers after I compared circumference measurements and found that the original rollers were 1/8″ smaller around than the new ones.
The new rollers were purchased via Briar Press from the owner of an SP-15 who had an extra set to sell. I will email you all the info. on the packaging labels directly, as there is quite alot.
Please note– the photo I posted of the roller above shows the roller already inked. The marks are not on the roller when cleaned of ink.
I will try switching the rollers and see if that helps. It didn’t occur to me that they could be a difference between them.
Thanks again, Sylvia
You indicated a previous problem with your old set of rollers on an October 29, 2008 posting–and these are replacement rollers? If you could email me (nagraph@ekiva.net) with the name of who you bought the press from, I could see how recent these rollers are. We normally ship rollers direct from the roller maker, so I’m curious about the NA Graphics packaging. Those splotches are not normal on new rollers, but I think they are unrelated to your inking problem. If you can switch the gear from one roller to the other, you could try reversing the rollers to see if that does anything. For some time now, on new SP-15 cores, we have supplied all rollers machined for use with the gear and originally Vandercook saved a few pennies by providing 2 different cores, one plain and one for the gear.