Recently, and all of a sudden (or perhaps having reached their tipping point), the rollers on my SP20 are not laying ink correctly. I get the sense that the rollers are sliding over the form (I use photopolymer plates) and the look of the prints produced (scuffed and uneven) support this idea. The sliding is accompanied by a chattering or grinding sound that would indicate that the back form roller gear is disengaging with the rack (though I seem to hear a similar sound from the operator side as well). Finally, I notice that the oscillating roller stops moving when the sliding occurs.
I’ve been through the suggested solutions on the troubleshooting page but to no avail. The gear has a woodruff key and its set screw is tight. Magnesium carbonate has been used to increase the ink’s tack or I’ve used sufficiently tacky ink to begin. My rollers ARE glazed over, though speaking to Craig Black of Don Black Linecasting, they’re made of Nitro PVC, a material that is fairly steadfast, and probably don’t need replacing (I’ve had them for 2.5 years or so). I also notice that the nylon support wheels or “top carrier rollers” are somewhat seized up and don’t spin consistently, though all the carriage bearings do.
By the way, I posted last week about a pattern of wear on the rails of my SP20 where the “top carrier rollers” sit when the carriage is at the feed board. I was told by Fritz Klinke that they might be set too tightly to the rails. Might this be part of the problem?
Anyway, I’m at a loss for how to resolve this and I’d appreciate any advice put to me.
Eric’s suggestion is good, but I would also replace those Nyliners and check the starter gear on the gear track that the roller gear engages. This piece may be missing, bent, or not moving correctly.
If I were you I would order all the parts and as send the rollers out for recovering. Once it all is back together correctly you are going to have a new love for your press.
The Arm Letterpress
Maybe the worm and crescent are the problem. When worn or unlubricataed they can seize up. If the form roller gear really is OK, this is the next obvious thing to check.
I would also check whether the screws that hold the roller bearings in place have not worked loose. When they move out and press against the side frames, they can bind the rollers as well.