Wrong size of the plastic runners

Hello everyone. I just received new plastic runners from printerspartsusa web store. It took almost a month to deliver them from USA to Russia. And now I’m a little upset since the diameter of the runners is 53.2 mm instead of 51 mm. So now there is a gap under the roller. Is it normal? Should I return it or order to turn them to the desired size of 51 mm?

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I-0RcxzE7b4.jpg

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you need to find out from them if they even have the size you want. if they do they should send you the correct ones, in which case,you could find a plate and shim out your forme until they arrive. if they don’t you may have to try adjusting the press.

you need to find out from them if they even have the size you want. if they do they should send you the correct ones, in which case,you could find a plate and shim out your forme until they arrive. if they don’t you may have to try adjusting the press.

Just adjust your roller tracks accordingly to give you the correct type height.

Michael
Nickel Plate Press

It seems to me that the different diameter of the runner and the roller will lead to the difference in the speed of roller surface on the form and this will lead to incorrect application of paint.

Did you try adjusting the roller tracks to get the right height for your type form?

I think you will find, in this instance, that adjusting them to the correct height will not lead to incorrect application of the ink.

Michael

No, I haven’t tried printing with these runners. After reading several posts on this forum, I thought that such a difference in radii is unacceptable.

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rollers.png

I suggest that you find a local machine shop and see if they can turn them down to 51mm. It looks like there is enough plastic on the runners (or trucks as we call them), to do that. If there isn’t enough material, a local shop could use the runners you have for a pattern and make new ones locally. It would be a pretty easy job for a machine shop.

I’ll explain what the problem is here. Since the radii of the runners and the roller are different, and the angular speeds of rotation are the same (since they are fixed to the same shaft), the speeds of movement of their surfaces will be different. Therefore, the point of contact of the runner with the rails will move at one speed, and the point of contact of the roller with the form or polymer plate will move at another speed and the roller will begin to slide along the form or the plate.

Yes, Geoffrey, that is the best option now since the return will take so much time and will cost more then the price of this runners.

Your rollers are not going to slide along the plate if the bearers are set to make the correct height above the plate. That’s why there are adjustable bearers on some platen presses. Use a roller gauge to get the correct setting and start printing. The theory you read (and posted above) can’t be proven.

Michael

I believe Fram is correct about the rollers slurring ink on the forme, but adjusting the bearer height will not solve that problem. Turning down the runners is the best solution, and a machine shop can do it quickly. You are only removing 1.1mm of material. The rollers look like rubber, and if so they should not change diameter over time, so turning down the runners should be a long-term and fairly quick solution.

Bob

Fram’s trucks (plastic runners) have a circumference of 167.13. the roller has a circumference of 160.22. If the trucks remain in firm contact with the rails, the distance of travel per revolution will be determined by the circumference of the trucks. The rollers will be dragged 6.91 per revolution, resulting in slurring and ink piling on the lead edges of the form.
If, however, there are roller bearers in place that are taller than the rails, then the trucks will be lifted off the rails. The distance of travel per revolution is then determined by the circumference of the roller.

The ink will not slur if the rollers are adjusted to the correct height over the plate (form). The difference in height between form and bearers (rails) will compensate for the difference in circumference between rollers and trucks.

Michael

Actually, if the roller bearers, the sides of the bed on which the runners roll, is not adjustable the point is moot — though you could shim behind the forme to raise it to the same height as the rollers, there would still be slurring. Best bet is turn the runners/trucks to the same diameter as the rollers. If you have a bolt the exact same diameter as the cores, and put the runners on it in a drill chuck, bracing the drill against a solid block and easing it down to sandpaper fastened in place so the trucks just touch the sandpaper, and gently increase the pressure, stopping to measure frequently, you should be able to remove 1.1 mm of diameter and make the trucks the same diameter as the rollers. I would glue the sandpaper to a flat piece of wood and fasten that firmly to a workbench, and take it slowly.

Bob

Nickel Plate - I used to make the same argument until I drew it out. The fact is the distance of travel is determined by the largest circumference. While the points of each circle will always lineup, the shorter surface of the smaller circle is forced to travel a distance equal to the surface of the larger circle.

Some printers lockup type high rails (roller bearers) in their form, outside the print area. If the bearers are taller than the rails that the trucks ride on, the trucks will be lifted off the rails and the rollers will control the distance of travel.

Sharecropper

As I wrote …

The difference in height between form and bearers (rails) will compensate for the difference in circumference between rollers and trucks.

trucks need to be same size as the rollers, or only a few thou under. then adjust/tape rails to type high or slightly under. different diameters of trucks and rollers leads to dragging the face of the roller across the type- the larger the difference, the more effect. sharecropper has it right

Nope, as long as the rollers are set to the correct height above the form there would be no “drag” nor slur.

Okay, for everyone—the rollers and trucks must be the same diameter or you will get slur or drag. There is no way around this.

The linear vs. angular velocity of concentric circles is a very fairly old paradox, referred to as Aristotle’s Wheel Paradox since he is presumed to have started writing about it. A nice person on YouTube made a simple video about it.

https://m.youtube.com/watch?v=mrVg9GM5h7Q

This topic is also one of the most discussed on the forum, with many people correctly demonstrating this.

Bottom line is—you can’t tape the trucks. You can get away with that on a very small tabletop, because the quality won’t be there anyway, but not on anything a pilot or bigger.

G.F. Schulze
APA 990

wow…. 19 posts to discuss a very simple problem.

The trucks are indeed too large, and need to be adjusted to the right size or replaced to achieve best inking. For me, that’s a simple thing since I have a lathe. I’d just turn them to size.

For those without a lathe, like Fram, it’s still a simple fix. All you need is a power drill, a piece of sandpaper, and a bolt the same diameter as the roller axle.

Put the bolt through the axle hole on the truck and tighten it down with a nut. Then put it into the drill chuck. With the drill running, hold the truck against a piece of sandpaper, and sand it to size. That would take me about 5 minutes per truck…. easy-peasy. It probably took longer to read all of the debates about slurring than it would to actually fix the problem.

The only things to keep in mind are to keep the truck edge square to the face. To do this, you’ll probably want to tack the sandpaper to a piece of wood. Also, check your diameter regularly to make sure you don’t sand away too much…. BUT if you do, you can always bring them back up to size by taping them.

Remember, this is not rocket science…. it’s printing. This particular problem should not hold you up for a long time. Just fix the trucks, and get back to putting ink on paper.

That is fair. Apologies for contributing to getting off track.

Dear friends, thank you for the discussion, I went to the workshop and they turned the runners into the right size 51 mm. To do this, they pulled out a special rod. It turned out that initially the runners were very crooked. The beating on the axis was 0.2 mm.

Fram,

It was a good idea to take them to a workshop for turning.
Seems like you are all set now, Good! Happy printing.

Michael