Effect of incorrect form roller diameter

[cmcfarling]

We recently sent out some form rollers for a Presstek 52DI to be resurfaced. After the fact I was doing some checking and discovered that the OD's were ground to specs of a Ryobi 3404 press. The presses are virtually identical but the specs the roller company was going by were slightly different than what the 52DI manual shows. So we now have rollers that are slightly larger by the following amounts:

Form1: +.002"
Form2: +.005"
Form3: +.003"
Form4: +.029"

As you can see the difference for rollers 1-3 is very small although form 4 is almost 1/32" larger than spec. What problems, if any, might this cause and should I be concerned?

 

[junker1984]

CMC - The 2,5, and 3 thousandths variance is so slight you will experience no ill effects, the 29 thousandths variance could cause a striping issue, or the roller may stripe acceptably but may not lift off the plate fully. On larger format Heidelbergs, .5 millimeter (@20 thousandths) plus or minus doesn't affect printability. Good Luck Steve

 

[bob120348]

President, Stealth dampening manufacturer

President, Stealth dampening manufacturer

The first three rollers are well within tolerence for rubber rollers. Your last roller at .029 is actually .0145 per side and should not be a problem.

 

[[email protected]]

Presstek 52 DI rollers

Presstek 52 DI rollers

I am surprised the Presswreck cops on the site have not emailed you or PM’D you for wanting to use non Presstek parts. A set of 52 DI rollers is only about $13000.00. LOL.
Ryobi made rollers are ok but there are USA companies that make better quality and the settings hold true. One I recommend is Litho Roll and second is Syn-Tac. In fact the ptek boys offer Syn-Tac under the VMC name for the 3302 series.
If you use non Ptek rollers won’t they cancel your service contract? They like to use their leverage since it is such a proprietary machine. Imagine Heidelberg or other printing press manufactures doing that.
Make sure the durometers are right also.
Good luck with your rollers
OG

 

[cmcfarling]

Reduced sale price is only $12500

Service contract is already canceled. A quick internet search shows a full set of new Syn-Tac rollers would be around $7500, does that sound about right?

Note that the rollers we have now are not made by Ryobi. We sent the old rollers to a company to have them re-covered (old rubber stripped, new rubber put on the core). I mentioned Ryobi because apparently they sized the new rollers to specs they had for a Ryobi press. Is there any reason to be concerned with re-covered rollers?

Speaking of durometer, the new ones measure about 35 while the Presstek manual specs 30. Should that be much of a concern?

I'm getting involved in this project after the fact and I'm trying to clear up some things that possibly weren't thought through or researched to the fullest extent.

 

[[email protected]]

Presstek

Presstek

My only advice at this point would be to install one set of rollers in the last unit, set them to spec and see how they perform. If all looks good than you are good to go.
Both roller diameter and durometer are critical. Especially in a copier type of machine such as the DI that uses chilled oscillators and special plates rather than a toner and drum output.
I have worked on Ryobi presses where the owner had rollers made by some local people or a small roller company and I have seen problems in performance and output. I would never trust an operator’s manual for proper roller diameter or durometer specs. Especially when the machine is designed as a consumable burning engine such as the DI. Maybe a typo was made….wink.
The right way is buy a few Ryobi rollers for that press NEW and send them to a large roller company like LithoRoller, Syn-Tac, Botcher etc, for exact matching.
I would recommend you call Syn-Tac or Litho Roll and discuss this with the tech support people there, they would love your business and it would allow other DI users to have a second source for rollers and be competitive with pricing.

Good Luck

OG

 

[Disappointed]

Hi all, interesting stuff here,

does anyone know why roller life is so bad on a DI?

The only reason i can guess is that the lack of alcohol or fount is causing them to dry out and shrink prematurely, reasonable idea or not?

Ours seem to last about 1 year then rapidly shrink.

 

[Happyprinter]

We run a QMDI Plus and so far after 2 years and occassional restrip our rollers are performing great. Maybe were just lucky because I have heard other printers talk about short roller life on the DI's but, we have not had this problem and when the time comes we will send them out to be recovered. We have a Komori 26 that we have had great success over the years in using recovered rollers. Granted, 2 different presses and printing styles but, for the cost savings and past performance it's worth it.

 

[turbotom1052]

im thinking that as long as the larger diameter rollers can be backed off enough to get the correct stripe to both vibrator and plate then you will be ok

 

[Disappointed]

Ok, i can update my post above now based upon experience, roller life on a Di is not short, it was caused by a batch of rollers that were of substandard material, since we had a new set fitted about two years ago, they have given excellent service with minimal readjustment at each service. The material is critical i feel but as we get a very good deal with our contract, i have no need to go looking elsewhere for roller substitutes.

Especially in a copier type of machine such as the DI that uses chilled oscillators and special plates rather than a toner and drum output.
OG

This makes no sense at all, have you ever used a Presstek Di? If you did then you would know that they are just bog-standard litho presses with a bit of technology added. There is no resemblance to a 'copier' as they do not have a scanner interface and have a minimum run of around 500 sheets, they still have plates, blankets, ink, impression cylinders and stream feeders. Chilled oscillators? So what, many quality presses have chilled rollers, we also have chilled ink ducts too.

I think the thing that causes most of the Di negativity is the fact that i could put more quality printed jobs down on the floor every day compared to a standard (same format) press and with a lot less effort that there is some jealousy around amongst supporters of the older style machines. I know which system i would spend my money on.