Auto impression settings on CI press

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Re: Auto impression settings on CI press

Postby Leadpress » Wed May 08, 2019 10:52 am

Barb, it sounds to me like there should be a control on the press that guages your cylinder repeats. For example, if you're running a 75 tooth, then you're guaging the press before you run to that 75 tooth gear. You're smashing on the stock too hard, but you're anilox is too far away, that's why you're getting low spots when you back off of the impression. you're cylinder isn't guaged properly. You need to set the print to where you're cylinder touches the anilox first, but barely enough to where you're plate receives the ink but no impression on paper, or both at the same time, depending on the press. I would check where you're cylinder is in relation to the gear size and setting for that gear size on the press first. I also get the feeling that you're using your manual control to print with and then somehow switching to auto, causing a double impression. I don't know. But put you're cylinder in before printing and look at it first, bring it down on clean stock and clean anilox and guage it. Zero out all your settings, so you have enough play during your process!
Last edited by Leadpress on Wed May 08, 2019 11:47 am, edited 1 time in total.
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Re: Auto impression settings on CI press

Postby Leadpress » Wed May 08, 2019 10:55 am

Guys, I don't think this is a plate mounting tape issue, I think it's a guaging issue. Someone is not guaging the station to the tooth size before printing. Is it a Mark Andy?? Can you tell me what process you're taking to get to the printed image?
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Re: Auto impression settings on CI press

Postby Frank Burgos » Thu May 09, 2019 5:51 pm

Hi Leadpress,

This is a wide web CI press with auto-register. The likelihood is that we're talking about speeds close to 1,000 fpm. So, there's a combination of wide image plus high speed = impact that lifts the cylinder off the films and anilox, causing skips. In this scenario, the firmness of the mounting tape and the design of the images become huge factors.
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Re: Auto impression settings on CI press

Postby Gorilla Printer » Thu May 09, 2019 11:15 pm

Frank Burgos wrote:Hi Leadpress,

This is a wide web CI press with auto-register. The likelihood is that we're talking about speeds close to 1,000 fpm. So, there's a combination of wide image plus high speed = impact that lifts the cylinder off the films and anilox, causing skips. In this scenario, the firmness of the mounting tape and the design of the images become huge factors.


You've brought up an important point Frank - speed.Does the image consistantantly print good at a lower speed?Are there misses?Because if it does then yes hardness of mounting tape or T.I.R of the print/anilox cylinder could be at fault.Does it only happen on one station?Interesting indeed.
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Re: Auto impression settings on CI press

Postby Gorilla Printer » Sat Aug 31, 2019 1:51 pm

Hi Barb
It has been a while.Any upddates on the root cause and fix?
Cheers

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Re: Auto impression settings on CI press

Postby barb » Fri Sep 20, 2019 2:02 pm

Hi guys,

I'm currently waiting on more information from our tech support on testing for TIR issues.

Aside from impression problems, would TIR issue also cause problems with register settings?

For example, let's say you have a machine that can print 1000mm wide image but due to some other nonsense in company you end up printing mostly 500mm wide jobs and when the time comes you finally get a job that's 900mm wide and you can't possibly set the register on one end. Could that be also be the caused by faulty sleeves?
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Re: Auto impression settings on CI press

Postby Frank Burgos » Fri Sep 20, 2019 2:31 pm

Hi Barb,

Yes, and you'd want to rule that out right away, rather than messing around with remounting and all that.

Measure sleeve diameters precisely, at multiple place across the sleeves. Use a dial indicator to measure TIR. Investigate whether the same tapes are used on any colors that present registration challenges.

Per FIRST 6.0, acceptable TIR at 1,000 fpm = 0.00020". That is not much, at all. That said, it's mainly because of vibration introduced by the eccentricity of the sleeve. You'd probably be OK with 0.00050", and I would be surprised if they were that true.
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Re: Auto impression settings on CI press

Postby barb » Fri Sep 20, 2019 2:40 pm

Thank you Frank!

That would definitely confirm that I need to proceed with this testing.

What do you mean by same tapes - same type of hardness or?
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Re: Auto impression settings on CI press

Postby Frank Burgos » Fri Sep 20, 2019 2:53 pm

Same exact tape, period. Different hardness or different supplier.

The reason I ask is that different tapes can perform differently, including impression depth and thickness of tape.

At this point, though, finding out is part of the investigation. I am not suggesting you make any changes, yet, even if you discover that different tapes are used. You just need to know as part of the investigation.
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Re: Auto impression settings on CI press

Postby barb » Fri Sep 20, 2019 2:56 pm

Correct. I already found out how tape hardness can affect registration problems due to thickness deviation. Not all the time but there were cases.

Yes, this TIR testing is now priority.
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Re: Auto impression settings on CI press

Postby Frank Burgos » Fri Sep 20, 2019 3:12 pm

Awesome. We all look forward to what you find.
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Re: Auto impression settings on CI press

Postby Gorilla Printer » Fri Sep 20, 2019 3:58 pm

barb wrote:Hi guys,

I'm currently waiting on more information from our tech support on testing for TIR issues.



Hi Barb
You can actually do the test for TIR yourself on the machine to see if you're on the right track.It's quite simple and quick .Buy a magnetic dial test indicator and set it up on any convenient part of the machine.You can usualIy tell by spinning cylinder/anilox and measure both ends and middle on cylinder.With the anilox usually around the dead band area is enough.Mind you if you tested in the middle of the anilox i don't believe the guage will mark it as the pressure is so light. I have also used it with the machine running at 5 mpm .Our maintenance workshop has one.We used to have one of our own in the printing department.All print shops should have them on hand .Handy to have-not that expensive either.

Gorilla

Good luck
Last edited by Gorilla Printer on Sat Sep 21, 2019 5:12 am, edited 1 time in total.
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Re: Auto impression settings on CI press

Postby longtimefan » Fri Sep 20, 2019 9:32 pm

Gorilla Printer wrote:
barb wrote:Hi guys,

I'm currently waiting on more information from our tech support on testing for TIR issues.



Hi Barb
You can actually do the test for TIR yourself on the machine to see if you're on the right track.It's quite simple and quick .Buy a magnetic dial test indicator and set it up on any convenient part of the machine.You can usualIy tell by spinning cylinder/anilox and measure both ends and middle on cylinder.With the anilox usually around the dead band area is enough. I have also used it with the machine running at 5 mpm .Our maintenance workshop has one.We used to have one of our own in the printing department.All print shops should have them on hand .Handy to have-not that expensive either.

Gorilla

Good luck



Yes!.

Couldn't think of the name but used them in olden days of steel cylinders
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Re: Auto impression settings on CI press

Postby barb » Tue Sep 24, 2019 2:55 pm

Ha, you guys are full of tricks! Thanks, I'll forward the shop list to my boss :smile:


Aside from TIR issue, I can't find where I read it but someone also mentioned auto settings may end up crappy if the operator doesn't have a feeling for it, this stuck very well in my thoughts and today I've confirmed it!

May seem stupid to you but I was so damn happy afterwards... Standard procedure, machine auto sets the impression and operator is like 'there you go, your sample'. The problem is, dot gain is horrible on minimum dot area which was almost 50% of the design. The operator of course has no idea what to do, we were already on minimum viscosity and highest line anilox possible.
And then this thought hit me and just said to him to move over so I can try something :smile: Pulled of the plate-substrate impression waaaaaay off to the point it went missing and then just slightly increased the anilox-plate impression. The result - fantastic, perfectly shaped minimum dot. After half the run, check up - all clean and good!

Thank you all!!
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Re: Auto impression settings on CI press

Postby Gorilla Printer » Tue Sep 24, 2019 9:03 pm

barb wrote:Ha, you guys are full of tricks! Thanks, I'll forward the shop list to my boss :smile:


Aside from TIR issue, I can't find where I read it but someone also mentioned auto settings may end up crappy if the operator doesn't have a feeling for it, this stuck very well in my thoughts and today I've confirmed it!

May seem stupid to you but I was so damn happy afterwards... Standard procedure, machine auto sets the impression and operator is like 'there you go, your sample'. The problem is, dot gain is horrible on minimum dot area which was almost 50% of the design. The operator of course has no idea what to do, we were already on minimum viscosity and highest line anilox possible.
And then this thought hit me and just said to him to move over so I can try something :smile: Pulled of the plate-substrate impression waaaaaay off to the point it went missing and then just slightly increased the anilox-plate impression. The result - fantastic, perfectly shaped minimum dot. After half the run, check up - all clean and good!

Thank you all!!


Hi Barb
It's good that you have a good result.But to tell you the truth I would have expected a manual reset to have been done before you posted the problem.Because it is quite a basic fix.I was assuming that when you posted the problem here that the pics etc..were the best result you could get.I didn't know that no one had tried resetting inkers/impression.
I'm assuming others here thought the same.So by assuming the basics have been done properly,we start moving on to TIR ,hardness of mounting tape etc. TIR might not be an issue now?

Well for starters ,you know the auto impressions are out now.They can be reset.Auto impressions are a good science but they still aren't exact.You can understand there will be a lot of difference in pressure printing a screen vs printing big solids.So there might need to be tweaks in the set sometimes.Our guys understand this and adjust accordingly.
I don't work on a press that automatically sets impressions ,but the press next to me does,it auto registers too.When I see them first setting up the press it is running between 40 - 60 mpm.If it was me I would let it set it up at 40 mpm ,reason being, that is what I slow press down to when locking out extrusion line splices.But after the impression and inkers are set I'd probably up press speed to 50+ to tweak registration.Which is exactly what I do now on my press.

One other thing is,on my press there is an auto setting where the press puts on and take off impression and inkers according to what speed you are running.I'm assuming all auto impression presses would have this function as well.I would make sure this function is working/set properly .One should know though as you would be getting build up /missing/impression/squash issues after speed changes.

OK thats my two cents
Congrats on the results and good luck

Gorilla
Last edited by Gorilla Printer on Tue Sep 24, 2019 11:24 pm, edited 2 times in total.
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