Coating Problems

[bdk]

Have 5 COLOR L 28 w coater - Having problems with getting the best from the coater. Set the 3 roller system
to the book specs. But this thing should not have so many problems! Ideas... best packing... best roller settings ... Have Perry dryer-optimal settings?
Run the coater speed @ 33 for gloss and about 40 for satin
with the ratio for both @ 160. Any input would be
appreciated.

 

[Bruce]

bdk, what kind of problems are you having? I run a 528L w coater also. I have one problem but I'm not sure what it is. I think its a shock or gap streak. I tried all sorts of settings (set and ratio) but no difference.
Also set to specs. Here are what I set the coater to: speed 30, gloss and satin. Ratio 180-200. With a 3 ply .67 coater blanket I pack to .47. Perry dryer 1st pass set at 100 degrees. Back up at 90 degrees. Hot air at 450.

 

[bdk]

Bruce - Thanks for the reply. I run the same blankets
.67. Packed about the same .46. Run the heat at 105 1st pass, 95 2nd, with hot air @ 400. Where is your "shock"
or gap streak located? I sometimes notice something similar about 3/4 of the way back on a 19 x 25 sheet.
Looks like it just ran out of coating. So I turn up the coating roller speed and the coating ends up tailing off the back of the sheet and the loads stick at the tail. (Cutter operater loves me for this) Still doesn't solve the problem.
It's not real noticeable. But I notice and it shouldn't be there. ??

 

[Bruce]

bdk- That sounds about right on the gap(?) streak, 3/4 back of the sheet. When I first started working for this company we had two komori's, a 628 with coater and a 528 with coater. Both presses had the same problem with the streak. We had customers question it and were not very happy.
So we contacted komori about it and they sent a komori tech from Japan to take a look. It was hard to understand him (accent), but he did continue to say -anilox,anilox,anilox...So this lead me to believe its a inherited problem with this press. Oh I forgot to mention that we bought a new 528 with coater and guess what? Same problem. Anyway we have noticed that different coatings from different companies would not show as bad. We get by. Bdk, can you be more specific about the problems your having as posted on you first thread. Komori demonstrator (Paul), Richard K. if you read this can we get your input on this problem?

 

[bdk]

Bruce... Thanks again for the reply. Our shop has moved from Heidelbergs to Komoris. My L28/5C is about 6 years old, in our place about 5 months. The 6C 40 (Komori) is about 4 years new. It has a Harris and Bruno (sic?) coater. The thing is sweet! Vaccuum chamber, one dimpled roller,
every sheet has the exact same amount of coating on it. The pressmen on it love it. I have never worked on a press with a real coater. (We have run "fakquious" coating, as one of the nite shift pressmen loves to call it... ink train coating.) Anyway I'm finding myself coating way more jobs than I used to, the product is better. The results aren't. Coating 12.5 x 19 sheets with minimal
trim with crop marks that bleed into the color bars is ...
well...a challenge. ( The press was upgraded with a PDC Lite Scanner, so the coating on the bars affects the scan results.) I'm thinking the coating metering roller needs replacing as the adjustment settings are about maxed out.
So my problem is getting sheets with nice even layer of coating without having tailing off the back of the sheets.
So thanks ahead of time for any replys.

 

[bdk]

Okay, had the same streak again, satin coating on dull stock. It's almost exactly 16 inches from the lead edge of the sheet. The streak looks like it has less coating in that spot, it's not as satin as the rest of the sheet. It is a bump
streak caused ?? from I think the edge of the aplicator roller when it contacts the the coater blanket. So I think that setting needs to be less. Any ideas? But think I'll try that for now.

 

[5150pressman]

Satin, matte, dull coating will leave a streak.
Sometimes a better form roller for the coater will help.

You can also try this and it does help.
Since the coating unit is 3 rollers. Take an old ink form roller (The A position one which is the biggest) and put it between the rubber coater form roller and the metal roller. This will help carry more coating.

THIS IS THE IMPORTANT PART.....you will need to put something on the end of the ink form roller bearings to the keep the roller from moving to the side and leak/drop coating outside the pan. You can take a piece of think rubber hose that is the same size as the bearing and have it cut so the ends are to the frame.

good luck.

 

[Bruce]

adding roller to coater

I to was given that tip to try out by a pressman from the SF bay area. Humm. I never did for fear of it flying out of the unit and causing damage. I'll try it next time I have a job that it might help. Bdk, let me know if you try it. Thanks for reminding me about that tip, SF area pressman.

 

[carolusquercus]

Probably too late to reply to this one. BUT we had the same issue and it was solved by getting a very ROUGH textured coating roller from Bottcher Roller. The rougher texture carried more coating and hid the streak quite well. I would contact your roller manufacturer and see if they think they could help you.

 

[bdk]

Thank you for the reply. I had heard that before, it's good to know that the textured roller is a solution to the problem. Never completely got rid of the problem to any degree that would qualify as a first rate printing job.
We have since moved on. Komori LSX 5 color (23 x 29) with Harrison Bruno coater. BRAND NEW!!
First NEW one for me. It's GREAT. It's NEVER to late to reply because there is always someone else out here
with the same problem.

 

[Lignum]

Probably too late to reply to this one. BUT we had the same issue and it was solved by getting a very ROUGH textured coating roller from Bottcher Roller. The rougher texture carried more coating and hid the streak quite well. I would contact your roller manufacturer and see if they think they could help you.

A rough roller will definitely hide any patterns in the dull/matte coatings, but as far as the streak goes, we pack our blankets at .48, and run the impression cylinder pressure as high as it will go and still print smoothly. Usually as a rule of thumb for me is if we are running 80# cover, pressures set at .20, and the coater set at .30. Another thing we do when streaks occur is use thinner packings instead of the normal .010's and .008's, we use .005's and that seems to help out a lot.

Another thing I did not catch is what kind of stock are you running when this streak occurs?

 

[stevesamuels]

We have a Komori 28 five colour with coater which is about 10 years old now and we have been getting problems with the backup on a work and turn section not drying properly and it seems to be wet causing set off and sticking, plus the stacks look really uneven. We have had the Baldwin dryer serviced, tried different temp settings but it does not seem to have cured the problem. Any ideas from anyone is welcome. Thanks

 

[Kaoticor]

There are several things that could cause this. Here are a few remedies which could vary depending on your problem.

1. Check exhaust to make sure air is being vented properly.
2. Make sure the hot air knives are functioning correctly.
3. Check impression to blanket height.
4. Run lower coating feed.
5. Packing should be cut sharply. If you are using several packing sheets, remember that when you wrap them aroudn the cylinder, the top packing sheet will need to be cut slighty longer. If all of your packing sheets are cut the same length and you are using several, this could create a steady drop off from the aplicator roller.

Also, make you have a good ink/water balance. Might not be the most obvious thing, but if you have run with your ink console off while coating by accident, you know how much trouble this can cause! Hope this helps some

K

 

[Yorkshire Gripper]

We have a Komori 28 five colour with coater which is about 10 years old now and we have been getting problems with the backup on a work and turn section not drying properly and it seems to be wet causing set off and sticking, plus the stacks look really uneven. We have had the Baldwin dryer serviced, tried different temp settings but it does not seem to have cured the problem. Any ideas from anyone is welcome. Thanks

Is the coating dry after you print the first side? If yes then it could be that coating re-wetting when you do the back up. Run the first side with the minimum IR setting you can get away with and the airknives set with high volume but not so high temperature. On the back up run with no IR, there will already be plenty of heat energy in the sheets already. Does the problem happen if you leave the sheets overnight before backing up? What kind of coating are you getting the problem with?

YG

 

[George Talpo]

Maybe time for a new one

We have a Komori 28 five colour with coater which is about 10 years old now and we have been getting problems with the backup on a work and turn section not drying properly and it seems to be wet causing set off and sticking, plus the stacks look really uneven. We have had the Baldwin dryer serviced, tried different temp settings but it does not seem to have cured the problem. Any ideas from anyone is welcome. Thanks

I know that this isn't really the kind of reply you're looking for, but it might be time for an upgrade. We had a 14 year old Komori that was acting up. We decided to scrap it and upgrade to a new one and we couldn't be happier. Works like a dream and is really worth it. The fact of the matter is your Komori isn't getting any younger and it certainly isn't getting any better.

George Talpo- www.lasvegasprinting.com