Ink sweep settings

[prepper]

Hi, trying to determine whether our sweeps are too high or not? Light coverage, say two 2" spots of yellow on a 19x25 sheet and the pressman has yellow sweep set to 90 out of a possible 93 max setting. Heidelberg 72SP press, seems like average sweeps for all inks is 70-80, even though we are only printing 4 photos that are 3.5x4" on the whole sheet.
I'm suspecting that he runs the sweeps way too high which causes him to have to keep increasing the water (which he's always saying he has to do that), and is in part, the cause of some of our mottling problems.
Any insight? Seem too high or am I off base in thinking that?
Thanks

 

[Meny]

if it is right or wrong you can tell by the actual density on the sheet.
could have to do with press condition , water conditions , roller condition ,roller setups, plates and more.
at the end of the day , it is the final result that matters , not the way to get it.
How is the result you are getting ?
do you check density ? it is at the right tollerance ?

 

[prepper]

Sweeps

Ok, guess my question is more a difference between operators, one pressman increases density by increasing sweeps, other pressman just opens keys a little where needed, difference is the one increasing with sweeps has to keep upping the waters also to keep the rest clean where as the other pressman doesn't.

Minimum ink, minimum water is best right? He chases startups by increasing and decreasing the sweeps too much I think. Density too high he shuts sweeps off to get ink out of press, then it drops too low and he ups sweeps again to bring it back up.

Are large swings in density normal on a startup? Ours go from 30-40 high down to 30-40 low, up to 20-30 high, down to 20-30 low, up to 10-20 high, down to 10-20 low, up to 5-10 high, down to 5-10 low and then finally settle in the middle somewhere between 2500-3000 sheets later. This isn't an isolated run, I've been there and seen it on run after run over the years, yes years, 20+.

Pressman has been told he's chasing it way too much, working way too hard at it, adjusting too quickly before the changes happen, but refuses to change his methods. Uses 1000-1200 startup sheets each run. Has been told to do 100 sheet charges, make adjustments and 2 or 3 of those should get you pretty close, provided you make the right adjustments I guess. He starts out at 3000/hr, speeds up in about 500/hr increments as he goes thru his adjusting process, has to adjust register also as speed increases, and has to keep adjusting densities also because they change with speed changes somewhat, right?

This is all on a mid-90's HEI 72SP that is in excellent shape, we've owned for 14 years and run very low volume, 1 shift, 4 days a week, not running every day either. All on 100# text, gloss paper, aqueous coated. No uncoated and very little sheet size changes. No ink presets though.

Any suggestions? Is this normal? Way off base or no?

 

[jaed]

It's kind of hard to explain all of the reasons behind whats going on but a tip that seems to help most people is... once he's up to color and running have him cut back on the water untill the lead edge of the plate starts to tone up stop and check the densities of the inks, for example when the magenta is toning and you check the density and say it's 1.75 or 1.80 and your target has been set at 1.50 cut back on the ink (sweep or keys) untill your density is 1.50 again. Then start over and bring the water down again untill it tones and check the densities again. If your ink is around 1.50 now and it's still toning bring the water up slowly untill you get a clean lead edge of the plate. Once that is done your water settings really shouldn't change that much unless you go from very light to very heavy coverage.

I follow a group of guys who run the press for 8 hours before I come in and I won't touch the press untill I have gone through this process and know that my waters are set correctly.

hope this helps

 

[luke]

I'm given MAX 150 sheets extra on most jobs this is to be for make ready and overs for bindery. If it's a booklet, it can be as little as 50 sheets for overs per form.
I try save sheets to use as run ups but not much can be salvaged from such a piddly amount of overs.
Last long run I had was 140000 imp, on a low pile press so many stack changes and I was given 500 sheets as overs, to be used as colour makeready, overs for stack changes & to ensure there was still overs left for bindery issues.
Any printer knows this is un realistic.

As for the high sweep - low duct key opening VS low sweep - high duct key opening. It is a personal preference, some printers run with sweep in the 70%+ range and low duct key opening as it can give you faster density changes, but it can have you over shooting your target densities if your not careful.
Somewhere in the middle is best for sweep on medium coverage jobs, as long as you can achieve this without duct keys needing to be wide open.
Running low sweep - high duct key opening settings I find even worse for giving you density control.

The only reason I can see that printer A is having to increase his waters, where the other printer who controls his ink the other way doesn't have to increase water is that printer A is feeding too much ink per image area and is in an uncontrolled state.

 

[Meny]

sounds very bad to me...

how on earth can you make money this way ???
go @preset@ and save a lot of time & paper , and get better results faster and cheaper.

 

[prepper]

The only reason I can see that printer A is having to increase his waters, where the other printer who controls his ink the other way doesn't have to increase water is that printer A is feeding too much ink per image area and is in an uncontrolled state.[/QUOTE]

Yes, that's what I'm thinking also, because it's mostly low or light coverage work. On one job that only had 4-color in 2 small 1" spots on the sheet he was running yellow sweep at 90. His general complaint is that he is always having to increase waters a lot as day goes on, he thinks it's because press is warming up, ink is flowing better and that is probably somewhat the case, but if you are applying higher than needed ink on low coverage doesn't it also require then that you would have to run higher amounts of water to keep all that non-image area clean?

 

[FSA]

prepper
Your operator needs to learn what an ink/water balance is. High sweep is for a large image coverage. Small amount of image is a low sweep. At Heidelberg school they teach operators to start at a sweep of 50 or half way is a "starting point", that is for average image, more sweep is for more image and a sweep of 20 for light of very little image. Now water, that is where experience really comes into play. You have to know what the plate needs for water and how much will be soaked up by the paper, coated less uncoated more, how old are the rollers in the water system it makes a difference. On the 8c 102, coated paper new or newer rollers water at 17% - 22%, where the uncoated sheet needs to be closer to 28%. I do not have to change my water setting and ink lays down smooth, less water means more ink. But your operator says it's scuming so he turns up the water to clean it up, why not nip down the ink and only give the water a shoot, thats what that button at the front of the press is for, that no-one uses.
It is very hard to brake some operators bad habits, some never change, too bad for them. I go into some shops and help owners fix issues and it does end in termination sometimes, cause some operators think that I've been doing it this way for years and that is the right way, until someone shows them up, like me, then attitude usually kicks in.
prepper you have a issue with an operator and his methods, I thinks he needs to be put at the back of the press and shown the right way.

FSA

 

[pressman57]

Yeah I agree that the sweep's way to high and as a consequence he's chasing the ink with the water until he has an emulsified mess in the train. You only need a sweep of nintey with solids, and then only when the ink lacks enough pigment.

 

[glenner]

It sounds like you have a pressmen that does it his way or the highway .We have A komori 6 color + coater .Let just say that if we have A 50% coverage job ( note our ball or sweep goes up to 99 and ink keys go up yto 99 also ) If the job is 50% coverage on 19x25 stock our press is 29 inch . We would start our sweep at about 25 and our ink keys at about 22 and then go up or down from there .We always keep our sweep 3 to 4 numbers above our key settings that is for all pressmen ! and it seems to work just fine

 

[turbotom1052]

You never did mention what kind of experience your pressman has? Is he a guy that just got promoted from the broom? Is he a feeder operator that just got bumped up and is still learning? Or is he someone who sold himself as an experienced pressman, that your paying top dollar? If its the last then it sounds like you've been had. If its either of the first 2 then I think some training is in order before you judge him too harshly. Do you have anyone on your staff to properly train the guy, or are you just hoping to get him to do things your way by showing him this thread and saying I told you so? Fact of the matter is this.... Your Heidelberg 72 has an over engineered inker. A Speedmaster 102 of the same vintage, which can print a sheet 8 full inches longer from gripper to tail, makes do with all the same diameter rollers as your SM72 The inkers are also configured with the same amount of rollers and position. That being said, it would stand to reason that ink feed into each units inker should be initially set up with a bit less flow. How you arrive at that flow is often a matter of a pressman's personal choice. You could either run lots of fountain sweep with very tight key setting on each zone, or you can run a very open fountain with the sweep set very low. Or you could go somewhere in the middle.
Bearing in mind what I said about the 72s inker a compromise needs to be found. Ive mostly run full format Speedmasters where my preference was to set up my fountain keys where I could run my sweep starting out in the 45 range. When i wound up on a SM72 I quickly found I had to compensate. On the 72 i would try to both tighten up a bit on the key settings, in addition to dropping the sweep down to 35 or 40 range. Once I had my sweep set in the 35 to 40 range Id try to leave it there and make overall ink adjustments whenever possible with each units overall key percentage setting.
If the guys been around awhile running presses my guess is that he is probably not gonna be receptive to you telling him how to run the press. If he is a rookie, then perhaps a little training is in order from a seasoned pro. Good luck in getting stuff right however you go. You will be needing it. This is the very reason why a press pro gets paid the top dollar that so many company owners balk at!!!