hey guys, i've been printing large run jobs and generally figuring out the bugs with this american tempo for the past couple of months. i think i have it pretty dialed in except for an issue with ink lay down on any color following the first. it almost appears like the ink has dried in the screen, but it's definitely not the case because it's almost every pull and it will be a different pattern. i've adjust the pressure and peel every which way which can tend to fix it with enough pressure, but i risk muddy edges and i've been wearing screens out less than 300 prints into a job. two passes will fix it but i know that it should be able to hammer it out fine with just one. maybe more off contact? i don't know, having a hard time wrapping my head around this one, any help is greatly appreciated. here's some pics of the issue-
this is about as bad as it gets and it's only on the left side of the bed, which is nice and flat and very clean.
here is a less crappy one
and one with two passes
OK then. that's not the issue.
There is no real reason that your prints should look like this. So it has to do with your setup.
My guess is your ink is not clearing your screen, then the next print it does but puts down twice as much ink and smooshes onto the back of your screen.
#1 check that your press bed is flat and level.
#2 check that your carriage head is level to your press bed.
#3 check that your squeegee is not warped.
#4 switch the durometer of your squeegee
#5 make sure all your vacuum holes are covered while printing. Make sure your vacuum is working properly.
#6 slow down your print speed
#7 increase your squeegee angle
#8 lower your off- contact, lower your peel.
#9 then raise your off contact, raise your peel.
#10 your screen tension could be crap
#11 if your reg tabs are thick make sure your squeegee isn't running over them or that your boarders are big enough so it doesn't matter.
#12 try a more open mesh.
Mechanically a press can falter on one side like you are seeing. Depending on the way the press is built..
#1 check that the chop is descending at the same time on both sides and not see-sawing down.
#2 make sure both sides are getting adequate air supply and that no air lines are kinked.
#3 double check all the bolts holding the squeegee clamp bar in place to make sure non are wiggling during printing.
#4 Check your pressure micrometers to make sure the are fixed properly and aren't striped. If they are striped you will feel a soft spot when dialing in pressure.
#5 If the gearbox that brings the carriage assembly up and down is a oiled unit make sure there is enough oil in the gear box or replace oil.
#6 listen for any hissing or loss of air during printing. If you hear more air hiss during the print vs flood stroke you may have a damaged line or a stuck air switch.
#7 If your vacuum bed can be raised and lowered make sure that everything is locked in place.
#8 make sure your air line are free of water and that your oil/water condenser trap is empty. Water entering the lines can damaged the chop cylinders if your press has them.
#9 double check all daily/weekly/monthly oil and grease procedures are met.
It's true for hand as well, but the pressures for semi-auto is greater so it's more exaggerated. Sometimes we can purposely shorten an image if reg is wonky by adding some brown paper packing tape to the bottom of our screens. I guess as long as you are consistent with your tape job it will be consistent.
hey thanks squeegee, a great checklist for me to go through. i think i've narrowed it down to a new durometer blade or maybe a stronger vacuum. the blade that's on there is pretty stiff, maybe a 90? every auto press i've ever operated prior has had a 70 so i figure i'll pick one of those up.
This is my 4th auto but my first American brand. I ran through this thing with a pretty fine toothed comb before we started running it. Over about 3 days I pulled everything apart to clean and grease, replacing damaged items like stripped turnbuckles on the peal, and changing the oil in the gear box. We just stretched new screens and found that the same thing is still happening between the old and new screens. Its an older tempo so there is no pneumatics or compressor to deal with. Leveling may help I will check closer that but that wouldn't explain why it works on a new piece of paper yet has difficulty over printing. 2 hits seems to do the trick but that can really compromise detail on a keyline. Faster printing seems to work along with faster floods but either way the first color down is never a problem its always the color overlays on top.
I am concerned with the pressure. as you can see the flood bar here is "backwards" but thats the only way we can get it to run a clean flood with out having so much pressure on the flood bar that it causes the flood bar to remain down and actually printing while the squeegee is running. When we flip the flood bar around we are literally flooding and printing with the flood bar while the squeegee is just coming in behind and cleaning up... though the flood bar has yielded some surprisingly good prints it also tears screens in no time. its like the entire carriage is sitting too low on the head. With the flood bar in this way we barely have to put any pressure on it for it to flood evenly which is also alarming because it makes it tough to print on anything that is thicker than a 200lbs paper.
I am thinking its probably a combination of: peal, off contact, and vacuum strength. I think this because it usually has some consistency or grouping to the placement of these spots in the ink around areas where the ink in the previous colors is thicker (more overlays or bigger fills) which would indicate some moisture related wave in the paper that a week vacuum wouldn't be able to hold flat causing the paper to double touch or not touch the screen at all , depending. But you'd think just hammering pressure on the squeegee would cause it to clear the screen regardless of the vacuum.
thanks for the help everybody we appreciate it and we will consider all this and future input and keep you updated as we continue to work through the issue.