SM-74 Coating & Sheet Detectors

We are having one heck of a time, hopefully this is just a learning curve. When aqueous coating do you have to make sure that the coating is not going to hit where the sheet detectors are? What is happening is that we can run the fist pass without problem but then no matter what we do we can't get the 2nd side to run. If we flip the paper back over or put in raw material were good to go. Were always getting a late sheet detect with the side with the coating. Were going to cut the lead edge off and try that but it just doesn't seem right that the eyes would be that sensitive.

Thanks
JW

 

Try turning off the auto sheet arrival.

 

the press should take a sheet thats coated overall. as exheidmech has stated you may need to turn off the auto sheet travel and adust timing manually. The midi display should give you an indication of whats happening at the register table and you will act accordingly. For a more detailed view of whats going on you can pull up the feeder section of the press on your cp2000. Any time i have a feeding problem that wont be resolved within a few attempts i opt to not only turn off the auto sheet travel but also auto sheet cocking. In doing this you will gain manual control over both the timing of the sheet to the infeed and also if the sheet is crooked coming down the feedboard. The reduced friction of a sheet thats coated on one side makes it more slippery as it comes down and often needs manual adjustment just to get the sheet into the press. It should be noted that its very important that on the edges of the coating there are no hard coating lines to stick the sheets together or impede its travel. If you can feel with your fingers a raised coating line on the coatings edges then you need to remedy.

 

Thanks, I'll try shutting off the auto cocking as we haven't done that yet. We did shut off the auto sheet timing but could only run about 6800iph or it would just shut off. We printed a job last night with the packing pulled back from the lead edge that seems like it might of done the trick I'll find out for sure here this morning.

 

Also check to see if your front allignment eyes are set correctly. Fairly easy to do this. Inch press to 65-70 degrees with feeder on and no paper. Move headstops to minimum gripper bite (8mm). Put a sheet into the headstops and tape it to the feed board so it cant move. Now move your headstops tword maximum bite, the headstops should move forward but the sheet should stay, you should start seeing a gap. Make sure your safetly button is on at feeder. You should see your front allignment eyes on at the feeder MID as you begin the procedure. As you move your headstops forward the eyes should turn off after they have moved 1.3mm away from the sheet, or when you have moved your headstops to 9.3mm bite, and hopefully both eyes very close to each other. They may not turn off at exactly 9.3mm but should be pretty close. I think its +/- .10mm. Hope this isnt too confusing but this is the easiest and fastest way to check eyes.

 

after turning off the auto modes did you follow it up with a manual adjustment to optimize the sheet arrival time? How about your coating line? you need to be sure that your not laying down a hard coating line for the shingled sheets to get tangled up in. Im guessing here that your problem is with a text weight paper??? If so you need to also be mindful that for all the modern technology these presses are equipped with you still need a well jogged and relatively flat laying sheet to make it into the infeed properly. Ive found it to be not that unusual to have to break an upcurl both gripper and tail when flipping your load over to back up. Especially if your printing on anything less than an 80# coated text weight stock.