SM-74 Pull Problem

We have a SM-74 that does not like 26" 100# cover, when the pull guide pulls that size the sheet wants to catch on the head stops. (any suggestions?)

 

What about raising your head stops?

 

While you cannot raise the head stops on a SM74, you can raise the cover guide height. It is possible that with the thicker stock the grippers on the swing arm are not opening enough for the thicker stock. This can be done manually in the feeder section of CPtronic or CP2000. If this solves your problem this can sometimes mean there are other issues going on with your swing gripper because this setting is preset when paper thickness is selected. Maybe grippers need to be reset, cam follower is going bad, pretention is off, etc. Usually a tune up of the swing gripper solves this problme.

 

Dont go that far, exheidmech. I'd check simple things first, like "is the bloody servomotor for opening the swing arm grippers working?" and "are the sheet smoothers maybe breaking the sheet?" And the most simple of all "does the printers enters the correct paper thikness , or does he just assume the thikness and enters it wrong?"

 

What are you talking about dont go that far??? I was simply saying to go to the consol and push a button, how hard is that? Yes, that servo can be bad and by simply manually opening the cover height you can see if that motor is bad. If the value selected continues to blink the motor is bad with CPtronic, or with CP2000 if the value does not turn from grey to black the motor is bad. I dont really feel that pushing is going too far in initially troubleshooting this issue.

 

The swing arm does open enough for the thicker stock, the trouble is on a 26" sheet the sheet gets pulled against the lower pad or the head-stop before the swing arm grabs the sheet causing alot of bounce or the sheet not pulling.

 

Ok, there is a couple things you can check. First make sure your head stops that the head stops for the 26" sheet you are using are turned on and touching the front edge of the feed board. You can get a feeler tape or a thin stip of paper to ensure the head stop is touching the feed board by putting it between the stop and feed board, the strip of paper should be tight when the head stops are all the way up. If this is not happening you have a bad cam follower under your feed board. Next you can check the height of the feed board to the very front of the your infeed where the head stops touch. The feed board should be slightly above or the same height as the infeed in this spot. This is most easily checked with a razor blade. Also make sure you lifting time on your side guide is ok (66 degrees) and your closing time on your infeed grippers is ok (71 degrees with sheet thickness of .10 and feeder on). If all of that is ok you should have a icon in your format screen which allows you to select the side guides to be shifted to one side or the other slightly for this problem. If I remember correctly the icon looks like a +/-, its in the same screen you select your sheet length, width, and thickness.

 

Didn't mean to desrespect you, sorry. I just got the impression that you took the "simple things" for granted. I' m sure you have met customers that have failed to notice a malfunctioning stepmotor, even if its simple to check

 

Gene, Do you mean that the sheet is jamming the side of the head stop as it's being pulled to the side guide? On a SM 102 we are able to bow the head stops forward or back. Does the SM 74 have that option? If so, perhaps the centre stops are too far forward allowing the edge of the stock to travel just past level with the outer stops.

 

When you say "catching", are you saying the corner of the sheet is catching on the front lay nearest the side lay when the side lay pulls the sheet over ?

 

Exactly Mr.H

 

You may have to run that particular paper slightly off center, so it doesn't catch the lay.

Regards.

 

im not familair with a speedmaster 74 but i know that on a 102 and a 72 that the placement of the headstops on both the 72 and 102 are placed so that the comon sheet sizes are usual clear of these issues. 26" is very common. you might want to check on the surface of the knurl on the segment under the sideguide roller. ive noticed a tendancy for the sement to wear in them highly used areas particulary if the press has run the same size over the course of many milions of impressions