sheet register problems

I am running a 2004 D3000 6 color and am having sheet miss register on a regular basis. the sheet doesn't seem get in to the head stops by as much as 1/16th when this happens I very rarely can make it get any better or worse no matter what I do. it was mainly on 40 inch light weight stock. today it was on 23x29 100lb text and 19x25 100lb text. both on the second pass. one on the gear side while guiding to that side and one on the operator side while guiding to that side. any help or advice is appreciated

 

Perhaps your side guides are out of time, and coming down before sheet reaches headstops

 

thought of that but it is usually ok on 1st pass. but I believe it has something to do with the side guide. thanks for your input. I am going to check the timing to make sure

 

Sounds like the wheels on your feeder board may need to be adjusted. How do you set the tension on your side guides?

 

I would look at the feeder forwarding drive roller. Im talking about the one that is split to allow making adjustment to straighten out crooked sheets as they are coming down the feedboard. Both halves of this steel drive shaft couples together. Its this coupling that wears out and causes a jerky motion of the drive roller. The best test would be to adjust the wheel that straightens out the stream to the middle of its travel. Then grab ahold of the wide feed board belt closest to the operator side. Move that belt forward and backwards a few times briskly. While doing this look at the wide feeder belt on the gear side. This belt should move along with the operator side belt the same amount and at the same time. This will give you an indication as to wear in the coupling. if your coupling is worn then post and I will offer you the solution.