Thread: Ink Dwell Problem ???

We have a CD102 that has a problem with its Duct roller.

What happens is:

While running jobs the dwell starts to slow down gradually, the operator then reacts by increasing his key levels thinking its just the normal reaction when running.

This continues to happen slowly during the job, then heres the funny thing, the operator decides he will up the dwell by as little as 1%, the dwell then shoots forward to its initial value before it started slowing down. This inturn gives a massive difference in color.

Heidelberg guys have replaced the Potentiometer and checked the workings of it, they are also stumped as to why this is happening.

Any thoughts or maybe someone has had a similiar problem???

I have seen this problem before. This is not uncommon if you have alot of impressions on the machine. What happens is the spindle (threaded rod) that the motor turns on the operator side will have less and less resistance over time. some resistance is needed to hold the position selected by the operator. The fix is to remove the entire mechanism on the operator side. It is fairly easy to remove and can be out in maybe half hour or 45 minutes. Remove the spindle and on either end of the spindle you will find an axial needle bearing and 2 races. Replace these bearings and races. You will also find shims at the top of the spindle. These shims will allow you to increase the resistance to the spindle. Usually 1 or 2 shims is enough. Just make sure you can turn the spindle by hand with moderate resistance before you reinstall it in the machine.

Thanks - I will give it a shot and will let you know.