Loss of pressure on CD74

We recently has a slight loss of pressure on our 2010 CD74. We went from 16 mils. under the blanket to 18 mils. Any ideas?

 

are you relying on what the packing has printed on it or are you measuring it with a micrometer?

 

When printing a dot screen on any substrate, we get a mottled effect when using 16 mil packing. Back in the beginning of 2016 this wasn't the case. By putting 18 mil. under the blanket, the effect dissappears. This leads me to believe that there is a lack of contact between the plate and the blanket. We mesured with a packing gauge and with 18 mil. the squeeze is spot on..(?) Kind of strange. It could be just the new plates we're using, Aquasolve or something like that, they're not developped.

 

Could the plates be under 0,30 mm say 0,28 hence the change of squeeze?

 

It is what I suspect. There is also the fact that the automatic water purge on the air compresser wasn't doing its job. I opened the valves manually and proceeded to wash the floor with the water that came gushing out.

 

We've been using the same box of packing since the beginning, no, I haven't measured it yet.

 

Did you try dry solid breakaway? Could be jacket issue and not squeeze of plate/blanket

 

If its a straight press than it wont be a jacket issue, as turbotom mentioned you must measure packing with micrometer to get better idea.

 

Does your problem go away when you increase back cylinder pressure? Maybe confirm that the pressure between blanket and impression cylinder is ok. Very quick and easy check. Set paper thickness to .10mm, put unit on impression and use a long .35mm feeler (.014"). You should be able to slip the feeler between blanket bearer and impression cylinder with a heavy drag.

 

We tried increasing the pressure, but it changed nothing. Be it offset or coated stock, the result is the same. Since I added 2 mil. squeeze, the problem has gone away. Although we haven't changed the packing on the coater so I noticed we have to increase the pressure a bit more in that head compared to the other units. Definitely something screwy here.

 

I think were it a jacket issue, the squeeze would be uneven, a contour around the 25 in. format. This is not the case.