Technotrans chiller qmdi

the chiller on the 46 classic di is running for 10 seconds, then stopping for 20 seconds, then running again. it keeps doing this over and over...the pump seems to be working but no matter what temperature I adjust it to it just keeps doing the same thing, it is running between 26 - 28 degrees as it does not stay on for long enough to cool the machine down. any ideas before i call someone much smarter than me?

 

Make sure the water pressure is at 2 - 2.5 bars. Clean the condenser out, if it is full of powder and paper dust it will throw the thermal overload because it cannot draw enough air to cool itself.

 

Thanks Paul, I thought the bar pressure should be 1 - 1.5 when machine is off and 3.5 - 4 when machine is running.? that is according to manual I have.

 

Your right on the bar pressure. We used to put it at 2 to 2.5 with the power off because it would settle down after a few days to 4. The blow off valve will open at 2.5.

 

Got it fixed, it was my original thought, it was out of gas, got it redone, works like a charm, so after 30 million impressions the gas was gone, but i think it also had a small leak which they fixed. Thanks Paul for your reply.

 

This may or may not be chiller related as we have played with all temps.
Only on gloss coated text weight stocks (80# & 100#) all units pile ink on the blankets a to the point ink is missing on the "Trailing" edge of all solids. Even on just bold type the training edge builds up ink. After we wipe it, it is back within 50-sheets. This does not happen on text weight uncoated stocks or and cover weight stocks both coated and uncoated. any thought would be appreciated.The only work around is to reduced all inks with too reducer but this creates color control and density issues as well as likelihood of toning.

 

Especially coated papers give this problem (try another brand) ink density at startup can be to low (the amount of revolutions before starting to print must be set higher)

 

Marc, we have did all that. we have been in the printing business for over 40-years but this problem is puzzling. It may be something mechanical but just not sure. We have tried 4-brands of ink and always go back to Toyo but need to add their reducing fluid. The piling/picking is always on the trailing edge of solids (all colors depending on the color of the solid), screens never pick or pile. Our chiller is always kept at 4-bars while running we have tried cooler temps, warmer temps, quick release blankets, under packing over packing of blankets, several manufactures of coated text weight stocks with little change.Its almost as though when we required more squeeze for the text weight that is when the problem comes up but what makes no sense is we are able to print on uncoated (60#) text without any problems.?

 

The problem is not a mechanical one. It comes familiar to me on coated stock. Print with as little pressure u can wil help. Increasing the amount of preinking wil also reduce the picking. It starts with the first sheets and debries is sticking to the blankets and wil stay there. What ink density you are printing.

 

We do start up heavy with our inks as light simply does not work. We print with minimum impression and densities may vary a little if we are trying to color match others work but we like to run C120,M125, Y95, K170-185 but again these can vary depending on the work. No doubt the heavier you can run helps but you do end up with more frequent blanket washes as the inks do transfer forward pretty bad with this press. Our start ups in the morning without reducing the ink on text/coated can take a couple of hours if we do not automatically reduce the tack. We run both Toyo LZ (Light tack and Toyo MZ (Medium tack)inks but it seems the LZ still needs some reducing but just a little too much and you'll tone right away so we run more of the MZ and reduce. It's crazy but the ink manufacturers have not come to any good resolve and local DI operators are not experiencing this problem that why Ive been thinking its maybe mechanical?

 

What is your room temp. (should be 21-22 degrees celcius) preferable all day long even overnight.

 

Again, we have tried all temps. We have a fairly controlled environment. We use a digital infrared thermometer to check our roller temps as well as our plate and back cylinder temps. Too warm you tone, too cool the ink does not transfer correctly and you will need to really open up your keys and sweep. I feel we have a fairly good control over our temps that is why it is so darn puzzling. On uncoated longer run jobs we need to run our chiller around 22 to avoid toning but on coated jobs Toyo recommends and it does run the best around 24.5-25 but that can change again with coverage etc. If you run too cool on this press solids do not lay down well at all. We always build rich blacks as it can not print much of a black solid but we know this and do work arounds as needed. One thing that has been done over the years is that 3-4 short stroke pistons have been replaced by our operator not sure if that could have anything to do with piling though? We have not replaced any of the pneumatics that control the plate to blanket bearer to bearer impression.

 

You are correct about the coated text weight paper as it relates to the release/tack because uncoated paper (little tack) is no problem and a stiffer cover weight sheet even though it is coated is able to release from the blanket without much problem. Just seems like others should be having the same issue locally but they claim they are not?? We have tried every blanket available for this press with very minimal improvement.

 

You tried different brand off ink. I had very good experience with this on (http://www.classiccolours.org.uk/)

 

Could you tell me roller,oscillators and cylinder temps? Also when you put chiller at say 20 temps what reading you get?
Could you tell me your temps at rollers, oscillators and cylinders

 

I have not tried lowering the chiller to 20c yet, but running it at 24c the oscillators are at 25c and the rollers at 26c (give or take little depending on which unit you are checking as the higher (cyan) runs a little warmer than the yellow (we took off our dryer bulb as all it did was add heat) We also do not have our chiller under the scaffold due to heat. In the morning the average press & pressroom temp is 22c but I can say that we really have tried all temps. It makes no difference what time of day or how much the press has been running, if we don't reduce the ink it will pick/pile on text weight coated paper.

 

"One thing that has been done over the years is that 3-4 short stroke pistons have been replaced by our operator not sure if that could have anything to do with piling though?"

This can have something to do with piling.

The short stroke pistons are set from the factory. There are special tools used to adjust them and they are directly related to the bearer pressure. While they may seem easy to change, if the operator did not measure the old ones within .02mm and set the new ones accordingly before installation there will be issues. Not only do the short stroke pistons affect bearer pressure, they are also responsible for the alignment of the drive gears on the impression, blanket and plate cylinder.

The only way to set these properly is with a special gauge set.