Thread: Toning on QMDI 46 4

When running all 4 colors on our QMDI 46 4, we begin to get some light toning on the lead edge of the stock after around 500 impressions. It is almost always on the blue unit, and sometime on the black as well. We have tried taking out the third form roller, and it still happens. We put the third from back, and it still happens. We are currently running without any third forms in. We have also checked the bead lines regularly. We run Toyo medium tack ink. Our temperature is at 22 degrees. Our shop does not have humidity control or air conditioning. Any ideas on how to fix this would be appreciated, as we have tried everything we can think of.

I know in our case pressures are critical on form to plate. If there not just right ours will tone also. The other cause could be the room temperature were the press is located. If it gets above 75 F in our shop we start to tone. We always keep our room temp between 68 - 73 F. As for humidity control we are about 7000' and dont have alot of humidity. This seems to work best for us. If it gets say 80F then back comes the toning. We are also running Med Toyo and have had great success as long as these conditions exist. Hope this helps.

I've dropped my roller temp all the way down to 19.5 is certain instances to correct it when toning would show up. Overall room temperature is a major factor as well. If you have too much squeeze on your blanket to impression cylinder will also cause toning.
One thing I've noticed as well is the toning bar will move it's location based on the press speed, and I have noticed the faster you run the press, the less the toning will occur.
Sometimes if you change the press speed from say 6500 to 8500, the toning will go away for a short time, then will reappear again, so another option I have resorted to in the past is to continually vary the speed of the press during impression to get the toning to not build up in one spot. It is kind of a pain to alter the speed like that, but when you have to get a job done...you do what is necessary.

Cheers,

Tracy

Toning issues and how to address them.

In most instances this is a problem due to the magenta ink itself, as it is the most difficult color to formulate for waterless printing, also because Magenta causes calcium deposits, due to the pigments used, on the rollers. But first, to determine if the ink is the problem, there are a couple of things you can do.

1. Swap the magenta with another color in another unit and see if the problem moves with the ink. If it does not, then the unit the ink was originally in is the problem.

2. If the unit is the problem, roller stripes need to be addressed. Information on setting roller stripes can be found in the operation manual. Also the bearings on the rollers need to be checked for wear and replaced if necessary. The rollers also need to be checked for excessive endplay, this needs to be reduced by adding shims. Stripes to distributors should be 3.5mm, stripes to all the forms should be 3mm. The third form can be moved to 2.5mm as this roller helps smooth the ink. Removing the 3rd form completely from the plate masks other issues. If this must be done to stop toning there is another problem. Very important... Always check your stripes to the distributor rollers first before adjusting them to the plate.

3. Temperature of the room should be a maximum of 23 Celsius (74 F). Anything over this will cause toning/tinting. Usually in this instance it is apparent in the 2nd unit first, as it is the highest unit and heat rises. Then the other units start to exhibit the problem.

4. Check to make sure there is 4.0 bars water pressure in the cooling unit and the temperature is around 22 Celsius on the Classics, 25 Celsius on the Plus and Pro machines. Once again if this is low on water the 2nd unit starts to tone/tint first. DO NOT TURN THE COOLING TEMPERATURE DOWN, THIS WILL CAUSE THE ELECTRONICS IN THE CONTROL CABINET TO CONDENSATE AS THE CONTROL CABINET IS ALSO COOLED BY THE COOLING SYSTEM.

5. If it is found ink is the problem, talk to your ink manufacturer to see if you can have the ink formulated for your situation.

6. Too much pressure and over packing the blankets can also cause tinting/toning. Blankets must be packed to zero bearer height.

7. If none of the above repairs the problem, contact the HEIDELBERG Service Department for further assistance.