Tear-Drops on my 52

[Drexus]

I'm finding that the image from our 52 has had a dot issue for quite some time. Close examination shows the dots are smeared, like tear-drop shape - falling in the direction of the grip edge. I know the press operator is quite green so far as running a 5-colour press, but he's all we have right now. It's been years since I've run a press, so I can't offer too much advice.

I know the press has had the packing adjusted on various units. I'm thinking there isn't equal diameters between the blanket and the plate.

I'm leaning more towards the blanket-plate relationship than blanket-impression cylinder, as the dot shape is consistent. One notable point is: some units produce a shorter image overall (marks can't reach the others for height), giving us a fit nightmare. Also, there are times where some units drag the dot into a line/geo-dot. This I attribute as far too much packing on the plate cylinder.

My question is: If the tear-drop shape "falls" towards the grip (pointed ends point toward the tail), is it the plate packing or the blanket packing that is too large? One cylinder has a surface speed greater then the other. Is the tear-drop shape made because the contact point flattens the dot and then drags (smears) it slightly to create the "point" on the tear-drop? Or is it the height of the ink that contacts the blanket first - dragging until the full dot makes contact?

Each scenario will produce the tear-drop, but in opposite directions. Am I looking at some other issue entirely?

 

[The Heidelberg Guy]

Hello,

Just a few things;

#1 - If you are using metal plates, there should be NO packing in the plate cylinder.

#2 - All blanket cylinders should be packed the same, equal amount of packing sheets in each unit, and be packed to at a maximum of .001" over bearer.

#3 - You cannot diagnos an issue without the #1 and #2 being gone through and corrected.

Let me know what exactly you have at the moment, and then what you corrected it to.

Tim

 

[Alois Senefelder]

Slur

Slur

Hello Drexus,


What you are seeing is a classic sign of - "Halftone Dot Slur" see the PDFs


Regards, Alois

 

[gordo]

Some more links on slur and doubling with photos:

Quality In Print: Every letter tells a story - print problems revealed in type reproduction.

Quality In Print: Doubling

Quality In Print: Slur

best, gordon p

 

[turbotom1052]

like heidelberg guy said get all cylinders either packed or not packed as the case may be to specs. try to reach specs with blankets that arent too old or hammered if possible. Be sure blankets are torqued to proper specs. Then you at least have a baseline to begin your testing. im sure the heidelberg guy is correct in saying that on the 52 there is no plate packing required but im not sure if thats going with the assumption that your running plates .012" thick. I know some guys like to run the thinner .008 thick plates to save money on the metal. Either way you need to make sure your plate height is at spec and get there however you need to get there. If you wind up either adding or subtracting packing from under your plate you need to also adjust your form roller pressure to the plate the required amount. Id strongly suggest that after making sure all the above mentioned steps are done you begin your testing with a long grain sheet of a well conditioned, good quality coated paper of at least 80# text weight, preferably 100# text weight. Be sure your printing at minimum back cylinder pressure on all printing units by printing a break away solid. Do NOT trust the scales for impression either mechanical scales or led scales. Do the break away solids on each unit till your certain your printing at minimum squeeze. if after doing all these steps your still encountering that same problem its probably time to call in a mechanic. Good luck and let us know how it works out. You also mentioned that your pressman might not be all that experienced. if thats the case you need to be reasonably certain that during testing he has a good ink water balance and not running too much ink.

 

[turbotom1052]

like heidelberg guy said get all cylinders either packed or not packed as the case may be to specs. try to reach specs with blankets that arent too old or hammered if possible. Be sure blankets are torqued to proper specs. Then you at least have a baseline to begin your testing. im sure the heidelberg guy is correct in saying that on the 52 there is no plate packing required but im not sure if thats going with the assumption that your running plates .012" thick. I know some guys like to run the thinner .008 thick plates to save money on the metal. Either way you need to make sure your plate height is at spec and get there however you need to get there. If you wind up either adding or subtracting packing from under your plate you need to also adjust your form roller pressure to the plate the required amount. Id strongly suggest that after making sure all the above mentioned steps are done you begin your testing with a long grain sheet of a well conditioned, good quality coated paper of at least 80# text weight, preferably 100# text weight. Be sure your printing at minimum back cylinder pressure on all printing units by printing a break away solid. Do NOT trust the scales for impression either mechanical scales or led scales. Do the break away solids on each unit till your certain your printing at minimum squeeze. if after doing all these steps your still encountering that same problem its probably time to call in a mechanic. Good luck and let us know how it works out.

 

[mrheidelberg]

I'm finding that the image from our 52 has had a dot issue for quite some time. Close examination shows the dots are smeared, like tear-drop shape - falling in the direction of the grip edge. I know the press operator is quite green so far as running a 5-colour press, but he's all we have right now. It's been years since I've run a press, so I can't offer too much advice.

I know the press has had the packing adjusted on various units. I'm thinking there isn't equal diameters between the blanket and the plate.

I'm leaning more towards the blanket-plate relationship than blanket-impression cylinder, as the dot shape is consistent. One notable point is: some units produce a shorter image overall (marks can't reach the others for height), giving us a fit nightmare. Also, there are times where some units drag the dot into a line/geo-dot. This I attribute as far too much packing on the plate cylinder.

My question is: If the tear-drop shape "falls" towards the grip (pointed ends point toward the tail), is it the plate packing or the blanket packing that is too large? One cylinder has a surface speed greater then the other. Is the tear-drop shape made because the contact point flattens the dot and then drags (smears) it slightly to create the "point" on the tear-drop? Or is it the height of the ink that contacts the blanket first - dragging until the full dot makes contact?

Each scenario will produce the tear-drop, but in opposite directions. Am I looking at some other issue entirely?

I presume you are talking about a Heidelberg Speedmaster 52 ???

 

[marktonk]

If it is a Speedmaster or a GTO 52, the plates are typically 6 mil.

Regards,

Mark