Cd 102 6+L Dot gain

Gentleman,

I have 3 offset machine,2 CD & 1 Rolland ,all 2006 model. Now I am facing the problem dot gain in both CD Machines.Using same plates and fountain solutions for all machines. The dotes 20%bigger than the actual size.so final printing result getting dark and not clear while running process colors,somebody can help me to analyse the problem. CTP calibration same for CD & Rolland?.From where I start to solve this problem.I hope a positive information,
thanks all,

 

Do a finger print of all machines for 3 kinds of paper -high gloss,satin and uncoated-, run uncalibrated plates with color bars of CMYK ranging from 5% to 100% with 5% increments in various places of sheet -gripper tail and sides- reach your densities for all colors measure your current dot gain for each kind of paper and then make calibration adjustments. Do this with new blankets/packings and make sure your rollers stripes are correct.

 

You need to understand that every press has a different dot gain curve and as mantman said you need to fingerprint all the presses and then compensate the values in prepress for each press accordingly.

 

Hi, sir,
I you send me , email
i will send you the SFTG, from Flint Ink Company
in order to fix it his problem printing.

 

Thank you Mr,Qazi & Mantman,
Yes, I miss understand, I think all press same dot gain. Rolland printing result very clear. Both CD unclear screen for same plates. Somebody give me more information to confirm this dot gain problem coming from preprss.

 

You need a densitometer with dot area or dot gain function -xrite and techkon are as far as i know good brands- to measure color bars on paper.
If you can afford or borrow a densitometer that can read plate too to eliminate the possibility of plate not exposed/developed correctly.
Make sure your packings are in spec with manual of each press -blanket/plate height to bearer rings- your dot gain could be result of too much pressure to the paper.

 

You need measuring devices to measure your plates and your prints. This will give you an idea of where things are getting wrong.
I would prefer a Techkon spectroplate to measure plates. Also a spectrodensitometer.

 

I would just add that when fingerprinting the press I would recommend 4 different sets of curves. In addition to a curve dedicated to an uncoated sheet I would also recommend a curve for super calendered uncoated sheets. This would be any really smooth surface uncoated sheet like for example Mowhawk Superfine. These type of papers tend to have different dot gain characteristics then say a Cougar Opaque sheet.
In addition I would say, that when doing this fingerprinting, you perform an averaging of readings from both sides of the sheet, as we all know that felt side tends to print different than wire side.