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DI press - how to perform best laser diode calibration?

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  • DI press - how to perform best laser diode calibration?

    Last 4 years my primary job is printing on HD Quickmaster DI Classic press.
    From time to time laser diodes must be calibrated for better imaging results.
    My question: is there any kind of "tip & trick" how this can be done more precise.
    Imaging 60% screen and checking prints is too slow and unprecise even with densitometer.
    Better result give me my eyes than densitometer. I can see diferences on printed sheets (lighter or darker tracks) with my eyes but with densitometer - not. Is it possible?
    What is with calibration on Presstek DI 34&52 presses, there are multibeam laser diodes if i have good information?
    Did anybody know for some kind of "laser power meter" or similar things what can help in calibration?
    Did exist any DI press model which have itself-laserdiode-calibration installed?

    Thanks on any kind of help.

    Davor Smokovic

  • #2
    Re: DI press - how to perform best laser diode calibration?


    On our 52DI, there are 10 lasers i believe, split into four paths per diode, each one covers about 50mm of plate surface so they need to be accurately matched.

    This is done by printing what Presstek call a "Worm-dens" print. This is a 50% Stochastic/FM screen tint with patches for each laser diode and each subdivision.

    The eye is the best way to match the densities and the changes are entered on the press.

    As far as i know, outside of the factory, there is no machine capable of doing this for you, it needs to be done under printing conditions.

    Others may know more.

    Dave K


    • #3
      Re: DI press - how to perform best laser diode calibration?

      Can i ask you why are you "Disappointed"? Is your press reason? Sorry what i am asking but i am disappointed too every time when must recalibrate diodes. I hate this. Before 2 years i was in printshop of my friend who have CTP system. This system has 128 diodes (HDQM DI Classic have "only" 64 diodes). I ask him - how are you calibrate all these many diodes? He say - i don't. (normaly) There are one reader who read and calibrate every diode in system on required power level. And plates are imagged briliant. I must ask peoples in Presstek - why DI systems are made that primitive? PRIMITIVE! I don't see that like step forward. This is step in past. This step will destroy all DI's. It was that expensive to implement power reader in cabinet with lasers. Now i see that also "their" presses (34&52) haven't it. Presstek engineers probably newer see printing press before patented his products (lasers) i think. They have own powermeters on his desktops and they like it. But we in printshops have only our eyes and desktops with many sheets with tracks which must be removed. Is Pressteks peoples heard that somewhere exist "things" which are more precise that our eyes? DI is a great idea but with this mistake haven't future. Prices of those kind of presses going down every day but why? Have anything Presstek with it? Once i was try contact Presstek but they forward my mail to serviceman (i know him) who is specialised in Presstek technology. Great technology. They know what they done. But mouth are closed.
      Maybe somebody from Presstek will read this and start new bussines - with laser calibrating hardware.

      Only with "Presstek" disappointed. Rest stay alive.



      • #4
        Re: DI press - how to perform best laser diode calibration?

        here me again. Forget to thank you. I will try 50% FM instead of 60% AM. Maybe can be easyer.



        • #5
          Re: DI press - how to perform best laser diode calibration?


          the reason behind my choice of name goes back quite a few threads on here and i really dont want to re-live those times!

          I should change it but thats a pain to do. I would say its now "relatively contented" :-)


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