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Ink Density on 34DI

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  • Ink Density on 34DI

    What kind of density do you other 34DI guys run on process? I can't run as much ink as I did on the conventional machine I had, it would be to much ink from what I'm seeing so far. I have been running our monthly newsletter on uncoated 70# offset and I see about 1.45 for black, 1.00 for cyan, 1.10 magenta and only about 0.80 for yellow. That is where it matches color best and it seems to stay right there throughout the run. I have only printed a couple coated stock jobs and it was slightly lower than what I used to run on the old press.

    rhutson in NC

  • #2
    Re: Ink Density on 34DI

    Roger:
    The black density seems a little high for an uncoated stock, assuming this is Status T. The others look reasonable.
    John Lind
    Cranberry Township, PA
    724-776-4718

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    • #3
      Re: Ink Density on 34DI

      Three questions:
      1. Which Ink Manufacturer are you using?
      2. Who/How are your Curves set up?
      3. Are you sure of the accuracy of your [Spectro]Dens?

      Traditionally, based on different ink manufacturers, the Yellow does run light.

      Peter Furnee
      Link: [STOCHAST|http://www.stochast.com]

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      • #4
        Re: Ink Density on 34DI

        Please remember that this is because of waterless inks which is less forgiving than conventional inks. Please post this question at dipressforums.com and see what everyone has to say.
        We use Toyo Medium Tac ink. Also make sure that the temp. of the room is less than 72 F. Very Important.

        Shawn

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        • #5
          Re: Ink Density on 34DI

          Hi, we would be running uncoated at:-

          Cyan:-1.25
          Magenta:-1.20
          Yellow:-1.15
          Black:-1.60

          Using Toyo MZ inks with the room and press set at 21deg C.

          This gives us a close match to the ISO12647 standard we wanted.

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          • #6
            Re: Ink Density on 34DI

            I guess it is what your used to running and seeing. I've been running a little hotter than my first post. Toyo ink is what we are using, I guess it's medium tac, whatever they gave use to start with is what I've been getting. I'm totaly lost on the ink curves, what do the numbers mean? I remember him breezing through it and he scrolled through the numbers fast and would stop in a certain range and make adjustments but I'm gonna have to get some more help on this. When I go to set ink curve it shows the graph but I scroll up through the numbers and don't know what numbers are for what colors or even why it is this way.

            banjoman

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            • #7
              Re: Ink Density on 34DI

              It is complex, we have been running about a year now and i have just requested some extra training on curves.

              Ours is set up with 3 bands corresponding to the ink volume in the job i.e. 1-30%, 31-60% & 61-100% coverage. Each band uses four curves i.e. 41,42,43,44 then 51,52,53,54 then 61,62,63,64. The numbers relate to the press colour setup - 41,42,43,44 = K,C,M,Y, or unit 1,2,3,4 whatever.

              On the left of the graph is ink key opening and along the bottom of the graph is dot area%, here is where it gets tricky, as if you are in the 41-44 band, 100% on the bottom is really only 30% in real life if you get what i mean? Dont forget you also have to throw in the ductor contact setting i.e. 10/10 or 3/10 etc, ours is currently set at 30% band = 3/10, 60% band = 6/10 & 100% band = 10/10.

              They could write a book on the curves alone and it would be very useful as it is here that money and time can be saved on a job.

              Dave

              Comment


              • #8
                Re: Ink Density on 34DI

                Hi,
                I am not disappointed but I agree with him. The standards are:
                Cyan:-1.25
                Magenta:-1.20
                Yellow:-1.15
                Black:-1.60
                and in general you'll not have too much problems with it.
                Your yellow seems too low to me.

                Regards,
                Gerhard

                Comment


                • #9
                  Re: Ink Density on 34DI

                  Gerhard:
                  You seem to hail from Germany, and I would guess that the densities you post are measured with a narrow band densitometer. You would have a much bigger number than Roger for the same amount of ink on the sheet. Density numbers alone, without specifying the response, are misleading. I still think that 160 black on uncoated would present drying and marking issues.

                  John Lind
                  Cranberry Township, PA, USA
                  724-776-4718

                  Comment


                  • #10
                    Re: Ink Density on 34DI

                    We are using "Status T" measurement.

                    Comment


                    • #11
                      Re: Ink Density on 34DI

                      Well I'm running another month of our newsletter (54,000 2 sides) and I'm easily getting 27,000 which is half the run, on one set of plates. I have settled in on what looks good for our newsletter and is close to what our old press printed as far as color. Yellow is about .90, magenta is about 1.05, Cyan is about 1.00 and Black is about 1.30. This is on standard 70# offset uncoated paper. I can run my powder at about .75 and it is fine. I think this press prints good and I have had very litlle trouble with anything. I don't like the universal feeder as well as the stream feeder we had but it works pretty good. I have been running with the electronic double sheet detector off, it is to much of a pain to constantly clean the sensor and the mechanical detector works perfect so you realy don't need it.

                      banjoman

                      Comment


                      • #12
                        Re: Ink Density on 34DI

                        The numbers Roger stated are more inline with the SWOP standards for uncoated offset. Although this is a question about the 34DI, ink density is ink density no mater what press your laying ink down with. I personally run a QMDI 64-plus. I use .95 yellow 1.05 cyan 1.12 magenta and 1.25 black for uncoated offset. I also recommend a larger grained anti offset powder for uncoated offsets. DI inks seem to take much longer to setup for turn around handling on uncoated offset. I recommend adding dryer to the ink for large solids and heavy dark photos on uncoated offset. (not a plug but Speedy Dry is the best I have found so far).

                        I find that the ink bead is heavier on a DI press than on a conventional offset press. Owing to the fact that the image on the plate is a pit burned into the plate surface verses an above surface image on a conventional grained offset metal plate. Not to mention the DI inks are a tad thicker than conventional offset inks.

                        Also try to get your Graphics artist to limit 4 color blacks to no more than 220% to 230% coverage. (20% yellow 40% magenta 60% cyan and 100% black.) 400% area coverages to get a dark dark black ON any paper on the DI is a NO NO.

                        Trying to lower the density as much as possible, without affecting color will help with dry times and turn around times as well.

                        For coated gloss I use 1.00-1.05 for yellow 1.30-1.35 for cyan and depending on the color of the piece anywhere from 1.25 to 1.40 for magenta, black is at 1.70-1.80. I use a densitometer set to T scale. Again these numbers are close to the SWOP density values for coated offsets and covers.

                        Please remember that density numbers are a baseline and you should not always base a job solely on those numbers some twiddling to get close to a proof or a customers desired color is sometimes a necessary evil.


                        Disclaimer. I have been a printing pressman for 30 years. The above is based on what I have found works during 7 years of grappling with a QMDI 64-plus. Your mileage may vary.

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