a Simple Blanket to Plate Question......???

Discussion in '1-Color and 2-Color Offset Presses' started by demel, Mar 14, 2009.

  1. FFR428

    FFR428 Senior Member

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    Multi 1250 there is a overall pressure adjustment on the handle you move down to engage impression. Right below the handle you'll see a nut. You can use your T wrench to loosen it, tapping the lever to the right takes off pressure, to the left adds pressure. Then tighten the nut and check your stripe. On both operator and non operator there are eccentrics to parallel the plate cyl to the blanket cyl. As Multi's get old the cyl shaft and bearings get worn and can give false readings down the blanket. So keep that in mind too. Blanket to impression can be adjusted also and a eccentric adjustment is on the non operator side. Not sure if this is what your asking or not but please let me know. Oh and running 4/C on a 1250 multi takes some skills! Very good!!!
     
  2. Marco Cobucci

    Marco Cobucci Member

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    tank you, but i runnig 4/4 colors in especial paperĀ“s and i create a pre register and other stuffs to increase my time to run the service job. when i have time i post hear how can i do to print. some times i ony expend 1 sheet to target the register, is incredible. and my thecniq it can be used in other machines like bigs if you see you love it.
     
  3. demel

    demel Senior Member

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    Thank you lildaddy50, FR428 for your valuable inputs...

    Dear Lildaddy50,
    could you please clear me up about the 1.5mil...
    i think are you referring to 1.5mm not 1.5mil.....1mil=0.0254milimeters
    i am very sensitive to these value cos i am having serious problems due to
    incorrect settings of my machine.....


    Dear FR428,

    as Lildaddy said my machine is a spring loaded one....not a bearer to bearer press.
    what you are also telling is extremely correct........you got the point...
    that is waht i wanted to adjust......i mean i can adjust these settings from
    the eccentric adjustment finely and smoothly....
    all i want to know is the strip widths.....

    Ok, now you all have given me a good knowledge about Blanket to Plate....
    but what about the Blanket to Impression strip....
    i mean if i put impression to full state without feeding a paper then
    what should be the maximum strip i should get on the impression cylinder.....

    greatly appreciate you sharing....

    Thanks in advance,

    demel
     
  4. lildaddy50

    lildaddy50 Member

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    Demel,

    In my 30 years of printing, I have never heard of checking a stripe blanket to back cylinder.The gap between the blanket and impression cylinder is preset from the factory and you use the dials to change it on each job based on the thickness of paper you are running. If you think the pressure between the blanket and impression cyld. if off, you need to contact your mechanic. Do not try to mess with it on your own!

    Back in the old days I started out on a spring loaded AB-Dick I ran everything on the lowest possible setting except for envelopes . Those will smash you blanket if you run too much pressure. I can tell you a trick on how to run envelopes with nice even pressure if you are interested?

    Lildaddy
     
  5. demel

    demel Senior Member

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    Hi Lildaddy,

    First of all i would like to know the envelop trick.........:))))
    i am so interested in that subject......thanks for asking me Lildaddy......
    Please share..........others might be interested too........

    About the Bl to Imp Cyl. pressure can you please tell me how to check
    the .001 or .004 squeeze pressure between the two cylinders.....
    it there a way to calculate that using a conversion.......i mean .001 of pressure=??mm strip like that.....
    please dont laugh at me.........i am finding a way to fine tune these settings.....cos one technician came
    and ruined my setting.......


    Thanks

    demel
     
  6. lildaddy50

    lildaddy50 Member

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    Ok to get your blanket to back cyld. presure back in order, do the following.

    1) make sure you put on a new blaket with the correct packing to factory specs.

    2) Get some stock and use a mirometer to check the thickness. Use card stock apox. .008

    3) use a sheet that is the full width of your blanket.

    4) Take your back cyld. pressures up as high as it will go like if you were running envelopes or something really thick

    5) Ink your plate up solid (no water) and run a few sheets through. You should have no image because your back cyld. is way to far away from the blanket at the highest setting.

    6) now start coming down on the pressure even on both sides until you have a nice solid on your sheet.

    7) After you get your solid, look at your pressure dails. Your pressure dails should now be set at whatever the thickness of paper you have is. If you used 8 point stock (.008) then your dails on each side should be at 8. If it is not then someone has messed with it. Take off the dail and put it back on in the right place (8)

    let me know what happens and remind me to tell you about the envelope trick. It's late now and I'm going to bed

    Lildaddy (30 yrs. exp.)
     
  7. Mechanic

    Mechanic Senior Member

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    If you know the Cylinder diameter, multiply by 7% to find the apropriate nip (strip). If not , measure the perimeter (circumferential length) and divide by 3,14 to get your diameter. Example, if your perimeter is 350 mm
    , then the diameter is 111,5 mm and the apropriate nip would be 7,8 mm. Set the pressure with the impression ON.
     
  8. Mechanic

    Mechanic Senior Member

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    Blanket to Impression is a totaly different thing. This is adjusted every time , according to stock, The basic settings of the dials : If your plate setter is OK, Print a plate with solid AND 95 % screen. When you get correct density and screen all over the sheet, your pressure is ok. Set the dials on the stock, and thats it.
     
  9. demel

    demel Senior Member

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    Thank you so much Lildaddy50 for your step by step instructions.....
    still i am struggling with it.....

    recently i bought down some feeler gauges, some lead solder to measure the gap between the cylinders....
    so i think i will be able to find the exact undercut and fine tune my machine according to the standard squeeze
    pressures.....


    Dear Sir Mechanic,

    first of all i must thank you for allocating your valuable time to answer my questions....

    i would like to follow your cylinder diameter method also........
    but my cylinder Diameter is nearly 7 inches (177.8mm)...so when i apply your formula
    to this diameter the stripe width should come as 12mm if i am correct......

    don't you think this is too high....

    Please Help .....
     
  10. Mechanic

    Mechanic Senior Member

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    These rules were given to me by a Jap mechanic. I dont believe that the Japanese are untouchable, I m just saying that, it s not something that I made up. That, plus the fact that I saw once a strtip on a SM 102 (diameter ca 240 mm) and it was roughly 15 - 20mm. If you do the math, its spot on. The Heidelberg might run on bearers, but the strip was there. If you are afraid to go half an inch (12mm) make it an even 10 mm.
     
  11. exheidmech

    exheidmech Senior Member

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    I must say this is one of the craziest things I have ever heard. I have worked for Heidelberg for over 18 years and not once have I ever heard of a mathimatical formula for setting bearer pressure. Years back we would set bearer pressure with a feeler gauge and then move the bearing bolts a preset distance afterward. Now it is set with pressure sensitive papar and a meter. If this is how the Japanese want to do it on their machines fine, but never ever use any principles or methods learned on a japanese press on a Heidelberg. Setting bearer pressure on a Heidelberg, especially on a GTO is very simple and takes basic tools. If one would like to know how to set bearer pressure correctly on a GTO correctly I would be more than happy to give instruction on doing do.
     
  12. Mechanic

    Mechanic Senior Member

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    The formula is for mashines with NO BEARERS, old school. Read the thread carefully next time. I was just comparing the two mashines.
     
  13. exheidmech

    exheidmech Senior Member

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    If you go back and read the original post, it is refering to a Heidelberg GTO, which in fact does have bearers.
     
  14. Mechanic

    Mechanic Senior Member

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    Hmmmm, I missed that part, sorry:(. Yes, you cannot set a strip on mashines with bearers , like Heidelberg. The 7%rule only applies to non bearer mashines.
     
  15. demel

    demel Senior Member

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    Thank you Mechanic & exheidmech...

    Could you please tell me is it impossible to check the stripe width of a properly set or packed GTO.
    in other words i just want to compare the Heidelberg GTO's strip with the Non Bearer machine.

    i think 5mm strip is also too high as Blanket to Plate cos it tends to wear out the plate prematurely.

    Any Help would be greatly appreciated....


    Thanks

    demel
     
  16. exheidmech

    exheidmech Senior Member

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    If you want to check for a stripe between plate and blanket, the only way that I can think of to do it is much like checking roller stipe. Ink up the plate and blanket as if you were going to print solids. Check for stripe just like you check on a roller.
     
  17. demel

    demel Senior Member

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    Thanks for your quick reply exheidmech,

    Yeah! that is how i am checking B/Plate and B/Impression cylinder also....
    what i want is the exact strip width in mm......

    my machine is a NoN bearer to bearer GTO size one....but i am going to follow the Heidelberg GTO's
    strip width as an initial approach.....have you got any idea about the stripes....

    Thanks

    demel
     
    Last edited: Aug 14, 2009
  18. exheidmech

    exheidmech Senior Member

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    I understand what you are doing. My experience is in bearer to bearer machines so I can only guess on what the stripe would be, although I have never checked for a stripe. My guess would be around 4-5mm, but could be more depending on thickness of plate you are running. If i remember correctly you can run 2 different thickness of plates on a GTO 5 and 8 mil. With the thicker plates you are supposed to underpack the blanets a bit, but most guys werent doing that. Just make sure you have blankets packed correctly for the plate thickness you are using. Blankets should be packed to bearer height with the 5 mil plates.
     
  19. Mechanic

    Mechanic Senior Member

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    Let us know the width that you measured, just out of curiosity
     

  20. demel

    demel Senior Member

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    Dear exheidmech & Mechanic,

    Thank you so much for both of your advices.

    I think so far i have been able to come for a good stop thanks to all of your advices..
    actually the B/P strip is now nearly 3mm when i set the squeeze pressure to 0.07mm......
    but i find it is little under pressure when printing solids.....so i decided to adjust it by raising
    the thickness of my under packing slightly............all these done by carefully checking the under cut of
    the both cylinders by feeler gauges and adjusted the eccentric bolts located in out side the cylinders..

    for final fine tune could any body tell me what is the good setting for B to Impression squeeze...
    is 0.1mm squeeze is enough or do i have to go further.....other wise it wont be able to print
    NCR kind of papers i think...


    Thanks in advance

    demel
     
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