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Thread: C6501 Skew

  1. #1
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    C6501 Skew

    I have a 1mm skew on the prints that I can't seem to correct. The skew is consistant.. it is always 1mm... I have found every other adjustment but cannot find a skew adjustment. I have cut my paper to 330mm x 487mm so that it is dead straight. Its really annoying on duplex jobs.. as the 1mm on each side = 2 mm on duplex. Because the machine is very very consistantly 1mm.. there has to be an adjustment for it... any assistance would be greatly appreciated.


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    Senior Tech 100+ Posts Si@danwood's Avatar
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    Quote Originally Posted by resolute View Post
    I have a 1mm skew on the prints that I can't seem to correct. The skew is consistant.. it is always 1mm... I have found every other adjustment but cannot find a skew adjustment. I have cut my paper to 330mm x 487mm so that it is dead straight. Its really annoying on duplex jobs.. as the 1mm on each side = 2 mm on duplex. Because the machine is very very consistantly 1mm.. there has to be an adjustment for it... any assistance would be greatly appreciated.
    Within spec.


  3. #3
    FSS / SPM 100+ Posts Setright's Avatar
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    Yes, I have to concur. 1mm is within the specs/tolerance for the machine.

    You might be able to reduce it 0.5, and effectively hit 1mm in duplex...if you are patient :-)

    First off, the LCT paper cassettes (4&5, if fitted) are best to use, since this assembly has a sensor to monitor the edge of the paper and make electronic corrections for skewed paper feeding.

    Any cassette should have the guides fitting snugly on the paper stack, any slack down here will make further efforts superfluous. Again, the internal cassettes are less well suited to this, but you can usually glue a plastic stip onto the guides to ensure a tight fit against the paper.


    Right....


    On the display panel, you should have a button in the bottom of the copy menu, that reads "Adj. Both sides" or something similar. It's the second one from the right.
    This allows you to move the print indepently in simplex and duplex, zoom to compensate for paper shrinkage, and increase the registration loop. The latter being where I would begin, try a value like +30. In essence this increases the time the printer uses to straighten up incoming paper. You will know when you increase it to much, because the paper will start to buckle and get crease marks.

    If this useless, try printing the chart adjustment. It will output a page with lines for you to measure. Enter these measurements into the provided spaces and the printer will try to compensate for the paper's tendency to twist/shrink during the printing process.

    Best of luck :-)


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    Technician BVulgaris's Avatar
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    Re: C6501 Skew

    I have a similar issue where i am getting a skew within spec, however its annoying because the skew is for the most part consistently in the same direction (if it was 100% consistent, i can fix my other machines to compensate). The skew is across stocks ranging from 13x19STD (or non standard sized around there.... skew actually gets worse with standard sizes), to 12x18 and seems to straighten out around 11x17STD to 8.5x11STD.

    There is also an issue with the way it prints... seems to have a warp to the image considering i will duplex on cardstock 13x19 with a 12x18 fine point rectangle front and back, i can get the centers to line up but cannot get the rectangles to match as a result of what I originally thought was the skew but after measuring the dimensions of the rectangle I find the rectangle is slightly warped as well.

    This is printing from Tray 5 LCT btw. The default for this tray's preregistration is set as -60 (is this correct?).

    So i guess my question is how can I tell if this is just a physical issue with the tray/machine setup, or whether something more worrying is occurring in the print engine?

    (yes, i have followed the proper setup for the FD and CD mag as well as CD skew, etc. I get 280mm cross wise in both directions for CD-skew.)


  5. #5
    FSS / SPM 100+ Posts Setright's Avatar
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    Re: C6501 Skew

    Skewing within spec, mostly to the same side....sounds frighteningly familiar to me!


    We had a machine that we spent days and weeks on, but nothing could solve the skew. It is within spec, but I agree with, when it's always to one side, and consistently the same amount, you would think it could be corrected somehow.

    Please don't waste your youth on this problem. Sounds like you have already been through all the correct adjustment methods.


    There are two things you might want to check:

    Squareness of the customer's paper. Slight trapezium shapes, where one end is wider than the other will confuse the edge sensors.

    Level of the print engine and the paper cassettes. If the floor is soft, the machine will sink further than the cassette, and need re-adjustment after a week or two. If the cassette and engine aren't aligned, you will have trouble with skew and registration.


    BEst of luck!!


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    Technician BVulgaris's Avatar
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    Re: C6501 Skew

    i've been trying to learn as much as I can about this product because i'm not sure its actually setup right (A tech to production is like the christian messiah, if you cant trust to follow him there are bigger issues in heaven's kingdom (no i'm not religious it just seems like a good analogy)), that being said my policy is i'd rather know whats right than be right. I've had some situations where I wonder if following the suggested setups are overkill as has been suggested to me, however i'm sure there is a reason its in the servicing manuals etc if it mentions it. (ie, disposing of 2 the PFU leveling feet, only having 2 diagonally from each other supporting the PFU as was suggested to me). Thus i'm trying to learn as much as I can both for myself and so the tech and I can communicate effectively if an issue arises.

    As far as I can tell the chasis of the engine and the PFU are level (using a 2ft construction level on the top of both units). However what do you mean by the paper cassette? (the tray hold where the paper rests?... sorry a little fuzzy on terminology some times). Im guessing if the chassis is not level and the trays try to hang plum to ground.... (on the right track?).

    We do have carpet in production, but it is a tight weave hotel grade carpet with no extra padding added between the carpet and the cement (interesting renno job). I have read a comment about not placing these things on shag..... i could just imagine the problems that would cause.

    As for the paper geometry, i have painstakingly tried to eliminate this by weekly assuring our cutter setup is straight and even cutting the paper to the print size when needed (stock left slightly larger in storage and then cut before loading the trays. I try to look for ways to eliminate human error, but its possible i'm over thinking some things. (btw, what is the sensor tolerance or accuracy? are we talking about a difference of .1mm or are we talking a fraction of that?)

    Thank you ever so much for your time and effort in helping to solving this problem


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    Trusted Tech 50+ Posts TonerMonkey's Avatar
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    Re: C6501 Skew

    Quote Originally Posted by Setright View Post
    Please don't waste your youth on this problem. Sounds like you have already been through all the correct adjustment methods.

    BEst of luck!!
    Agree.

    BVulgaris: Do you think your tech/s are not the most switched on of fellows ?

    If a digital machine is skewing by 1mm and it's not satisfactory you really need to take the next step up - buy a litho press, HP Indigo, NexPress or iGen. You get what you pay for.

    Come on fella, 1 mm ? .... our lives are hard enough, have some tolerance.

    It may not be achievable, and as I'm sure you may have picked up it's within spec for this machine. The members of this forum would I'm sure help you the best they could if it was possible to get a better result and there's a whole wealth and many years of experience here.

    Good luck on reaching Nirvana, I've never been there ...........

    Last edited by TonerMonkey; 03-23-2012 at 01:02 AM. Reason: Fuck off and die.

  8. #8
    FSS / SPM 100+ Posts Setright's Avatar
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    Re: C6501 Skew

    TonerMonkey..you forgot one machine: Canon imagePRESS


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    FSS / SPM 100+ Posts Setright's Avatar
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    Re: C6501 Skew

    Oh yeah, with respect to leveling/aligning, it's the metal frame of the engine and PFU that must line up vertically. The spirit level across the top is good as a guide, but ultimately, the plastic covers cannot be trusted to be perfectly straight.


  10. #10
    Technician BVulgaris's Avatar
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    Re: C6501 Skew

    Toner Monkey,

    I completely agree that what I would like to see is probably pushing it which is why I am trying different venues and see what others have done to come up with a solution. Having 2 machines printing side by side with one printing perfectly out of the bypass putting the PFU registration to shame is strange considering the design.

    I do not fault my tech for the work he does. I fault myself if i want to lower the tolerance and gett a better result. There are things that i've begun to question but again I am not a tech so who am I to judge? I do however wish to continue learning as much as possible, mainly because i find these machines fascinating.

    I am however puzzled why numerous posters comment that trying to get better registration with the bypass without a PFU attachment is insane when the bypass proves more reliable in this respect (i feel i can only be led to believe that something is not right but i'm open to the possibility that i am wrong).

    I have acquired a copy of a service manual/parts manual, and user manual in the attempt to reach "nirvana" with this machine but I do not expect heaven to appear in it's output. Any help that can be offered would be greatly appreciated however


    Setright,
    Thank you for the suggestion, i'll see if the metal framing is level etc.


    To all,
    To make it perfectly clear, i am not sitting on my tech whipping him to get the in tolerance skew fixed... I am simply wishing to raise my hand and ask what Me, Myself, and I can do about it if my employer has chosen this machine as making the most sense for our operation and pocket book as far as the digital side of things
    Again, thank you all for your time and help.

    I have youth to waste on something... im just not choosing sex, drugs and rock and roll just yet. (though i miss the good music of the 80's .... i mean just compare HART-Alone to the remake Alone Again..... sorry side rant)


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