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Too much Humidity

  1. Apr 28, 2008 #1
    Hi all,

    My team is developing a Ticket vending machine. in this machine the tickets are rolled on rollers and are made from paper(not regular paper but thicker ones). This ticket goes into the ticket printer and at the first stage it is cut into the required size with use of a cutter in the printer and then the information is written on it and then it is dropped out of the printer.
    The case is every morning there will be some tickets which are cut short and are stuck inside the printer or are not completely dropped out and are stuck at the final gripper of the printer.
    since here is SOOO humid, so we believe that this problem is mostly because of humidity since it mostly happens in early mornings or rainy days.

    Please give me your feedback on what you think the reason of this problem is.

    Also if you also think that this is because of the humidity please inform me what solutions you suggest,
    actually I have used a type of humidity absorber in the machine but after a day it was full of water and it is impossible for us to change it every day and I dont think it had any effects cause the problem happened again.

    Thank you in advance for your help
  2. jcsd
  3. Apr 28, 2008 #2


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    Staff: Mentor

    Humidity is an extremely common cause of paper roller problems and it is quite possibly the problem you are experiencing. One easy way to test this is to fix the humidity problem where the equipment is installed (or use a test setup) and see if the paper feed problem goes away.

    If the humidity problem can't be fixed (ie, if the machine has to be outside), you'll need to find a different material for the rollers and perhaps a differen type of paper for the tickets.
  4. Apr 28, 2008 #3
    thanks for your answer but the problem is:
    1. the machine is ticket vending machine and should be outside.
    2. the paper is provided by the client and has been supplied for a long time and there is absolutely no possibility of changing the paper.
    3. The roller doesn't have a problem and is rolling fine (since we are using bearings)

    I believe the problem lies inside the printer and its mechanism. something goes on inside (because of humidity )the printer and will cause this ticket not going out and things like that.

    So now, what can we do to solve this humidity problem?
    Of course there are some humidity absorbers that we can use but when I used one of them, i saw that next morning it was full of water somehow that you couldn't see the materials anymore.
    the second fact is that electrical dehumidifiers are so big that we cannot use them in our machine.

    So what is the solution? what do you think?

    Thanks in advance
  5. Apr 28, 2008 #4
    Humidity can be measured in 2 ways...absolute and relative. Absolute humidity is the actual amount of water for a given volume of air. Example...1 oz. per cubic foot of air. Hardly anybody uses this measurement. Relative humidity is the % of water in the air compared to the amount it is capable of holding for a given temperature. If you had low relative humidity in your machine when the air temp. was 90 degrees and then lowered the temp. to 30 degrees, the relative humidity would go sky high even if you never opened the ticket machine. By warming the air inside to ticket machine, you automatically lower the RELATIVE humidity, not the absolute humidity. You said you do not have a problem once it is warm out.

    So what's the solution? warm the inside of your enclosure. This can be even be done with a low watt light bulb.
  6. Apr 28, 2008 #5

    The thing is that the warming up that I mentioned is not the warming up of the machine but it is that the printer is warmed up and also im not sure this is the reason that the problem is solved or not because in rainy days although the printer is warmed up but still we have the problem.

    Second is, although we talk about humidity by relative humidity and not the absolute humidity but it is just a mathematical talking. in reality the absolute amount of water which is present in the air leads to these problems whether the relative humidity is high or low due to the temperature and equations. machine is hot inside, actually very hot inside because it is a closed box with with almost no air circulation and many electrical boards and the weather is humid, it is like a hot wet air in the machine that leads to the paper of the ticket be soft and not proper for cutting and other things.
  7. May 2, 2008 #6
    This is kind of funny in that you have identified your own problem in that the changes to the paper affect the ways in which the machine's parts interact with the paper. Since you can not change the humidity, this can only leads to two solutions as follows:
    1. Change the paper to something which is not so affected by humidity.
    2. Change the mechanism so that it can work properly with the changes that the paper undergoes.

    You say that you can't change the paper, so change the mechanism. First you have to examine the paper and quantify the changes which it undergoes so that you can make adequate changes to the mechanism. If the paper gets too "mushy", then nothing may work, so I'd make sure that the paper maintains enough integrity under your conditions. If so, then you may need to remove the rollers and substitute some sort of linkage based mechanism which grabs the paper over a wider surface area, than a roller does, and feeds it in defined sections. You may also need to provide guides which provide close, non-stick contact with the paper to keep it from bucking and jamming. Lastly you may need to devise some method of cutting the paper which works well with the changes that humidity brings on, (say a teflon coated roller cutter for instance). Good luck, sounds like a challenge !
  8. May 3, 2008 #7


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    Staff Emeritus
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    If you can heat the inside of the machine so that it's about 12 C or 22 F warmer than the surrounding temperature, the humidity should never get above 50% or 60% inside it.
    Last edited: May 3, 2008
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