1. #1
    Afternoon all.

    Planning another build, this time plasma. This time i shall try rack and pinion with single shaft drive. something like this

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    As much as this at the moment is the rough plan, as with most things I will make it up as I go along to a certain extent. Would welcome any feedback at this stage though.....


    WHERE DO I BUY RACK AND PINION FROM? Seems expensive at Zapp?

  2. #2
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,724. Received thanks 179 times, giving thanks to others 5 times.
    Looks good. A plasma cutter is something on my long term 'to build' list, as I do quite a few things where one would come in handy.

    HPC gears do rack, but it's something I've never seen a noticeably cheap source for. I suspect it's because it's quite a pain to machine. Gears can be hobbed in whatever reasonable size with minimal effort, but rack takes a lot longer to machine.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  3. #3
    CNC4YOU has it also: https://www.cnc4you.co.uk/MOD1-Rack

    Good luck, will look forward to seeing it come to life :-)
    .Me

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  5. #4
    Have you calculated the inertia of that shaft? At that span is like spinning a ball screw

    What motors? Plasma needs to be fast
    project 1 , 2, Dust Shoe ...

  6. #5
    Thanks for replies;
    Boyan: im hoping I wont have to worry about the inertia in the shaft, because, unlike a ballscrew I can place inline shaft support bearings to reduce the whip?

    After shopping around, Zapp doesnt seem overly expensive when taking into account they do free postage at that type of money, and you do get good service and can ask stupid questions.

    My linear rails have arrived (SBR25 for X) SBR20 for Y, and SBR16 for Z (please dont wince, for my application they will be fine)
    im half way through building the frame (il apply pictures of the frame once done)

    Before, I order the Racks, Im hoping to harness some brain power from you guys

    Although this isnt going to be a commercial machine, I hope to make it well enough for it to be used a lot, and on a wide variety of thickness material, in order to achieve this, based on my limited research the maximum cutting speed I think i need to achieve is 6000mm a minute

    Im hoping to get away with stepper motors (only because I have them and some 70v drives), and a old computer with parrelel port

    (but servos and ess are not out of the question) I know how good they are from other machines...

    MOD1 rack seems cheapest, assume I use a 22 tooth pinion, driven from, lets say a 200 input belt off a 100 tooth drive off a stepper motor. so essentially per stepper rev, Im achieving 44mm actual movement

    i shall illustrate this as follows

    a) 22/200/100 = 22 1:2 == 44mm
    b) 22/100/400 = 22 1:4 == 88mm

    assuming I have the servo drives set at 400 pulses per rev, my parrelel port will need to kick out 6000 / 44 = 136 * 400 (54,400) PULSES PER MINUTE which I think is achieveable from a < 1khz parrelel port kernal?

    but im tired, so can somebody shed some light?

  7. #6
    I think a plasma cutter should be faster for thin material. Depends on your PC, but yes you could achieve even faster . i have managed at least.

    also http://www.cncrouterparts.com/why-do...ive-p-213.html
    project 1 , 2, Dust Shoe ...

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