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  1. #1
    Join Date
    Apr 2015

    suggestions, help on first small cnc plasma build

    Could use some pointers on details of a 2x3 cnc plasma build.

    long story short I've lurked here and other sites for year dreaming of a cnc machine then a plasma cnc machine. purely for making my own parts for other projects not really for profit at all unless it was from the other projects I planned to build. I've welded off and on since I was 15, worked on cars since I was 10, currently a network/sim/electronics tech at almost 40 now. Figure it's time to take a shot at it. I bought a lot of this stuff almost 4 years ago so bear with me as I see a lot of linear rails flat type are actually cheaper now but this is what I have so trying to work with what I got. I'm looking to build a 2x3 ft table (was 3x3 but this 3x2 steel box came to me for free its heavy solid and already fairly square. I'm a little stuck on how to go about making the most cut area and most rigid gantry. I can also order another or newer rail for the y if it makes more since but here is what I have so far

    4 1000mm fully supported rails with 8 12mm bearing blocks
    a steel box roughly 2x3ft
    a cheap cnc kit 3 years ago with 4 nema 23 240oz 8mm shaft stepper motors
    5meters of 15mm wide timing belt, with the gears on order as I apparently ordered to small diameter hole gears originally.
    I plan to run two x axis motors to hopefully keep racking down.
    eventually THC so a z axis will be considered but as of now later down the road.
    I have a Lotos plasma cutter with pilot arc which my hinder the build but I'll just wait and see as it does what I need for now, so not trying to spend $1K or more on a hyperthem (I'd love to but if this works from my simple cuts I'll be happy)

    currently just did my best to screw one set of rails to the box and keep them parallel.

    Questions I apologize I've tried searching but maybe I'm looking for the wrong terminology? As it has difficult finding info on these type of rails being used without a lead screw set up.

    1)Is there any advantage to putting the rails on the side versus top as I've seen on other builds?
    2) is everyone just making there attachment hardware as in the bracket from bearing block to gantry to drive motor? all I seem to come up with is stuff related to extrusion connections (I get it, its easier to attach and keep 90degrees but Id like to work with the steel I have).

    Ive included a picture of what I'd like to mimic but without the lead screw. also the reason for the different stock sitting on top is me trying to decide on best gantry frame steel.
    Attached Thumbnails Attached Thumbnails cncsupportedrailexample.jpg  

  2. #2
    Join Date
    May 2015

    Re: suggestions, help on first small cnc plasma build

    I went with side mount rails tucked as much as I could out of the road of plasma dust. The disadvantage is that its harder to align the rails vertically but with a good THC that is not such a big issue.
    Here is some inspiration for you

    Re your gantry, there is no need to use extrusions. I used a 40mm x 80mm Aluminium Box section. Remember, acceleration and velocity are king in plasma so the lighter you make your gantry the better. I had my ganty ends folded up from 6mm aluminium for this reason with the sides adding some stiffness as the design make sthe ends pretty long.

    Here is a bit more recent footage that might give you a better view of the gantry at about 5:20
    Rod Webster

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