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  1. Are any of the forum members interested in designing an open source cnc project?

    I have some initial ideas for design criteria:

    The project should be for owner / users of a basic mdf machine wanting to upgrade to a mid level machine

    The build cost should be less than ??? (not including steppers or drivers) and as little as possible

    The machine should be capable of a tolerance of +/- 0.MM

    The final design should be available as GCode DXF and PDF and open source
    Last edited by Wotsit; 09-12-2009 at 05:41 PM. Reason: Cost

  2. #2
    Tom's Avatar
    Location unknown. Last Activity: 02-01-2014 Has been a member for 4-5 years. Has a total post count of 172.
    As someone nearing the end of my first build - that's a good idea.

    What's the aim though? An MDF machine more solidly constructed, or something more fancy (alu sections, etc)? For 200 it's probably either sticking to MDF, or possibly alu with leadscrews rather than ballscrews? But alu would need decent rails to get any benefit - is that achievable with 200?
    What are you thinking?

    Anyway, I'm happy to contribute my learnings so far...
    1) Leadscrew whip is bad.
    2) My next router will be more rigid (although the secret aluminium skinning stage for this router isn't complete yet).
    3) Ballscrews would be great, but would also be ruined (and pointless) on an MDF machine.
    4) Cutting alu takes a properly sorted machine.

  3. #3
    this is my arduino mega controlled cnc machine....

    and a video of my machine working...

    [ame=""]YouTube- CNC TESTING GIRL using arduino mega[/ame]

    it is all open source........ if you want i can post codes and stuff

  4. Ok, I think i think the budget should be left open but lets try to keep costs down.

    What constitutes a mid level machine? I'm thinking ball screws, linear bearings a rigid frame and sold / flat bed.

    What are our material options considering it will need to be cut with a home brewed MDF machine?

  5. Might also be an idea to choose a supplier that people are happy with so we can use off the shelf parts that are available in the UK, they might even help us along the way.

    How about ZAPP automation? (I have no affiliation with this company)

  6. #6
    Im on board.

    If this is mid level then its a good idea to go with linear rails or at least supported round rail. Ive not had a good experience with leadscrews and delrin but many have, and espesially if the rest of the machine is well designed. :whistling: might be a way to compromies on the cost......

    My machining skills are limited and cnc knowledge is growing but I do understand structures and forces so could help here if required.

    I'm currently looking at a composite beam design that uses mateials to their best and combine to form an effecient structure.

    As I understand it Cast iron is the choice of a professional machine as it is rigid, strong and dense enought to damp vibration. and it is the small movements (deflection)from the vibration that cause poor surface finish or in worst cases tool breakage.

    But the high density has the problem of being heavy so requires large motors to move. I propose to use an aluminum skin as a former, and for asthetic reasons, but filled with concrete and steel of the correct proportions and place to make a cheap beam that is much stonger than ali extrusions, able to provide moderate damping but not be to heavy.

    I know this sounds similar to the epoxy granite idea but will be much cheaper and hopfully stronger. Its still only an idea and I havent done any calcs yet but the principle has been used in buildings for many years and yeilds a 50% saving in materials for the same strength.

    Sorry if this is off topic but seems a logical approch to an affordable mid range machine.

    Any one have any data on cutting forces? I seem to remember 20N for Ali for some reason :whistling:Probably wrong tho.

    Ok wake up. I've finnished :heehee:

  7. I like the epoxy granite idea and have followed the thread for a long time but it seems to me a bit to involved for a mid level machine, and has some complicated problems. Do you agree? - Would make a great bed though.

    I think the composite idea is a good one, alu box filled and reinforced? Sand in polyester resin / concrete with rebar. Thoughts? Calcs? I wonder what 5kg of resin's exothermic reaction is like?

    I agree that linear rails or supported round rail are the minimum for a project of this type

    What is a good enevlope? For me it would be 2' x 4' ish
    Last edited by Wotsit; 09-12-2009 at 10:23 PM. Reason: More thoughts

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    Last edited by Wotsit; 10-12-2009 at 06:20 PM. Reason: Deleted by wotsit to keep the thread on track

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