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  1. #71
    Hi Bart, welcome to the forum mate and don't stress over hijacking the thread, someone needed to bring it back to life.

    Jim, honestly everything is as it was few months back, i.e. in pieces. Once I've got the control panel built and I'm happy the way it works, I'll make a schematic and post it for you. It will be quite tricky though coz' it uses a few linked relays.

    Jazz, nice to see your back and in full swing.

  2. #72
    Bart's Avatar
    Lives in Krakow, Poland. Last Activity: 08-03-2016 Has been a member for 2-3 years. Has a total post count of 12.
    Thank you for your interest in my design

    I guess I should have started with some spec of the design.

    Frame dimensions
    W x L: 1400mm x 1800mm

    Red and Blue is steel
    Yellow is aluminium 10mm thick

    Linear rails
    X: 1800mm x 25mm
    Y: 1350mm x 20mm
    Z: 380mm x 20mm

    Motors:Four Sanyo Denki 103H7823-1730@$80 each - 4A, 2,2 mH, 0,65R, ~2 Nm up to 600 RPM
    any suggestion of better value for the money?

    Driver :TB6600

    Steel square profile 80x200x (4 or 5)mm

    Z axis aluminium plate is all 10 mm

    Quote Originally Posted by JAZZCNC View Post
    #1: This guy is ok. Most of them are the same spindle and probably out the same factory.?...
    That's what I'm hoping for but almost every seller has a picture of slightly different design so I was wondering if any of them is better or more reliable then other.

    #2: Honestly there is no solution to match driving from both sides whether twin ballscrews, R&P or belt drive it's by far the best and easiest way to get accurate stiff machine. The wire/drum is just a bodge and best doing it correctly first time.?. . You'll only end back there in the end.!!
    Unless your machine is narrow format, which it doesn't look, then single screw just won't work good. Making gantry wide helps but there's a limit before it gets unusable or feasible.
    I've just google wire/drum and it's called cable drive and it's not as easy and cheap as it seams - if it is to be precise.
    Belt drive is ok but it has a disadvantage of not reducing the moment of inertia of ballscrews. Right now, one ballscrew
    has an equivalent mass of 60 kg, that is as mach as moving mass for X axis and same moment of inertia as motor.

    #3 Can't answer that question without knowing which make and what size linear rails. What I can tell you is even the lower quality units are capable of handling forces far beyond what you throw at them or what your machine design will handle, so it will fail long before they do.!!
    Yes, I've seen the spec for the linear rails and linear guideways and bot of them are pretty strong for the size.
    So for the X axis, moving mass is 60 kg and max force when cutting would probably be around 500N which gives (simplifying) 125N per linear bearing.
    However, when i asked about flexing of open bearing, what I had in mind was an order of magnitude. Is it 1 um, 10 um or 100 um of flex.

    #5: Show us and will comment but until then not sure what you mean.?
    Homemade PCB milling machine - YouTube
    start watching at around 1:35

    Now your design.?? . . . You have a problem Houston (several actually).!!! . . . . but this one Is a common mistake easily missed.!
    The linear bearings on the Y axis can't possibly be fastened like you have them drawn.? Chicken and egg problem.!! Fasten plate on one set and you can't access the bolts for the other bearings.!!
    Absolutely right :) - I've noticed it some time ago but i was too lazy to change all the constraints :)
    here is an updated photo

    Click image for larger version. 

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    I'd also consider using different thickness material for the Z axis.? Those thin plates, even with the bracing will resonate while cutting which will affect quality of finish.
    It's 10 mm aluminium plate - what do you think it should be?
    I was thinking about making a sandwich of wood and aluminium to dampen vibrations. What do you think?

    Sorry for slow replay but i was too busy to write a post

    Best regards
    Last edited by Bart; 01-08-2013 at 02:32 AM.

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