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  1. #1
    http://www.ebay.co.uk/itm/1523042469...&ul_noapp=true

    i'm looking to machine wood only on it, no metal and maybe some plastics. do you think this will be ok. Tolerance is not too important as it will be all arty type stuff. opinions please

  2. #2
    It *should*. Accuracy will likely be the issue however if this is not too much of an issue for you, might be fine.

    There are many of these around, I'm sure ive seen them cheaper.

  3. #3
    hi chaz. any idea where you have seen them cheaper. the only place I have seen is china and then you get vat and import on them so doesn't work out

  4. #4
    cheaper. shipped from Germany as well.

    what about this one? harmonic drive they say.

    I cannot see any accuracy problem, maybe only in the axis alignment. the issues are resolution and torque. with the 6:1 reduction, at 100 mm diameter one full motor step will translate in 0.27 mm of movement.

    harmonic drives are in a different league, if they are for real inside..

  5. #5
    Quote Originally Posted by johngoodrich View Post
    hi chaz. any idea where you have seen them cheaper. the only place I have seen is china and then you get vat and import on them so doesn't work out
    When I ordered my ballscrews the import tax should have been 68 when they arrived they were marked as 2nd hand ballscrews with a value of $10 each, customs didn't buy this but only put 15 in import tax on.

    Import tax is luck of the draw but personally from China I'm pretty lucky anything from the US I get screwed on to the full value.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  6. The Following User Says Thank You to Desertboy For This Useful Post:


  7. #6
    I thought these bolt to the bed rotating chuck things usually came with a worm drive and an index wheel/pin.
    Sticking a stepper in place of the index handle is a CNC conversion.
    Replacing the worm wheel with a toothed pulley sounds like a Chinese CNC conversion. More for selling than using.
    Maybe you want to engrave toothpicks and this is exactly what you need.
    Alternatively, maybe if you bought it as an incomplete conversion, played with it, decided what resolution your usage required, replaced their timing pulley with a nice anti-backlash worm from HPC gears, tried it with the stepper then replaced the stepper with one of those singleton servo drives doing the rounds on eBay.
    That could work.

  8. #7
    I have one of the type in the first link in the OP, I chose it for the decent through capacity which you don't get with harmonic drive versions, it worked well enough as standard but I added a link bar and bearings outboard at the back behind the belt to take bending load off the stepper shaft and was then able to add a belt tensioning pulley bearing.
    A few hours work and a few quid in bearings yielded something which is up to 4-axis machining in Ally and Steel using tooling up to 12mm and 7000rpm.

    I had a good indexing head but I believe that a converted/ home brew worm/wheel job is more of a bodge than pulleys, belts & bearings because long term under CNC use gears and plain bearings will require more maintenance, more expensive maintenance and more complex maintenance.

    - Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  9. #8
    Double Post, Sorry guys, gremlins on the interface!
    Last edited by magicniner; 17-08-2017 at 05:44 PM.
    You think that's too expensive? You're not a Model Engineer are you? :D

  10. #9
    What is a harmonic drive? Do they mean epicyclic?

  11. Harmonic is a brand name and people recognise it just like hiwin,but yes its epicyclic.

    Quote Originally Posted by Robin Hewitt View Post
    What is a harmonic drive? Do they mean epicyclic?

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