1. #1
    So I am looking to build a CNC machine designed for cutting wood and aluminium. I haven't fully decided but I think I want a cutting area of about 750mm x 500mm. I don't have any access to any milling machines currently and so would like to buy a Z axis kit to make sure it's good. I'm only a real budget because I'm a student and so probably have around 750 to spend over around 6 months so this will be a gradual long term project. I plan to use supported rail and timing belts for cost, if it's worth it I will go with screws. I've been looking around and ebay seems to be the cheapest place to buy this sort of stuff (I need everything) however I think I will put an advert in the wanted section to see if anyone has anything second hand.

    I'm an electronic engineer and very skillful with my hands and designing mechanical objects so a challenge is not scary!

    Thanks
    Boscoe.

  2. #2
    You wont cut aluminium using timing belts and no screws, it's simply not stiff enough. 750 is probably just about enough to make the machine with ballscrews, but not if you have to pay people to make parts.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  3. #3
    Welcome to the forum, have a read through some of the build logs to get you started, you may well find you need to look at building it over a longer time period so you can save more money for the project.

  4. #4
    Quote Originally Posted by Jonathan View Post
    You wont cut aluminium using timing belts and no screws, it's simply not stiff enough. 750 is probably just about enough to make the machine with ballscrews, but not if you have to pay people to make parts.
    Not even if I use wide belts?

  5. #5
    Is ebay the best place to get cheap items? Is the quality of the items acceptable?

  6. #6
    Quote Originally Posted by Boscoe View Post
    Not even if I use wide belts?
    Maybe, but I expect you'd end up paying more for the belts then the ballscrews. In addition you'd need to gear the motor down substantially to get enough resolution.

    Quote Originally Posted by Boscoe View Post
    Is ebay the best place to get cheap items? Is the quality of the items acceptable?
    Often it is, but there's also AliExpress.com - Online Shopping for Electronics, Fashion, Home & Garden, Toys & Sports, Automobiles from China.. Quality of the ballscrews I've had from eBay has been perfectly adequate.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  7. #7
    Quote Originally Posted by Jonathan View Post
    Maybe, but I expect you'd end up paying more for the belts then the ballscrews. In addition you'd need to gear the motor down substantially to get enough resolution.



    Often it is, but there's also AliExpress.com - Online Shopping for Electronics, Fashion, Home & Garden, Toys & Sports, Automobiles from China.. Quality of the ballscrews I've had from eBay has been perfectly adequate.
    Wow it's a lot cheaper on there. Is there something I should look out for?

  8. #8
    I've just bought ballscrews and ballnuts from Chai on eBay. Very cheap, very fast delivery (3 days from China) AND they'll machine the ballscrews for you to a high standard for next to nothing. You're looking at about 150 for 3 ballscrews, ballnuts, bearing blocks and machining, including shipping. Bargain!
    Last edited by birchy; 16-07-2013 at 06:53 PM.

  9. #9
    Quote Originally Posted by birchy View Post
    very fast delivery (3 days from China)
    Wow Birchy think you have the record there at 3 days delivery, thought Chai getting stuff to me in 4 days was a record..

    Quote Originally Posted by Boscoe View Post
    Not even if I use wide belts?
    Yes they will cut aluminium ok see this machine I built for a guy using 15mm Belts and alu profile scrounged. It's cut every thing from Alu to PCB's. It went to Ireland so not seen it since left my hands but it's still going strong I believe and without any issues other than the initial setup and settling down.
    New Machine Build Belt Driven extrusion framed wee beasty!!

    That said Jonathans spot-on It's actually cheaper and far easier to buy Ballscrews from chia. We had the stuff or got it cheap but if building again it would have screws has by time you bought bearing,housing, belt, pulleys etc they will cost more.
    By far the best and quickest for someone new is buying screws and BK/BF bearings pre-machined from Chai. It's basicly makes it a simple bolt on affair.

    By far the easist hole to fall down is the Electrics, it's also the most important to get right.
    DONT buy the cheap ALL-IN-ONE TB chip based boards you see on Ebay they are bad news.
    Like wise be careful of some of the kits which sell motors, drives, BOB(breakout board), PSU etc.!! Often the motors and drives are ok but the PSU is under sized and the BOB rubbish quality.
    PSU size or more importantly Voltage makes a big difference to performance you'll get from a stepper and often they'll sell drives which are rated at 50v and can run comfortably at 46-48 along with motors which can take much higher voltage than that but supply a 36V PSU.
    Not much difference you'd think but to a stepper it can mean upto 1/4 less usable speed/torque than 48V would give. Poor quality BOB can give you night mares and many wasted hours chasing problems.

    Regards linear rails then you can also get these from Chai has well. Don't be tempted to buy unsupported rails you'll only regret it.

    Best advise is don't buy anything until you 100% know it's what you need and will do the Job. Ask if not sure.!!
    Also while it's inspiring and tempting to see motors spinning on bench Don't buy electrics until you need to fit them on machine, they only have 1 year warranty and can fail in use so you want them last of all.
    Same goes with spindle, it won't be needed until your ready to cut which could be weeks at best and most likely months.

    Good luck.
    Last edited by JAZZCNC; 16-07-2013 at 10:01 PM.

  10. #10
    I wouldnt recommend belts. I remember once working on a plasma machine with twin X axis belt drives. 50mm wide reinforced belts. Major pain to get the machine square and keep it that way.

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