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Thread: where to start?

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  1. #1
    Hey guys,
    I want to start my own DIY build so I've been reading the forums for quite sometime along with watching lots of videos on youtube but I'm still really pretty clueless about a lot of the terms and jargon that's being used.
    Is there anywhere I can find a "idiots guide" to building your own cnc machine? because it seems the more I research the more I find different systems that all seem to do the same job which ends up confusing me even more :confused:

    The machine I need will be mainly used for cutting 8' x 4' sheets of 18mm MDF using a 8mm bit and maybe thin perpsex but nothing more than that.
    I don't know how realstic my budget of £1000 is but that's really all I have to play with.

    Any advice or where I should start would be greatly appreciated.
    Cheers in advance.

  2. #2
    Is there anything specific you would like clarifying?

    £1000 sounds just about possible for that size machine.

    I would start by finding pictures of similar size machines and pick and choose from them. Please post a drawing before you buy anything...

  3. #3
    Quote Originally Posted by chip View Post
    is this what you had in mind jon http://www.youtube.com/watch?v=iaRc8c4Qwn4 for a grand i,d like to see it done.
    Nah, can do better than that. Give me a grand and I'll prove it :lol: You and JohnS reckon I'll be a millionaire 'soon enough' so I'm sure you'd get the money back!

    The critical point is '18mm mdf ... nothing more than that', so the machine does not need to be massively rigid and a 50mm Z-axis should be fine. If you're sticking to that budget then start with a simple 8x4 rectangular steel frame mounted on a strong table or the floor which shouldn't cost much. Use linear bearings from ebay (linearmotionbearings2008), or to get it cheaper explore one of the other methods.

    No mention of required feedrate, so I'm sure 3nm motors would be plenty... I reckon it's possible though in my opinion you'd be much better off in the long run spending more to start with.

    Quote Originally Posted by luke11cnc View Post
    Because as I found out it's more than likely wrong,to small or to weak
    don't cut corners on the frame and ask ask ask away
    By all means cut corners, as long as they're square. :naughty: Not going to be much of a frame without corners. Mine was far too big and too weak to start with.
    Last edited by Jonathan; 05-09-2011 at 08:36 PM.

  4. #4
    Thanks Guys, been doing more research up until the small hours and starting to get a better undertsanding.
    Whats the general rule for frame size vs the actual cutting area? I'm limited for space so I'm hoping that 10' x 5.5 will be enough for 8' x 4. I only ask because I was looking at the linear bearings on ebay and the nearest size I'll be needing are 2750mm which is a fair bit past the actual cutting size.

  5. #5
    I agree don't buy a thing until you've got a good idea what you want.

    Because as I found out it's more than likely wrong,to small or to weak

    don't cut corners on the frame and ask ask ask away

    James & Luke

  6. #6
    You can have them cut to size
    if you email him and give the length you want he will give you a price

    James

  7. #7
    Quote Originally Posted by trounce View Post
    Hey guys,
    The machine I need will be mainly used for cutting 8' x 4' sheets of 18mm MDF using a 8mm bit and maybe thin perpsex but nothing more than that.
    I don't know how realstic my budget of £1000 is but that's really all I have to play with.

    Any advice or where I should start would be greatly appreciated.
    Cheers in advance.
    Hi,

    First what tools do you have access too and what skill level or experience do you have working with metal.? . . . IE: Welding etc.

    Building what you want is just about do-able for a grand but will need you to have the right tools and skill level, OR friends that do.! . . Along with some savy purchasing. Plus you'll need a rock solid design that you know will suit your needs along with good plan of attack because you'll have no room for error if your wanting to do it for around £1000.

    Steel box frame and Rack & pinion on the X&Y Axis with ballscrew or lead screw on the Z axis is the route I would take for a Really strong accurate machine of this size.
    Belt drive would also be an option which is relatively cheap and very accurate and lends it's self well to machine this size.

    Best advice DONT BUY A THING untill your 110% sure the design you have choosen will do what you need, then have it checked out by others for reassurance.
    Then and only then start buying materials needed and even then dont buy to far in front because plans have a nasty habit of changing on the fly very easlily rendering some parts or materials unsuitable purpose. . . . . It's like eating an elephant.? . . . best done in small bytes.
    Like any good constructuion it all starts with good foundations(the frame), weak foundations will tranfer into a weak machine. . . . Equally poor materials will render poor results.
    Also like any other construction the methods and skill levels of the builder will have a massive affect on the end result. I've seen some very good strong designs built with very high quality components that have been completely FUBARD due to poor skill levels built with caveman tools.
    Equaly I've seen fantastic machines built with basic tools and cheap components when mixed with good skill and reasonabe tools, mix with a good dose of imagination and the results can even blow away some big buck machines.

    Don't rush and ASK Q's then some more Q's and then more Q's not matter how dumb you feel or think they sound, keep asking untill you fully understand and are comfortable to go.

  8. #8
    Quote Originally Posted by JAZZCNC View Post
    Hi,

    First what tools do you have access too and what skill level or experience do you have working with metal.? . . . IE: Welding etc.

    Building what you want is just about do-able for a grand but will need you to have the right tools and skill level, OR friends that do.! . . Along with some savy purchasing. Plus you'll need a rock solid design that you know will suit your needs along with good plan of attack because you'll have no room for error if your wanting to do it for around £1000.

    Steel box frame and Rack & pinion on the X&Y Axis with ballscrew or lead screw on the Z axis is the route I would take for a Really strong accurate machine of this size.
    Belt drive would also be an option which is relatively cheap and very accurate and lends it's self well to machine this size.

    Best advice DONT BUY A THING untill your 110% sure the design you have choosen will do what you need, then have it checked out by others for reassurance.
    Then and only then start buying materials needed and even then dont buy to far in front because plans have a nasty habit of changing on the fly very easlily rendering some parts or materials unsuitable purpose. . . . . It's like eating an elephant.? . . . best done in small bytes.
    Like any good constructuion it all starts with good foundations(the frame), weak foundations will tranfer into a weak machine. . . . Equally poor materials will render poor results.
    Also like any other construction the methods and skill levels of the builder will have a massive affect on the end result. I've seen some very good strong designs built with very high quality components that have been completely FUBARD due to poor skill levels built with caveman tools.
    Equaly I've seen fantastic machines built with basic tools and cheap components when mixed with good skill and reasonabe tools, mix with a good dose of imagination and the results can even blow away some big buck machines.

    Don't rush and ASK Q's then some more Q's and then more Q's not matter how dumb you feel or think they sound, keep asking untill you fully understand and are comfortable to go.
    Thanks Jazz, that looks like a lot of great advice.
    When it comes my tools I don't really have that much in terms of metal working. I want this machine to cut out cabinet pieces for my arcade machines so I guess most of my tools are woodworking.
    I have experience with welding so that's not a problem, sometimes it doesn't end up looking that pretty but then I have my grinder to clean it up :tup:

    I have a 110 amp Mig welder, angle grinder, bench grinder and bench drill along with the usual hand tools, drill, jigsaw, sanders, dremel etc.

    I saw a very nice belt driven home build on youtube and I'm very tempted to use this on the X & Y axis, Im presuming that due to the size of my machine I would need two motors on the Y axis as apposed to just one on the machine I saw as it was much smaller?

  9. #9
    Quote Originally Posted by trounce View Post
    I saw a very nice belt driven home build on youtube and I'm very tempted to use this on the X & Y axis, Im presuming that due to the size of my machine I would need two motors on the Y axis as apposed to just one on the machine I saw as it was much smaller?
    Hi Neil,

    Sorry didn't notice this bit, read that meny posts I tend to skim things and miss bits. . .Lol

    Post the link and lets have a look.!. . . but NO you shouldn't need 2 motors just one decent size connected to a shaft linking the 2 sides.
    With Belts you tend to have quit high reduction to get the resolution down to something usable (for your needs something in the 20mm pitch range) and this reduction ups the torque which helps the motor. The trick is getting the reduction right so the meat of the motors torque is delivered at the optimum feed rate (for nema 34 this usually around 600rpm) and still give good resolution.


    Problem with belts at the lengths you need for the long axis is keeping them tight enough they don't flap around but not so tight the stretch. . . . . So Something to consider could be switching from the conventional narrow gantry layout moving along the long axis and instead have a long gantry moving across the short axis.? This way you could use short twin motor driven belts on the narrow axis and R&P on the other long axis. . . . OR even ballscrews on the short axis.? Chinese ballscrews won't cost much more than belts,pulleys,bearing blocks etc so something I'd consider and ballscrews are very much easier to impliment.!
    Last edited by JAZZCNC; 08-09-2011 at 12:49 AM.

  10. #10
    JAZZCNC you have given some excellent advice in this and other threads and I am sure that myself and others will benefit for your experience.
    A question, how does rack and pinion compare to ball screws in repeatibilty and accuracy, and does the pinion ever jump teeth under load?
    Sorry if this sound dim, but curious.

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