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  1. #21
    Quote Originally Posted by Jonathan View Post
    Yep, that's just what I was thinking. I'd like to try one of those on my machine.
    Ok just for jonathan Here's what 10mm pitch gets you.!!

    Johnathan if you want the code your welcome to it, or any body else for that matter. It's a 17mb file thou and over a million lines of code, If I remember correct it took about hour n half.
    I did another after that but with the Welsh dragon on the back side but didn't take any pics. . . . Looked good thou.!!

    Enjoy and the pics don't show all the detail or do it justice. . . 150mm diameter 10mm Ali plate cut with a 6mm 90deg carbide chamfer/spot drill.
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  2. #22
    Quote Originally Posted by JAZZCNC View Post
    Ok just for jonathan Here's what 10mm pitch gets you.!!
    Was amazed when I first saw that - I still am.

    Quote Originally Posted by JAZZCNC View Post
    Jonathan if you want the code your welcome to it, or any body else for that matter. It's a 17mb file thou and over a million lines of code, If I remember correct it took about hour n half.
    Yes please! I've got some aluminium that size so why not...I believe you did it with a 6mm spot drill, 90? As better excuse than most to finally buy some spot drills I guess.

    I agree that 10mm pitch is definitely the way to go if you want good feed-rates.

  3. #23
    Quote Originally Posted by Jonathan View Post
    Was amazed when I first saw that - I still am.
    Ye me too I must have looked at it for days and every time I saw a bit more detail I'd missed.
    It's also mesmorizing to watch the toolpath do it's stuff the bloody thing bounce's all over the place, so much so when first started cutting I very nearly stopped it because I thought it had FUBARD.


    Quote Originally Posted by Jonathan View Post
    Yes please! I've got some aluminium that size so why not...I believe you did it with a 6mm spot drill, 90? As better excuse than most to finally buy some spot drills I guess.
    No better excuse IMO. . lol . . . . . I'll dig it out and send your way.

  4. #24
    Quote Originally Posted by JAZZCNC View Post
    Personally I'd go with 1610 it's a better all round pitch. Not sure what you mean by only buying the screws and sorting the nut later because it's normal to buy the ballscrew and ballnut together.
    RE: Turning. Even thou I have a good lathe and capable of turning my own screws I dont bother and buy them pre-machined from china, It's just not worth me doing it my self for what they charge.

    I'd save and buy the ballscrews before buy cheap and replace later as it's often more than just quick swap over job due to the differant way the connect or work, Plus cheap acme lead screw is rubbish and good quality acme lead is more expensive than ballscrews from china.!!
    Ah, I don't think my post was as clear as it should have been, my apologies.

    I'm planning to go for ballscrew+ballnut, but I noted that, depending on where you look, there seems to be a big jump in price from the ballnuts without preload/zero backlash to the ones that do have it (which I would think are preferable). Going cheaper would get me running sooner, and having a working (albeit lower precision) machine to play with while building up more funds is preferable to me. There also seemed to be suggestions for ways to increase the effectiveness of the lower end ballnuts, though now that I think about it, they may have been talking about the acme setups. Hmm.

    As for turning the ballscrews, I suppose that's a matter of perspective. If you have the skills and equipment but your time is money then yes, turning the ends down to fit the bearings probably is better left to the supplier. Would I do it that way? Ask me in 5 years

    1610 rather than 1605, you say? I shall run that though the collection of calculations I'm building up.

    The following picture is a rough mockup of what it's running - working area was originally planned at 200mmx200mm for the table, will have to be bigger simply to fit the stepper in the location parallel to the screw. The gantry will be close to the table but large so the X can run up quite high and still be supported, for reasons discussed elsewhere. "Scale" is a dirty word as far as this picture is concerned, don't read too much into it. The XY will not be completely seperate from the gantry, it was just easier to draw that way!

    Click image for larger version. 

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  5. #25
    Quote Originally Posted by JAZZCNC View Post
    Ok just for jonathan Here's what 10mm pitch gets you.!!
    That is several steps beyond awesome, and something to aspire to in the future. Is there a drool icon? If not, why not?

  6. #26
    Quote Originally Posted by Rogue View Post
    As for turning the ballscrews, I suppose that's a matter of perspective. If you have the skills and equipment but your time is money then yes, turning the ends down to fit the bearings probably is better left to the supplier. Would I do it that way? Ask me in 5 years
    Not really I have the time, equipment and the skills but ballscrews are hardened and the indexable tips required cost me nearly as much as what I get charged.
    So to me it's not worth the hassle and all thou unprobable still possible risk of error.

    RE: 1610 or 1605. I should clarify this depends on the intended use of the machine. If your going to use it to cutt intricate jewelry or want very fine detail then the small pitch is better but for a general allround machine then 10mm pitch works best in my experience.

  7. #27
    All round, I'd guess. If I understood the earlier posts correctly, if I had a system for changing pulleys I could get the higher precision if needed, at the expense of speed? If so, this is one of the things that interest me about pulley systems.

  8. #28
    Quote Originally Posted by JAZZCNC View Post
    RE: Turning. Even thou I have a good lathe and capable of turning my own screws I dont bother and buy them pre-machined from china, It's just not worth me doing it my self for what they charge.
    That's precisely what I thought. I would machine a ballscrew if someone asked, but it's just not worth is with linearmotionbearings2008 prices on eBay.

    Quote Originally Posted by Rogue View Post
    All round, I'd guess. If I understood the earlier posts correctly, if I had a system for changing pulleys I could get the higher precision if needed, at the expense of speed? If so, this is one of the things that interest me about pulley systems.
    That is correct. Lets say, for example, you have a standard stepper motor so 200 steps per revolution. The travel per step on a 10mm pitch screw will be 0.05mm with direct drive or 0.1mm or 0.025mm depending on if 2:1 or 1:2. Using microstepping will get finer resolution up to a point.

    Though I would normally advise 10mm pitch screws (I probably did earlier!) since this is such a small machine it may not make a lot of difference...having said that the main thing is getting high acceleration, otherwise you'll run out of travel before it hits top speed and has to decelerate. To do that a 2:1 (bigger on stepper) with a 10mm pitch screw would be ideal since the motor has to input only a quarter of the kinetic energy into the screw when accelerating compared to a 5mm pitch screw.

    Your 'system' for changing pulleys is just an allen key plus a bit of space.

  9. #29
    Agree with what jonathan says just one thing to point out 2:1 10mm pitch is effectivley 20mm pitch. If you can live with this loss of resolution then it's a good way to go.

    What's your main intended use.?

    Edit: Jonathans comment about accelleration is even more important if you plan to do lots of 3D and intricate V carving. 3D and intricate carving is very time consuming, esp vcarving, with lots of very small moves required with the Z axis dancing around all over the place. The problem with low accel is the commanded feed rate actually never get's meet and therefore the cutting time increase's. On very large 3D jobs this can run it several extra hours or even days.!!
    Last edited by JAZZCNC; 05-09-2011 at 10:34 PM.

  10. #30
    Quote Originally Posted by JAZZCNC View Post
    Agree with what jonathan says just one thing to point out 2:1 10mm pitch is effectivley 20mm pitch. If you can live with this loss of resolution then it's a good way to go.

    What's your main intended use.?
    5mm, 10mm .. . it all depends on what motor is driving the screw. If it's a 3nm motor then clearly a different ratio will be optimal when compared to using a 1nm motor.
    If you're using it for PCBs then you'll want good resolution, so probably best to use swappable 1:2 pulleys. Can't really thing of anything else that would require it. Maybe engraving, but generally for engraving it's relative position that matters more than absolute which means microstepping is more valuable.

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