Thread: It's begun....

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  1. #81
    Point taken - I knew I was pushing my luck running it like that, but was eager to get some movement after the machine had been dormant for so long.

    I'm running the motors in bipolar parallel and the drivers are PM752's and IIRC the PSU (Zapp PS806-5) produces 68V.

    Funnily enough I have ordered another stepper (wanted a spare and could always use it for 4th axis assuming I can get the 3 running first), so I could cut the extension down and run 2 motors - would I need another driver or wire them both in parallel off of the same X axis driver? I also thought running 2 motors was a bit risky if one starts losing steps for some reason?

    I could also go the two belt method you suggest - I have a 3rd pulley coming also, which I was going to use for tensioning. The problem I foresee with that is finding the right length belts will likely mean some kind of custom motor mounting plate, which I'm not setup yet to make - if only I had a CNC machine ;)

    Good to know that the heat isn't immediately fatal to the drives, thanks for that.

    I'll have a think over the weekend and see which option for "sorting" out the drive to the second ballscrew I should go for (read easiest).

    8-9 m/min sounds scary enough, let alone 16-17.........

  2. #82
    Quote Originally Posted by Washout View Post
    Funnily enough I have ordered another stepper (wanted a spare and could always use it for 4th axis assuming I can get the 3 running first), so I could cut the extension down and run 2 motors - would I need another driver or wire them both in parallel off of the same X axis driver? I also thought running 2 motors was a bit risky if one starts losing steps for some reason?
    2 x motors will be your easiest route with how it's setup already.

    Most common cause of missed steps is motors being tuned too high with folks trying to have both Acceleration and velocity too high.
    If you keep tuning to sensible speeds then you generally won't have a problem, only other time you can run into issues is if your running very long jobs like large 3D work that can have cycle times well in excess of 20hrs. Because 3D work is usually lots of small fast moves and higher accelerations are often used then steps can get missed over time period.

    Keep sensible motor tuning and you'll be fine with slaved motors but unfortunately you'll need another drive.

    Run 2 x motors and with 68V you'll easily see 6mtr/min with good Acceleration without any issues provided everything is aligned properly.

  3. #83
    Thanks as ever Dean,

    I could probably do with another Driver in any case, so will add that to my order with Zapp - will have to see if the 806-5 transformer will be good for a 4th Driver or I'll have to get another of those as well (4th Axis would have needed it anyway I expect).

    I did a bit of tinkering over the weekend and one of the x axis ballscrews was out of alignment, so have also rectified that whilst waiting for parts.

    More as I work on it.....


    Chris

  4. #84
    Quote Originally Posted by Washout View Post
    I could probably do with another Driver in any case, so will add that to my order with Zapp - will have to see if the 806-5 transformer will be good for a 4th Driver or I'll have to get another of those as well (4th Axis would have needed it anyway I expect).
    Erm . . well 6A is low for 4 drives and personally I would.!! . . . But worth trying first and will probably only cause you problems if pushing hard.

    Being honest with you and Gary probably won't thank me for this.! . . Instead of buying another then I'd build one to suit your requirements exactly. It will be cheaper, take just the same room in control box has the one you have now. If you need the 5V then buy a cheap linear supply for 5.
    If you then sell the existing 806-5 it will end up costing you next to nothing.!!

  5. #85
    LOL would you believe it, just as I think "yep, I'll go with the dual motor setup on the X-Axis" Sod's law kicks in and the PM752's are not easily available (ebay from China only), but there are comparable digital drivers available and my guess is I'll have to switch out the Z Axis driver to be the 2nd X Axis and run the new driver in its place. That's assuming MACH3 has no problem with a mix of drivers (provided they are tuned to the same steps per rev etc.?)

  6. #86
    Quote Originally Posted by Washout View Post
    That's assuming MACH3 has no problem with a mix of drivers (provided they are tuned to the same steps per rev etc.?)
    Mach doesn't know or care what drives you use it just sends pulses to the drives based on your preferences in motor tuning.
    You'll see a difference between digital and Analogue drives but it will be positive not negative and the smoother Digital drive will work good on Z axis anyway.!

  7. The Following User Says Thank You to JAZZCNC For This Useful Post:


  8. JAZZ, Not quite that fast but have gotten it up to 12.5m/min rapids with an acceleration of 1.5m/sec^2. These days I am running it most the time at rapids of 7m/min on the x and y axis and 5.2m/min on the z axis with a acceleration of 1m/sec^2. Which with the mentioned motors and drivers and a well set up CV mode gives me cutting speeds possible of 4.8m/min with a 4mm Single Flute Lapped end mill with a 6mm shank. As JAZZ asked what voltage are you running at. I could run in crazy land IF I moved acceleration down to about 500mm/sec^2 but let me tell you 12.5m/min gets scary on my machine. -Michael
    CAD software Shark Pro v10, Also Aspire v9.0
    CAM Software Aspire v9.0, CamBam v1 beta12
    CNC Machine: http://www.mycncuk.com/threads/3661-...Second-machine
    3D printers: 2 x Prusa MK2S soon to be 2.5's and 1 x mini Delta (180 x 180)
    Work with Solid Surfaces, Acrylics, Woods, Foamboard, PLA, ASA, PMMA
    Work Computer: Lenovo D20, K4000, Tesla C2070, 64GB RAM

    www.marino-customs.com

  9. #88
    Hi Michael

    Sorry I missed your reply - I'm pretty sure I'm running the steppers at 68V (that's the output voltage of the PSU).

    Those are some pretty hairy speeds you're getting on your machine and I'll be very happy to get near that.

    I also had some bits arrive today:

    a. some components to brace and tension the belt between the two ballscrews (and support the "wobbly " extension. I had ordered these anyway so will try them out, as I redid the second ballscrew alignment and I must have missed a step in my haste and it was well out (2mm or more). Chances are that's where my overheating stepper was coming from and gantry binding.
    b. Also a spare M752 came from ebay (China), so will use that as plan b, should a. above not work out. I'll also likely need a custom motor mount as the T-slots don't line up with the mounting bolts on that side of the machine.

    More as I get on with stuff.....


    Chris
    Last edited by Washout; 12-09-2013 at 03:42 PM.

  10. #89
    Hi.
    First pic looks like a mechanical beast,but good!
    A little tip for tapping holes. I use my B&d pivot driver saves a lot of work and no aching hands!
    meerkat.

  11. #90
    Hi Meerkat,

    Thanks - "beast" is the target after Dean' comments further back :-)

    I made a little progress last night after putting a bracing structure and bearing onto the 2nd ballscrew extension - this has cut down flex considerably (i.e. hardly any movement even when leaning into it) and I did a test by jacking my motors up to 4000mm/min in MACH3 and had no stalling on full speed jogs. So a step in the right direction methinks. I'll likely push the speeds up again tonight and see where the stalling starts, but I'm quite happy with 4m/min, as in its original guise the machine wouldn't go above 2.5m/min reliably with the single ballscrew configuration.

    To do tonight will be to put the belt tensioning pulley on and take the slack out of that (the bracing has improved that also anyway). Then run some more tests to see if there's been improvements.

    I'll then think about plan b dependant on the results of that.

    Chris

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