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OX Balls - 1605 Ballscrew Powered 1000mmx1000mmm OX derivative

Discussion in 'CNC Mills/Routers' started by Julius, Jun 21, 2016.

  1. gta18

    gta18 New
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    Hi Julius,

    I have my machine finally running on the N23 on 50v ps and only able to max out the no load feed rate to about 2500mm/min before one of the y axis stepper stalls out.

    What motor/driver and power supplies are u using on ur 25mm ballscrews?



     
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  2. Julius

    Julius Well-Known
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    I dont know what your motors or screws are, but you should be able to get 700rpm from the motor easily.
    Thats 300ipm with a 10mm pitch screw.

    I used tb6600 at 42V and the standard OB motors and got 5000mm/min or so. New machine has 14000.
     
  3. gta18

    gta18 New
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    My machine is 1500x1500 with 2505 screws and Nema 23 motors at 50v with ST-M5045 drivers set at 1/4 step from amazon.

     
  4. Gary Caruso

    Gary Caruso OpenBuilds Team
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    If you know the exact motors you have that is important info, high inductance motors (higher than "normal" rated torque) will have poor high speed performance..
     
  5. gta18

    gta18 New
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    That's most probably what my issue is.

    Are the OB motors good or should I go maybe Nema34 route?


     
  6. gta18

    gta18 New
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    I found the specs of my motor from the Ebay store I got it from and its 6.8mH vs 4.0mH from the one here on OB. I guess that really the cause of it stalling out too early and not getting near 300ipm or 150ipm in my case (2505 screws) per Julius.

     
  7. Gary Caruso

    Gary Caruso OpenBuilds Team
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    There are plenty of low inductance motors to try, yes the openbuilds ones are good.. some of the 8 wire steppers where you can run the coils in parallel get you very low inductance like 1.8mH range.
    What's the rated torque and amps of the steppers you have?
     
  8. gta18

    gta18 New
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    its 425oz-in 3A 6.8mH, What's the acceptable inductance range should I look for?

     
  9. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Lower is better for speed but you are limited with driver current, so as the Henry's get lower the current demand for a given torque will be higher..
    take a look at www.omc-stepperonline.com they have spec sheets for everything and about the best prices you will find.
    It's very hard to say exactly what improvement you will get, friction, driver performance, microsteps, inertia will all affect how fast you will be able to run (and change directions).
    Just looked back.. You are only getting 2500mm/min.. 500RPM.?. 5mm lead is so slow..can you run the X faster? maybe you have a friction issue?

    Here is a good example you can see the red line with coils in parallel (low inductance - high current configuration) how well torque is maintained all the way to the end of the graph compared to when in series (high inductance - low current), they only tested to 390rpm but I would hope it keeps going for a bit more. Graph from https://www.omc-stepperonline.com/download/24HS34-3504D_Torque_Curve.pdf
    upload_2018-1-8_15-53-33.png
     
  10. gta18

    gta18 New
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    The x axis jus moves about 2800mm/min. Im able to run the y at 3200 to 3800mm/min sometimes but it stalls after about 2 secs. Thats why i slowed it down to 2500 to be able to run reliably.

    I checked for gantry friction and it rolls freely when disconnected from the screws and turned the screws by hand and they are fairly soft and doesnt take much effort to turn by hand.

    I have all the axes on 20mm hiwin linear rails.

    Dq542 stepper controllers. Motors are just warm to the touch after cutting 128 20mm holes on the bed.


    I didnt loose a step after that cut, i had thr machine go back to zero position that i marked. (Visually aligned to the home point.)

    I have 3 8 wire nema23 motors i can try your suggestion.


     
  11. Julius

    Julius Well-Known
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    6.8mH requires over 80V to run properly. Sell em and get something more around 3mH or less. Look at longs motors. I recommend a dual shaft too and get some dampeners. It's an issue on mine but I cut at my Max rapids 1/2" deep, otherwise the spindle stalls. Not the motors.

    Really recommend always using 10mm pitch screws for everyone reading, except for Z axis.

    Take the coupler off too and see what the motors Max is without any load!
     
  12. gta18

    gta18 New
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    Julius,

    What's your microstep settings that you use with your setup? OB motors are at 3.8mH. What dampers are you referring to?

    Thanks!

     
  13. Julius

    Julius Well-Known
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    1/2 or 1/4. 80 steps/mm.

    It goes on the back shaft and reduces motor resonance. YouTube explains it
     
  14. Daniel Fisher

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    Hi Julius,

    Great build! I have all the parts for this build and actually live pretty close to Seans shop. I was wondering if you would be willing to share your plate design with me? I talked to Sean about milling another set for my CNC project. Thank you for the details about your project.

    Dan
     
  15. Joe Santarsiero

    Joe Santarsiero OB addict
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    What do you mean by run properly?
    The torque differences I've seen between 6.8 and 3 have been negligible to a router build. Same for the differences between one run at 48 vs 80v
     
  16. Julius

    Julius Well-Known
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    6.8mh requires more voltage to be usable in the higher RPM ranges.
    I see a difference between 42V and 48V, so I suggest playing with your rapids with both power supplies. If you arent going over 500rpm or have a heavy load it wont be noticeable. So many people here run overkill motor sizes.
     
  17. Zach S

    Zach S New
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    Julius,

    Super sweet build! I’m very interested in doing this modification to my machine. Would it be possible to get the end plate’s dxf file from you (the four corners)?

    Zach
     
  18. adhot_hot

    adhot_hot New
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    Hi Julius,
    great work i like it

    im building like this , can you help me i want to see your cad file for this machine
    [email protected]
     
  19. HulkSmash

    HulkSmash New
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    Hi @Julius

    Great machine and build. You working on another now as you mentioned the 2010 balls screws ?

    Did you ever publish your cad files... without the the logo plates ?

    Reason I ask is Im currently designing an openbuilds ball screw ox derivative machine.

    It wil be approx 1000 x 1200mm running on 1610 ball screws.

    Now the machine will be a router but also convert to a plasma cutter.. with a tool change and the removal of a base plate.

    I am unsure if to use the the 2080 v slot or look into c beam territory..... but I dont think the ball screw would be useable in the c extrusion shape.

    Any help is appreciated.

    Thanks

    Mike
     
  20. wastelandfab

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    I would recommend C-beam for your gantry beam, regardless of what your building.The Y rails can be made from V rail and can be very rigid... As long as they are supported..

    If your going to 1000 wide-I would recommend making a built up beam- (bonding/bolting sections together) as even one c beam has some deflection when cutting soft metals. You could also do as others have done and build a built up V-rail beam. In my journey to a large functional cnc that can "do-it-all" I have come to the conclusion that I need to source my x beam from somewhere else. When I have time to use my machines, i want to be able to fit a big sheet of material in there and get a lot done.

    From my experience:

    Bolting together an 80x20 v rail to a c-beam does make it more rigid. It's not the magical cure for deflection at the tool tip though. I think a better route would be to bolt (and bond with epoxy or other high tech glue) two c-beams back to back.. By the time you have gone through the expense of this though, your better buying an extrusion from 80/20 or their competitors. The only downside is you need to make your own plates. Oh and switch to a proprietary linear movement system.... This is why I have not gone this route yet.

    Money doesn't buy the best CNC. I work at a company that builds packaging machinery. They use UHMW and polycarbonate for many things, along with other plastics. The CNC router they use cost upwards of $100,000. It's not new, but maybe 7-8 years. 5x10' with a vacuum table. Uses rack and pinion and servos, and I have gotten a better finish on parts with my cobbled together roughty $1300 set up.

    What I'm trying to get to here is that without rigidity, your ballscrews will do you little good. Yes, they will work fine. But if your into the territory of spending that kind of money on ballscrews, you better make sure your support for your cutting tool is sufficient.

    Long post, but just sharing my previous 10 years of DIY CNC.

    Good luck, show us how it goes.
     
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  21. HulkSmash

    HulkSmash New
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    @wastelandfab

    Thanks for all that advice - Yes C beam seems favourite however rather than add more aluminium I plan to re-enforce with steel. I have some ideas that I have started to sketch and I am gonna try get something down on CAD.

    My area is probably gonna have to be 800 x 1200 mm now, as its sitting on a steel unit in my garage - as I am limited for space.

    The gantry is gonna be 1200 mm as its against a wall so to have the gantry as 800 mm it would mean I would have to place the work piece in from the side rather than the front.

    What do you think - is loading from the side a problem ? All I can think is wood is not that heavy but if I was gonna plasma cut 15mmm - 20mm steel (which my plasma will cut) lifting from the side could be problematic.

    any help appreciated

    Mike
     

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