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  1. #1
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    Is this possible?

    Hi everyone,

    I'm interested in converting my belt driven CNC to use lead screws on all 3 axes. I have no problem making the parts to actually install them, but I know very little about Steppers.

    I don't have control over the firmware at all. Is it possible to put a controller between the main board and the motor?

    Or do I even need to? The motors are Minebea 17PM-K044 bipolar. Their site doesn't list it, but I've asked them for help. They have a very similar motor that comes pre-attached to the leadscrew, but presumably it will have different resistance and induction.

    Finally, what to do about the gear reduction? The speed will be all wrong if it's turning that lead screw at the same rate. Any ideas?

    Thanks for any help!

  2. #2
    Community Moderator Jim Dawson's Avatar
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    Re: Is this possible?

    Yes this is possible. You would need to adjust the steps/inch in the controller to get the correct ratios. Without knowing anything about your controller I would have no idea how to accomplish this. It the current controller values are not user accessible/adjustable, then a new controller might be needed.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: Is this possible?

    Thank you... So, they're being controlled directly from the inaccessible main board, which does need to be there (obviously). There doesn't appear to be a controller board that can be replaced. Is it possible to have a controller that accepts the output from the main board, and then feeds modified steps to the motor?

  4. #4
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    Re: Is this possible?

    easy to build the one like that.
    Isn't it easier to build a new controller from scratch?

  5. #5
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    Re: Is this possible?

    Quote Originally Posted by Alphastar View Post
    Thank you... So, they're being controlled directly from the inaccessible main board, which does need to be there (obviously). There doesn't appear to be a controller board that can be replaced. Is it possible to have a controller that accepts the output from the main board, and then feeds modified steps to the motor?
    It's hard to imagine a CNC controller that does not have at least some way to change the motor settings. How about posting some pictures and/or model numbers so we could see what exactly you have?

    A "steps converter" is theoretically possible if you have the access to the STEP/DIR signals. Practically, it would probably be more expensive and more problematic than replacing the entire CNC controller.

  6. #6
    Community Moderator Jim Dawson's Avatar
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    Re: Is this possible?

    Quote Originally Posted by Alphastar View Post
    Thank you... So, they're being controlled directly from the inaccessible main board, which does need to be there (obviously). There doesn't appear to be a controller board that can be replaced. Is it possible to have a controller that accepts the output from the main board, and then feeds modified steps to the motor?
    It would be possible to build a converter board, but not very easy, just depends on your electronics design skills. There is no off-the-shelf board that would do what you want. If you are not able to adjust the machine operating parameters from the main board, then replacing the main board with a new one that you can control would be the easiest option.
    Jim Dawson
    Sandy, Oregon, USA

  7. #7
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    Re: Is this possible?

    Thanks guys... The main board is completely integrated with an ATC, sensors, carriage board, etc. I suppose replacing the entire logic system is doable, but it's actually very well made, and other than belts, it's the best machine I've worked with. It's a Roland MDX-50.

    Here's a pic of the Yaxis drive: Reprolabels.com/images/Yaxis.jpg

    Maybe I'm better off leaving the exist stepper where it is and using an anti-backlash gear to turn a leadscrew. I've never actually seen a leadscrew that wasn't pre-installed in the stepper, though.

  8. #8
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    Re: Is this possible?

    It's probably possible, but is it necessary? Are the belts giving you problems? It's never going to be a mill that can cut steel, but if it's in working condition, why not sell it and get something that fits your needs better? That would be a lot easier than trying to turn it into a machine it's not and never will be, Just getting the ATC to work with a new control system would be a nightmare, and once you managed to swap the belts for screws, you'd find other things, like the slides, that limit its performance just as much as they did.
    Andrew Werby
    Website

  9. #9
    Community Moderator Jim Dawson's Avatar
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    Re: Is this possible?

    I have to agree with Andrew. After looking at the machine, it is very light duty, suitable only for very light work.

    I guess the real question is: What is your end goal here?
    Jim Dawson
    Sandy, Oregon, USA

  10. #10
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    Re: Is this possible?

    I agree with Andrew. You have a nice and expensive machine, don't try to butcher it into something it will never be. Use it for what it can do well, or sell it and get something that suits your needs better.

    All components of a well designed CNC machine have roughly the same level of performance. Improving just one of them will simply reveal the next weak link (most likely lack of spindle power or lack of rigidity).

  11. #11
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    Re: Is this possible?

    I really don't want to modify it if it can be avoided. This is my fifth purchase of a light CNC, and I like it for what I need with the exception that there is a lot of backlash. Not traditional backlash that can be accounted for in the toolpaths, but a variable, feed-rate-dependant backlash. It can only be explained by belt stretch, really. Is there simply a more rigid belt I should consider? This appears to be 5mm TPU, with no visible steel reinforcement.

  12. #12
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    Re: Is this possible?

    Oh, and I only cut wax with it. It's essentially built for wax, but they sort of dropped the ball with the belts. Everything else is truly impressive. Rigid structure, great programming, high quality rails and parts, etc.

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