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A Dumb Idea? Stepper Motors As Power Feeds.

Discussion in 'SHERLINE, TAIG, TITAN & SIEG MINI-MACHINES' started by tomw, Jun 14, 2015.

  1. tomw

    tomw United States Active Member Active Member

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    Dear All,

    I really don't know anything about CNC or stepper motors. Whew, I confess. But, I notice that these motors are very small. Can stepper motors be adapted to be a power feed for an axis? I am thinking of some simple controller that allows you to:

    1) adjust the feed speed
    2) change direction of feed
    3) start and stop feed

    One would have a CNC ready machine, but with the 'manual' controls of a typical power fed lathe or milll.

    This would be beneficial for:

    1) me
    2) others?

    I am thinking of X and Z axis power feed on the lathe, and X and Y axis power feed on the mill.

    So, how badly have I embarrassed myself?

    Cheers,

    Tom

    P.S. I don't need a safe space. Feel free to threaten my manhood due to my ignorance.
     
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  2. uncle harry

    uncle harry United States Active User Active Member

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    Steppers are routinely used to drive a machine axis. They are made in many sizes. Check for posts here that address or describe what others have done.
     
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  3. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    No reason that you can't run a stepper manually. Just select one with enough torque to run your feed. The steppers on my Tormach 770 are Nema 34 500 oz-in. torque. Your requirements may differ, depending on the size of your mill.
     
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  4. JimDawson

    JimDawson Global Moderator Staff Member Director

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  5. tomw

    tomw United States Active Member Active Member

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    Cool. Thank you for the information.
     
  6. Takingblame

    Takingblame United States Iron Registered Member

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    tomw, I would also do some research on the 3d printing front.

    Stepper motors are key in running a quality 3d printer. There is an open source collective known as the RepRap community. This collective specializes in building 3d printers from scratch. I would imagine there is a treasure trove of info about the best stepper motors and how to control them. Best of all its open source!! You can use an arduino with a stepper shield to control a motor, then get fancy with it and make it Bluetooth enabled or something. The possibilities are endless.
    I will be happy to answer any of your 3d printing questions in the future, I have been printing for about 5years now and have just ventured into machining. But I don't want to intrude, seeing how this is a machinist forum and not a 3d printing forum.

    P.S. RepRap stands for Replicating Rapid Prototyping

    Thanks

    Sent from my XT1097 using Tapatalk
     
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  7. MozamPete

    MozamPete South Africa Active User H-M Supporter-Premium

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    I'm thinking about motorizing the X axis on my mill in a similar way - with a simple manual system (left, right, stop push buttons buttons and a speed control pot), plus a couple of moveable limits so it can automatically change direction and move back and forth between two positions (say, while I manually feed the Y axis each time it changes direction).

    My thought was for a simple system like this a dc motor would be more suitable, and using a stepper motor would over complicate it. Stepper motors are great if you want to keep track of position (i.e. moving a fixed distance can be controlled but sending a fixed number of steps). But if you just want simple movement and speed control a dc motor can be used without the need for all the control electronics (and expense) needed to control a stepper motor.

    Obviously of you want to do it as a stepping stone towards full cnc control them using a stepper motor is the way to go. But if the system you describe is the end result I think it can be done simpler with a dc motor.
     
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  8. Eddyde

    Eddyde Active User H-M Supporter-Premium

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    What kind of DC motor are you planning to use, how would you handle the speed control? As far as I know, unless it's some kind of DC Servo it won't have much low speed torque which is what you need for a power feed. You could use a gear reduction with motor but by that time, I think, the complication/cost would be on par with using a stepper or DC servo motor with a driver.
     
    Last edited: Nov 5, 2015
    ronboult likes this.
  9. MozamPete

    MozamPete South Africa Active User H-M Supporter-Premium

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    In my situation I will need a couple of gears (or a belt drive) to connect from the motor mount to the lead screw anyway - the mill already has a mounting flange arrangement below the leadscrew on the leadscrew bearing plate at the opposite end from the handle. So yes I was planning to have reduction gear.

    I have a couple of 24Vdc, 100W, 2700rpm motors from an old automatic gate opener and was planning to try and use one of those. A 10:1 gear reduction (my initial guess, still have to work out what number of teeth, DP, etc that will work in the space available) would give me a max table speed of around 1250mm/min with my lead screw and speed control would just be by reducing the motor voltage.

    Maybe a stepper motor wouldn't be so complicated if you could source a suitable stand-alone controller/driver that just took the necessary control inputs. My (limited) experience with them has always been with a driver board, then a breakout board, then a PC with controller software which would obviously be overkill for the system proposed. My proposed control design requires only 3 push buttons, three relays and a potentiometer.
     
  10. JimDawson

    JimDawson Global Moderator Staff Member Director

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    You don't need a PC to run a stepper, just the motor, a drive, and a pulse generator. I have a couple on the shelf that I use for testing systems.

    From my post above:

    You can use one of these to run the stepper manually http://www.ebay.com/itm/Stepper-Mot...d87660&pid=100338&rk=6&rkt=26&sd=281570110066

    Or a little more sophisticated, with drive,
    http://www.ebay.com/itm/Reversible-...d=100338&rk=8&rkt=26&mehot=pp&sd=281570110066

    Or even with remote control,

    http://www.ebay.com/itm/Adjustable-...87660&pid=100338&rk=11&rkt=26&sd=281570110066

    And this controller will give you almost 100% torque at zero RPM with a DC motor
    http://www.ebay.com/itm/MAX-10-50V-...689235?hash=item2ee45b6013:g:w1kAAOSwHnFVvr2I
     
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  11. MozamPete

    MozamPete South Africa Active User H-M Supporter-Premium

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    Thanks Jim.
    That PWM driver for the dc motor looks like a great idea for the price. Would be much more efficient than a simple voltage divider.
    I had considered using a more sophisticated voltage control but initially thought it would be too expensive to be worth it for the limited time the motor would run - still amazes me how cheap you can get electronics out of China these days.
     
    Last edited: Nov 6, 2015
  12. JPigg55

    JPigg55 United States Active User H-M Supporter-Premium

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    MozamPete,
    I've had the same idea for awhile.
    I priced dedicated power feeds fom my mill and for the price it looked like I can buy a 3 axis CNC conversion kit for the price of one or two power feeds.
    I haven't started on mine yet so I'll be watching to see which way you go and how it works out.
    So I hope you post the good with the bad and if there ends up being anything you'd wished you'd done different or lack of certain functionality.
    Good luck with the project.
     
  13. ronboult

    ronboult Australia Active User Active Member

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    Jim can you please elaborate on how one can actually determine what is the minimum size stepper that is needed for a particular mill. I assume larger mills require larger steppers but I would like to keep the stepper I select for my X& Y axis as compact as possible.
    Thanks
    Ron
     
    Last edited by a moderator: Mar 7, 2016
  14. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Ron, I fixed your post above, you had your text inside the quotes;)

    That is a really good question. My theory on CNC is to go as big as possible, then cut back the power on the drive if needed. Consider that a 1200 oz/in NEMA 34 steppers would run any axis full size knee mill just fine. That motor is about 5 inches long and about 3 inches square, so pretty small. Many of the mini mill conversions are using 400 oz/in NEMA 23 steppers, a little shorter and about 2.5 inches square. It also depends on if you are using ball screws or the original screws. It takes a lot more torque to turn the Acme screws.
     
  15. ronboult

    ronboult Australia Active User Active Member

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    Thanks Jim
    I saw what had happened but didn't know how to fix it.
    With regard to the stepper size I think I will try the larger torque NEMA 23's for the X&Y but probably use a NEMA 34 to raise and lower the head
    Ron
     
    Last edited by a moderator: Mar 7, 2016
  16. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Ya did it again:grin: That's OK, I fixed it again. Note where your cursor is at before you start typing.

    That is the common arrangement on the small mills.
     
  17. ronboult

    ronboult Australia Active User Active Member

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    Hi Jim
    Sorry but I am not sure what I am doing wrong.
    I am writing on an iPhone and I am unsure how to reply such that my message is outside the quote. My first message required the first part of the quote because your post was somewhere up the thread.
    Will try better next time.
    Anyway thanks for your help
    Ron
     
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  18. Steve Shannon

    Steve Shannon United States Rocketgeek H-M Supporter-Premium

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    Ron,
    Using the iPhone, the quoted text will be terminated with "[/QUOTE]"
    You want to be sure that your new text come after that.


    Steve Shannon, P.E.
     
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  19. ronboult

    ronboult Australia Active User Active Member

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    "
    You want to be sure that your new text come after that.


    Steve Shannon, P.E. [/QUOTE]


    Thanks Steve
    See if it works this time.
    Ron

    Success!!!!!!
     
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  20. rourkek4

    rourkek4 France Iron Registered Member

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    Hi Jim,

    I found myself here thinking about a similar solution, but i am out of my normal zone. How would this setup handle manual turning of the leadscrew handle? I assume one wouldnt have to overcome the holding torque as power would be off the motor, but arent there issues with turning over steppers and it driving a voltage back towards its drive? Is this somehow accounted for here? Apologies if that is a stupid question, as i mentioned i'm (as yet) out of my depth on this.

    Thanks,
    Kevin
     
  21. JimDawson

    JimDawson Global Moderator Staff Member Director

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    There no stupid questions at Hobby Machinist:) and this is a really good question.

    The best way would be to simply unplug the motor (between the motor and the drive) when using the machine manually. This could also be done with a 4 pole switch or a relay. It is possible to fry the drive by turning the motor, but it is unlikely that you could turn it fast enough by hand to do that.
    .
     
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  22. rhynardt

    rhynardt Swaziland Active Member Active Member

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    I have had a similar feed situation on a small russian lathe. I purhased a 12V wipermotor from a car scrapyard, built a simple two speed tumbler gearbox and connected the whole lot headstock end to the leadscrew. A PWM drive drives the wipermotor and there is loads of torque, even and deadslow speed. I used a pc powersupply as a powersource and car relays to control forward/reverse and jog. A pot on the pwm drive regulates speed

    The 2speed tumbler box has a neutral position so the leadscrew can still be operated manually
     
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  23. Try to find motors with shafts on both ends. This should allow you to fabricate a handle to manually operate the mill when the motors are not powered.

    Steve
     
  24. rourkek4

    rourkek4 France Iron Registered Member

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    Jim, thanks for that. I will keep that in min if/when i get round to this job. As others have mentioned, i like the idea of steppers as it is a step (Geddit?!) in the direction of a cnc conversion at a later point. Im working on an old (but tight) Beaver mk2 knee mill) Am i right in saying that some drives now have some protection built in for this too? I will take your word for it, i just noticed your signature, seems i caught the right guy to ask! ;)

    Coincidentally, just looking at the map, i only drove within 10 minutes of your office last summer, was over from Ireland working down in Corvallis and spent some time around Portland and Seattle. Small world!

    Kev
     
  25. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Normally to get the back EMF protection for a drive you would install a regen clamp. This dumps the regen power across a resistor, and protects the drive. This would be rare on a small CNC machine axis drive, more commonly used where the load can over run the motor, like an elevator or very large Diesel-electric earth moving equipment. Also use in the braking circuit in VFDs.

    If you ever come this way again, let me know. I'm always happy to meet the members here.
     

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