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  1. #1
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    Martin's RF30 Build

    I guess I'll document my build here for the benefit of others.

    I just got the machine about a week ago. It's in good condition but requires a lot of cleaning (dried-up grease and gunk). Working on that right now.

    Attachment 269350

    Attachment 269352

    Attachment 269354

    Attachment 269356

    Attachment 269358

    Attachment 269360

    Attachment 269362


    I am thinking of ordering this setup for the motors:

    4Axis NEMA 34 Stepper Motor 1600oz Driver CNC Router Mill Longs Stepper Motor | eBay

    I don't need a 4th axis. The 3 axis kit is $450 so I figured it is well worth another $50 to get the fourth axis motor, driver and power supply. The only detractor is that shipping costs $125. Not sure how this might compare to other offers with free shipping from China and the potential to have to pay Customs fees. I'd appreciate feedback on this.

    I have three Oriental Motor Super Vexta stepping motor drivers I am going to be selling on eBay. They are great but they are not powerful enough for the size of motor I want to put on this machine. I should be able to break even between selling the motor drivers and buying the kit I need for the mill.


    As far as construction, I am going to convert the mill with the standard screws and convert to ballscrews as a second step later on. I might get brave and do it all in one step. It really depends on what kind of machining I have to do to make parts for the ballscrew version.

    I am going to borrow ideas from Flashcut CNC and build my transmissions inside rectangular aluminum tubing. I just got a length of 4 x 2 x 0.25in 6061-T6 for the three transmissions.

    Attachment 269364

    These brackets should not be all that difficult to make manually. It'd take longer than CNC but I'll use it as an opportunity to teach my oldest son about machining: Counting turns and learning how to deal with backlash by hand, feeling the cut, etc.


    Thoughts, ideas, criticism and donations always welcome.


    -Martin

  2. #2
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    Re: Martin's RF30 Build

    I am thinking about replacing the existing thrust bearings with angular contact bearings. I can't see how the existing bearings will deal with the tension I have to place on the pulley as well as general vibration of higher RPM operation under CNC.

    The original bearing counterbore is 30mm in diameter by 9mm deep. The OD of the machined end of my shaft is 17mm.

    Attachment 269378

    The smallest ABEC-3 angular contact bearing at McMaster has an OD of 40mm and width of 12mm. It looks like I'll have to have the brackets counterbored to fit the new bearings. Not a problem, there's enough material there to remove and still have a pretty strong bracket.

    McMaster-Carr

    Am I over-thinking this?

    Are the exiting thrust bearings adequate?

    How do I remove the remaining portion of the existing bearings? They are either lightly press fit in there or got glued in with gunk of some sort. I tried using a right angle pick but that didn't work as I have no purchase point where the bearing race plate meets the bracket. The next idea was to throw them in the oven for an hour and see if things expand enough and in the right direction to get the parts out. Any recommendations? If I am going to have this counterbored I suppose there would be no harm in getting in there with a dremel tool anda diamond cutoff wheel and cut the bearing plate into two halves.


    Thanks,

    -Martin

  3. #3
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    Re: Martin's RF30 Build

    Martin,
    Your making me dig back into the deep dark recesses of my mind on this one:})

    When I converted mine back around 2000, as I remember, the thrust races you show came out with no problem. They are probably just "glued" in with age and gunk.
    As for the bearings, on the thrust end I used:
    7201 ang contact bearings which are 12x32x10mm. I bored the original end cap out and put one on each side of the plate. Be sure to counterbore the hole to allow clearance for the rotating center race of the AC bearings. (Learned that one the hard way)
    On the other end, I used a sealed
    6201 12mm x OD: 32mm x W: 10mm bearing.
    Oh and I got my bearings from Buy Bearings Online ball bearings, roller bearing,, pillow block, linear bearings - Bearings Direct and have also bought some from Ball Bearings | Bearing Specialist | VXB Bearings Online. Usual disclaimer, just a happy customer.


    I notice you plan to use rectangular tubing to make the "transmission". I also did that, but failed to have it on "standoffs" on the end and lost about an inch of travel on the X axis as I put it directly on the end of the table.

    Oh and I used 5/8" 5TPI ballscrews for the X and Y axis. The ends were obviously turned down to accept the 12mm bearings and on the thrust end, I used 7/16-20 nuts which is a tight fit for the 12mm shafts, but has worked all these years.
    Art
    AKA Country Bubba (Older Than Dirt)

  4. #4
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    Re: Martin's RF30 Build

    Quote Originally Posted by Bubba View Post
    When I converted mine back around 2000, as I remember, the thrust races you show came out with no problem. They are probably just "glued" in with age and gunk.
    Art,

    Thanks, that gave me the confidence to get a little more assertive. I used a sharp punch at the dividing line and a few taps with a light hammer made the thrust race pop right out. Excellent!

    Attachment 269394

    Attachment 269396

    Thanks for the other tips as well.

  5. #5
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    Re: Martin's RF30 Build

    OK, I am leaning heavily towards these motors now:

    SHIP from USA WH 4Axis Nema34 Stepper Motor 1232oz 5 6A DM860ACNC Router Mill | eBay

    At $595 including shipping from their US warehouse this seems like a good deal. No customs issues to worry about. I also get a full extra motor-driver-power-supply set for a fourth axis or some other project when the time comes.

    In researching timing belts and pulleys I am now finding that the 14mm shaft on the motor is somewhat troublesome. I looked at McMaster, Stock Drive Products and Misumi (ouch!) and couldn't find pulleys with this ID. I found a couple on eBay but have to look further. I'd rather buy from a more traditional industrial supplier if possible. Any recommendations?

    Whenever possible I prefer for as much in common in designs as possible. That's why I was hoping to have a ballscrew turned to 14mm in order to match the stepper motor diameter. Not necessary, but the perfectionist in me would feel good about that. Again, the apparent lack of choice in pulleys is getting in the way at the moment. I might have to find a set of pulleys first and then use that to set the OD of the turned-down portion of the ballscrew.

    Any recommendations on the type and width of belt that might work best of this application?


    Thanks,

    -Martin

  6. #6
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    Quote Originally Posted by martin_05 View Post
    OK, I am leaning heavily towards these motors now:

    SHIP from USA WH 4Axis Nema34 Stepper Motor 1232oz 5 6A DM860ACNC Router Mill | eBay

    At $595 including shipping from their US warehouse this seems like a good deal. No customs issues to worry about. I also get a full extra motor-driver-power-supply set for a fourth axis or some other project when the time comes.

    In researching timing belts and pulleys I am now finding that the 14mm shaft on the motor is somewhat troublesome. I looked at McMaster, Stock Drive Products and Misumi (ouch!) and couldn't find pulleys with this ID. I found a couple on eBay but have to look further. I'd rather buy from a more traditional industrial supplier if possible. Any recommendations?

    Whenever possible I prefer for as much in common in designs as possible. That's why I was hoping to have a ballscrew turned to 14mm in order to match the stepper motor diameter. Not necessary, but the perfectionist in me would feel good about that. Again, the apparent lack of choice in pulleys is getting in the way at the moment. I might have to find a set of pulleys first and then use that to set the OD of the turned-down portion of the ballscrew.

    Any recommendations on the type and width of belt that might work best of this application?


    Thanks,

    -Martin
    Sdp/si pr Misumi

  7. #7
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    Re: Martin's RF30 Build

    Martin,
    Again, back in the dark ages, it was necessary to get pulleys with a "pilot" hole and then bore to suit. For belts, I used XL037 size and am glad that I did. Yes, they are strong enough for everyday tasks, but I have also found that they make and excellent "fuse" when you do a hard crash into the hard stop. I had it happen a couple of times when I had inadvertently disabled my limit switches. An XL belt is cheap insurance.
    Art
    AKA Country Bubba (Older Than Dirt)

  8. #8
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    Re: Martin's RF30 Build

    For a machine that size, 1600 oz-in motors would be MASSIVE over-kill, and would likely perform poorly to boot. Even 1200 oz-in is FAR more than needed. A full-sized knee-mill typically uses motors in the 700-900 oz-in range. For an RF-30, something more in the 500-600 range should be MORE than adequate. With stepper motors, more is NOT better. Bigger motors will have higher inductance, and higher inertia, which means worse high-speed performance.

    Regards,
    Ray L.

  9. #9
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    Re: Martin's RF30 Build

    Quote Originally Posted by SCzEngrgGroup View Post
    For a machine that size, 1600 oz-in motors would be MASSIVE over-kill, and would likely perform poorly to boot. Even 1200 oz-in is FAR more than needed. A full-sized knee-mill typically uses motors in the 700-900 oz-in range. For an RF-30, something more in the 500-600 range should be MORE than adequate. With stepper motors, more is NOT better. Bigger motors will have higher inductance, and higher inertia, which means worse high-speed performance.

    Regards,
    Ray L.
    I was actually wondering about that last night. I've been using specs from Flashcut CNC. On this page they mention size 34 640 oz-in motors:

    Benchtop Mill / Lathe & Router Kits | FlashCut CNC

    However, if you click on the "Specs" tab both stepper motor configurations they showcase come with 940 and 1,151 oz-in motors. Which is it? Why would they ship you these larger motors if the smaller one's will do?

    Thanks for bringing this up. I'm all for saving money and not burning it where it isn't needed.


    -Martin

  10. #10
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    Re: Martin's RF30 Build

    Quote Originally Posted by martin_05 View Post
    I was actually wondering about that last night. I've been using specs from Flashcut CNC. On this page they mention size 34 640 oz-in motors:

    Benchtop Mill / Lathe & Router Kits | FlashCut CNC

    However, if you click on the "Specs" tab both stepper motor configurations they showcase come with 940 and 1,151 oz-in motors. Which is it? Why would they ship you these larger motors if the smaller one's will do?

    Thanks for bringing this up. I'm all for saving money and not burning it where it isn't needed.


    -Martin
    Probably a mistake by their webguy, 640 is a common nema 34 size stepper, never heard of 940. You should also "borrow" from flashcuts specs too. Note they use a 70vdc power supply for their drivers which would benefit a common nema 34 higher inductance. You see that a lot from these packages from china, super high inductance on the motors and completely underpowered power supplies.

  11. #11
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    Re: Martin's RF30 Build

    I've been humming and hawing over converting my round column mill fro 2 years now...everything I"ve read has pointe dme towards 570 oz motors, using direct drive (no belts/pulleys)....looking forward to watching your progress....

  12. #12
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    Re: Martin's RF30 Build

    Quote Originally Posted by shepdog View Post
    I've been humming and hawing over converting my round column mill fro 2 years now...everything I"ve read has pointe dme towards 570 oz motors, using direct drive (no belts/pulleys)....looking forward to watching your progress....
    Yeah, I am re-evaluating this right now. I'm glad I didn't pull the trigger on the purchase.

    On the point about direct drive. I definitely like the simplicity.

    The Y axis kinda bugs me when it comes to that just because of having this motor sticking out right in front of you. And so I wonder if there might be room UNDER the mill base to mount a direct drive Y axis direct-drive motor. Yeah, OK, if you have to do anything you have to lift the mill. The solution might very well be that you cut a service hole on the table (the one with legs on the ground, not the machine) right under the machine at the right spot.

    The other solution is to weld a table out of beefy steel pipe and only support the machine under the bolt-down holes (and bolt it down). This now opens the entire bottom for the motor.

    The third solution would be to permanently bolt the machine to something like 6 x 6 steel pipe, creating a permanent access space either front and back or left and right.


    I wonder, has anyone done a direct drive conversion on this machine? I've read a few posts about the belt being a great "fuse" in the event of a crash. That's certainly worth considering.


    -Martin

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