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Re: [mill_drill] Re: RF-31 CNC Conversion

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  • Art Eckstein
    Mel, I have a converted RF-31 with zero backlash ball screws and yes it will do an admirable jobv of cutting all kinds of shaped. I made a coolant pump which
    Message 1 of 21 , May 2, 2013
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      Mel,
      I have a converted RF-31 with zero backlash ball screws and yes it
      will do an admirable jobv of cutting all kinds of shaped. I made a
      coolant pump which has vanes that are based on a logarithmic curve
      and it cut them very nicely. Resolution and accuracy are functions of
      the installation you make and how closely you calibrate it.

      I personally know of no actual "step by step" guide sheet or list
      that is available. My suggestion is to follow builds on various sites
      with one of the biggest being cnczone.com. There are several people
      that have build threads there that you can follow. Don't restrict
      yourself to just RF-31 machines as the process is similar for most of
      the machines of this type.

      I am not sure what you mean about "compatibility", but I would study
      the white papers on the Gecko site as they are very informative in sizing etc.

      Good luck and I am sure others will be able to give you more and
      better info than I

      Art
      Country Bubba


      At 11:33 AM 5/2/2013, you wrote:
      >I have a RF-31 and the CNC conversion intrigues me since it could
      >save me a lot of table cranking. I have three questions:
      >
      >In plastic material (UHMW or HDPE) I need to cut a radius. Would a
      >CNC mill have the precision to cut a curve that was smooth and without "steps"?
      >
      >I'm a real novice at even planning a conversion. Is there a step by
      >step guide from start to finish?
      >
      >I have three pacific scientific stepper motors and a matching
      >controller, is there a reference source that can tell me about compatibility?
      >
      >Thanks
      >Mel Stanley, Utah
      >
    • mrwhiz49
      I converted my RF-31 using stepper motors and the stock leadscrews and am quite happy. For direct drive 425 oz-inch will do the trick. You can expect about 15
      Message 2 of 21 , May 3, 2013
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        I converted my RF-31 using stepper motors and the stock leadscrews and am quite happy. For direct drive 425 oz-inch will do the trick. You can expect about 15 to 20 inches per minute. It's faster than you can spin by hand and won't tear up the lead screws. You can see pictures in the photo section under Paul's CNC. I've sold 7 kits and everybody has been happy. I use Mach3 and it does a good job compensating for backlash. The key is to finish with a light cut. It does accurate turning in the spindle which is demanding on positioning accuracy. I adopted an unconventional scheme for mounting the motor drives. The lead screws support everything. They are plenty strong and the assembly just slides on where the handle goes. All you need to do is stop the drive assembly from rotating. I use a worm drive clamp around the bearing boss. The beauty is nothing needs to be modified, it goes on and off in seconds and you still can use the handles. The pictures show gear drives for all three axes but now I use direct drive for X and Y. Either way works fine. I also converted an X2 mill using the same methods.

        --- In mill_drill@yahoogroups.com, "mpoore10" <mpoore10@...> wrote:
        >
        > I am going to convert a Jet JMD-15 (RF-31) mill to cnc. It seems that most everyone that does this upgrade does it a little differently. It also seems that a lot of people sell stuff that I could use, but very few sell a comprehensive kit and the prices for the kits are unaffordable to me.
        >
        > This is totally new to me, so I have done a lot of reading. Here is a general list of what I think that I need:
        >
        > Mill
        > 1. Upgrade to ball screws
        >
        > Software
        > 2. CAD
        > 3. CAM
        > 4. Controller
        >
        > Hardware
        > 5. Breakout box
        > 6. Motor drives
        > 7. Stepper Motors
        > 8. Power supply
        > 9. Mounting brackets
        > 10. Timing pulleys/belts
        >
        > Here are my questions:
        >
        > 1. I have seen good prices on Ebay. Does anyone have suggestions on what fits best on a RF-31, TPI, installation ease?
        >
        > 2. & 3. I am looking at some open source CAD/CAM software. Anyone know of a really good and inexpensive package?
        >
        > 4. I was planning to use Mach3. I noticed that it comes with LazyCam. Is this decent enough or should I look for something else to generate the G-code?
        >
        > 5., 6., 7., & 8. Seems like there are a lot of reasonably prices packages on Ebay that would work with Mach3. My concern is getting steppers that have the needed torque. Does anyone have a recommendation. It seems that others have used motors in the 350-420oz/in range. Is this about right for low-med volume on this machine? The price on steppers goes up with torque. I want something that will work, but I don't want to waste money on overkill.
        >
        > 9. I have not found brackets sold individually, so I guess I am on my own.
        >
        > 10. McMaster-Carr looks like they have everything I'd need, but does anyone have advice on ratios? I did a little quick math and realized that a ball screw with 8 TPI matched to a stepper capable of 200 steps has a resolution of .000625". My first thought was to gear it to minimize motor load, but then I thought about getting a round number such as one step being .00025" making 4 steps .001". Not having used a a cnc before, I am not sure if it matters to have round numbers or not. Is this an issue?
        >
        > Seems like $1200-$1500 for everything is where I'd be on this project. Does that sound high, low, about right? Have I missed anything that I'll need or can save money doing it differently?
        >
        > Lastly, I'd also like to use the mill manually especially as a drill press. Are there any special design considerations to make this possible? Can the steppers be put into "neutral" to spin freely or would I have to remove the belts?
        >
      • Guenther Paul
        Mrwhiz I have a big red and have bean thinking about converting to a cnc. Don t have a fine quill down feed yet but will be building it. Do you have any
        Message 3 of 21 , May 4, 2013
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          Mrwhiz
          I have a big red and have bean thinking about converting to a cnc. Don't have a fine quill down feed yet but will be
          building it. Do you have any recommendations 
          GP

           


          From: mrwhiz49 <pthomps2@...>
          To: mill_drill@yahoogroups.com
          Sent: Sat, May 4, 2013 1:10:11 AM
          Subject: [mill_drill] Re: RF-31 CNC Conversion

           

          I converted my RF-31 using stepper motors and the stock leadscrews and am quite happy. For direct drive 425 oz-inch will do the trick. You can expect about 15 to 20 inches per minute. It's faster than you can spin by hand and won't tear up the lead screws. You can see pictures in the photo section under Paul's CNC. I've sold 7 kits and everybody has been happy. I use Mach3 and it does a good job compensating for backlash. The key is to finish with a light cut. It does accurate turning in the spindle which is demanding on positioning accuracy. I adopted an unconventional scheme for mounting the motor drives. The lead screws support everything. They are plenty strong and the assembly just slides on where the handle goes. All you need to do is stop the drive assembly from rotating. I use a worm drive clamp around the bearing boss. The beauty is nothing needs to be modified, it goes on and off in seconds and you still can use the handles. The pictures show gear drives for all three axes but now I use direct drive for X and Y. Either way works fine. I also converted an X2 mill using the same methods.

          --- In mill_drill@yahoogroups.com, "mpoore10" <mpoore10@...> wrote:
          >
          > I am going to convert a Jet JMD-15 (RF-31) mill to cnc. It seems that most everyone that does this upgrade does it a little differently. It also seems that a lot of people sell stuff that I could use, but very few sell a comprehensive kit and the prices for the kits are unaffordable to me.
          >
          > This is totally new to me, so I have done a lot of reading. Here is a general list of what I think that I need:
          >
          > Mill
          > 1. Upgrade to ball screws
          >
          > Software
          > 2. CAD
          > 3. CAM
          > 4. Controller
          >
          > Hardware
          > 5. Breakout box
          > 6. Motor drives
          > 7. Stepper Motors
          > 8. Power supply
          > 9. Mounting brackets
          > 10. Timing pulleys/belts
          >
          > Here are my questions:
          >
          > 1. I have seen good prices on Ebay. Does anyone have suggestions on what fits best on a RF-31, TPI, installation ease?
          >
          > 2. & 3. I am looking at some open source CAD/CAM software. Anyone know of a really good and inexpensive package?
          >
          > 4. I was planning to use Mach3. I noticed that it comes with LazyCam. Is this decent enough or should I look for something else to generate the G-code?
          >
          > 5., 6., 7., & 8. Seems like there are a lot of reasonably prices packages on Ebay that would work with Mach3. My concern is getting steppers that have the needed torque. Does anyone have a recommendation. It seems that others have used motors in the 350-420oz/in range. Is this about right for low-med volume on this machine? The price on steppers goes up with torque. I want something that will work, but I don't want to waste money on overkill.
          >
          > 9. I have not found brackets sold individually, so I guess I am on my own.
          >
          > 10. McMaster-Carr looks like they have everything I'd need, but does anyone have advice on ratios? I did a little quick math and realized that a ball screw with 8 TPI matched to a stepper capable of 200 steps has a resolution of .000625". My first thought was to gear it to minimize motor load, but then I thought about getting a round number such as one step being .00025" making 4 steps .001". Not having used a a cnc before, I am not sure if it matters to have round numbers or not. Is this an issue?
          >
          > Seems like $1200-$1500 for everything is where I'd be on this project. Does that sound high, low, about right? Have I missed anything that I'll need or can save money doing it differently?
          >
          > Lastly, I'd also like to use the mill manually especially as a drill press. Are there any special design considerations to make this possible? Can the steppers be put into "neutral" to spin freely or would I have to remove the belts?
          >

        • mrwhiz49
          I would recommend the same approach as I used in the pictures. You can use direct drive and avoid making some of the gears. They stick out a lot farther
          Message 4 of 21 , May 9, 2013
          • 0 Attachment
            I would recommend the same approach as I used in the pictures. You can use direct drive and avoid making some of the gears. They stick out a lot farther though. The mounting scheme is very flexible and you don't have to figure out how to mount a bracket or have to make new bearing blocks. Two kits I sold were easily modified to fit RF-45's. One bit of advice is to avoid the temptation to mount the motors with too much rigidity. This requires you to use a flexible coupling to avoid an over-constrained design. That is, you might develop tight spots as you turn the shaft. You can use one of the popular stepper drivers that come combined with a breakout board. I see them referred to as TB6560. These are very attractive price-wise and are compact but I haven't had much luck with them, especially at 36 volts (24 seems OK). It is a good thing I bought five extra chips because I've replaced three so far. Also, they require at least a ten microsecond pulse. Mach3 puts out about one microsecond pulses and operation can be erratic. You can fix this in motor tuning configuration at the bottom of the page by telling it fifteen or whatever it lets you put. Good luck with your project. It is so worth doing.




            --- In mill_drill@yahoogroups.com, Guenther Paul <paulguenter@...> wrote:
            >
            > Mrwhiz
            > I have a big red and have bean thinking about converting to a cnc. Don't have a
            > fine quill down feed yet but will be
            >
            > building it. Do you have any recommendations GP
            >
            >  
            >
            >
            >
            > ________________________________
            > From: mrwhiz49 <pthomps2@...>
            > To: mill_drill@yahoogroups.com
            > Sent: Sat, May 4, 2013 1:10:11 AM
            > Subject: [mill_drill] Re: RF-31 CNC Conversion
            >
            >  
            > I converted my RF-31 using stepper motors and the stock leadscrews and am quite
            > happy. For direct drive 425 oz-inch will do the trick. You can expect about 15
            > to 20 inches per minute. It's faster than you can spin by hand and won't tear up
            > the lead screws. You can see pictures in the photo section under Paul's CNC.
            > I've sold 7 kits and everybody has been happy. I use Mach3 and it does a good
            > job compensating for backlash. The key is to finish with a light cut. It does
            > accurate turning in the spindle which is demanding on positioning accuracy. I
            > adopted an unconventional scheme for mounting the motor drives. The lead screws
            > support everything. They are plenty strong and the assembly just slides on where
            > the handle goes. All you need to do is stop the drive assembly from rotating. I
            > use a worm drive clamp around the bearing boss. The beauty is nothing needs to
            > be modified, it goes on and off in seconds and you still can use the handles.
            > The pictures show gear drives for all three axes but now I use direct drive for
            > X and Y. Either way works fine. I also converted an X2 mill using the same
            > methods.
            >
            > --- In mill_drill@yahoogroups.com, "mpoore10" <mpoore10@> wrote:
            > >
            > > I am going to convert a Jet JMD-15 (RF-31) mill to cnc. It seems that most
            > >everyone that does this upgrade does it a little differently. It also seems that
            > >a lot of people sell stuff that I could use, but very few sell a comprehensive
            > >kit and the prices for the kits are unaffordable to me.
            > >
            > > This is totally new to me, so I have done a lot of reading. Here is a general
            > >list of what I think that I need:
            > >
            > > Mill
            > > 1. Upgrade to ball screws
            > >
            > > Software
            > > 2. CAD
            > > 3. CAM
            > > 4. Controller
            > >
            > > Hardware
            > > 5. Breakout box
            > > 6. Motor drives
            > > 7. Stepper Motors
            > > 8. Power supply
            > > 9. Mounting brackets
            > > 10. Timing pulleys/belts
            > >
            > > Here are my questions:
            > >
            > > 1. I have seen good prices on Ebay. Does anyone have suggestions on what fits
            > >best on a RF-31, TPI, installation ease?
            > >
            > > 2. & 3. I am looking at some open source CAD/CAM software. Anyone know of a
            > >really good and inexpensive package?
            > >
            > > 4. I was planning to use Mach3. I noticed that it comes with LazyCam. Is this
            > >decent enough or should I look for something else to generate the G-code?
            > >
            > > 5., 6., 7., & 8. Seems like there are a lot of reasonably prices packages on
            > >Ebay that would work with Mach3. My concern is getting steppers that have the
            > >needed torque. Does anyone have a recommendation. It seems that others have used
            > >motors in the 350-420oz/in range. Is this about right for low-med volume on this
            > >machine? The price on steppers goes up with torque. I want something that will
            > >work, but I don't want to waste money on overkill.
            > >
            > > 9. I have not found brackets sold individually, so I guess I am on my own.
            > >
            > > 10. McMaster-Carr looks like they have everything I'd need, but does anyone
            > >have advice on ratios? I did a little quick math and realized that a ball screw
            > >with 8 TPI matched to a stepper capable of 200 steps has a resolution of
            > >.000625". My first thought was to gear it to minimize motor load, but then I
            > >thought about getting a round number such as one step being .00025" making 4
            > >steps .001". Not having used a a cnc before, I am not sure if it matters to have
            > >round numbers or not. Is this an issue?
            > >
            > > Seems like $1200-$1500 for everything is where I'd be on this project. Does
            > >that sound high, low, about right? Have I missed anything that I'll need or can
            > >save money doing it differently?
            > >
            > > Lastly, I'd also like to use the mill manually especially as a drill press. Are
            > >there any special design considerations to make this possible? Can the steppers
            > >be put into "neutral" to spin freely or would I have to remove the belts?
            > >
            >
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