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  1. #1
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    Lathe Conversion, PM1228 to CNC

    A few years ago I converted my G0704 mill to CNC and can use it it make most of the parts I need. However without a lathe, there is a lot of stuff I can't do. So I purchased a Precision Mathews 1228MV lathe. As a small manual machine, it's pretty good, but some of the parts I want to make have complex curves that are a pain on a manual machine. So, I found myself doing a conversion of it as well. Since I love looking at others photos of machines, here are mine.

    Here is a full shot of the system. The only thing remaining to complete is some software for the LCD panel on the console. I will be programmed to display the spindle speed and will set the switches for multiple functions.


    Closeup of the cross slide. The RED parts are 3D printed parts. Mostly they are covers. The tube that goes from the front to back of the saddle is how I routed the cables to some electronics on the front of the saddle.


    I built some covers for the cross slide ways and to cover the 1204 ball screw that replaced the manual lead screw.


    I used ClearPath servo's on both Z and X axis. Both are direct drive. Z has a 1605 screw hidden under this cover. The Red object with the stainless socket screw is a carrier for the magnet that triggers the Z limit switch. It can slide back and forth so there is less chance of running the tool into the chuck.


    There is the X Axis servo hiding on the back of the saddle under the cover. I used a cable drag track to get the wiring onto the saddle.


    Designing and building the spindle encoder was the most difficult part of the conversion. The spindle has a 65 tooth gear that used to drive all the other gears on the head. I bought another gear and use it to drive a rotary encoder. Since I didn't want to make any new holes in the casting unless I had to, this is where it wound up. Unfortunately It sticks up above the top of the spindle housing so the cover door no longer fits. Oh well, who needs the safety covers anyhow.


    Another shot of the encoder and a a completely clean spot where there used to be a bunch of greasy gears.


    A quick and dirty AXA tool rack.


    I will put the electronics in another post.

  2. #2

    Re: Lathe Conversion, PM1228 to CNC

    Nice Job! :cheers:
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: Lathe Conversion, PM1228 to CNC

    What a stunningly clean conversion. Beautiful work. Would also love to see the electronics enclosure.

  4. #4
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    Re: Lathe Conversion, PM1228 to CNC

    Some more photos when the machine was more naked.

    X Axis ballscrew was a pain to get it installed with clearance for the nut. I would have liked to use a 1605 screw but there was no way that nut would fit in that cavity. 1204 is hopefully enough.


    This replaced the gearbox on the front of the saddle.


    I have not installed it yet, but there will eventually be a ballnut on this side of the saddle as well to get to zero backlash.


    Here is a closeup of the spindle encoder carrier.

  5. #5
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    Re: Lathe Conversion, PM1228 to CNC

    The electronics enclosure. The brains are an Ethernet Smooth Stepper. The interface cards on the lower left are my own design. Each card handles a function and converts the signals to the ESS. There is a board for the limit/home switches, servo control, spindle/encoder interface, and Console interface. All the internals run off a single 12Volt DC supply.


    The door of the enclosure has the main power switch E-Stop and a power monitor display.

  6. #6

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    Re: Lathe Conversion, PM1228 to CNC

    You make it look so easy! Almost makes me want to tear down my Southbend.

  7. #7
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    Re: Lathe Conversion, PM1228 to CNC

    Enclosure looks great! Nice work, very professional.

  8. #8
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    Re: Lathe Conversion, PM1228 to CNC

    Finished. I put the safety cover back on.


    Now all I have to do is teach myself how tool and fixture offsets work and I will be good to go.

  9. #9

    Re: Lathe Conversion, PM1228 to CNC

    I think that is the nicest looking conversion I have ever seen. Great job!
    Jim Dawson
    Sandy, Oregon, USA

  10. #10
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    Re: Lathe Conversion, PM1228 to CNC

    Have you ever cut with the lathe yet ? How fast x axis with 1204 ballscrew ?

  11. #11
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    Re: Lathe Conversion, PM1228 to CNC

    Quote Originally Posted by asuratman View Post
    Have you ever cut with the lathe yet ? How fast x axis with 1204 ballscrew ?
    I have done a few delrin cuts but nothing to push the machine. I think as far as speed, I will be limited most by the spindle. The max I can get from it is 1300 RPM so my surface speed won't be huge. The servo's max RPM I have set to 1000 so that puts rapids at 150 IPM on X and 175 on Z. The mechanicals could probably do twice that but I found that the Z ballscrew starts to flap around 2000 RPM.

    Currently I am chasing problems with the Brushless DC motor. When I repurposed the motor I found that the phase cable was just long enough to reach inside the cabinet. Unfortunately about half the cable doesn't have a shield on it and this is generating a lot of noise on the electronics inside the cabinet. I have some more cable on order along with some ferrite chokes. Those will be in tomorrow and I can, hopefully, solve that problem. I found this out when I updated the code in Mach so that it monitors the motor error feedback signal. The feedback, if bad, will stop all motion of the servos.

    So when I get back up and running I will do some tests to see what it's limits are and report back.

  12. #12
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    Re: Lathe Conversion, PM1228 to CNC

    Quote Originally Posted by Jim Dawson View Post
    I think that is the nicest looking conversion I have ever seen. Great job!
    Thank you Jim. It has taken a while to complete and all along I was wondering if I was going to miss my manual lathe. We shall see.

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