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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > PM1022 lathe CNC Conversion
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  1. #1
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    PM1022 lathe CNC Conversion

    I have a new PM1022 lathe which I plan to convert for CNC. It is reportedly the same as a Grizzly G0602, at least it's the same size.

    Click image for larger version. 

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    It arrived a couple of weeks ago. I purchased the stand with it but have found that stand to be very unstable. A new stand has been built which feels much better.

    Click image for larger version. 

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    I ordered ball screws from linearbearingmotions and have those in hand. The Z axis is a 20mm screw with a double ball nut. That for the X axis is a 12mm ball screw. I purchased the X screw with two nuts. The plan was to use both back to back to reduce backlash. However, after a preliminary look at the cross slide I doubt both nuts will fit. We'll see when I get further into it.

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    I have not found a cnc conversion of a PM1022 (or PM1030). If anyone knows of one please let me know. I've studied the conversions from Russtuff and WadeO who have each done nice conversions of G0602 lathes. Based on their designs I ordered the ball screws before seeing the machine. I ordered the PM1022 the end of May and it was delivered, as I said, a couple of weeks ago.

    I don't know if this will take a couple of months or a couple of years. You are all welcome to come along for the ride.

    Thanks.
    Attached Thumbnails Attached Thumbnails Crated.jpg   BallScrews.jpg   OnStand.jpg  

  2. #2
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    Re: PM1022 lathe CNC Conversion

    A little more information on this planned conversion. The idea is to have a fairly basic CNC lathe upon completion. No turrets or live tooling, just a plain vanilla usable machine.

    The electronics will likewise be simple. I'm planning to use steppers on both axes, likely with Gecko drivers. The controller will be LinuxCNC with, most likely, Mesa cards. There will be some type of encoder for threading. The speed sensor in the PM1022 has a pickup with four magnets on the spindle. This is unlikely to give adequate resolution for threading with LinuxCNC, and I'm not confident I could decipther its signals. Thus, I'll add a slotted disk on the spindle shaft, or an encoder driven via a small timing belt from the spindle shaft. I'm betwixed and between on adding limit/home switches. Will likely be done but isn't a high priority. (The soft limits in LinuxCNC work quite well on a small machine.)

    I hope to mount the X axis motor under the apron. Space is critical so not having the stepper sicking out from the machine is very desirable. It will connect to the cross slide screw via timing belts. This might be a 1:1 or 2:1 ratio. I'm leaning towards a short NEMA 34 rather than a longer NEMA 23, but that's to be determined. The plan for the Z axis motor is to place it where the existing gear box is. If possible I'll remove the gearbox, and apron, intact and save if the lathe is converted back to manual. A box, or partial box, is to replace the gear box to support the Z axis thrust bearings and stepper motor. Like the X axis it will be timing belt driven with the stepper below the Z axis screw. A box will replace the apron with support for the Z axis screw, and X axis stepper.

    An enclosure is planned to capture chips. I'll likely run mist coolant but no flood coolant.

    So that's the basic plan. If anyone sees problems on the horizon please let me know.

    Thanks.

  3. #3
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    Re: PM1022 lathe CNC Conversion

    I'm going to start with the cross slide. From all the conversion logs I've viewed I anticipate this being the most difficult part of the conversion. It's just real tight to get a ball screw in. I started by taking the cross slide apart for measurements.


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    I thought it would look more like the G0602 pictures I've seen. However, the castings seem to be quite a bit different. This is likely due to the cross slide drive mechanism. The G0602 looks to have a U shaped opening in the top of the cross slide with cast iron closing the bottom of the U. The PM1022 is closed on top as shown with just a slot for the cross slide nut. looking down through this slot, in the picture above, you can see the bed ways. In the G0602 conversions I've looked at they've cut out the bottom of this U for ball nut clearance. Can't do that with the PM1022, the first thing you run into are the bed ways. From what I've measured, the 12mm ball nut I have will just fit above the ways. That is after trimming the ball nut flange considerable (as others have done). The cross slide is some 1/2" thick where the nut mounts. It would be possible to take a little off this to gain a touch of clearance.

    Without major surgery I don't see a way to cram two ball nuts into this space. A ball nut just fits sideways into the slot. For use of two ball nuts there would have to be some structure holding them together. The space is just not there.

    PM advertises the 1022 as having 5" cross slide motion. I measured this as 4.2"! Seems a 10" lathe should have 5+" of cross slide travel. The slot for the nut is 6" long and the existing nut measures 1.2" long. That would be 4.8" travel, however the cross slide table hits the bearing mount with 0.6" travel left to the end of the slot.

    The ball nut is 35mm long (1.4"). Mounting it slightly forward of the existing nut location would use some of that 0.6" and easily maintain the existing travel. The slot can be extended towards the front of the machine about 0.9" without hitting the first casting web. If this were done the travel could be extended some 3/4" by mounting the nut further toward the front. This would leave an opening for chips to fall through and onto the ball screw though. Maybe a rubber flap connected to the cross slide to cover this new opening? With that extra 0.9" the travel would be near 5". I didn't note how much dove tail engagement this left, or if the travel is in a usable position (it could be too far back to have any advantage).

    It may also be possible to extend the bearing block forward leaving more room for the table to move forward. That would extend out the front of the machine a few more inches.

    I need to take some measurements vertically and see where the ball screw axis will come out. That will effect the bearing block and its clearances. So far a work in progress. Lots of trade offs.

    Any suggestions will be gladly considered. Thanks.

    Hugh
    Attached Thumbnails Attached Thumbnails StockCross-2.jpg  

  4. #4
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    Re: PM1022 lathe CNC Conversion

    Thanks for posting your lathe build..... I have been wanting a CNC lathe for several years so will be very interested in following along.

    Robert

  5. #5
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    Re: PM1022 lathe CNC Conversion

    It will use MESA Linux CNC ? Its interesting, which card you will use ? I have retrofit my lathe to mach3 but no threading yet. I read in one thread here about linux development, much better screen, maybe I will try this route in the future.

  6. #6
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    Re: PM1022 lathe CNC Conversion

    Robert:

    Thanks for the note. It's always good to know someone is coming along.

    Hugh

  7. #7
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    Re: PM1022 lathe CNC Conversion

    asuratman:

    It could change but my current thinking is to use a 5I25 in computer card with a 7I76 breakout board. It is stepper oriented and sold my Mesa as a kit ($208). I believe the combination is well supported by Mesa and LinuxCNC.

    I recently replaced the parallel port driving my knee mill with a Mesa 5I25 card. That was a little tricky since I kept the very old breakout board (PMDX-131). Previously it connected the parallel port and breakout board with a standard parallel cable and the Gecko drivers plugged directly into the breakout board. Thus, reconnecting pins would be difficult. That required finding a compatible firmware and LinuxCNC combination. With a 5I25+7I76 combination the wiring from the breakout board to drivers, encoder, spindle control, etc is discrete and easily adjusted to a given Mesa firmware version.

    I also have a Frankenstein Sherline combo-machine, lathe and mill. I put an encoder on the spindle for threading in lathe mode. This was pretty easy to set up under LinuxCNC and works very well. The G-code to cut a thread is involved and requires careful study each time I use it, but it works flawlessly.

    I highly recommend LinuxCNC.

    Thanks.

    Quote Originally Posted by asuratman View Post
    It will use MESA Linux CNC ? Its interesting, which card you will use ? I have retrofit my lathe to mach3 but no threading yet. I read in one thread here about linux development, much better screen, maybe I will try this route in the future.

  8. #8

    Re: PM1022 lathe CNC Conversion

    Cool project! I am planning on converting a PM-1228VF-LB sometime soon. I'll probably run it manually for a while as I use it to make parts for the conversion, and other stuff of course. But your progress should be a decent guide for what I am going to run into. Good luck! I'll be watching!

  9. #9
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    Re: PM1022 lathe CNC Conversion

    Well, let's see. Since the last installment I've taken a bunch on measurement of the lathe.


    With these in hand I went to the CAD system and stared working out the configuration. I still do this in a "large" 2D layout drawing. It's the easiest way for me to see how everything fits together. No one else will ever be able to make heads or tails of these "sketches" but it helps me. Then, when things are close I build 3D models of each part and assemble these in 3D space. Here's the first model assembly.


    The large blue piece at the top is the existing saddle. Mounted at the front of the saddle (red) is a bearing holder. It's similar to the original but modified. It is longer to maintain cross slide travel with the new ball nut, and has a second flange for the stepper motor plate out front. Inside are two angular contact ball bearings with grease seals. The inner races are clamped to the ball screw between a shaft shoulder and the timing belt pulley (green). The outer races are clamped between the (red) bearing housing and a bearing cap (just visible in yellow). Spacer rings at the inner and outer bearing races between the bearings will be adjusted for bearing pre-load. It's anticipated these rings will be adjusted upon assembly. Similar rings will hold the grease seals.

    The stepper looks like it will be a short NEMA 34. The longer NEMA 23 I was considering is too long and would interfere with the Z ball screw. No model yet for the Z mounting but looks like it will be a long NEMA 23. The NEMA 34 is too big around to fit into the old gear box space. This is backwards, the Z axis should have the more powerful stepper, but with 2:1 timing belt drives both should work well.

    To get space for the Z stepper, where the gear box was, I moved the thrust bearings to the tail stock end of the machine. The head stock end will then have a floating single deep groove ball bearing and a 2:1 timing belt drive to the NEMA 23. I moved the axis of the Z lead screw some 3/8" out, towards the operator, to allow room for spiral steel tape ball screw covers. Retrofitting these spiral tape covers typically stops the carriage 2 or 3" short of hitting the head stock with corresponding loss of travel. A problem. But since the apron is being gutted it can be used as a cavity for the spiral tape to compress into. So no loss of travel.

    The X and Z systems seem like they should be more interdependent. But the only places they interact is clearance for the X stepper motor from the Z ball screw and apron. Nice as they can be considered separately.

    It always amazes me how much work detail design is. How hard could it be to bring a simple concept into being? But with spacing and clearances plus finding purchasable parts it is iterative and takes a very long time. Hopefully it's now coming together.

    I should have detailed parts for the X soon with more descriptive visuals. Stay tuned.

    Thanks.

  10. #10
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    Re: PM1022 lathe CNC Conversion

    CL_MotoTech:

    Nice. A 12" lathe should be just right for a hobby shop.

    I'm sure there will be differences but hopefully this thread will give you a direction. Maybe what not to do but that's also valuable information. It is painful taking off all the gearing in the apron and the gearbox. We paid good money for those but they are not needed on a CNC lathe.

    I'm lucky, I have another lathe for building the parts. It is difficult to convert the machine you're using to do the conversion with. Quite possible but will require excellent planning. You'll know the lathe well after taking it apart several times.

    I do hope this is helpful to you. Thanks.

    Quote Originally Posted by CL_MotoTech View Post
    Cool project! I am planning on converting a PM-1228VF-LB sometime soon. I'll probably run it manually for a while as I use it to make parts for the conversion, and other stuff of course. But your progress should be a decent guide for what I am going to run into. Good luck! I'll be watching!

  11. #11
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    Re: PM1022 lathe CNC Conversion

    Is anyone having trouble seeing the pictures on this thread? Please let me know if you're not seeing them, or if you can see them.

    Thanks.

  12. #12
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    Re: PM1022 lathe CNC Conversion

    Quote Originally Posted by currinh View Post
    Is anyone having trouble seeing the pictures on this thread? Please let me know if you're not seeing them, or if you can see them.

    Thanks.
    I see no pictures

  13. #13

    Re: PM1022 lathe CNC Conversion

    I see pictures in post 1 and 3.

  14. #14
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    Re: PM1022 lathe CNC Conversion

    mountaindew & CL_MotoTech: Thank you for letting me know. There should be pictures on Posts #1, 3 & 9, so far. This thread will make no sense if the pictures don't show up. Anyone else seeing them, or not?

    If pictures won't work for me I'll likely move the thread where they do work. What forum would you prefer I move it to if I have to?

    Thank you.

  15. #15
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    Re: PM1022 lathe CNC Conversion

    Is anyone having trouble seeing the pictures on this thread? Please let me know if you're not seeing them, or if you can see them.
    I didn't see any pictures ... how to see them ...

  16. #16
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    Re: PM1022 lathe CNC Conversion

    I can't see the pic's in post #9, but can see the earlier ones.

  17. #17
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    Re: PM1022 lathe CNC Conversion

    The thread is very dependent on pictures. Let's see if they can be seen through attachments. Here are the pictures that should be in Post #1.

    Thanks.

  18. #18
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    Re: PM1022 lathe CNC Conversion

    These two pictures should be shown with Post #3.
    Attached Thumbnails Attached Thumbnails StockCross.jpg   StockCross-2.jpg  

  19. #19
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    Re: PM1022 lathe CNC Conversion

    And finally getting into the detailed design. These two pictures should be with Post #9.

    If these show up OK I'll continue with attachments. Would really prefer in line pictures but until that is figured out I'll go with attachments. Should have more details to post soon.

    Thanks.

  20. #20
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    Re: PM1022 lathe CNC Conversion

    Quote Originally Posted by CL_MotoTech View Post
    Cool project! I am planning on converting a PM-1228VF-LB sometime soon. I'll probably run it manually for a while as I use it to make parts for the conversion, and other stuff of course. But your progress should be a decent guide for what I am going to run into. Good luck! I'll be watching!
    Here is my thread on my PM1228 conversion. What CAD package are you using?

    https://www.cnczone.com/forums/verti...-software.html

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