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Thread: Central machinery 8x14 CNC build

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    Default Central machinery 8x14 CNC build

    So, I've been bitten fairly hard by the CNC bug, and I had always wanted to build a CNC lathe. This coupled with the fact that I got to do all the programming and prototyping for our CNC lathe at work, pretty much forced me into it. So I started looking for a cheap-o lathe that would make a good base build. Having a Logan 200 lathe already, I wasn't overly worried about the size as anything large I can always do in there. So when a central machinery 8x14 popped up on craigslist for $100 I snatched it up. It worked out really well actually, as my very first lathe was a HF 8X12, (which is pretty much the same thing), so I knew it's flaws fairly well already. Here she is when I got her:



    So I tore her all down and started the fun of designing the CNC conversion. Which, if anyone is interested in the model, I'm happy to share.


    That deign is actually REV-A. My original design was all belt driven, but I switched to a direct drive while I was trouble shooting the closed loop steppers I had originally bought for it. You can read all about it here if you like


    So anyways, I ordered all the elctronics, ballscrews, ball nuts, ect.. and started machining all the mount. So here's what I have so far. The motor and VFD are mounted temporarily just so I could play with it. I have all the steel I need to make a really nice stand for everything, but that has to wait until I move into the house I just bought No mocking the ducks! ok, go ahead, they are pretty silly.



    I also decided to machine a custom spindle for it. I'm not a huge fan of the chuck that came with it, and I already have a c5 collet chuck for my Logan, so I figured I'd try machining a direct fit C5 spindle. I turned the OD features on my logan, and ordered some cheap radial bearings. After I installed the spindle I machined the collet mating surfaces right on the mahine. It worked fairly well, but it's not a concentric as I would like. I think it has to do with the fact that the bore after the taper isn't long enough and the back end of the collet can move around a bit. That combined with my, not so perfect, drawbar jerryrigging, it's just not as good as it could be.

    back side adds preload to the bearings with a custom machined nut. Notice the cool little brackets tat I made to assist in installing the rear bearing.
    the belt drive is also temporary and will be replaced with a timing belt eventually.


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    Default Re: Central machinery 8x14 CNC build

    I had to make a few modifications to the saddle to get where I wanted to be. I wanted double nutted ballscrews to help alleviate backlash, especially on the X axis. But of course the "standard" cheap ballnuts wouldn't fit so I needed to machine out both the nuts and the saddle. Here you can see I lopped the top of the nuts off and machined a slot for the nut flange to sit in. This nut is the spring loaded and "floating" nut. You can see the belville washer stack that I'm still working to get just perfect. You can also see that the screws thread into the ballnuts. That was fun to do. I tried tapping them, but they are so hard, it was a waist of energy. So I machined some little threaded inserts and welded them to the nuts. They seem to be holding up very well so far.


    Here is the replacement for the split nut carriage assembly. I added some brass tipped (custom made of course ) set screws to pinch the saddle in place to make sure there was no vertical movement allowed. There are spots for 4, but I only have 2 installed right now. I also put an additional set screw in to lock the brass tiped one in place. I need to get shorter ones i know, lol.


    Maybe not as fun as the lathe itself, but the electronics are all packed into an old computer case I had kicking around. I have a USB smoothstepper controlling 2 Geck G251X drives, which are mounted on a custom heat sink. I also have a safty charge pump pump, spindle trigger, and spindle speed board crammed in there.





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    Default Re: Central machinery 8x14 CNC build

    So you'll notice the large aluminum block under to QTC. I was originally going to make an automatic tool changer, but I have a lot of tools already for my other lathe, so I figured why not make them interchangeable? So i made that block so that I can keep the height settings on the tools the same between both lathes. It works pretty good, and as you can see it'll come in handy as i have quite a few tools that I can use for both lathes now (that's the little black things hanging on the wall).



    So that's all for now. I still have lots of little things to do, so I'll update this as I go. the short list of things I know i need:
    - limit switches and estop button
    - Central oiling system
    - ballscrew covers!
    - I may reinstall the old spindle and see if I can get my collet chuck to mount to it
    - spindle trigger/tach sensor installtion
    - hook up VFD computer control
    - timing belt pulleys
    - finish mounting cable carriers

    so that's all for now, but I'll leave you with a couple little do-dads that I made just for fun:




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    Default Re: Central machinery 8x14 CNC build

    Worked on the lathe a bit more this weekend. Got the spindle trigger all hooked up and the VFD is now under mach3 control. I also decided to put the stock spindle back in. The 5C spindle was nice but i think I like the ability to swap out chucks better. So i modified the headstock a bit for the spindle trigger.





    works good

    major things left to do:
    - limit switches
    - chip covers
    - new stand



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    Default Re: Central machinery 8x14 CNC build

    CS900 -
    I have one of these lathes and want to modify it also. I see you have a solid model; any chance I could get a copy? I can read pretty much any format.

    Thanks, Andy



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    Default Re: Central machinery 8x14 CNC build

    Been a while since I posted, but I finally got the CSS working. Also made a custom post for bobcadcam. So here's my first take with the post, using CSS, and a thread canned cycle. Part looks greeat, I'm very happy with the lathe now! This is also the fist time I'm tried using the tool table as well. Works pretty good!





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    Default Re: Central machinery 8x14 CNC build

    Sweet setup! Sorry to hear about your issues with the closed loop steppers, I run the HanMarte closed loop nema 34's on my mill and LOVE them. They are STRONG, quiet, spin high RPM and have never given me as much as a whimper even running my loaded down Z axis at 400ipm with fast acceleration.

    I just picked up a 7x10 lathe to supplement my turning work and will be converting it to cnc shortly and plan on using the nema 23's on it direct driven with double ballnut as well. I want to try out Hoss's idea for the using a 5C spin indexer shaft as a spindle to increase my spindle bore and allow the use of 5C collets for smaller turning pieces.

    Awesome build and nice video! Have any other updates?

    Sent from my XT1080 using Tapatalk



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    Default Re: Central machinery 8x14 CNC build

    I also have the nema34's on my mill, and i love them. I loved them so much that i got the 23's for this project. The 23's are weak sauce though.

    Only real update has been the addition of ballscrew covers.



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    Default Re: Central machinery 8x14 CNC build

    So another small update. Ballscrew covers are on the Z axis and homing switches are installed and working.

    Z axis limit switch.


    X axis limit switch:


    How it sits now:


    Started making some tool holders for my taig mill. The lathe is holding it's own so far. Easily machines 1215 hex stock!




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    Default Re: Central machinery 8x14 CNC build

    Nice work!!! Need to post up some video of that badboy doing work!!!

    Sent from my XT1080 using Tapatalk



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    Default Re: Central machinery 8x14 CNC build

    will do. I've got lots of those tooling adapters to make so I'm sure I can make a few videos.



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    Default Re: Central machinery 8x14 CNC build

    Nice conversion. I especially like the wainscot and duck border in the workshop



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    Default Re: Central machinery 8x14 CNC build

    I never claimed to be a classy individual, haha.

    Hopefully soon I'll have a real garage to work in, but gotta finish the rest of the house before I can move in.



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Central machinery 8x14 CNC build

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