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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > First build! 3-Axis Gantry-style CNC
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  1. #1
    Join Date
    May 2008
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    14

    First build! 3-Axis Gantry-style CNC

    Hey everybody!

    I'm finally building a CNC machine to further my goals of world domination!

    I'm a complete nüb when it comes to this stuff, and am going to have some questions, but I'm a fairly smart guy and a fast learner.

    I have a rough idea of the design worked out in 3D, but I have to finish nailing it down today now that I have all the components in-hand.

    For its guts it has a Keling Inc 3-axis package with KL-4030 drivers and 425oz-in NEMA23 steppers.

    Its construction consists of a bunch of 80/20 extrusions that I got good deals on from their eBay surplus store.

    The linear motion is 1/2-10 Acme screw, and precision steel shafts with linear bearings.

    The (maybe temporary) brain is a very old Athlon 1800+ machine running the custom Ubuntu EMC2 linux distro.

    The spindle is a Bosch 1617 in a mount from K2CNC.

    Hopefully this will turn out really well. You can look forward to my detailed status reports (And lots of pictures!) as things progress.

  2. #2
    Join Date
    Mar 2003
    Posts
    35538
    Do not use 1/2-10 acme with those motors, you'll get poor performance. Use something that gives 2 to 4 turns per inch max for best speed.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

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    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
    Join Date
    May 2008
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    14
    Quote Originally Posted by ger21 View Post
    Do not use 1/2-10 acme with those motors, you'll get poor performance. Use something that gives 2 to 4 turns per inch max for best speed.
    Thanks, I'll keep that in mind in case it doesn't run as well as I'd like.

    For now though, what's bought is bought. Based on my currently limited understanding of this stuff, I was going for high positional resolution, with a pitch that offered nice round numbers to deal with. Speed isn't really my top priority.

    I am not free of concerns regarding the design however. For instance, I think I might need a second stepper and screw for the Y axis...which frankly I don't have the money for right now, heh.

    We'll see

    The last components arrived today, so I can really get to work on the design. (I'm very hands-on, so I wanted to have the parts and really see how everything goes together before I tried to get more specific with the design.)

  4. #4
    Join Date
    Oct 2008
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    1147
    I think what Gerry is saying is that with those motors and driver you won't be able to hit the sweet spot since the driver won't be able to provide enough juice to drive them at their optimum. You may end up, buying new screws and nuts, downgrading your motors, or a new driver and power supply. All three are kinda pricey. Since you havn't used them yet, perhaps you should exchange the package for one that better suits your needs.

    The only reason I'm pointing this out is I wanted the same motors. But CR talked some since into me.

  5. #5
    Join Date
    May 2008
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    14
    Hmm, that DOES sound rather problematic. What would you recommend for motors instead? Though I'm not sure I understand how the driver and power supply wouldn't be able to 'provide enough juice'. The rated draw for the steppers fits well within the specs of the drivers and power supply.

    Speaking of the steppers though, I was wondering, should I have them wired in series or parallel? If I've been reading correctly, I probably want Parallel. Series and Parallel both offer the same torque, but Series will stall sooner.

  6. #6
    Join Date
    Oct 2008
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    1147
    Quote Originally Posted by TheBakachan View Post
    Hmm, that DOES sound rather problematic. What would you recommend for motors instead? Though I'm not sure I understand how the driver and power supply wouldn't be able to 'provide enough juice'. The rated draw for the steppers fits well within the specs of the drivers and power supply.

    Speaking of the steppers though, I was wondering, should I have them wired in series or parallel? If I've been reading correctly, I probably want Parallel. Series and Parallel both offer the same torque, but Series will stall sooner.
    I'm still learning myself. So I wouldn't be the right person to ask. There is a guy named Crevice Reamer. Send him a PM and tell him your setup. He'll be able point you in the right direction. He really gave me some solid advice.

  7. #7
    Join Date
    Feb 2004
    Posts
    1086
    Ger didn't say anything about the motors -- your motor package is fine. What he's saying is that you should use multi-start ACME screw. I agree with him on this. For the hobbiest, multi-start acme is the sweet spot -- higher efficiency, higher linear speed for lower rpms (which keeps steppers in the lower rpm, higher torque range), and less chance of screw whip due to the lower rpms. All this for a modest increase in price. I did this on my machine (using 5-start ACME), and it was by far the best upgrade I made.

    Best regards,

    Ahren
    www.cncrouterparts.com

  8. #8
    Join Date
    May 2008
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    14
    Hopefully the choice in screw won't be a problem in just getting the thing up and running. Speed isn't really a concern. The intended uses of the machine are rather varied. For example; routing/cutting large pieces of flat material (Like say MDF or something), cutting and drilling sheets of carbon fiber composite, milling and drilling PCBs, machining small parts from various materials including billet aluminum, and really anything else I might want to do.

    The screws are turned down to 5/16" at each end for mounting into bearing blocks. (And again to 1/4" on one end for coupling.) The couplers are the flexible shaft couplers from Keling Inc and will be housed in a motor mounting block with the stepper mounted on the one end, and capped with the bearing block on the other. The nuts are machined Delrin, from the people who did the screws, bearing blocks, and motor mounts.

    On another note, after testing the motors in both series and parallel, I'd say parallel is the way to go. The 2.8 amps per axis-- versus 1.4 for series --is still well within the bounds of my power supply.

    Once I finalize the design of the machine itself, I'll post some pics.

    Right now, the big question is whether or not the Y axis needs two drives instead of one. But I'm fairly confident that my choice of bearings will make the gantry glide with relatively little effort.

  9. #9
    Join Date
    May 2008
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    14

    Now, with pictures!

    So I have the design for the X half of the X/Z stage worked out. (Minus whatever is going to attach the X-axis nut to it) This is a VERY accurate representation of the parts, considering I modeled everything basically freehand in a 3D animation package instead of a CAD program. (My trusty Lightwave 3D)

    Bah. Picture exceeded size acceptable, so just click here.

  10. #10
    Join Date
    Oct 2008
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    1147
    Can't argue with that Z axis. Nice job. Nice rendering too. Are all the parts for it orderable or will you have to fab any of them?

  11. #11
    Join Date
    May 2008
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    14
    Thanks.

    I have every part pictured, with the exception of maybe one length of hex cap screw. (Which I'll have after my next smallparts.com order)

    The delrin nut, bearing blocks, and motor mounts were machined by the folks at Precision Tech Machining and bought off their eBay store. (Along with the acme screws which they turned down to match)

    The clamps for the 12mm steel shafts were purchased from VXB.com, along with the 20mm ones used for the other axis.

    The 20mm pillow blocks with linear bearings (Along with the 12mm ones that will be on the tool half of the Z stage) and the 12mm steel shafts were purchased from Misumi USA.

    The extrusions were purchased on the cheap through 80/20's surplus and overstock shop on eBay. (Along with a bunch of aluminum blocks and flat stock to try out the machine on.)

    The 20mm shafts for X and Y axis, motor shaft couplers, as well as the electronics and steppers, were purchased from Keling Inc.

    The router mount was purchased from K2CNC along with an 1/8" collet adapter.

    The Bosch 1617 was purchased on Amazon.

    And as I alluded to earlier, all the screws and other fasteners and hardware are from smallparts.com

    That about covers it.

  12. #12
    Join Date
    Jan 2006
    Posts
    628
    Great looking Z axis. I'm looking forward to updates on your build, and I always enjoy seeing the creative uses for 8020. This is a great project and you'll have a lot of fun with it.

    I totally agree with FandZ, Gerry, and Ahren on the motors/screws issue. I wish I had sought more advice before I put my machine together. Don't get me wrong, I love my machine - but I'm definitely not using it to it's full potential.

    You might be completely happy with 45 - 90 IPM rapids - hard to say. Perhaps you'll get more, but I think the screws/motors are going to hit a wall about then. I'm not familiar with EMC2, but the computer hardware may also factor in. Get it running and you can always improve it later on.

    Steve

  13. #13
    Hi, I like your Z Axis, I may even copy it! Just one thing, it doesn't seem to have a fixed end bearing block on the top, or am I wrong?

    Good luck with your build.

  14. #14
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    May 2008
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    14
    Quote Originally Posted by stevespo View Post
    Great looking Z axis. I'm looking forward to updates on your build, and I always enjoy seeing the creative uses for 8020. This is a great project and you'll have a lot of fun with it.

    I totally agree with FandZ, Gerry, and Ahren on the motors/screws issue. I wish I had sought more advice before I put my machine together. Don't get me wrong, I love my machine - but I'm definitely not using it to it's full potential.

    You might be completely happy with 45 - 90 IPM rapids - hard to say. Perhaps you'll get more, but I think the screws/motors are going to hit a wall about then. I'm not familiar with EMC2, but the computer hardware may also factor in. Get it running and you can always improve it later on.

    Steve
    Thanks.

    Yeah, that's generally my thinking. If it doesn't perform the way I want, I can always upgrade it later. Especially the screws, they were relatively inexpensive compared to most of the stuff... But I'm not sure how big an issue the motors will be.

    EMC2 is really interesting... At first glance it actually seems more polished than mach3, but I have very little experience with which to compare the two.

    If you're interested in checking it out, they have a live CD you can use to try it out without having to install linux over at linuxcnc.org.

    And yeah, I have concerns about the computer hardware... Funny story about that. (Which I may share later, hehe)

    However, I haven't noticed any performance problems with that old machine in EMC2 and I've been running some g-code through the whole thing to test the motors. It didn't seem to be missing steps or anything as far as I could tell. But I still plan on replacing it with an inexpensive modern machine later on.

    The thing I really like about the computer system is the case... But I'll talk about that later, when I get to the electronics.

  15. #15
    Join Date
    May 2008
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    14
    Quote Originally Posted by thkoutsidthebox View Post
    Hi, I like your Z Axis, I may even copy it! Just one thing, it doesn't seem to have a fixed end bearing block on the top, or am I wrong?

    Good luck with your build.
    Thanks.

    Yeah, a bearing block identical to the one on the bottom sits between the motor mount block, and the top piece of aluminum extrusion, so the screw is held good and centered on both ends with some nice bearings.

    I hope to have some more updates to show off today or tomorrow.

  16. #16
    Join Date
    May 2008
    Posts
    14
    I sort of have the table portion of the machine designed. Mostly though, I was mulling over it in my head while adding photoreal detail to what has already been visualized, heh. (Having already gone so far, I decided to see it through, in the hopes of having accomplished MULTIPLE cool things.)

    Picture updated!

  17. #17
    Join Date
    May 2008
    Posts
    14

    Mostly Completed

    So I have the table and gantry design out. The only thing missing is the tool platform itself, though really all it is is a slab of aluminum with 12mm linear bearing pillowblocks bolted to the back, and K2CNC's Bosch 1617 mount on the front, so use your imagination in the meantime

    Here it is!

  18. #18
    Join Date
    Oct 2008
    Posts
    1147
    Looks great, I circled some problem areas. And they are not really problems, its just with tweaking they could become much stronger.


    The bottom 4 circles, if you could shorten them and rotate them 90 degrees upwords created a box, you would get a lot more stregth. ANd the mddle two circles. If you could rotate them and slide them under your spoil board, again it would go to reinforcing your design.


    The upper two, just move them inside your gantry. I'm not sure if you could do it but it would be great.

    Let me know if you don't understand what I mean. I still haven't had my morning coffee.
    Attached Thumbnails Attached Thumbnails cnc suggestioins.jpg  

  19. #19
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    May 2008
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    14
    Quote Originally Posted by FandZ View Post
    Looks great, I circled some problem areas. And they are not really problems, its just with tweaking they could become much stronger.


    The bottom 4 circles, if you could shorten them and rotate them 90 degrees upwords created a box, you would get a lot more stregth. ANd the mddle two circles. If you could rotate them and slide them under your spoil board, again it would go to reinforcing your design.


    The upper two, just move them inside your gantry. I'm not sure if you could do it but it would be great.

    Let me know if you don't understand what I mean. I still haven't had my morning coffee.
    Thanks for the feedback Yeah, I get what you're saying.

    Moving the beams on the gantry in is not doable, that was actually the original design, but it became obvious that the balance would be better if the shafts and stuff were moved to the center, and the beams to the outside.

    As for the two front-to-back beams on the outside of the table, they're mostly there to give an inch of clearance under the table with the extra rigidity as an added benefit. I see how making it a box frame like that would improve rigidity, but I'm not sure how much more rigid it needs to be.

    Don't know about the middle two though.

  20. #20
    Join Date
    Jan 2006
    Posts
    628
    I'd be cautious about the bed design. 8020 is a wonderful thing, but attaching those frame pieces on edge isn't going to give you nearly the same rigidity and triangulation as butting/bolting them to a piece of rigid plate, IMO. Your square base might go parallelogram if you're not careful. Make sure you have limit switches installed, or a runaway gantry could really do a number on your frame.

    Also, the unsupported rails are another concern. You mentioned modest speed needs, for tasks like drilling holes, milling pcbs, but then you also say you'd like to be able to mill billets of aluminum. I don't know what size rails you're using, but I would definitely recommend rigid rails (or supported round rails) mounted directly to the 8020.

    I'm not saying your design isn't "strong enough" - it all depends on what kind of work you really want to do with it. Strong enough for drilling and light milling, but you could have issues with modest loads on the frame and router.

    Just my 2 cents.

    Steve

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