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  1. #1
    Join Date
    May 2012
    Posts
    29

    12"x12"x3" $400 Build

    Hi,
    I've spent a lot of time on CNCzone and other websites learning and researching CNC machines.
    I've also spent a very long time drawing and designing my CNC machine on Inventor.

    Right now, I have a fixed gantry, 12"x12"x3" cutting area, and a budget of $400 (student's budget).

    This week I will be buying all of my parts. Tomorrow, I'm going to the local metal shop to buy angled aluminium, 3/8" Al. rod for motor spacers, 1 1/2" Al. rod for homemade couplers, and 1/4"x1'x2' Al. for reinforcing plates.
    Check out my design, it took 2 months of drawing a few dozens pages and designing it in Inventor. Hopefully everything works out!

    Quite excited to start,
    John





    Attached Thumbnails Attached Thumbnails IMG_5944.jpg   Progress10.jpg  

  2. #2
    Join Date
    May 2007
    Posts
    428
    John, looks great! Keep up the good work... And having fun!
    Dolphin CAD/CAM Support

  3. #3
    Join Date
    Aug 2011
    Posts
    998
    Agree, looks great! I guess you will need to be very creative in sourcing so that you don't blow your budget.

    Good luck with the build!

  4. #4
    Join Date
    Jun 2012
    Posts
    0
    Good luck man, I almost went trough the same process and started my machine 2 weeks ago. I think the budget will be the hardest part, for me the rails and screws are the most expensive thing.

  5. #5
    Join Date
    May 2012
    Posts
    29

    Update 2

    Here's what I've been up to:
    -Not going to the metal shop to pick up metal, visiting a friend's father's machine shop, who has all the scrap metal I need (saving me $60 ).
    -Got a old Dell PC from my school's tech room for free! (I hope it doesn't break, there is only 40 more of them in a closet haha)
    -Set up XP on the Dell.



    -Got a power supply off Freecycle (like craigslist, but all free).
    This power supply is incredible, its 1300W, about 20lbs., and does 42V at 27.5A!









    I am going to Fastenal and Home Depot, then ordering everything else from Enco in the next few days. Hope to be building by the end of next week, very exhilarating!


    By the way, can I get by with some Nema 23s from MPJA? They are so cheap, I don't know about the quality of them.
    4.5V, 2.5A, 1.8 Deg. NEMA 23 Step Motor-MPJA, Inc.
    or
    5.7V, 2.3A, 1.8Deg. Dual Shaft NEMA 23 Stepmotor-MPJA, Inc.
    Attached Thumbnails Attached Thumbnails IMG_5945.jpg   IMG_5947.jpg   IMG_5946.jpg  

  6. #6
    Join Date
    Mar 2012
    Posts
    12
    John,
    I have a Zen Toolworks 12x12 that is very similar to the one you are going to build. Checkout the Zen Toolworks website especially the Wiki. You may get some information that will help you.

    I would also recommend LinuxCNC for your controller software. It is free and works well.

    Hope this helps, good luck.

  7. #7
    Join Date
    May 2012
    Posts
    29
    Arnell, thanks for the resources, between the Zenworks and microcarve's builds, I decided to do some last minute redesigning of my machine. I cut down about 20 MDF parts, about 75 less bolts, and made a much simpler design.
    I also took microcarve's PVC idea and placed more aluminum around bolts, I hope he doesn't mind!

    Hopefully this cheaper, simpler idea will work better.



    Attached Thumbnails Attached Thumbnails Progress12.jpg   Progress12_5.jpg  

  8. #8
    Join Date
    May 2012
    Posts
    29

    Update 4

    Yesterday I recieved the metal I needed from a nearby machine shop(for free, thanks!), got a tour and learned tons. I really liked their Haas machines.
    Today I got 42 lbs. of hardware from Enco, totaling 1,405 parts for $170.






    Also received some end mills from ebay, six 2 sided, slightly used bits for $11!



    I was most interested in how the bearings would work, for the needle cage is quite small, but it turns easily with minimal preload and there is no noticeable axial movement.

    You may notice that I'm not using ACME rods, between the cost of the rods and nuts, I'm saved $30-40...probably will change out for ACMEs in the future(maybe if this machine makes me some money ).




    Won't get my MDF cut until next week, so research on stepper motors is the next step!

  9. #9
    Join Date
    May 2012
    Posts
    29

    Update 5

    I have been quite busy! In the last two days, I have worked for 22 hours and got 11 hours of sleep. I have gotten my parts cut at my high school's shop on their AXYZ 4008 machine.


    Also, I tried cutting my AL parts, which was much more difficult. I started at 15IPM and cutting 1/16" off at a time. The AL was getting stuck on the end mill, so we turned down the RPM of the spindle. After cutting halfway through the 1/4" AL the machine's origin point was erased and I did not start it in a repeatable place. Looks like I will hacksawing alot!


    I also started to work on my couplers, I turned 1 1/2" AL on a metal lathe and got holes drilled. Already, they look really cool.





    Next up is painting and drilling more holes!



  10. #10
    Join Date
    Apr 2004
    Posts
    5728
    Good work so far, John, But those solid couplers aren't such a great idea. If there's any misalignment in the relationship between the screws and the motors (and with a build like yours there can't help but be), then coupling them together solidly will eventually snap the shafts off your motors. That's why people use Oldham, Lovejoy, and helical couplers. Those are a bit difficult to make, but you could make Taig-style couplers pretty easily by producing coupler halves, one for each side, putting 4 matching holes in the facing surfaces in a square pattern, and using pieces of nylon tube fitted in the holes to connect them and transfer motion.

    Andrew Werby
    ComputerSculpture.com — Home Page for Discount Hardware & Software

  11. #11
    Join Date
    May 2012
    Posts
    29

    Update 6

    Quote Originally Posted by awerby View Post
    you could make Taig-style couplers pretty easily by producing coupler halves, one for each side, putting 4 matching holes in the facing surfaces in a square pattern, and using pieces of nylon tube fitted in the holes to connect them and transfer motion.

    Andrew Werby
    ComputerSculpture.com — Home Page for Discount Hardware & Software
    I was wondering about alignment issues but with low rpms, I wasn't too worried. I believe you are describing a method similar to this one? http://www.cnczone.com/forums/diy-cn..._couplers.html
    I will probably take your advice, thanks!




    Also, update. Painted my MDF with shellac-based primer/sealant. Should prevent warping and is a very tough shell. I can't scratch or dent the painted MDF easily. I paid $14 for a quart but it was worth the $.
    Once assembled, I will coat exterior surfaces with regular interior paint (maybe yellow?).



    If anyone is curious, I used Zinsser BIN shellac-based primer from good old Home Depoo.

  12. #12
    Join Date
    Aug 2009
    Posts
    291

  13. #13
    Join Date
    Apr 2007
    Posts
    8082
    Note also that John uses nylon spacers to mount the motors. If there is any very minor misalignment at the motor shaft, the nylon tends to absorb it a little.

    I have had one shaft break due to misalignment. I was surprised to find that they are two piece shafts with an electric weld joint that is apparently intended to break as a safety feature. The coupler was a DumpsterCNC delrin part. Obviously, it was a very bad misalignment situation that was self induced from lack of experience with these things.
    CarveOne
    http://www.carveonecncwoodcraft.com

  14. #14
    Join Date
    May 2012
    Posts
    29

    Update 7

    Thank you for your inputs, will have to think more about building proper couplers now.

    Anyways, I received my 220oz.-in. dual shaft motors from MPJA and a HobbyCNC Pro board. Needless to say, it was a day of electronics.
    During my building of the PRO board, I found out I got shipped the wrong 3-lead chip. I ended up with a L7824 instead of a LM317. I had an extra LM317 I took from my bin of LM317s(desoldering old electronics saves time and $). Dave, from HobbyCNC, contacted me already. He was very prompt and friendly.
    I added 3 matching heat sinks I took out of an old something. Its thin AL and somewhat small, but there is so much surface area(big factor in heat dissipation) that I think it will run cool. A fan will accompany heat sinks soon.





    I also got my motors spinning with mach 3 today, glad to not be dealing with any electronic problems for now.
    Haha, the messy wiring is driving me crazy!

  15. #15
    Join Date
    May 2012
    Posts
    29

    update 8

    Today I built the torsion box base. It went quite smoothly, I squared and wood glued the edge pieces one at a time and used little 1" nails(brad nails?) to keep everything in place. Then I filled in the inside and secured with glue and nails. I cut the last row of inner spacers down because they did not fit entirely.
    My torsion box is flat, heavy, and does not flex a bit! I would have to jump on it before it would flex.
    If anyone else is interested about torsion boxes, this video is pretty useful:
    Torsion Box Assembly Table | The Wood Whisperer




    Weighing down torsion box with heavy things to get glue to stick, haha.

  16. #16
    Join Date
    Dec 2011
    Posts
    155
    you can get some love joy style flexible shaft couplings on ebay for under $10 a piece. Check out love joy or the rotex catalogs to learn more about couplings and sizing.

  17. #17
    Join Date
    May 2012
    Posts
    29

    Update 9

    Working on the x-axis, progress is good.
    I finished my torsion box base and added the mounts for my x-axis. I put in PVC with 1/4" threaded rod inside for extra rigidity. Each mount is attached with 6 bolts, in groups of 2 with AL blocks to keep them from smashing down the MDF. I was too cheap to buy cross dowels, so I chiseled square holes in my torsion box and inserted regular nuts. Same principle as a cross dowel, just less pretty.
    So far, everything is very rigid, I couldn't be more satisfied with the lack of movement, granted I have not built much, but it is still incredibly strong.



    Also, I finished the 4 clamps to hold my 2 x-axis drill rods in place. They are very similar to the JGRO design. However, I have seen other similar clamps, but made with expensive plastic, tap bolts, or nice hardwood. Among many reasons, I believe some humans build these clamps with other materials to keep the threads from stripping in MDF, not necessary! I took t-nuts, bent the tangs down and off(they split 3/4" MDF), and smashed the t-nuts into slightly smaller holes in my clamp.


    They stayed firmly in place, glue would definitely keep them from moving at all. When you use them, the force against the drill rod smashes them down even farther, awesome.
    Too cheap to buy t-nuts? Buy t-nuts, they're useful in many situations. Or use regular nuts! They won't work as well, but pressing them into the clamp with pliers and gluing would be adequate. Note that a regular nut takes up more space, so a bigger inner circle is needed. It was cheaper for me to use the extra wood, bolts, and nuts than to buy expensive plastic or other part.

    These clamps hold the drill rod in place with a tremendous amount of force, its not going anywhere.
    Note the clamps are at a 45 degree angle so that gravity doesn't rest the rod on one bolt, but between two.

    I actually cut out 5 of these clamps, giving me one to experiment with. Glad I did, split it up and built the rest better.
    If I were to build new clamps, they wouldn't be squares, they'd be triangles! Seriously, a triangular clamp is easier to adjust and still would hold the drill rod in place firmly. You could make an argument that a square would let you adjust the rod in the x or y direction without effecting the other direction(i.e. adjust drill rod left without moving it up or down).
    But I already have to turn all 4 bolts to move in any direction, a triangle would be a more beneficial arrangement IMO. I vote triangles.

  18. #18
    Join Date
    Jun 2012
    Posts
    0
    Very nice build, I have been looking into torsion boxes after checking your link also. Now I have a good reason to start rebuilding my machine héhé.

  19. #19
    Join Date
    May 2012
    Posts
    29

    Update 10

    Update, lots work, some progress. I have been working on my work table and x-axis, might have a moving axis in a few days.
    I drilled holes in my sacrifice work surface for t-nuts, and sunk them in with a bolt.




    For the lower part of my work table, that has moving elements attached to it, I planned to glue 3 pieces of PVC to it. The outside PVC have bushings for the drill rod to slide on, and the inner one has delrin to act as a backlash nut.
    To attach the PVC, I drew 3 lines, and used a hand saw to make a shallow V groove.


    I took a scrap piece of PVC, taped sandpaper to it, and put a handle on it to make a homemade rounded sanding block. It worked great, but there was ALOT of sanding to do, maybe 1 1/2 hours of sanding.


    I could have initially cut a bigger chunk of wood out, or if I had a router bit that was rounded, it would have saved lots of time. Anyways, the PVC fit very well, I proceeded to glue the 3 PVC pipes in with epoxy. I don't have good pictures on keeping everything parallel, I'll get some in the next post.



    The bushings fit almost perfectly into the 1" PVC. With some epoxy, they remained very secure. I recommend while the glue is drying the bushings to the PVC, slide the drill rod through the PVC and the bushings, so that the bushings are parallel to each other.
    I also got a good price on a 7/8" rod of delrin from Enco, $9 for 4' of 7/8" rod. It was about 1/8" to big to fit in the PVC, I filed down the diameter, and filed the inside of the PVC some also. It was about .1" to big, and with the help of a good old hammer, I smashed it in, its not going to turn or slide a bit, very very secure without glue. I put another 2" piece of delrin on the other side.
    I made a homemade tap(it's awesome), drilled a 7/16" hole, and tapped the delrin on one end of the PVC. On the other end, there is no threads, just a 1/2" hole the slides over the threaded rod.


    I've also made progress on my couplers, they are really cool. I drilled two 1/8" holes through the couplers, and chopped it in half. I took my 7/8" delrin rod, and filed down two 1/8" delrin pins to fit through the holes I drilled.

    With ~1/8" gap between the two halves, the coupler can flex quite significantly. Its more than enough flex, the plastic does not twist while the motor turns(did not introduce backlash). I am not worried about the plastic breaking and I am not worried about stressing the motor shaft, thanks for the advice everyone.


    Next up, spacers. I got a 3/8" aluminium rod that I chopped into 2 1/2" segments. I cut, drilled, and smoothed them out on the metal lathe at my school's shop, the drilled holes were still up to 1/16" off from being centered, but that's OK. Making the all the same distance was somewhat tedious, it would be hard to cutting spacers at the same length and drilling straight holes while keeping the ends flat without the help of a metal lathe. I would hate to see how these would look if I hadn't used a lathe.
    I had a old #10x32 tap to tap the holes on the spacers, but after 2 holes, the lower 5 threads on the tap were almost gone and it had bent axially from too much force(oops, never tapped before). Cheap taps start at ~$6 online, and I would probably break those also. Additionally I have a small budget. I took the screws I would be using for the spacers, dremeled flutes, and tapered the end; its a homemade tap that works, awesome.


    Even if these taps only last for about 4 inches of tapping (is that how tap life is measured?), its about 5 cents per screw, and I'm going to end up with tons of extra screws anyways. I don't know how fast professionals tap, or how much force they apply, but it took awhile for me(maybe 3 inches an hour?). I had small flutes and did not using tapping fluid. Note, if tapping fluid says, "Do not use on aluminium", do not use on aluminium! I thought it would be only less effective, but it turns red and bubbles!

    After ending up with 4 tapped spacers, I mounted them to my motor, no wiggle, flex, or twisting.


    I debated between mounting the stepper and spacer to the MDF base or an AL block mounted to the MDF base. It was less work to drill the MDF, and if there are alignment issues in the I holes drilled, the softer MDF will give me more flexibility than a hard block of AL. If the MDF later on gives me trouble, with wiggling and it starts to compress, I can always mount it to AL easily enough, I am happy with it.
    I know there are a number of ways to mount a stepper, if you have the ability to make good AL rod spacers, I recommend it. 3/8" is a good diameter, #10 screws work perfect, and mounted to MDF, it doesn't twist, wiggle or shake. It's more stable than I would have expected.



    I will have an x-axis moving within a week hopefully. Right now I am trying not to think about the time it will take to finish 2 more couplers and 8 more spacer rods. Unless you are on a tight budget, and $10-20 per coupler is too much, buy premade couplers! It's alot of work to build them!
    I did write a lot, but when I was researching other builds, I wished there was more written about details of rigidity, ease of building, and time constraints about different features. Hopefully I have gone into sufficient detail to help others in their research. If anyone ever has questions, let me know.

    Also, HUGE thanks to microcarve, his ideas and techniques that he has shared is invaluable.

  20. #20
    Join Date
    Jan 2012
    Posts
    66
    good build man and excellent documentation.

    some advice, you mentioned hacksawing your aluminum parts free. Why not use a table saw to do that job, much faster and accurate. A jig saw and straight edge at the least.

    as far as tapping goes, it can be done from beginnings to end in a matter of seconds. There is a very good set of high quality taps from greenlee for a little over $25. Its a tool you will use alot in your life. Save up and Get some when you can.

    [ame=http://www.amazon.com/Greenlee-DTAPKIT-6-Piece-Combination-Drill/dp/B0041FIR1E/ref=sr_1_1?ie=UTF8&qid=1345780903&sr=8-1&keywords=greenlee+tap]Amazon.com: Greenlee DTAPKIT 6-32 to 1/4-20 6-Piece Combination Drill and Tap Set: Home Improvement[/ame]

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