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  1. #1
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    Apr 2006
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    Homemade Linear Slide System

    Building my own CNC machine, for both plasma cutting and for slinging a dremel around, and after pricing ebay/used/new THK slides and competitive products, I decided to at least try making them myself.

    Turned out not to be anywhere near as difficult as I thought it would be. I hope I posted this in the right place; After looking at several forum names I guess it could fit in multiple places, but I chose this one "just because"

    Some bearings, some square stock, a few drill bits, and a digital caliper makes this easy work. Figured I'd share this since I see a bunch of threads about how to make such things yourself.

    Step 1: Making the saddle chassis (need four of these):


    Step 2: Making sure all the holes line up well enough to bolt together:


    Step 3: Machine two spacers per bearing (eight bearings total per saddle). Whit the bearings I selected the two spacers need to be 0.152-0.153" for a tight fit:


    Step 4: Bolt it together and hope it fits:



    Step 5: Make more!

  2. #2
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    Looks nice but you can't support the rail with that design.. unless you leave out the bottom 2 bolts (think upside down U instead of an O)

  3. #3
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    I like the way you have positioned the bearings around the shaft - much better than the popular angle design as you will not need to load the shaft to maintain bearing contact. You also have flat faces to mount the next component.

    Just when I thought it had all been done before another great idea pops up.

    Well done and let us know how they perform.
    cheers,
    Rod

    Perth, Western Australia

  4. #4
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    Randy - You're are absolutely correct - the rail can only be supported on the ends because the slides (saddles) are fully enclosed. I'm doing this on purpose actually, because my original design was held together by gravity, and I wasn't happy with the outcome. The original design started off as a homemade pattern copier, actually:

    Old design still:


    Old design moving:
    http://frederic.midimonkey.com/cnc/IM001188.AVI

    Anyway, this machine as you can see isn't going to be that large, (30x21" work area, machine about 3" larger in both directions) so I'm hoping the rails won't flex because of the small size and reduced weight of the thing not being so large. If your concern turns out to be a problem, know that I can fix it with this design

    The design of my end supports for the rail and the leadscrews just below, has enough space in the design that I can install up to a 1.25" diameter rail, therefore I can gain more stiffness in the rails if necessary. The saddles as you can see in the pictures I posted already are adjustable - longer bolts and wider spacers - means I can ride the saddles on larger diameter material. The "rail" in the picture is a short section of 1/2" thin wall tubing I had laying around and used to illustrate how the saddles will mount, but the "real" rails are 1/2" diameter hardened round stock, which is by far stiffer than the thin wall tubing in the picture. How much stiffer? I don't know. I can bend the tubing against the back of my neck, whereas the solid, hardened round stock I cannot. I can barely flex it. But like I said I can increase the diameter of the rails up to 1.25" without having to machine new supports, make new leadscrews, and so on.

    While I do intend to make a dremel head eventually, the main purpose of this machine is to perform plasma cutting, which is an advantage - plasma cutting heads don't weight that much, and if operated correctly "floats" about 1/16" above the material being cut, so there is no contact that will cause resistance in the movement of the machine. So at least for plasma cutting, the rails/saddles only have to support it's own weight, plus the weight of the other axis' installed on top.

    One of the intermediate designs I came up with would have allowed for a supported rail, and still force the saddle to only move in the direction of it's assign axis - using three bearings per end, in a "Y" type of arrangement, looking down the length of the saddle. I made about six of these types of saddles before I finally accepted *I* was unable to make an accurate enough "Y" mounting arrangement so I went the easy route with a square, four bearing arrangement. Though I was making the "Y" style saddles by welding steel flats in a wooden jig I made, trying to get the 135 degree angles as accurate as possible. I just couldn't do it. If things do flex really bad, and upgrading the diameter of the rail for stiffness doesn't help enough, I may have to revisit the "Y" arrangement, and support the rail underneath with say, a 1/4" wide flat of appropriate height.

    If I had a milling machine at my disposal, making the "Y" arrangement would be easy - I'd just make them out of solid aluminum stock and machine the shape, and machine slots for the bearings, then drill through to tie it together.

    One of the things that was important to me, is to have the bearings supported by bolts that are in double sheer.

    For about a year I was looking for a used "all in one" lathe/mill combo, however being unemployed for the past 18 months didn't help me afford such a unit, so I ended up with a used Clausing lathe instead:


    Anyway, good eye Randy. Also, just in case it's not obvious, I'm not arguing, merely sharing my thinking at the time I started on this adventure. I realizing my writing style doesn't always facilitate that. One too many corporate memos I guess. Anyway, I very much appreciate the comments.


    Rod - having a flat surface to attach the other axis too is key, and I put a fair amount of thought into it. Randy's concerns above concern me as well, however as I stated above if there is too much flexing I have an upgrade path outlined to reduce or eliminate that.

  5. #5
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    Progress as of 2006.05.25

    Drilling out the ends of the stainless, hardened rod to 27/64"


    Tapping to 7/16 course:


    Completed rail, with rail supports. I still have to chuck the end supports and skim them with a carbide cutter to make sure as both ends of the rail are the same height off the chassis. You can see the saddle floating in the middle.


    Completed second rail, with supports, still have to skim the bases of the four end supports. I'll do that in a few days once I swap lathe chucks.


    Anyway, back to making 3/16" ID, 0.153" long bushings

  6. #6
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    Nice home made rails system.

    I may have missed it, but what is the diameter of the rod?
    And is the rod regular round? or the grinded shaft material?

    If one were to do something similar, what kind of bearing be appropriate?

  7. #7
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    I'm using mild steel 1/2" diameter tubing at the moment (as in the above pictures), as a place holder while I'm still experimenting and engineering "on the fly". It will be replaced with hardened stainless solid 1/2" round.

    The small diameter seems okay so far, but it is a small machine, and the plasma cutter doesn't apply torque to the material the way a router would. It just hovers over the material (1/16" being ideal).

  8. #8
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    Quote Originally Posted by midiguy732
    Building my own CNC machine, for both plasma cutting and for slinging a dremel around, and after pricing ebay/used/new THK slides and competitive products, I decided to at least try making them myself.

    Turned out not to be anywhere near as difficult as I thought it would be. I hope I posted this in the right place; After looking at several forum names I guess it could fit in multiple places, but I chose this one "just because"

    Some bearings, some square stock, a few drill bits, and a digital caliper makes this easy work. Figured I'd share this since I see a bunch of threads about how to make such things yourself.

    Step 1: Making the saddle chassis (need four of these):


    Step 2: Making sure all the holes line up well enough to bolt together:


    Step 3: Machine two spacers per bearing (eight bearings total per saddle). Whit the bearings I selected the two spacers need to be 0.152-0.153" for a tight fit:


    Step 4: Bolt it together and hope it fits:



    Step 5: Make more!

    hi midiguy732


    very nice concept with the linear bearing arrangments , keep up the good work

    cheers

  9. #9
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    Thanks!

    Actually the machine is almost done. Got the pulleys yesterday, have to make the stepper mounts, and measure for belts. I'm behind on the pictures

    http://frederic.midimonkey.com/cnc-gantry2.html

  10. #10
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    Jul 2006
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    Very Nice!!! Thanks for the construction detail.

  11. #11
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    Jun 2006
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    I was thinking about as I would be to make a table x,y with this bearing/spacers slide system... hmmm ... maybe ?

  12. #12
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    hi
    midiguy732 , i come across this skate_bearing rail setup some where of the net

    alot more maching required , but if someone is thinhking of making a larger plasma or router table needing more support for ridgity under the mail rails this could be a simple solution

    less bearings one side so only three bearings hug the mail rail allowing for a bridge arrangment so the skate_bearings( ballscrew ) doesnt hit the mail rail supporting feet .

    I'm sure even with ur setup midiguy732 , one could leave out one side of the bearings and fit on the ends of both sides a U - shaped bracket and drill and tap holes and screw them to the ends of the skate_bearing for extra ridgity so they dont flex apart from the rail .

    see what u think guys/
    Attached Thumbnails Attached Thumbnails Skate-o-rail-1.jpg   Skate-o-rail-2.jpg  

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