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Round shaft linear bearings questions for Router/metal mill table

Discussion in 'CNC Mills/Routers' started by Olivier Létourneau, Jan 23, 2018.

  1. Olivier Létourneau

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    hello i would like to know if it is possible to just add more round rod linear guides to add lenght on an axis ?

    would these be good for a cnc router/mill ?

    i guess the merge point has to be very sharp and aligned but it sounds possible to me

    i am in the process of designing my own router/mill CNC table for metal , the OX Metal build has pretty nice ideas but i really dont like the use of about 30 small wheels and 60 bearings and 3000 fasteners , at the price these rails go for on ebay i dont see why they are not more used in these setups, if someone can shine the light on my interrogations it would be greatly appreciated !

    i could easily see an A shape side gantry plate using two bearing blocks and a long acme screw moving them. with a 45 degree brace between the side gantry plate and the crossover beam it would cover the side to side flexing. same thing for the X the Y and the Z would result in no rollers/wheels/bearings/fasterners and eccentric adjusters .

    just my thoughts , im not a trained engineer and i never built a table so i may be overseeing some details , please feel free to educate me if you want !!

    they sell 2X 600mm guides with 4 bearing blocks for 50$ on ebay , could add guide lenghts untill i get the 2000 mm X axis i want , i cant really find V-Slot extrusion in the dimensions i need locally and the 20x40/60 extrusions look pretty flimsy to me who wants to build the table for metal routing and plasma cutting. the good V-slot wheels Openbuilds sell are going for 7$ each and the OX Metal build i was looking at uses 28 so its about 200$ just in wheels , then 35$ of eccentric adjusters and tons of fasteners spacers and shims. so basically almost 300$ worth of stuff without the rails. these linear shafts would simplify the assembly by a lot and let us use any frame materials.

    2pcs SBR12 600mm 12MM Support Linear Rail Shaft Rod + 4pcs SBR12UU Block CNC Set | eBay

    linear guide.jpg

    thanks
     
    #1 Olivier Létourneau, Jan 23, 2018
    Last edited: Jan 23, 2018
  2. Kevon Ritter

    Kevon Ritter Master
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    Don't expect to have a machine that can do it all. A machine that it twice the size is four times LESS stiff (assuming that all else is equal). Build to a specific goal and you'll have a machine that accomplishes that goal fantastically. If you build to meet every goal, then you will either have to sell your children, or would have a machine that does an alright job at everything, but nothing great.

    As for the supported rods lining up, I have no idea. It is done frequently with linear rails though.

    You still need material to mount that supported shaft to. Whether you build a steel frame or use larger extrusion, you can't ignore that cost just to make a point against the wheels.
     
  3. Olivier Létourneau

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    well , then my main question would be

    would these kind of slides be superior to the V-Slots and wheels in terms of alignment and stiffness ?
     
  4. Kevon Ritter

    Kevon Ritter Master
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    I don't have experience with supported rails to say for sure, but I would give them a shot for something heavy duty over the wheels. Make sure you absolutely avoid unsupported rails though...worst cnc experience ever.

    The downside is that you now have to mount them to something. I've read more times that the pre-drilled mounting holes are drilled by hand, which means they are inconsistent.

    Another thing to consider is size. Going bigger really isn't any more expensive. You were mentioned getting two 12mm rails with slides for $50. That would be good for one if you can mate them together, and would give you a 1200mm length. You can get a 1500mm length of 20mm for $120 for the pair with slides.
     
  5. Olivier Létourneau

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  6. Giarc

    Giarc Master
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    My only experience with linear rails and bearings is on my 3d printer. The linear ball bearings (made in China) that came with it are crap. I think the "you get what you paid for" seems to come into play a lot in linear motion. As for the 28 wheels for the Ox metal, that is what he used, but cutting with a spindle puts a lot more force on your parts than cutting with a laser, or plasma cutter. If it were me, and someday it will be :thumbsup:, I would mount 2040 v-slot (cheap and straight) on a steel angle iron frame for the linear motion part and the steel frame for the strength. I would use these to connect the pieces end to end Openbuilds V Slot End to End Connector/Alignment Tool by Huxlo and then use 4 to five wheels on the top of the rail to make the transition over the joints smooth. Eccentric spacers are not necessary if you cut slots in the gantry plates like the Acro and adjust them the same way. I did not use eccentrics in my laser cutter build because there are no significant forces pushing on my x and z axis trying to lift them. As for wheels, I would use the cheaper Delrin. I did not use Delrin wheels on my laser cutter build I am working on because I had some extreme wheels left over from my CNC build. Otherwise, I would have. Delrin has a higher melting temperature than the polycarbonate extreme wheels.

    So for 7 wheel kits per side ($4.85 ea) and 1500mm 2040 v-slot ($19.50) plus 500 mm 2040 v-slot ($6.50) = $59.95 per side. You do not need to buy 1/4 or 6mm spacers. You drill holes in scrap 1/4 aluminum pieces as long as they are all the same thickness. The spacers just make it easy and they look real nice. I cut my own spacers for my laser cutter from the scraps left over from cutting the gantry plates.

    The reason I did 1500 and 500 mm lengths in this little theoretical build, is because even though I may have 2000 mm total, I realize that I will mostly be doing smaller jobs, therefore I would have about 51 inches of cutting area using Ox plates without ever having to go across the joint. I get about 52 inches out of my 1500 mm axis with my cnc router, but I modified my plates a bit. But, that was just me thinking about it for the ten minutes it took me to pull all this out of my a$$ and now I want to build a plasma cutter. ;)
     
    #6 Giarc, Jan 23, 2018
    Last edited: Jan 23, 2018
    Peter Van Der Walt likes this.
  7. Olivier Létourneau

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    I plan on milling aluminum and i also want to mill wood panels with the router attachment With at least a 4x4fee cutting space. Will probably have 2 sets of work tables one for flat work and a bug grille for the plasma cutter . would also like to set it with a laser engraver and possibly a 3d print extruder with a heated plate. Also drag knife to cut leather for anbartisan who makes motorcycle seats and wanna cut vinyl with a spring loaded knife. I wanna build this thing to be over polyvalent. So i need strenght for the milling and pcrecision for the laser and printer.

    Will probably change the microstepping valueon thebdrivers for the printing


    I just converted my manual milling machine to cnc and i am going nuts about automation!!! Now thatbi understand the build i just did inwanna CNC everything!!!

    Also i could swap the axis wires from the mill to the router table steppers and just use a second profile in Mach3 to keep the machines parameters and calibration, wont need to assemble another full board of electricals. Control different machines with the dmsame kit. Maybe just add another set of drivers but use the power supplies from the mill
     
  8. Giarc

    Giarc Master
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    Can you run a 3D printer with Mach 3? I do not think you can. I could be wrong.

    Personally, I can see doing most of what you want with one machine, but I would have a separate 3D printer. I think it would be complicated to incorporate a heated plate you can level and you will not have much of a Z axis if you plan on having the strength and rigidity to mill aluminum on a 4 x 4 foot CNC mill/router. Also, some filaments need to be printed in a warmer environment so the printer bed is in an enclosure, or the printer itself is in an enclosure. I had considered doing this same thing but you can get 3D printers for under $200 now that with a about $10 in hardware store parts and some 3D printed parts can print as good as a far more expensive printer. I bought a printer in the $300 range and added some modifications, and it prints as well as a $1500 Lulzbot I have access to at work for PLA and better than the Lulzbot for ABS. Of course, mine is in an enclosure, the Lulzbot is not.
     
  9. Olivier Létourneau

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    The 3d print part would be kind of ezperimental but i planned on using it on my CNC bench mill which is very precise and leveled , got 7-8 inches of Z but have a narrow bed . will mount an extruder and a hot plate , woll be able to print some parts for the router table
     
  10. Olivier Létourneau

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    well i realised a print could take a full day to finish , i think its pretty silly to engage a CNC mill in such a long haul of work , found a pretty decently reviewed 300$ 330x330x400mm cube frame 3d printer i think it would be a better idea to have a standalone machine, was just researching the idea
     

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