Insert Cool Name Here 24x48 Build

Late last year I was going to build the Sidewinder CNC based on Dave G. plans but after some feedback I've decided to start from scratch and design my own. Phase 1 are the linear bearings for the X and Y axis. I wanted a modular design so I could crank out as many linear bearing assemblies as needed. I decided to go with 2" conduit for the rails (maybe overkill) and a bearing assembly "block" that can be placed wherever design dictates. I finished the prototype in MDF and so far it seems to have worked out pretty good.

https://youtu.be/9A2_wVjZmuc

http://www.cnczone.com/forums/attach...d=312248&stc=1

http://www.cnczone.com/forums/attach...d=312250&stc=1

http://www.cnczone.com/forums/attach...d=312252&stc=1

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I think you'll find that you need a method to apply a lot of pressure on the bearings against the conduit. And a way to adjust the pressure.

My machine uses 2" conduit, and the bearings are pulled tight to the conduit with threaded rod. They are tightened to the point just before the bearings stop spinning freely.
Being this tight, they ear flat spots on the rail very quickly.

The bottom two bearing carriers are in slotted holes to adjust for pipe diameter variance and initial wear on the pipe. I'm thinking that after the pipe is work hardened there should be minimal adjustment needed.

I find it hard to believe it will work harden evenly.

Don

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Originally Posted by atarijeff

The bottom two bearing carriers are in slotted holes to adjust for pipe diameter variance and initial wear on the pipe. I'm thinking that after the pipe is work hardened there should be minimal adjustment needed.

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You will need a way to tension them to the point of binding and then back off a hair. This takes a lot of force. Enough that it will deform your MDF carriers. Even then, with the MDF it will be springy. If you can find a way to make the MDF parts out of aluminum and add in some tensioners it is a good design.

I used MDF just to prototype the design. My intention was to use a high quality ply for the final version. I agree that aluminum or some other metal would perform better but I want to keep it buildable without a full machine shop. I'll give some thought to some sort of tension setup that can be adjusted easily without tearing the machine apart.

I built my first machine from MDF. I was excited and didn't mind-the-details too much. Cut trapezoids instead of squares. I did re-build using 11-ply furniture-grade plywood. Sturdy and purdy (pretty).
I can machine 3/4" MDF, I also isolation rout PCBs (can easily do .050" pads for surface mount ICs), and for engraving aluminum and plastic. I have done some serious damage to one of my aluminum mounting clamps, so torque is not an issue.
Anyhow, for a light-duty hobby machine, I'm very pleased with it. (of course, I use the HobbyCNC PRO stepper motor driver!)

http://WoodWorkerB.com and click the "DIY CNC Machine" link in the top menu.

I'm not too sure EMT will work harden all that well. No practice knowledge here but I've been watching the electricians at work do a major installation, the way that pipe gets bent it is hard to imagine that it will work harden on you. Rather i suspect what happens is the bearings wear a track, flatens the metal really so that it fully supports the load.

Either way I'm waiting to see more build pictures. It will be interesting to see the results you get with the large diameter conduit.

My conduit is flatter in the middle than at the ends, even after 6-7 years of use. I'm guessing my bearings have 10x the pressure on the conduit that you'll see with your design. I'd be surprised if you see much wear at all. other than the galvanized layer flaking off.

I have a 20 year old vertical panel saw using conduit and skate bearings, and It doesn't have flat spots at all.

I used 1" conduit on my first wood Solsylva build. I did make the mistake of first using anodized tubing, and the anodizing ended up flaking off and would occasionally cause the axis to "hop." You can take a sanding block and smooth the "tracks" where the bearings ride. Also, I learned to set up jobs on different parts of the table instead of just the middle, to help wear the rails out more evenly.

nice design