I manufactured a second copy of my bracket and used my hand drill to put a few holes in them to hold bearings. The idea is to mount 3 inline skate bearings at 120 degree increments around a pipe to limit motion to 1D (two of these on one side, plus two 2D mounts on the other side, make a Z-axis platform). I estimated the space taken up by the washers, and got it wrong, so if I wanted to use this design I will have to tweak my design and make a few “off-size” brackets to pair with the current ones I have. (Making all new brackets does not sound like fun, as each of them take almost 2 hours of routing time). The alignment and motion is a bit rough (I did eye-ball the holes) but I think I could improve upon that enough to make them passable with enough practice. However, due to the two-hour build time, I’m seriously considering using the “standard” angle-iron solution for my Z-axis.
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I have added limit switches to my X and Y axis. I always planned on adding them eventually, but after I stripped the nylon threads on one of my flange nuts in a router accident I decided that it was time. I’m using small micro-switches mounted such that they are closed when the X or Y axis nears the maximum extend of it’s motion. The ocean controls serial stepper controller has ports for limit switches on each axis, and when the circuit is closed that axis immediately stops moving and can only be moved one step at a time until the circuit opens again. I mounted the X-axis switches on a piece of wood from my 8 foot board I had to buy for the Y-axis pusher assembly (7.8 feet left!). I can’t decide what makes the router look more ghetto: The Ikea drawer rails, or the 45 degree screws holding the piece of wood down. (Also in the running is the blob of black epoxy-putty that pushes one of the X-axis limit switch.) Continue reading →

I purchased the 3 stepper motors from a surplus supply house for $25 each, and have been very happy with them. The fact that they include a screw drive mechanism has really simplified my mechanical construction. They are manufactured by HSI inc, and are Model 43000 external linear actuators.

The electronics that control the stepper motors on my CNC mill were purchased from Ocean Controls (An Australian company) in kit form. Specifically, I purchased Continue reading →

Since my last post I have constructed the Y table servo mount and pusher assembly. The Y-axis servo is mounted using a pair of L-Brackets, M4 machine screws, washers and nuts that were purchased specifically for this project and actually fit the screw holes on my servo! (Unlike the X-axis servo, which is connected with a 3/32 machine screw that doesn’t actually fit the threaded hole in the servo, and relies on friction to keep it from moving.) Since I was at the hardware store, I also bought an 8 foot piece of wood (2 inches of which I used for the pusher assembly with a lot left over for things like the X-axis limit switches.)

The video below shows the router drawing a diamond (twice as difficult as a square, because you have to make two motors move at the same time). I am controlling it using a small bit of python code to issue motor commands over a serial port to the stepper controller board. The diamond is drawn from 0 to 18,000 in stepper coordinates on each axis. (The 5.5 inch range of each axis ranges from 0 to 46,000 in stepper coordinates, so the working area is about 2.5 times larger than the drawn diamond.) As you can see from the (lengthy) video, the screw drive assembly on my (1.8 degree per step) steppers makes the actual motion speed of the X and Y axis quite slow. It is unlikely that I will have to artificially slow down my cutting speed when cutting actual material.

The device holding the sharpie marker is a (cheap, and inexpensive) “Dremel Drill Press” from Harbor Freight Tools that cost me $15. I can no longer find them on the Harbor Freight website, but they do have a “Drill Press Milling Vise” for $60 that is basically an X/Y table with 8 and 7 inch travel and a 5 inch jaw capacity. Adding a few servos to that would effectively replicate my X/Y table made from IKEA parts for only slightly more money and a bit less labor, although you’d still have to figure out a way to anchor the servos and connect them to the screw drives. I plan on raising and lowering my dremel drill press by hand to cut out the parts I need for my next generation CNC mill. So my computer control program will run the X/Y axis automatically, and then give on-screen prompts to the human Z-axis operator.

I am building a poor man’s Computer Controlled Router (Milling Machine). My first step will be to bootstrap the ability to mill needed components. Before I can make my own linear bearings, I am using cheap linear rails from the AS-IS (Surplus, Scratch & Dent) room of IKEA. Specifically, drawer rails make relatively good linear bearings. (Well, relatively good compared to what I could make myself without a mill.)
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