EIA 430/100 Frame, Steele design

[skiddaw]

My first attempt at a CNC Router is based on David Steele's book with an old EIA 430 Plotter (circa 1972) as the base which I purchased from goverment surplus some 25 years ago. The U-frame sides are substantial at 6.5" high, 3.5" wide and 1/2" thick. The internal dimensions of the frame are X-31", Y-43". The two X-rails are 1" D, and the Y-rail is solid 1/2"D. I've added 5.25" MDF to stiffen the gantry and a top rail of 3/4" conduit to support the Z-carriage.

The existing X/Y drives use 1mm cables which I might just try and run for starters before I go adding leadscrews. So far the local hardware stores have provided everything apart from the motors which I purchased from Toronto Surplus.

I drilled the holes in the conduit by clamping it to the supporting AL channel and running that along a guide in my drill press. I used 1/4"D square nuts inside the conduit and positioned them there using a 1/4"D magnet from Lee Valley sunk into a small wooden rod.

[skiddaw]

I have by now, but only just, routed a small pattern into a piece of masonite.

I used CorelDRAW to generate the pattern and saved it as DXF. I used DXF2G-CODE to create the G-code file. This was then transferred to an Ubuntu PC running EMC. There I edited some of the Z-axis parameters including the naming of several constants (#1 = -2.5) etc to simplify my adjustments. Moving the cutter onto the surface of the wood I used G92 X0 Y0 Z-2.5 to preset the position and then moved the Z-carriage up an inch before running the G-code. I say all this because I've no idea really how you folk go about setting up a job. Something funnny in the conversion in that I think Corel is outputting in inches and DXF2G-CODE thinks these are mm. I changed G21 to G20 and the dimensions are correct?

On the hardware side I have built three drivers and an isolated interface card using designs from Phil at pminmo. These are presently set for 2 amp as I'm only slowly daring to go up. Other settings are Vmax=0.5 in/sec, Amax=5, microstepping= 2, giving 14400 Hz @ Vmax. I'm still playing with this stuff. My power is from tw PC supplies with nylon hardware holding them off the metal. This gives me 24V at 10 amps. I'll try and upload a picture of the controller which is just an old PC chassis upside-down. The supplies are sans case and fit nicely into the hard-drive area, bottom left. All the PCBs are mounted on an aluminium plate, again using nylon hardware. An AC fan on the RHS pushes air over both sides. A 12V fan at the bottom pushes air over the two supplies. I originally rewired an old microwave transformer but it was getting far too hot for my liking.

On the table I've added six limit (micro) switches using some I've taken out of old microwave ovens. I've also added simple thrust ball bearings on the threaded rods, taken from old record players. (even had a 5/16" centre hole) My Emergency Off switch is from a PC power switch with a small lever added. In addition the Y-axis limits are easy to get at. My router is a 1HP Bosch but as yet I don't have control of it's power from the PC.