The machine will do a reasonable job machining soft materials like plastic and soft woods, and it does quite a good job of plotting PCBs. The idea was to use a Dremel tool for the cutting head and use the machine to engrave aluminum front panels.
I found a couple of old Datasouth printer chassis at a computer surplus place and the printhead mechanism supplied the linear bearings and 1/2″ hardened rods for the axes. I used the rods as is for the X and Y axes so they are quite long – about 18″. I discovered after building the machine that the rods will bend under load and the accuracy of the machine suffers as a result. OK for plotting but machining requires very stiff axes.
The rest of the machine is made from 3/8″ and 3/4″ MDF – its easy to work with, quite stiff and very stable. I have a few rough sketches of this machine but its very specific to the Datasouth parts so there’s not much point in reproducing them here.
Here is the X axis taking shape. The black parts are linear bearings (bushings, actually) that were cut off the printhead assemblies.
One of the side supports being drilled. I made a drilling template which helped keep the axis rods parallel. Its extremely important that the axes be accurately positioned and exactly 90 degrees from each other.
The X and Y axes are in place below. Here you can see the 1/4-20 threaded rod I used as leadscrew. Not nearly as smooth or accurate as a machined leadscrew but WAY cheaper. I dispensed with the “floating nut” as used on some other designs and simply embedded a T nut in the carriage of each axis. To keep the less than straight threaded rod from binding the free end rides in a fairly loose bushing. The threaded rod is joined to the stepper motor with a short piece of plastic tubing which serves as a flexible coupler. Small hose clamps keep the plastic tubing from slipping on the motor shaft.
Article by Rich at http://www.storm.ca/~rheslip/
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