My CNC Homepage

After rocking along with this for a few months, I got into another project which will require drilling pcbs
and my little brain said "Hey stupid, there are 194 holes in this board and you know the problem of
trying to drill them by hand!" This set me to thinking how I was going to do it and the light bulb went on.
You have the mill drill and it already has power feeds on the X and Y axis so why not put a little $$ and
update to full cnc.

Background: For a power supply for the power feeds, I had "rolled my own" transformer by taking a
defunct Microwave that was given to me, tearing out the transformer and doing a little work on it. This
entailed using a hacksaw and carefully cutting out the 2KV winding by sawing off one side and using a
punch to drive the remainder of it out. I bought some 14 ga magnet wire and made a one turn loop to
see how many volts per turn would be derived and then wound three windings on the intial trial. Two
were going to be for the power windings to the motors (remember origionaly two) and one for control
electronics. These were then fed into the usual rectifiers and filter capacitors (all from surplus houses)
to form the supply. My original setup was for approximately 20 volts per winding as the first drives that I
used had a max rating of 35V.

Back to CNC! As the original drivers had an analog input of 0-5V, it looked like I would need new ones as
all the cnc programs that I looked at required step/direction:{( Talking to a friend, I found he had
surplus some Gecko 320 and 340's that I could get for a good price. These were then connected to the
existing servos and a new mount was made for a servo on the quill micro feed and it was also
connected. Then a search began for a suitable cnc program and we settled on Turbocnc by DAK
Engineering .

This worked quite well, but we soon was very discourged by the amount of backlash and the limited
success at minimizing this problem. So the decision was made to spend $$$$ to upgrade to ball screws
for the X and Y axis. To do this, the existing "bearings" on the right hand end of the X axis and the one
for the Y axis were put on the lathe and bored out to accept 12 x 32 x 10mm angular contact bearings.
A new servo mount and bearing housing was made for the right hand end of the X axis and here a 12 x
32 x 10mm sealed ball bearing for the support at that end. For the Y axis servo, a mount was made to
attach to the bearing housing.

We also decided to "roll our own" pre-loaded ball nuts by making a socket for the lead nut which will
also hold wave washers for the pre-load and a nut to set the pre-load on the secondary nut that is
"pinned" to the socket by a 6-32 screw to prevent rotation. The ends of the ball screws were cut down
by means of converting my die grinder to a tool-post grinder as my Atlas is not rigid enough to cut
through the hard case of the screw. By grinding the screw, it was accurate and easy to do.