EMC Conversion
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This page is a
quick look at an EMC conversion done on an aging (1980) Mazak V5 with a Fanuc
7M (unsupported) control. The V5 is a 3 axis VMC with 30-inch travel in X, 15
inches in Y and 8 inches in Z (spindle) plus 24 inches of movement for the Z
head. The spindle is 5 Hp with a high/low gear-shift. Installation basically
requires a twelve-foot cube which allows for movement of the table and head
plus access to various parts of the machine. Weight is 9200 lbs. The machine
was not very expensive as purchased. Getting it loaded, moving it from
Albuquerque, NM to central Washington State, and unloaded at my shop about
tripled the price. |
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There are certain advantages to
buy a used CNC rather than converting a manual machine to CNC. They include
limit switches and home switches plus servo amps well matched to the servo
motors and the rest of the mechanics of the machine. In addition, the machine
probably has some kind of tool changer. |
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view of the Servo Dynamic's amps |
In the final analysis I removed
the servo amps which were phase controlled SCR's fed by 90 V three phase and
substituted Servo Dynamics 1525BR amps powered by the 90 V three phase and a
three phase bridge plus a 35000 mF capacitor. So far I've been unable to
demonstrate starving of the power supply even with rapids on all three axes
simultaneously. The controller is a STG I board using 'newstgmod.o' as a
driver. Spindle control is still manual but that will change soon. I used a
breakout board from Northwestern University (link on the Servo to Go site). |
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The motion sensing on the
original was syncro's off the servo motor shaft with a 1:3 gear drive. For
the X and Y axes I put 2500 ppr Koyo encoders on the end of the ball screws
(direct drive). The Z axis got a modular encoder (DRC) directly on the shaft
of the servo motor. All the encoders are differential and operated in 4X
quadrature. The machine has a 24-place tool
changer implemented with hydraulics. I removed the original TI plc and have
not replaced it with anything yet. A cursory look at tool changing indicates
that a minimum implementation will require about 20 inputs and 12 outputs. To
implement all the functionality of the original plc will require close to 100
I/O. At this time I'm doing manual
tool change that gives me about a minute chip to chip instead of the 5-7 secs
under plc control. Nevertheless, it does allow me to get something done |
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View from the house in
mid-April –this is probably as green as itıs going to get. ! |
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