Page 12 - CNC Robotics

CNC Robotics

These motors were used in an IBM product-probably a pr inter.
They are unipolar, but if you run them as bipolar the y produce
more torque (see Figure 1.3).

1also discovered that these stepper motors work better if they are
given 12 volts instead of the 4.6-volt rating on the motor body. The
strength of a stepper motor is rated in ou nce inches of holding
torque. The step-syn information 1 found indicated tha t these
motors are an ywhere from 90 to 220 ounce inches. I so metimes
work backwards, and bu ying the motors first is certa inly just that !
Normally, you would calculate what strengt h of motor you nee d to
run the machine and then purchase a suitable motor. Here's how
to calculate the strength of motor you need to run this machine. If
you can't find any surplus motors, investigate a company called
Pacific Scientific-they ha ve a variety of stepper motors and also
make available software for download, which you can use to
determine the size of motor you need. Speaking with them , I was
impressed with how well I was treated, considering 1 would only
need three of their motors.
Remember that although brand new motors are expe ns ive, you
know the y will work and you can match the strength to the
machine. New motors could also speed up the mach ine consider-
abl y. When 1 say "speed up," it is important to note that I am
referring to travel speeds, not cutting speeds. Cutting speeds for
most materials will be slow with this style of machine, regardless
of which motor you choose; you can't run a route r thro ugh wood
at 200 inches per minute and expect the cut to look good. Cutting
speeds of 10 to 30 inch es per minu te define the range we can
expect from this machine with these motors. A faster machine can
be expected to travel quickly when not cutti ng and slow down
when cutting through material.

Lineal Motion

There are a variety of off-the-shelf lineal motion products , but
most of the systems were too expensive for this proj ect. Thinking
that it would be useful some day. 1acq uired a NuArc copy camera
a few years ago (see Figure 1.4 ), so 1 took it apart and found it

4

,- - - - - - - - - - - - - - - - - - - - - - - - - - -