Page 216 - CNC Robotics

Chapter 9 / Motor and Lead Screw Installation

• Connectors for limit switches

• Connectors for the interface board

The use of limit switches is optional for this machine, but you can
choose to insta ll them as I did. W ithout limi t switches installed, the
machine has no way of identifyi ng the boundaries of the usable
area of the table. If your machine isn 't told to stop, it will continue
to travel past the boundaries of the usable area. It won't kno w that
it has stopped moving but the motors w ill be trying to turn the
acme screw and losing steps w ith every try. Th is will th row your
positionin g way off. The machine w ill not be able to go back to the
home position you have established. Of course, leavin g the bound-
aries should only occur if the th ing you want to make is wider or
longer than your machine can handle. You will be able to do this.
See if your project is outside the limits of your table after your file
has been imported into KCam. KCam w ill plot the file over the
dimensions you have input pertaining to the size of the X- , y-, and
z- axes. As an accuracy precaution, limit switches are beneficia l.
Also KCam 4. 1 wil l not let the mac hin e manuall y home the axis if
limit switches are not present. I located the li mit switches used on
this machine at a surp lus store. They aren't really microswitches
li ke the kind used in plotters. I think they came out of wash ing
machines or dryers; The first clue was the name Speed Queen on
the side of the switch (see Figures 9.27 and 9.28).

Figure 9.27
Side one of limit switch.

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