lcdpublishing wrote:
>While similar methods have been used on drilling machines WAY BACK
>in time, they too suffered from the lack of control. You would not
>have any way of knowing if it's too fast till you break the tools.
>With a controlled axis, you simply tell it how fast to feed in
>inches per minute. For small drills, the difference between 1 IPM
>
>
Spring/solenoid can actually work quite well, PWM the solenoid against
the spring and you have control, some things are done this way. But
it's more work to reengineer this new system than to just copy the
stepper system from the other axes.
If room isn't an issue, there is also a very simple way for stepper
control for a drill..
H H
D SM
Looking down, H and H are two hinges on a triangular piece of wood.
Come out about a foot, and D is the drill with SM being the motor. At a
foot out, the arc of the circle is very close to a line. Get the bit
aligned so it's tangent where it's drilling, and the error is probably
less than a couple percent for .2" of drilling through a board. Use two
standard $1 door hinges, mount half to the bottom and slightly cock the
other half against it when attaching the triangle and you will have near
zero play. If you come out 3 or 4 feet, this is almost exactly linear
for short depths while being very easy to construct, I've used it for
simple manual guidance on several occasions. Since it's so simple, I've
also looked at ways to correct it to truly linear, but haven't found one
yet that was viable over a rail system. Stepper mounted to either base
or triangle screwing through a nut on the other side gives it easy control.
Arc of the bit tip can easily be corrected for with the other axis to
make it fully linear in X, Y, and Z too. Tip would be precisely
located, the tool would just have a small change in angle to the work
surface at different depths. Not really needed for just drilling of course.
This is the minimum system I would use, not really any harder to make
than a spring/servo, 95% or more of the correctness of a full axis for a
short depth, yet easier to make and align than a full railed axis.
Alan