toolchangers

Smoke wrote:

>The electronics required for tool changes (or moving/rotating parts)
>does not require the use of any CNC components. It does require a
>signal to get the system started tho'. For a home shop or hobby
>environment, this signal could be provided by a manual pushbutton
>operated during a pause in the G-code. After tool changes are done,
>simply hit the "go" (or "continue") button for the CNC unit.

Yes.
I'll go one further and say it doesn't even NEED electricity.
Pneumatic 'logic' will work well. One advantage to air power is that
the compressibility of air means mechanical limits can be set and
adjusted as needed during development. It's also clean and powerful,
and you're probably gonna need it for the tool lock mechanism anyway!
(assumes std. 'taper' style toolholders)

As to that 'start-toolchange' button. Since you prob'ly don't want to
stand there to do tool changes... Most of the low-end S/W support M
code activated I/O (CncPRO, MaxNC, AhHa!,Flashcut, etc. Using
pneumatics, this would activate a solenoid-operated valve. OOPS!
there's electricity :-)

Otherwise you can program the tool path to include a move such that
the machine table or head 'presses the switch' FOR YOU! There are
other situations where this "trick" (pretty well known commercially)
can be used. Just think of the machine parts as 'fingers'
that "could" press/actuate a switch located in an appropriate place.
To index a rotary table to the next position, for example.

Hope this helps.

Ballendo