RE: [CAD_CAM_EDM_DRO] G-code interpreter/stepper controller

I would have the machine disable all drives, turn off all accessories
(spindle, etc.), and signal the condition (turn the light on, maybe a
beeper too). After that, allow the operator to do anything they want,
enable the drives, move (under program control) any axis away from the
crash direction, ignoring the limit switches until they close/open
again. E.g. the machine crashes moving -Z, stops and alerts, operator
enables drives and moves +Z. At this point the program begins checking
the Z limits again. The spindle, etc. remain off, of course, until the
operator turns them on.

You also might want to use a distinct key in your program to turn the
spindle on/off. For example, if you have a message box that says "Enable
drives? Y/N" and one that says "Turn spindle on? Y/N" the operator might
not be looking at the screen and press Y, thinking he can back the Z
off, but forgetting he already did, and turn the spindle on.

Regards,
JJ

Be Kind, Be Careful, Be Yourself

> -----Original Message-----
> From: bschwand [mailto:bschwand@...]
> Sent: Tuesday, November 05, 2002 2:30 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] G-code interpreter/stepper controller
>
>
> Hi everybody,
>
> I am in the finishing/debugging stages of a 3 axis stepper controller/
> G-Code interpreter.
>
> The missing part is how to handle endswitches.
>
> My assumption is that hitting an endswitch is a catastrophic failure,
> and it should never happen; therefore I was going to have the
> controller freeze all movements, signal the error (a big red LED) and
> let the operator shutdown the system, manually back off the tools,
> etc. and restart.
>
> I think that trying to have the tool be "smart" and back off the tool
> itself, etc. could possibly lead to damaging the machine and or part
> being machined.
>
> Does this make sense ? What is usually done, or expected in such a
> case ?
>
> Please let me know what you think is the best way to handle
> endswitches, and if you have experience with other systems or
> software, let me know how it is done.
>
> BTW, this system has the following features:
>
> - communicates with the host computer through a serial RS232 port
> (the host could be a palm pilot :-) ), use of hardware (RTS/CTS)
> flow control to ensure dataflow integrity.
> - embedded basic G-Code interpreter that supports linear and
> circular interpolation in all axis
> - extensible to up to 8 axis (through an extension board, to be
> designed)
> - automatically goes to low-current (holding) setting for a given axis
> if that axis has not been active for 100 milliseconds
> - active current control through integrated chipset, thus very little
> wasted power. Running and holding current are configurable through
> separate potentiometer, up to 3 amp per axis (although I have not
> tested this much power lacking the needed power supply...)
> - each axis can be configured as to what the positive or negative
> direction is (to accomodate for different machine configuration)
> - configurable "rapid transverse speed" (G00 code)
> - configuration settings are saved in permanent memory (eeprom) so
> they remain between shutdown/reset.
> - up to 10'000 steps per seconds (is this overkill ? my
> steppers stall
> after 900 steps/sec...)
>
> Currently supports unipolar steppers, in full-stepping mode. A bipolar
> stepper power board will come next.
>
> All feedback much appreciated, thank you.
>
> bruno
>
>
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