On Monday 24 March 2014 10:38:50 Marius Liebenberg did opine:
I found a solution. If you just put a (-) in front of the Z figure it
travels the opposite way. You also have to swing the incremental counter
for the no of cuts to add in stead of subtract as well.
The way your OP was worded, I thought you were asking about reversing the
spindle, but IF the spindle has enough relays to achieve the reversal, then
its a matter of issuing an m5 to stop it, killing enough time for it to
stop, then issuing the m3 to start it in fwd. This can be done
considerably quicker if the spindle is variable speed and encoded for speed
control.
Alternatively, an AC induction motor can have a dynamic braking stop added
with a separate DC power supply, current limited to about the motors normal
draw, which is switched on by the backside contacts of the run/stop relay.
That might need 100 milliseconds of dead time by staging it with two relays
in order to allow the armature currents to decay else the power supply
might be taking some large voltage surges at the moment of stop contact.
I have equipt mine with dynamic braking to speed up the stopping, in 3
stages, and have some hal trickery synthesizing the stop and can now run
the g33.1 rigid threading cycle in a loop I wrote that pecks it about 1/2
turn per cycle so I have a chance to hit the tap with an air hose if
quick enough some cutting oil. You have to figure on the stop coast
distance in your depth estimates, which on mine are about 1.5 turns at 300
rpm. 2.5 maybe at 700 rpm.
The rotating mass in a 5 chuck, and a 3/1 geared down 1HP treadmill
spindle motor are quite a bit higher than the OEM 3 chuck and motor.
And yes, 80 watts worth of the shacks 8 ohm 20 watt audio dummy load r's do
get warmed right up. :)
For lack of a way to dynamically measure motor current, or lack of my
ability to find power transistors with enough SOA ratings to do it that way
(the ones I bought 5 of, in TO-247 packages, would have needed about 50 of
them before the estimated currents per transistor would have stayed inside
the SOA ratings), I am staging the braking resistors with a wcomp module
watching the encoder, driving 2 ice cube relays, with terminates in a dead
short on the motor by the time its down to about 125 rpm at the chuck.
When the chuck is within maybe 5 degrees of stopped, the new direction is
then clocked on out to the speed controls by hal gates and it accelerates
from essentially zero speed in the other direction.
Po' folks version of a reversible VFD. :) Works, but the hal file is a
nearly 300 line monster. :)
If anyone is interested, I can have that file available on my web page by
tomorrow afternoon, although it is in a state of flux with the lincurve
module ATM. Its temporarily by passed so once I get the mechanics all
covered up again, I can program out any remaining non-linearity's in the
requested vs actual speed. Today I have a lengthy honeydo graphics job.
On 2014-03-24 15:49, Marius Liebenberg wrote:
I tried that Andy but is does not work as expected. I will have to
write the routine to explicitly do that.
I was hoping to find a shortcut and not have to write it from scratch.
No problem I like learning new stuff. It's what drives me :)
On 2014-03-24 15:33, andy pugh wrote:
On 24 March 2014 13:23, Marius Liebenberg mar...@mastercut.co.za
wrote:
Is there a way to
switch between these two modes with Gcode?
I _think_ you can just use a negative diameter and it works.
Cheers, Gene
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