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Neon Forests
- Jan 1, 1970
- 0
Neon Forests said:
john jardine said:An interesting read!.
The Roland should respond to something like "VS 1,1" added to the top of a
HPGL print file, (ie Velocity select #1, for pen #1). Is this not an
option?.
Neon Forests said:Thanks for reading.
It does respond to VS commands as low as 2 and that definitely helps in
slowing it down, but it's not quite slow enough.
I have to do multipasses on some materials to cut them.
Also I'm pushing the limits on the whole current vs torque issue.
As I slow down it down, it has a bit of a problem with torque or
overlapped stepper motor pulses (I haven't investigated yet) and so has
repeatability issues.
But I'm just a hobbyist here and it's a good start.
I may end up ditching the motors and electronics and starting off with
something better, but it was more along the whole "can it be done?"
thing than trying to end up with a piece of reliable production
machinery.
Kevin
john jardine said:Looks suspiciously like the stepper driver motors are being powered down
(too early) to a 'holding torque only' condition about 1/2ms after an X or Y
step pulse has ended (IC134).
A thought only, but maybe linking out R147 and R160 could keep motor power
applied all the time, thus can deal with the slower step rates at full
torque.
Personally, I'd be inclined to drive the motors directly from 2 external
stepper drives fed directly from that printer port. You could then set the
motor current at will. Seems lots of CNC progs available that will translate
HPGL (or G code) to printer steps under your direct control.
Or even, do the translate prog yourself with aBreshenam line and (maybe)
circle draw routine. Most CAD progs out there just seem to generate 'move
to' and 'line to' commands and ignore 99% of the available HPGL or G code
possibilities.
Having said that, I haven't a clue about Macs! and these things simply may
not be possible
[...]Keep in mind that the Rolands have steppers with around 38 ohms on
their coils.
One of the stock motors in the engraver is about 3 ohms per coil.
A huge load.
So I'd probably be apt to replace the motors or add a driver stage and
treat the old drivers as pre-drivers, but the whole PWM/chopper thing
is the first to get looked at.
You might have something there, though I think they're getting morejohn jardine said:[...][...]Keep in mind that the Rolands have steppers with around 38 ohms on
their coils.
One of the stock motors in the engraver is about 3 ohms per coil.
A huge load.
So I'd probably be apt to replace the motors or add a driver stage and
treat the old drivers as pre-drivers, but the whole PWM/chopper thing
is the first to get looked at.
Maybe it is the other way round, in that the Roland chopper is fixing the
current at say a constant 200ma feeding it's design 38ohms load, hence a
motor power of 1.5W but that same 200ma with a Chinese 3ohms only gives
120mW motor power!. The PSU voltage should have virtually no effect.
Anyway, I hope one day to have my own death ray.
Best of luck with the project (and please do a video of it cutting or
marking some plastic .