Hi,
is there a way not to turn off the stepper motors after a homing or framing?
As soon as I touch the laser head with my hand, I can simply shift it. I would prefer that it remains “fixed” and that the positioning is exclusively done via Lightburn. Only after a finished job i want the motors to turn off.
I googled a lot and i think i found a solution, but i want you to check it, so that I don’t break anything.
Overwrite $1=255 (don´t turn off motors) with LaserGRBL?
$1=255 Yes, this keeps power on the steppers indefinitely. However, you risk overheating them. Curious, why would you want to grab the laser at all after you power up? Everyone recommends you don’t because known location will be lost…
M18 I think this applies to select controllers only, like the Marlin. It does basically the same thing as the $1 command. In other words, don’t try using both.
Unless the controller and/or stepper motor driver in Your X-Y bed is designed to have a “lock feature”, keeping the full power on the windings can lead to all kinds of unwanted side-effects.
There’s all sort of reasons why one would want to “lock” a stepper motor, and it is one of the features that make stepper motors very versatile, but I for one can’t think of a reason why that would be in any way useful in a stationary X-Y (-Z) bed.
With micro-stepping being as common as it is, steppers can and will lose position every time you stop powering them - stepper drivers don’t generally remember which microstep they were on when unpowered.
There are plenty of users who run their lasers for hours at a time, during which the motors are fully engaged and don’t overheat, so no, you really don’t run the risk of overheating the motors unless the laser is very poorly designed from the start.
Or the stepper driver had its twiddlepot cranked up to set the current at a dangerous chattering whine:
If the motor current is correctly set, then the motor will not overheat
If the motor overheats, the current is set too high
More commonly, CO₂ lasers with stepper driver bricks have a DIP switch setting to reduce the idle current to (typically) half the normal value, specifically to reduce heat while locking the motor position.
I won’t ignore You, I still do agree that the possibility of overheating the stepper motors is there.
That said, I do agree with Oz as well, but only if the driver and/or the stepper motors can handle that.
Most likely most will, but I for one wouldn’t automatically make that assumption given the wide variety of more or less budget oriented -not to mention homebrewn- machines out there.
Granted, my opinions may be a bit biased once again, back in the day when I started to play with stepper motors and drivers they were a bit more expensive (lat least for someone with limited funds) than they are today, and it was a common practise to avoid ruining 'em with all means possible.
That line of thinking has stuck, even though most things nowadays cost a fraction of the price they went for in late 80’s or 90’s.
I sometimes lock mine if I need to get in the enclosure to adjust the workpiece and/or fixturing without moving the head. For example, send the laser to corner “A”, lock down that corner fixture, send laser to corner “B”, lock down “b” fixture, move laser back to “A” for confirm, etc. With the laser directly over the workpiece and close to fixturing the risk of bumping it is considerable.
Depending on bed and workpiece size, I could also see this being useful while removing completed work and setting a new (sequential) workpiece.
Typically my “square” fixture is locked down and I move the laser well out of the normal working area while loading/unloading, so I don’t risk bumping, but there have been times a stepper lock has been useful. Normally I leave it set to 100ms or so, tho.
the risk of bumping is high, Now that I know what can go wrong, I will either lock the steppers or re-Home the machine before hitting Run, which I tend to do a lot anyhow.
thank you, just tried it out and works perfectly. My steppers are not warming up when “holding” - they keep cool. Thats what i was looking for, thank you.
I won’t ignore You, I still do agree that the possibility of overheating the stepper motors is there.