M109 wait for temp hung, >M81< does nothing

[mrbi11]

I cant always be there when a print finishes, and dont want to wear out my machine or waste power.

I put a wait for a lower temperature at my close of a print, followed by powering off the motors.
But powering off the motors might drop the heat on the part, so I want to make sure it has cooled off.

I tried:
M109 S50
M84
M81

But came back later to find it hovering at 55C out of 50C, with display showing the hot end still getting power.
At least half an hour. When temp dropped to 54C, heater came back on.
So it never "finishes".
Does M109 only work if you start colder than the set temp?

Pulled that out,
and
M84 works and then
M81 does nothing, contrary to doc, which says it powers off.

Also tried M85 S5 to set inactivity timer to turn off, which also does nothing.

Any information on these?

[geneb]

Don't manually power off the motors - this will happen automatically after the printer hasn't moved for a while.

The settings I give in the manual are fine.

If you were running the machine 24/7 for a VERY long time, you might wear it out. Maybe.

g.

[johnoly99]

Havn't wore out any of mine The prototype Rostock MAX prob. has over 1,000 hrs on it, still prints! just looks like sin

That's weird, i always have an M84 in my code?

[mrbi11]

I was actually more concerned that M109 command hung,
as it is needed to make sure hot tip is up to temp.

Was it a fluke?
a bug related to low target temp of 50C?
A bug related to target being a lower temp, as in less than 230C?

ANNND my title is WRONG. (Be kind to your elders, its amazing i have a good grasp of my name. probably.)

It is the M81 that appears to do nothing.
Nothing visible happens with power off command.

[geneb]

If by "power off", you mean "turn off the power to the whole printer", then you're right. It doesn't do anything. That's what that funny little toggle switch is all about.

g.

[Lochemage]

If you've done your own PID calibration at a higher temp like 220-240... the problem is your are trying to set the temp too low, the PID settings at that low of a temp tell the machine to put in maximum voltage to the heater, which makes it to overshoot too much causing it to fail at maintaining such a low temp.

Like geneb says, motors should turn off after it has been inactive for a while. There is a firmware setting (also EEPROM: I think it is 'Stop stepper after inactivity') which lets you define how long it will wait before turning off. Set this to something long enough that by the time it turns off, your nozzle should be cool enough.

Also, I've never had a stepper motor go out on me. I've been using my first printer for about 2-3 years now and it is almost running non-stop all day and night. Unless you are worried about your power bill or something, I doubt there should be much concern even if the stepper motors never turn off.