Cancelling prints while heating



  • So I'm a bit absent-minded sometimes, and so it happens reasonably often that I start a print and then remember something I forgot. So I want to abort the print right away. Right now my options are not very satisfactory:

    • I hit "pause". It waits for the heating to finish (a few minutes), then tries to raise the nozzle (it's already homed to the top) then move it to near the Z tower (which results in grinding because deltas can't move horizontally from home). Then once it's got there, I hit "cancel", and am ready to print again. Or,
    • I hit "emergency stop" and everything shuts down immediately, including the hot end fan. I then have to type in the un-stop G-code (M999) before the machine will do anything.

    Any suggestions for better approaches? It'd be nice to have a G-code that cleared the buffer of pending moves (e.g. the whole rest of the print) but continued execution from wherever the command came from. Macros could then specify that they should interrupt whatever's happening. Even just supporting M108 Cancel Heating would simplify the process.

    More generally, cancelling a print that has gone bad is a little awkward: hit pause, wait for the pause to happen, hit cancel, switch tabs, hit home all so I can get at the mess on the bed. It would often be nice to have a "cancel" button directly available, though I agree that maybe it should take more deliberation to irrevocably end a potentially long print.



  • Edit pause.g to remove or change the line that sends the nozzle home.

    If you have a sys/cancel.g with a G28 in it, you won't have to do a manual home all after canceling the print.


  • administrators

    Pressing Emergency Stop should not turn off the hot end fan. Which fan output do you have it connected to? Also, the Emergency Stop button on the web interface sends the M999 command automatically.

    I already have it on the list to allow concurrent execution of compatible commands form different channels. When this is implemented, you won't have to wait for heating to complete before the print can be cancelled.



  • Emergency stop shuts off PS_ON (as it should), killing all the motors, all the heaters, and all the fans unless they run off 5V. My hot end fan is plugged into an always-on fan connector but I want it to shut off when the ATX power gets shut off since it's the loudest thing about the printer (except for the 80mm supplementary part cooling fan I'm trying out now), and I want to leave the MCU on all the time. I could hook the hot end fan up as a thermostatic fan, but this way I can hear when the ATX power is on - and since the steppers are continuously drawing power any time the ATX power is on, I want a reminder to shut it off (if the end-of-print code hasn't done it automatically).

    I don't suppose there's a nice way to gang two part cooling fans? So far my best option seems to be to actually wire them in parallel, which would require me to fool around with connectors and crimping tools. I can put both on separate PWM outputs, but slic3r only outputs control commands for FAN0.


  • administrators

    I forgot about PS_ON.

    The steppers don't necessarily take power whenever 12V or 24V power is on. By default they are turned off at power up, and when you execute M0. You can turn them off explicitly using M18. Also, when all motors have been inactive for the idle time (default is 30 seconds), the motor current is reduced to the idle current (default is 30% of the normal current). You can change these figures using M906.

    How about adding a 12V LED strip to remind you that the ATX PSU is on?

    You can get fan doubler cables on eBay.



  • Do you have a switch wired to your power supply? For me, I just cycle the power to get an instant print cancel, and still have the hotend fan running after (and cooling down without heat-soaking everything).



  • I approve of thermostatic fans, but I'm not sure how much they'd help me in particular. The ATX supply is turned on at the beginning of every print, and it's shut off at the successful completion of each print. The additional times it is on are when I'm tinkering with the machine, or when I cancel a job. The latter is useful because often I want to change some settings and resubmit, so keeping the hot end and heated bed warm is a good idea. In other words, the ATX supply is on more or less the same times a thermostatic fan would be on. It could happen that I leave it running, but these are more or less the same circumstances that I could leave the heaters running. So it helps to know no fan means no heaters or motors either. If I find a quiet enough hot end fan I might want an LED strip, though I sort of prefer sound as a reminder.

    Could I leave the ATX supply on all the time, as long as I turn off the motors, the heaters, and the fans? I could, and people without PS_ON configured do, but for fire safety reasons I feel happier when it's off. The chance that the 5V circuit will cause a fire is pretty remote, even with a relatively beefy 2.5A supply.


  • administrators

    I agree, you should turn the 12V power off when the printer is unattended. Preferably, turn the power off completely. Here http://forums.reprap.org/read.php?416,709591 is one way of implementing auto power off that doesn't require a 5V standby supply.



  • As I said before, I want a big red stop button!



  • It's not hard to rig one up to a spare endstop pin! The hardest part is getting a satisfyingly alarming-looking button. I've asked my father to dig through is collection of ancient war-surplus radio hardware for some cool-looking buttons.







  • Well you certainly couldn't miss it though LOL


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