Stop and continue 3D printing

Question

How to successfully pause 3D printing and turn off the printer and the next day, continue to print the model?

Answer 1

I recommend that you don't turn off the printer and resume the next day. If the heat bed cools down the part could become unstuck. The printer must be kept hot for the entire time that you need to print; unless it's PLA which tends to be more forgiving. Also Turning off the printer and turning it back on will cause it to loose it's position. Each time you home the axis of the printer it could home in a slightly different location. If you resumed the print under those conditions it would leave a clear line on the outer walls that is indicative of the layers not lining up properly. Lastly, if you let the nozzle ooze for period of time, you will have to purge the nozzle before you could print again. In this regard be prepared for some air printing for the first few movements. Depending on what you are printing, this could result in a build failure.

Needless to say, people have been able to recover a print under power off/failure conditions, but that's not a strategy to 3d printing. Those were mitigation efforts to exception cases.

Answer 2

If you enable M413 in Marlin firmware, the printer will write a resume printing file to SD card e.g. every layer.

From M413 - Power-loss Recovery documentation I quote:

Enable or disable the Power-loss Recovery feature. When this feature is enabled, the state of the current print job (SD card only) will be saved to a file on the SD card. If the machine crashes or a power outage occurs, the firmware will present an option to Resume the interrupted print job. In Marlin 2.0 the POWER_LOSS_RECOVERY option must be enabled.

This feature operates without a power-loss detection circuit by writing to the recovery file periodically (e.g., once per layer), or if a POWER_LOSS_PIN is configured then it will write the recovery info only when a power-loss is detected. The latter option is preferred, since constant writing to the SD card can shorten its life, and the print will be resumed where it was interrupted rather than repeating the last layer. (Future implementations may allow use of the EEPROM or the on-board SD card.)

This means if you cut the power you can resume the print layer, the only problem is that the part must remain attached to the plate, if it comes loose it is hard to resume printing. This feature is now commonly found on printers these days.

The regular pause and resume functionality of the printer will not work when the power is cut over night, i.e. no recovery file is written in such a case.

Answer 3

Set up your printer to be controlled by an outside source via USB or other protocol. Now set up a PC / a Pi / a Beaglebone / an Arduino / etc ... to feed GCode to your printer from MicroSD. I personally like the "an Arduino" option here because it's super-low-power and gives you tons of control over what you're doing... so I'll continue along the Arduino vein here.

Power your Arduino from a battery-backed wallwart. That'll give it plenty of guts to hurriedly write a record to a special file on MicroSD maintained for that express purpose. Or heck, write that record to EEPROM, which should be good for a hundred thousand power outages.

Next, rig up something that permits your Arduino to sense a complete power failure at the wall. You'll want a current transformer, perhaps, and little to no filtering so you get notified within 1/50 or 1/60 of a second when you detect a missing power excursion. Your Arduino should stop sending and record that record when it detects a power drop.

At power-up, your Arduino should detect that it wrote a power-off record and offer to resume pumping GCode to your printer after it sends the appropriate warm-up sequence to the printer. It should offer you the option of bagging the print or trying a resume. If you try the resume, it should seek() to the file position corresponding to the first GCode command after the last Z increment that was not a "Z hop". It should then step through all the G1 commands since that position, but traverse only, do not extrude, until it reaches the last command it had sent. It cannot know where along that G1 the printer paused, so it should repeat that one G1 line with extrusion active. You should get exactly one partially extra-fat line of filament at that one point in your print, but otherwise the stitching should be very good.

Provided, of course, that you've been ensuring exceptional print adhesion. The whole nine. Don't risk poor adhesion with a stunt like this, give yourself good adhesion. Really, your print should not pop off the build surface upon cooling. If it does, then you aren't doing enough to keep it there.

Answer 4

1) Cut the model up in several parts and print one each day. Remove each part every day and in the end, glue them all together.

2) Cut the model up in several parts and each day, add a G-code to the file to be printed so it lowers the heat-bed and thus starts to print on top of yesterdays print. This cannot be used when the printer is auto-calibrating as the printer-head would crash into the already printed part. It would probably be tricky.

3) Pause the printer in the evening, then resume next day (don't forget to lower temperatures and rise them again tomorrow).

Answer 5

Some printers have built-in functionality for resume after power-loss. I believe this is a standard part of the Marlin firmware now; I know the Creality Ender 3 has it and I don't believe it was a nonstandard addition (and if it was, their source was released in accordance with the GPL anyway, so it could be merged). So if you printer doesn't already have the functionality, but is amenable to a firmware upgrade/replacement to a version of Marlin that does, it should be possible to get it.

I have an Ender 3, but I haven't tried this feature so I can't speak to how well it actually works.

Answer 6

I already answered once more directly, but I think a better answer might be a frame challenge: design your model to avoid extremely long print times. Even if you didn't have all the problems of pausing and resuming to deal with, which include:

• warping and detachment from bed due to loss of bed heat
• possible motion of stepper motors while unpowered
• extrusion problems due to loss of material to oozing
• ...

you still have the fundamental risk that something goes wrong during the print, which increases significantly with the overall print duration.

There are lots of ways to design your model to be printed in multiple parts that don't amount to just "cut it at height intervals and glue the result". Glue isn't a terribly good solution, at least not by itself; it's hard to ensure perfect alignment, and creates points with different thermal and mechanical properties that are likely to break. Other options include:

• Snap fits, either reversible or permanent.
• Peg/hole press fit.
• Slide-in tension fit.
• Threaded interfaces. These can easily be directly between your parts if the parts are rotationally symmetric or orientation doesn't matter. If it does matter, you can design the threads to stop at the right point but it's more work.
• Threaded holes in one part, metal or 3D-printed bolts through the other to attach it.

In addition to letting you print the object in steps rather than all at once to reduce the chance/cost of failure, these techniques also allow you to print different parts of the object in different orientations, taking advantage of the orientation for ease of printing without supports, or for obtaining stength in the directions your object will be subjected to stresses in.

Most (really all) of the above can also be made permanent with glue, if you desire.