How to Save Large Print from Air-printing

For FDM 3D printer users, seeing a complete printed model would be the happiest thing for his or her day. However, things somethings don’t go well as we hoped and an air-printing would be the most frustrating one of all the issues. In this article, I will provide an effective solution to this issue.

What is Air-printing

Air-printing is a term used in 3D printing communities. It refers to the phenomenon that the nozzle is printing material in the air without any support and model underneath. Air-printing happens for two reasons. One is overhanging print, which is set by the user on poppers, like the bridge printing. The other one is a serious printing issue: the material somehow stops coming out from the nozzle while all other parts are working well. As a result, the printer keeps running without out-coming material until the print complete or the poor user notices the problem.

Issues Analysis

Air-printing is an obvious but despairing issue. Here are some reasons that may cause it.

  • Run out of material (this usually happens to printers without a filament runout detector).
  • Nozzle jam ( main reason, many factors).
  • Material break ( material breaks in between the runout detector and extruder).

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Solutions

When we face an air-printing issue during printing and look at our failed models, many users may just give up and start a new print job. It’s fine for small projects within a couple of hours, but not ok for large projects, which usually take many days to finish.

Solution A

Take out the unfinished part, measure its height and start a new slicing from where the model has stopped. In the end, we glue two parts together.

Solution B

Edit the Gcode file, remove certain data that has been read by the printer and continue the Gcode from where we want it to start.

Solution B Steps

I will use my model and experience as an example to demonstrate how the plan works. The steps are the same and universal even if everyone prints different models. The only thing is that you need to make sure your print is worth doing this modification.

Precondition

  1. The unfinished model must stay where it should be on the hotbed.
  2. The printer did not turn off since the print start. ( this is just to make sure the printer keeps all the data )
  3. you need to have some basic coding skills.
  4. Paitence and confidence.

Step 1 Prepare

  1. Stop the print ( If it’s still printing) and record the Z value.
  2. Manually move Z from the control panel down to the height where the model stoped ( Z140.3 for my print).
  3. slowly move the XY axis by hands and check the distance between the nozzle and model. ( similar to bed levelling) 0.2-0.3mm is a safe value.

4. Take out the SD card and insert it into a PC and find the Gcode of the failed print. Make a copy of it, in case you mess up codes inside the file.

5. Open the Gcode file with Notepad++ (or similar tools that can edit the file) because we need a function like [begin/end select].

Do not panic. Coding is definitly hard, but what we do is relatively simple.

Step 2 Edit G-code

The sections we need to edit/delete is very clear, so please follow the steps carefully and do not change anything else in the file.

  1. Change the heading—–Insert X Y after G28 to let the printer auto home only on X and Y (NOT Z).

2. Find the codes that have been printed (Start Point and End Point)

  • Start Point. The start point is very easy to find. It’s just before G92. We want to delete data from here since the printer already did all these things.
  • End Point. Finding the endpoint could be the most difficult part. But it is logical. Use the [find] function to find the certain Z height we want the printer to continue from. Although I searched for Z140.7, it’s this Z value is for retraction. the real Z value is below: G1 F300 Z140.27, it’s close to my measured goal, which is Z140.3. So, my endpoint will be before the code line G1 F300 Z140.27.

3. Delet selected data

Two changes in total: Add “X Y” after G28 and delete printed data.

After editing, save the file and run a simulation in a slicer. The simulation in Cura is what I expacted.

Step 3 Continue to Print

Now the Gcode is good to run. But we have to check our printer’s conditions and find out what caused this issue. Maintains and part replacement would be necessary to prevent the issue from happing again.

After all the checking and fixing, it’s time to countitue the print.

Two more days to finish this print. I can relax now even if the issue occurs again. Because I know how to deal with it.

Conclusion

As I use 3D printers more often, I face more issues and difficulties. But I believe any problem has a solution.

Air-printing, for example, could be the most frustrating issue we have faced. But with proper methods, we can make it up and save the models and time.

I hope this article could help you in some way.

If you have any questions or suggestions, feel free to leave comments here.

Update

This method will not work on CR6 SE and Max. These printers will force to auto-home all the axis when we start a print no matter how we mod the code lines!


4 thoughts on “Save Large Print from Airprinting”

  1. So I turned my printer off while the extruder was at {X96.028 Y49.268 Z127.32}, and when I turn my printer on it thinks its at {X0 Y0 Z0}, so when I go to print the G code it goes to Z254.64 instead of resuming on {X96.028 Y49.268 Z127.32} any advice? is it possible to move the GCODE in Cura so its flat on the bed and not floating in the air in the Preview?

  2. Thanks! So I got my GCODE’s preview to look proper in Cura but when I loaded the GCODE on my Ender Pro 3, it was being weird. Do I need to Auto home, or should I keep the extruder in the same spot it was in from when the print ended?

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