I have compiled a way to manually change filaments during the middle of a printing layer.

NOT changing filaments at the beginning of a new layer! You can change it anywhere during the nozzle's G-Code path.

This can be used for adding additional support material, different filament types, anything where you need to swap a roll of filament. It will work anywhere along the G-Code laying path.

I will try to replicate the steps as detailed as possible as I have yet to see a guide on this.

DISCLAIMER:

Modify G-Code at your own risk. You will need to be present to manually conduct the filament change. You'll need an SD Card and SD Card Reader. I have tested this on the Bambu A1 using Bambu Studio. Your experience may vary. As long as your printer accepts G-Code it should still work.

NEEDED SETTINGS:

(If you are not wanting to change colors mid print - skip this step)

• You will want to Enable a Prime Tower. This is a small area where the nozzle will deposit filament PRIOR to returning to the actual print. It's like a skirt just bigger. You don't need a big one. The default one is dumb huge.
• I set my Prime Tower to: (8mm Width) & (25mm³ Volume)
• I disabled brim for the Prime Tower.

REASON WE NEED A PRIME TOWER:

• Normally, the extruder will conduct a full filament purge when swapping filaments. Then it will return to the print to continue its slave work. Without an AMS the printer will still conduct this cycle of purging, even if it's pulling from the same filament.
• With the Prime Tower enabled. The Head will conduct a filament purge, THEN go to the Prime Tower to conduct some extrusion PRIOR to returning to the print. It's like a skirt...it helps get the flow going.
• OUR GOAL will be telling the head to PAUSE at the Prime Tower. Allowing us the opportunity to conduct a manual filament change. During that Pause, some filament may leak out of the nozzle. We want that leaking to happen at the prime tower, not on the print.

I'm going to give my PoV from Bambu Studio.

Here we go!

1. Finalize your filament color settings and slice your print. Add all the colors you want! (at your own peril)
2. Go to the top left hamburger (dropdown menu) > Export > Export G-Code.
3. Save the G-Code file. I put mine in the same folder as the original 3mf. file.
4. Open the G-Code file using your notepad reader or a similar app.
5. Keep the G-Code window minimized for now. Go back to Bambu Studio.
6. Go to the Preview Tab of your sliced print.
7. Find the very first layer you need to change filaments on. Use the vertical slider with the plus symbol to do this. Use arrow keys for more accurate layer viewing. Start looking at the very first bottom layer and go up.
   1. Pause once you find the layer when the prime tower begins being printed. (Or the layer you need to swap filament types on)
8. Using the Bottom Horizontal Slider, visually follow the nozzle to where you intend to switch filaments...NOTE:
   1. If you added two or more colors previously in the settings, the nozzle WILL purge itself and go to the prime tower. The Prime Tower will likely be where you change your filament.
   2. If color was not your intention, such as adding a different filament type, you may not be able to use a prime tower. For this case, you'll need to be extra quick when we pause the head to ensure minimal issues occur. Your experience may vary a bit from here.
9. When you started sliding the bottom horizontal slider, lines of code should have appeared. These are coordinates and commands (G-Code).
10. When the nozzle begins printing the first Prime Tower Layer, you'll see something like:

​

1634 G4 S0

1635 G1 X... Y...

1636 G1 X... Y...

1637 G1 X... Y...

1638 G1 X... Y...

​

MEANING:

​

1634 = The Line Number, it tells us WHEN this command appears in the G-Code.

G4 = "Dwell" (Pauses the command queue and waits X time)

S0 = "Seconds" (Set to Zero Seconds) (S60 would be 60 Seconds)

​

1. Open up the G-Code window from earlier. Have the G-Code window on half your screen and Bambu Studio on the other half.

2. In the slicer, take note (I used a pen & paper) of the Line Number of when the Prime Tower begins to be printed.

3. Find that same line number in the G-Code File. When you click anywhere in the G-Code, it may appear at the bottom left corner or elsewhere. Mine Was in the bottom corner and said "Line XXXX, Column XXX"

4. Take this:

​

M400 S300 ; (pause for 5 minutes)

​

1. Copy and Paste "M400 S300 ; (pause for 5 minutes)" right after the G4 command.

(M400 = the G-Code command for PAUSE.)

(S300 = 300 Seconds or 5 minutes)

Example:

​

G4 S0

M400 S300 ; (pause for 5 minutes)

G1 X15.000 Y221.500

G1 Y221.000

G1 X... Y...

​

1. This will pause the head above the Prime Tower PRIOR to it laying the first line.

2. Repeat this on all the layers where a Prime Tower layer is extruded.

3. Once finished, save the G-Code file. Plug in the SD Card to your computer. Copy and Paste the G-Code file to the SD Card. Plug the SD card into the printer. Use the LCD screen to Print the G-Code file from the SD card.

NOTE:

You cannot simply upload and print the G-Code file from Bambu Slicer. If you have a WLAN connection, I heard there was a way to directly feed the file to the SD Card inside the printer through the WLAN open port...P1S & P1P people.

1. Watch the printer print. Once it starts printing the Prime Tower, it should pause. When it does, hit the manual pause button on the LCD Screen.

2. The head will return to the pooper. Conduct a manual filament change as normal. Once done, hit the green resume arrow.

3. After one final purge, the nozzle should return to The Prime Tower and continue depositing the NEW color. It will then return to the print area and print the next color section of your print.

NOTE:

I used some tweezers to grab any loose filament that may have wiggled out of the nozzle during the pauses. I only did this while the head was sitting in its pooper prior to conducting a filament change.

MORE G-CODE:

If you want to read more about G-Code lines or lookup specific ones:

https://marlinfw.org/docs/gcode/G004.html

IMPROVE THE CODE:

If your printer has a noise maker, you could add that line of code into the file. Thus your printer makes a noise beeper when it's ready to be manually swapped out. Just an idea I had. Did not invest in testing it.

REFERENCE:

Much of the info here was derived from this post:

Bambu Lab X1 Specific G-Code - Community Wiki Guides - Bambu Lab Community Forum

Please share to anyone wanting a simple method for changing colors or filaments mid print. Call me out on any corrections that need to be made and I'll edit the post with correct info.

Thank you for reading my midnight post. <3