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  • 3DWatsch

How to make it

Updated: Oct 20, 2019

The filament buffer is one of the more complex things to make. Please read through the whole tutorial and take close attention to all the details. If you run into problems please contact me and I am happy to help:

Also if you find errors eg spelling errors it would be great if you let me know. English is not my first language (as you guessed already) so pleace be kind :)


printed parts:

1x buffer part 1 Buffer3_part1-buffer_part_1-17.stl 1x buffer part 2 Buffer3_part2-buffer_part_2-17.stl 1x silica gel box Silica_Gel_Box_with_mod.amf 1x check valve body Rueckschlag_Body2-check_valve_body-17.stl 5x pusher Schieber_gerade-pusher-17.stl 1x pusher lock Schieber_Verschluss-pusher_lock-17.stl 1x sealing Dichtung-sealing-17.stl 1x stand Stand2-stand-17.stl 1x ptfe tube clamping 1 Klemmung_1-ptfe_clamping_1_17.stl 1x ptfe tube clamping 2 Klemmung_2-ptfe_clamping_2_17.stl 2x clamp Verschluss-clamping-17.stl 2x t-nut T-Nut-t_nut-17.stl


Full set available here: full set of metal parts

4x screw M3x30mm DIN912 9x screw M3x10mm DIN912 2x screw M3x16mm DIN912 2x screw M4x16mm DIN912 2x screw M2x8mm DIN912 4x nut M3 DIN934 2x nut M4 DIN934

2x sheet metal comb Blech_Kamm_000001.pdf & Blech_Kamm-sheet_metal_comb.dxf metal comb 5x steel ball d=4mm


5x PTFE tubes PTFE_Tube_000002-17.pdf high quality ptfe tube

5x PTFE tubes 4x2.5mm 4x2.5mm high quality ptfe tube 1x Hygrometer hygrometer

The parts in detail

buffer part 1

For easy filament loading print with 0.1mm layer hights between 4.4mm and 16mm hight. Of course you can print the rest with bigger layer hights.

(Eddiding layers using the table like in slic3r is currently not available in prusaslicer but will be relaised in version 2.1.x, see ).

After printing: 1-straighten about 150mm of filament. You can use the filament straightener 2-cut the filament with sharp edges (worst case) 3-push it through, mind the orientation usually it does not go through as it should but get caught at the exit. 4-use a 2 to 2.5mm drill to smoothen down the holes at the exit until the filament does not get caught any more

buffer part 2

There is a bigger overhang but nothing too critical.

logo mod

It is an optional stl to add some color to your print and label your buffer with "printer" and "spools" and arrows.

check valve body


Layer hight: 0.15mm

Perimeters: 3-4

Material: PLA recommended

HowTo slice and add the pause:

This part is next to buffer part 1 the most critical for the buffer to function. Please follow the instruction closely. I use PrusaSlicer 2.0.

  1. Set the Layer hight to 0.15mm.

  2. Slice it and find the layer where a bridge infill closes the opening where you have to put in the comb metal sheets later.

  3. Remember the exact layer hight (in the screenshot "Find layer hight" below it's 24.35 but this might be different for you)

  4. Go to printer settings and insert the following at "After layer change G-code" where 24.35 is the layer hight you found before: {if layer_z == 24.35}M600 Y200; Color change {endif} it must read as a whole: ;AFTER_LAYER_CHANGE ;[layer_z] {if layer_z == 24.35}M600 Y200; Color change {endif} This line will add M600 Y200 to your G-code. This pauses your printer before printing the layer at 24.35mm. It works whether you use MMU2 or not.

  5. Slice it and export or send it.

Tip: Save the printer setting with a new name e.g. Original Prusa i3 MK3 MMU2 with brake.

This way you can use it every time you need to insert something into your print by the same process a discribed.

Find layer hight

Setting hight for brake

Now you are ready to print.

The printer will pause and move the bed to the front when reaching the set layer hight (here: 24.35).

When the printer pauses, add the balls and the combs (see video):

  1. Add the balls. One ball in every channel. The balls are quite tiny. I found it to work best to put a magnet on a flat screw driver. So the ball sticks to the tip of the screw driver. Then strip of the ball over the dedicated channel. The balls have to be more or less free to move inside the channels. A small resistance (caused by e.g. stringing) is ok though.

  2. After adding all five balls add the combs with the comb shaped side ahead.

  3. Make sure the combs are all the way in. They must be flat in and must not stick out because otherwise your nozzle will hit them. If you have problems getting them in you can shake them slightly and apply a little force. If you cannot get them in at all I am afraid you have to reprint the part and apply xy compensation so the slots are a little bigger. This never happens to me using PLA so you should be good.

  4. Finish the print after you insert everything by pushing the button on your printer. Follow the instruction on the screen.

  5. Remove your piece of art :)

Post processing

We are not finished yet. You'll need a piece of PTFE tube (100mm or so) for the next step.

You want to make sure the balls are moving freely.

  1. Insert the PTFE tube all the way in. It is important it's all the way in

  2. Straighten the end 100mm of about halve a meter of filament

  3. Push it through the PTFE tube and the printed part. You might have to fiddle around a bit. It helps to turn the filament while inserting. This will be much better later.

  4. Use the filament to move the ball up and down the channel until it moves freely.

Now it's done.

[Add Videos]

ptfe clamping 1 and 2

Use like 4 or so perimeters and 100% infill. Depending on your ptfe tubes you might have to bore the holes slightly bigger if they do not go through.


It is an uncritical part but use 4 perimeters so it is long lasting


I use nylon for this parts but maybe works with other (semiflex?) materials too. Use 4-5 perimeters.


Use flex material for this.


It's uncritical

pusher lock

It's uncritical


After printing you need to sand the parts until they fit in the corresponding grooves of the check valve body. Depending on the material you use it might be necessary to add a XY-size compensation.

tube clip

It's optional and uncritical

silica gel box

It is optional. You can use the .amf file to have the necessary settings done.

ptfe tubes

Cut them to length and chamfer inside. I used a stanley knife and it works ok

sheet metal comb

If you do not have the tools to cut this you can find it here: comb


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