Here is our FAQ where you can read about causes and solutions to common problems. Some of the tips are for a specific printer, others are generally.

Bowden tube gets pushed out of the Pushfit-connector.

Our bowden couplings can withstand a force of 14 kg for the 4 mm Pushfit connector and 22 kg for the 6 mm Pushfit connector under ideal conditions. If your bowden tube keeps getting pushed out it is not a problem with the extruder, the root cause of the problem originates from another source. Below we have listed the most common probable causes. It can originate from one of them or be a combination of several problems.

Very IMPORTANT! If the bowden tubes have been pushed out, you will need to cut off approximately 10 mm in order for the steel teeth of the bowden coupler to bite into a fresh PTFE surface.
As the tube get damaged after repeated pushouts, failing to refresh the bite area will invariably result in more pushouts.

Damagaged PTFE tube

Bowden tube diameter

For our 1.75 mm extruders the PTFE tube must not be smaller than 4.0 mm, imperial size 5/32″ is 3.96 mm nominal so it is too small in order to have an optimal grip in the pushfit.

With our extruders for 2.85/3.0 mm filament we recommend to use our PTFE tube that is 6.4 mm outside diameter and 3.18 mm inside diameter (1/4″x1/8″), this will give maximum gripping force of the tube and as an added bonus it will also reduce the hysteresis effect during retractions that will make it possible to use shorter retractions distances.

Nozzle temperature

Different materials uses different temperature settings, lower extrusion temperature equals higher extrusion force and if the temperature is too low you risk pushing the bowden tube out of the coupling.

Extrusion rate set too high

The volumetric extrusion rate is a combination of layer height, extrusion width and speed. If this combination of values give too a high volume / second the hotend does not have the capacity to melt the filament at the needed rate, this means that the extruder tries to push semi-molten plastic out of the nozzle orifice and this will also lead to too high extrusion force.


It is essential that the thermistor has a good contact with the heating block of the hotend. If not it will not report the correct temperature. This in turn might cause an over temperature that leads to heat-creap (heat travels up to the cold section and makes the filament soft and this results in a clog of the nozzle that creates very high extrusion pressure.

thermistor Image from E3D

Nozzle clogged due to dirt particles

If dirt particles enters the hotend there is a risk of getting the nozzle clogged if the particle size is in the range of nozzle diameter, smaller nozzles equals higher risk since smaller particles will block the nozzle. A good solution for this is to use a filament filter (a small sponge that the filament goes through and that cleans the filament before the hotend. Here is a good design from CreativeTools.


Nozzle too close to build surface

If the nozzle is too close to the build surface the extrusion pressure also goes up creating high extrusion forces. Bondtech Extruders can supply about twice the extrusion force when compared to other extruders but at some point it will of course reach the maximum holding force of the bowden connector.


Bowden tube not fully inserted

If the bowden tube is not fully inserted into the housing it can move that can lead to that the bowden gets pushed out, make sure the PTFE is seated all the way into the housing. For our 1.75 mm QR the distance is 11.0 mm measured from the top of the extruder to the bottom of the PTFE tube as in the image below.

Bowden clip is not used

If the bowden clip is not used the bowden tube will move during retractions, this can give the bowden enough momentum to break out of the bowden connector. It is also bad for your retractions since a part of the retraction distance gets eaten up of the movment of the bowden tube. If you do not have any bowden clips you can download them from the links below.
Bowden clip for 4 mm Pushfit                 Bowden clip for 6 mm pushfit


Hotend cooling fan

If the cooling fan for the hotend is not cooling the cold section of the hotend correctly it will lead to heat creep, this will make the filament soft where it shall be hard and stiff and this will lead to problems with too high extrusion force. Make sure that there is nothing that is obstructing the flow of the fan, make also sure it is running at correct speed and also make sure it blows in the correct direction towards the heat sink, not from the heat sink

 E3D-hotend Image from E3D showing E3D-V6 hotend.

Extruder turning in the wrong direction

Depending on the orientation of your extruder and if you use the top or bottom port as the output port to your hotend you might need to change the rotation direction of the motor.
There is two ways of doing this, either by reversing two of the 4 cables to the stepper motor or by doing a change of direction in the firmware.
In order to reverse two cables you can use a sharp tool to lift the little plastic tab on the connector on the cable and gently pull the crimping contact out of the housing.
Remove two cables (for 1 of the coils of the stepper motor) and let them switch place with each other. Please take note of how the two coils are placed in the connector.
Coil 1 is A-C and Coil 2 is B-D, this is valid for our geared steppers, other stepper motors can have different positions and different connectors, please look at the datasheet for your motor.


You can also change the setting in the firmware, the below picture shows the file Configuration.h in the Marlin Firmware for Ultimaker, to change the rotation direction edit the appropriate line from TRUE to FALSE or the other way round.

The below picture shows the configuration file for Smoothieboard, change the direction by adding a ! after the 0.22 on the line highlighted below.


E-step value

As the slicer tells how much filament should be extruded for each move the controllerboard uses the e-step value to determine how many steps it needs to send to the motor in order to feed the correct lenght of filament. Since drive-gear diameter and gearing ratio affects the number of e-steps needed it must be adjusted in order to get the correct extrusion lenght.
The estep value for our extruder is
Bondtech QR 1.75 E-step: 476.5

Extruder E-step value E-step set G-code
Bondtech QR 1.75 476.5 Link
Bondtech QR 2.85/3.0 492.45 Link
Bondtech Mini 140 Link
Bondtech BMG 415 Link

In order to set the correct e-step value different methods are available.
1. Download the small code above for the correct extruder from the table above and save it to a sd-card, put the sd-card in your printer and select to print that program.

2. Connect to your printer and start Simplify3D or your favourite slicer, go into command mode and send M92 EXXX and press enter, then send M500 and press enter. This will set the e-step value and save the value to the controller. Replace XXX with the correct value for your extruder.

3. Insert M92 EXXX at the start of your g-code by editing the start-section in your slicer, replace XXX with the correct value for your extruder.

4. For Ultimaker use Tinkergnomes Firmware that let you set the E-step value from the LCD-menu of the printer.
Use the correct version of the Tinkergnome for your printer.

5. Compile your own firmware by editing the section for the E-step value that is found under Configuration.h



Cable connectors

Different controller board uses different connectors for the cables to the steppermotors. We currently have 3 different options of cables. Our standard is the PC2510 connector but we also supply cables with JST-XH4 and the Dupont connector. Outside dimensions of the connectors are presented below. Further options of different types of connectors are available as customized products, please contact us if you have a need for any special connector.

Current settings

The geared Nema17 motor we uses are rated for 1200 mA (1.2A), at this current the motor will reach about 50 degrees in continues printing, when using PLA that get soft at about this temperature we recommend to lower the current for the motor to keep it cooler. The following table shows the temperature of the motor in continuous mode at each current setting.
Current setting          Motor temperature
1200 mA                       50°C
1100 mA                         47°C
1000 mA                        45°C
900 mA                        39°C
800 mA                        37°C
700 mA                        34°C

As your slicing parameters, nozzle diameter, temperature and polymer type all affects your extrusion pressure you will need to use a setting that works best for you.
Also one option is to attach a heat sink to the back of the motor to increase the heat dissipation to lower the temperature.

Depending of your printer and your controller different methods are used to set the correct current.
Stepper drivers that have an adjustable potentiometer is adjusted measuring a Reference voltage that corresponds to the current used. Example video of procedure. Stepperdrivers that are using a digipot can adjust the value by sending a G-code. If your system uses a digipot you normally adjust the current for the motor sending M907 Exxxx where xxxx is the current in Milliamps. So to set the current to 1000 mA for the extrudermotor send M907 E1000
In Ultimaker you can adjust the current for the motor from the LCD-panel directly.
You can of course insert M907 Exxx to the start section of G-codes in your slicer program.

Filament grinding

If one section of the filament has a bigger diameter than the normal it can happen that the filament gets jammed in the filament path inside the extruder. Our extruder for 1.75 mm filament has a filament channel of Ø2.0 mm, the extruder for 2.85/3.0 mm filament have a filament channel of Ø3.5 mm, If the filament is bigger than this it will get jammed in the channel and the gears will grind the filament since the filament is wider than the channel. This problem was more common in the past but as filament produces have better tolerances and higher quality now it is not a very common problem.

Direct mount applications

When the QR extruder is used in a direct application (Hotend is placed into the extruder and the whole unit is placed on the printhead) it is important to use a piece of PTFE tube connecting the hotend with the extruder, if the PTFE is not used there is a free space in the extruder where the filament can buckle and create jams. The length of the 4/2 mm PTFE tube on the 1.75 mm QR shall be 31 mm and for the 2.85/3.0 mm QR a PTFE tube 6/4 mm with the length of 2.5 mm shall be used. The PTFE tube in below pictures are highlighted in blue color.

X-section of QR 1.75                                   X-section of QR 2.85/3.0

QR-1.75 Direct   QR-3.0 Direct

Bowden Adapters

Our bowden adapters will let you connect a bowden tube to the bottom of the extruder, this way you can use the bottom port as the output port. When using it as an output port it is important to make sure that the PTFE tube extends through the bowden adapter as it otherwise will be a free space where the filament can buckle and create jams. The PTFE tube in below pictures are highlighted in blue color.

X-section of QR 1.75                                          X-section of QR 2.85/3.0

QR-1.75 Bowden adapter  QR-3.0 Bowden adapter

Filament guide

When using the top port of the extruder as the output port a filament guide can be used to help guide the filament into the extruder during loading.
The filament guide in below pictures are highlighted in blue color.

X-section of QR 1.75                                          X-section of QR 2.85/3.0

QR Filamentguide 1.75     QR Filamentguide 3.0


Stepper motors – Supply voltage

Stepper motors are normally driven in a constant current mode by the stepper driver and since the torque a motor provides is proportional to the current all the way up to the motor’s cornering speed the supply voltage controls at what speed the cornering speed happens. With higher supply voltage the motor can be run at higher speeds than with a lower voltage; this is the reason for why we recommend to use a 24V PSU on your printer. Below image is from a very nice write-up by GeckoDrives as you can find here.