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For a general guide to configuring RepRapFirmware, see Configuring RepRapFirmware for a Cartesian printer. Only the differences for hangprinters are described here.

RepRapFirmware is configured at run-time by means of files in the /sys folder of the on-board SD card. This means that you must have an SD card in the on-board socket to use RepRapFirmware. You do not have to recompile RepRapFirmware to configure it, so if you wish to update the firmware on your Duet or other compatible electronics board, you can download a ready-built binary.

The easiest way to generate these files is using the RepRapFirmware configuration tool .

Hangprinters are supported in RepRapFirmware 1.20 beta 11 and later.

The Hangprinter architecture in its current form was designed by Torbjørn Ludvigsen, his github repository has a large amount of information and is a great please to start to understand the hangprinter in general. . In brief, a Hangprinter has four positioning motors (A, B, C and D) mounted either on a large effector or mounted at the anchor points. Each motor drives a spool which draws in or lets out 2 or 3 lines that pass through eyelets and then go to fixed anchor points. The D spool has 3 lines connected to anchor points in the ceiling. The A, B and C spools each have 2 lines connected to anchor points on the floor. The hangprinter is under very active development so this may not match the current state of the art.

Movement section of config.g file

Telling RepRapFirmware that your printer has Hangprinter geometry

To tell RepRapFirmware that your printer is a Hangprinter and to define its parameters, put command M669 K6 Axx:yy:zz B xx:yy:zz Cxx:yy:xx Dzz Prr in your sys/config.g file on the on-board SD card. The parameters are:

  • Knnn Geometry class, 6 = Hangprinter<br>
  • Axx:yy:zz X, Y and Z coordinates of the A anchor
  • Bxx:yy:zz X, Y and Z coordinates of the B anchor
  • Cxx:yy:zz X, Y and Z coordinates of the C anchor
  • Dzzz Z coordinate of the D anchor (the XY coordinates of the D anchor are 0,0)
  • Prr Printable radius from the origin
  • Snnn Segments per second when smooth XY motion is approximated by means of segmentation [TEMPORARY until segmentation-free kinematics is implemented]
  • Tnnn Minimum segment length (mm) when smooth XY motion is approximated by means of segmentation [TEMPORARY until segmentation-free kinematics is implemented]

You will need to create an invisible U axis to handle the D spool motor, like this:

  • M584 X0 Y1 Z2 E3 U4 P3

In this example, the ABCD spool motors are connected to the X Y Z and E1 motor connectors respectively, and the extruder motor is connected to the E0 motor connector. The P3 parameter restricts the number of visible axes to 3.

Changes to other commands

In the M92 command, the XYZU parameters are the steps per mm of line extension or retraction by the A, B, C and D spools.

The Z movement limits should be set in M208 commands as usual.


Here is an extract from a sample config.g file:

''' Axis and motor configuration'''
M569 P0 S1 ; drive 0 (X motor output aka A) goes forwards
M569 P1 S1 ; drive 1 (Y motor output aka B) goes forwards
M569 P2 S1 ; drive 2 (Z motor output aka C) goes forwards
M569 P3 S1 ; drive 3 (extruder) goes forwards
M569 P4 S1 ; drive 4 (E1 motor output aka U aka D) goes forwards
M584 X0 Y1 Z2 E3 U4 ; create U axis for the D motor, attached to the E1 motor connector
M669 K6 A0.0:-2163.0:-75.5 B-1841.0:741.0:-75.5 C1639.0:1404.0:-75.5 D3250.5 P1500 ; set Hangprinter kinematics parameters
M92 X101.86 Y101.86 Z101.85 U101.86 ; set steps/mm for each spool
M208 S0 Z1500 ; maximum height 1500mm
M208 S1 Z-5 ; minimum height -5mm
M203 X6000 Y6000 Z6000 E3600 ; maximum linear speeds mm/minute
M906 X1000 Y1000 Y1000 E1000 ; set motor currents (mA)


Hangprinters do not have homing switches. To home your Hangprinter, we suggest the following:

  • Use the M913 command to temporarily reduce the current to the ABC motors.
  • Send a G1 S2 movement command in the -U direction to energise the D motor and shorten the line to raise the effector off the floor, e.g. G1 S2 U-100 F1000.
  • Run the ABC motors to tighten the lines. You may wish to use stall detection to stop the motors when the lines are tight, see
  • Measure the approximate XYZ coordinates of the nozzle.
  • Send G92 Xxx Yyy Zzz to tell the firmware where the nozzle is, where xx, yy and zz are the coordinates of the nozzle.
  • If your Hangprinter has a Z probe and you have set up a suitable bed.g file, press the Auto Calibration button in the web interface or PanelDue to run an auto calibration sequence. 3-factor auto calibration is sufficient to adjust the spool motor positions. Note: the less accurately you entered the initial coordinates of the nozzle, the higher the dive height (H parameter in the M558 command) will need to be, and the more iterations of auto calibration you will need to perform.

You may wish to create a homeall.g file that does some of these steps.

Auto calibration

You can use the following types of auto calibration:

  • 3-factor: adjusts the spool zero positions. Useful as part of the homing sequence (see earlier).
  • 6-factor: as 3-factor and also adjusts the B anchor Y coordinate and the C anchor X and Y coordinates
  • 9-factor: as 3-factor and also adjusts the A, B and C anchor Z coordinates. [This may be too sensitive to line buildup to work well.]

You must use at least as many probe points as calibration factors you want to use. More probe points is better and will give you an indication of the height errors after calibration.

Auto calibration is performed by sending command G32 (which is the same command used to do auto bed compensation on a Cartesian printer). This command runs macro file sys/bed.g, so all the work is done there. Here is a sample bed.g file:

M561 ; clear any bed transform, otherwise homing may be at the wrong height
M401 ; deploy the Z probe
G30 P0 X0 Y0 Z-99999 ; dummy probe, needed only if your Z probe gives less accurate results the first time it is used after deployment

''' Probe the bed and do 6-factor auto calibration'''
G30 P0 X0 Y-1050 Z-99999 ; towards A anchor
G30 P1 X-460 Y-340 Z-99999 ; between A and B anchors
G30 P2 X-920 Y370 Z-99999 ; towards B anchor
G30 P3 X-50 Y535 Z-99999 ; between B and C anchors
G30 P4 X820 Y700 Z-99999 ; towards C anchor
G30 P5 X420 Y-175 Z-99999 ; between C and A anchors
G30 P6 X0 Y-525 Z-99999 ; halfway to A anchor
G30 P7 X-460 Y185 Z-99999 ; halfway to B anchor
G30 P8 X410 Y350 Z-99999 ; halfway to C anchor
G30 P9 X0 Y0 Z-99999 S6 ; centre, and auto-calibrate 6 factors

M402 ; retract the Z probe
G1 X0 Y0 Z150 F15000 ; get the head out of the way of the bed

The probing is commanded by the G30 commands. You can have up to 32 probe points, numbered P0 to P31. The probe positions and order are not critical, but you should cover at least the centre and the extremities of the bed, both next to towers and opposite the towers, and some points in between the centre and the periphery. The XY coordinates are where the nozzle will be, so if the Z probe is displaced from the nozzle then you must ensure that the probe is always over the bed, even if this means moving some of the probe points in from the edge.

This example uses ten points: six around the periphery, one at the centre, and three halfway between the centre and the periphery.

If your Z probe has different trigger heights at different XY positions, you can add an H parameter to each G30 command. This gives the value that must be added to the G31 Z parameter to get the actual trigger height at that point. Set the G31 Z parameter so that it is accurate when probing the centre of the bed, and use the H parameter to correct for different trigger heights at the other bed probe points. The H parameter is supported in firmware version 1.09e-dc42 and later.

The S parameter on the final G30 command is the number of factors to calibrate.

Testing the motors individually

You can test the four motion motors individually by putting the printer in relative mode (G91 command) and then using the G1 command with S2 parameter. For example, after sending G91, sending G1 S2 X10 should increase the length of line between the A spool and the effector by 10mm; and sending G1 S2 U-20 should reduce the length of the line from the D spool by 20mm.

If a motor moves the wrong way, you can reverse it by changing the corresponding M569 command in config.g. For example, if the A spool motor moves the wrong way, change M569 P0 S1 to M569 P0 S0.


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