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GCodes

The following document documents the Gcodes implemented or modified by X-SCARA implementation

X-SCARA Specific GCodes

M360 - X-SCARA - Change Coordinates Transformation

 Parameters:
 
 M<int>  - transformation mode (0 or 1)
 
            0 - cartesian (default) 
                current X and Y coords. are cartesian coords. pointing to extruder's nozzle
 
            1 - angular (used by G28, when homing) 
                current X and Y coords. are angular coords. of shoulder and elbow position)

            1 - probe (used by G29, when leveling bed) 
                current X and Y are cartesian cords pointing to probe's center

This command will instruct the X-SCARA machine to switch the entire coordinate mapping system to cartesian, angular or probe mode.

Use this explicitly only for testing and calibration!

Cartesian mode

In cartesian mode X-SCARA will automatically transform the X and Y coordinates to angular positions for the shoulder and elbow joints, using inverse kinematics. This is the normal mode, using during printing.

Angular mode

The M360 M1 command allows you to move either the shoulder, or the elbow to an angle you expect and observe the result, usign standard GCode commands (e.g. G0, G1 or G92). For example, after invoking M360 M1 you can move the arm's shoulder to 0º using G0 X0 or the elbow to 90º using G0 Y90.

Used internally when homing with G28.

Probe mode

The M360 M2 command will switch to a transformation mode, similar to M360 M0, but this time pointing to the probe's center, instead of the extruder's nozzle. Used internally by bed-leveling G29 commands.

Used internally when running bed-leveling commands with G29.

M361 - X-SCARA - Move joints to angular position

 Parameters:
 
 S<float>  - Move to given shoulder angle (in degrees)
 E<float>  - Move to given elbow angle (in degrees)
 I<booL>   - Add the given to the current position instead of setting them

This command is useful to move the machine's joints to a specific angular position. When invoked, it will report back the angular position of each joint and the coresponding cartesian coordinates, even if run without arguments.

M362 - X-SCARA - Set current joints position

 Parameters:
 
 S<float>  - Set the shoulder angle to this value (in degrees)
 E<float>  - Set the elbow angle to this value (in degrees)

This command is the complement of G92 command for angular positioning. G92 sets the current absolute position for X,Y,Z axis and even E(xtruder), to a given value while M362 sets the current position of joints, to a given value.

For example, to reset the machine back to its correct position, you could move the arm perfectly straight and then run:

M362 E0 S0

This command tells the machine the current position is 0º angle for both shoulder and elbow joints. After that, you can move the machine safely in cartesian space.

Please note that the same effect can be obtained using G92, after changing the coordinate system to angular positioning using M360 M1.

Soon to become deprecated! Same as G92 when using M360 M1.

M364 - X-SCARA - Get X-SCARA version

 Parameters:
 
 D<bool>  - if `X_SCARA_DEBUG` is configured, enable or disabled verbosity

Prints the current version of X-SCARA implementation.

If X_SCARA_DEBUG is enabled in Configuration.h enables detailed log tracing using M364 D1.

Modified Marlin GCodes

G0/G1 - Move to destination

X-SCARA uses the G0 command to move directly to destination (without segmented moves) and G1 command to move to destination using multiple segmented moves.

To configure the number of segments for each move, use M665 D command to set the number of segments per second and M665 M command to set the minimum segment length.

If the G1 response is choppy and the linear movement is not fluent, lower the number of segments and/or increase the minimum segment length (e.g. M665 D30 M0.5).

Check Marlin documentation for more details.

G28 - Home axis

X-SCARA will home the Z axis using bed-probe and the X and Y using magnetic endstops.

The endstops for X (shoulder) and Y (elbow) axis must be positioned at -90 degrees.

When the axis is at -90 degrees, it point towards machine's right.
When the axis is at 90 degrees, it point towards machine's left.
When the axis is at 0 degrees, it point towards forward.

XY Homing sequence

The XY homing sequence is designed to avoid crashing the machine as much as possible.

The two axis are marked as codependent and can't be homed independently. Running G28 X or G28 Y or G28 XY will have the same effect.

The homing sequence is more elaborate for X-SCARA machine, and it happens as follows:

  • (1) - Coordinate transformation is set to angular (M360 M1)
  • (2) - X axis (shoulder) moves clockwise until it hits the endstop positioned at -90º
  • (3) - X axis applies configured home offset (via M665 X)
  • (4) - X axis moves back to 0º position
  • (5) - Y axis (elbow) moves clockwise until it hits the endstop position at -90º
  • (6) - Y axis applies hconfigured home offset ( via M665 Y)
  • (7) - Y axis moves back to 0º position
  • (8) - Coordinate transformation is set back to cartesian (M360 M0)
  • (9) - Axis are marked as homed
  • (8) - Moving to bed center (X0 and Y0 in cartesian space)

M665 - Set X-SCARA settings

 Parameters:
 
 D<seg-secs>  - sets the number of segments per seconds for linear moves (default is SCARA_SEGMENTS_PER_SECOND)
 M<seg-min>   - sets the minimum segment length in mm for linear moves (default is SCARA_MIN_SEGMENT_LENGTH)
 S<offset>    - sets the shoulder home offset in degrees (to calibrate homing)
 E<offset>    - sets the elbow home offset in degrees (to calibrate homing)
 X<origin>    - sets the offset on the X axis for bed center position (usually 0, default SCARA_OFFSET_X)
 Y<origin>    - sets the offset on the Y axis for bed center position (default SCARA_OFFSET_Y)

This command is used to configure Delta printers and also Scara machine in Marlin Firmware. Any of these values can be saved and restored to/from EEPROM using M50x G-Code commands.

Tuning segmented moves

Tune linear movements using M665 D and M665 M options. If the movement is choppy, lower the number of segments to a more reasonable value (e.g.: 30) and/or increase the minimum segment (e.g.: to 0.5).

Aligning bed's center

If the machine doesn't point at the bed's center correctly, use M665 X Y to setup the offset the current known center and save the value in EEPROM using M500. For example, running M665 X-5 will move the bed's center to the right by 5 mm.

Calibrating home position

This is the one of the most important configurations for X-SCARA: calibrating the home position.

When setting the endstops for the X (shoulder) and Y (elbow) axis, most likely you will not be able to mechanically position those at perfectly -90º angles. The M665 X Y command will allow you to do fine adjustements and save those to EEPROM.

Follow this steps to calibrate the home position:

  • (1) - position the X and Y endstops (the best you can) at -90º position
  • (2) - home the machine using G28 XY
  • (3) - move the arm to point forward by running M361 S0 E0 (i.e.: set elbow and shoulder angular position to 0º)
  • (4) - use the same M361 command to adjust the angular position for both axis so that the arm gets perfectly straight
  • (5) - get the resulted positions and store them as offsets them using M665 S E
  • (7) - home again using G28 XY
  • (8) - repeat (2)-(8) until perfect alignment is achieved
  • (9) - save the resulted values to EEPROM using M500

Note: bad alignment of shoulder axis will not result in deformed parts, but improper positioning of the elbow axis will do.