About Gskewer

Gskewer is a tool to skew transform gcode file coordinates to account for axis misalignment of a 3D printer.

In order to use Gskewer you will need to print a test cube, take accurate measurements of the cube, then input those measurements as arguments for Gskewer.

The G-code file to be modified, the measured error (in mm), and the distance from zero where the measurement was taken is then entered into skew.py before being run.

Preparing to use Gskewer

The task of measuring the error between axis pairs is shown in good detail at http://www.zs1jen.org/Station_Manuals/Reference/3D_Printers/14_RepRapPro_-_Axis_compensation.pdf

The files to be printed for the above process are at https://github.com/reprappro/RepRapFirmware/blob/master/STL/calibration_90mm.stl

The general idea of the measurements required and which arguments they correspond to is illustrated below.

These measurements are to be taken for each of the three axis pairs of the cube: XY, YZ, and ZX.

You will end up with six measurements/arguments: xylen, xyerr, yzlen, yzerr, zxlen, and zxerr.

The initial six measurements can be simplified to a tangent argument by dividing the error by length. (ie: xyerr/xylen=xytan) The three tangent arguments are: xytan, yztan, and zxtan.

Using Gskewer

gskewer [arguements] file

Gskewer will automatically generate a new gcode file with "-skewed" added to the file name. If the output file name already exists gskewer will delete the existing file and write a new one.

Examples

gskewer --xyerr 1.2 --xylen 80 Cube80mm.gcode will adjust the X coordinate proportionally by -1.2 mm for every 80mm in the Y coordinate. Also, only the XY plane is affected as other arguements are not used. The output file will be "Cube80mm-skewed.gcode".

gskewer --xytan 0.015 Cube80mm.gcode is equivalent to the example above, as xytan = xyerr / xylen.

Gskewer Arguments

--xyerr Error in the X-axis for the XY pair in mm. (This argument cannot be used with "xytan")

--xylen Length of the test cube side where the "xyerr" measurement was taken.

--xytan The error in the ZX pair as a tangent. (zxerr/zxlen)

--yzerr Error in the Y-axis for the YZ pair in mm. (This argument cannot be used with "yztan")

--yzlen Length of the test cube side where the "yzerr" measurement was taken.

--yztan The error in the YZ pair as a tangent. (yzerr/yzlen)

--zxerr Error in the Z-axis for the ZX pair in mm. (This argument cannot be used with "zxtan")

--zxlen Length of the test cube side where the "zxerr" measurement was taken.

--zxtan The error in the ZX pair as a tangent. (zxerr/zxlen)