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CAM software for SainSmart Genmitsu machines

How to use DeskProto with the SainSmart 4th axis rotary module


In 2023 SainSmart released a rotation axis option for the Genmitsu CNC milling machine that they manufacture: the "4th Axis CNC Rotary Module Kit".
We were approached by SainSmart 'guru' Graham Bland, who writes independent reviews and tutorials about SainSmart machines. He was working on a tutorial about using the SainSmart Rotary axis, and asked for our support in calculating toolpaths with DeskProto. It has been our pleasure to cooperate with Graham on this issue !.

Title page of this tutorial PDF file
The title page of Graham's tutorial.

The tutorial that Graham wrote is called Intro to CNC - Using the SainSmart 4040-PRO Rotary axis.
It shows you how to install, setup and test this device, why he choose DeskProto as CAM software, how to create a project and toolpaths in DeskProto (both continuous rotation and indexed machining), and finally two sample projects. The following paragraphs are present:
  • What is a 4th rotary axis?
  • Limitations of a 4th Axis
  • Mounting and Alignment of the Rotary axis
  • Setup and Testing
  • Initial setup, Making things easier!
  • Setting up a job
  • Software
  • Setting up DeskProto
  • Sample Projects
  • TROUBLESHOOTING
Graham published the tutorial on the SainSmart Genmitsu CNC Users Group on Facebook, and he permitted us to also share it via this website:
Intro to CNC - Using the SainSmart 4040-PRO Rotary Axis V1.0.zip (4.5 MB)

This ZIP file contains the tutorial, sample files and projects, macros, cutter definitions and some photos. Thanks for sharing !

The SainSmart laser engraving option

This paragraph applies only to DeskProto Version 8, as the previous DeskProto versions do not support laser engraving.

Most SainSmart machines can be equipped with an optional laser extension, offering laser engraving. The laser module replaces the spindle unit, so milling and laser engraving cannot be combined in the same NC file. In addition to changing the hardware you also need to set the control software to use laser mode, which can be done with command $32. Entering $32=1 sets the machine to laser mode, $32=0 sets it to milling mode. We do not recommend to include these commands in the G-code, just enter them as manual commands (you will need to change the hardware anyway).

Screenshot of the DeskProto machine settings dialog
Screenshot of the DeskProto postprocessor dialog
Laser settings in one of the SainSmart machines and the SainSmart GRBL postprocessor.
Click on an image for a larger version.

For the machine:
The laser unit and the spindle motor have the same position as the two units are exchanged.
The laser power has been set in a range from 0 to 1000, which is in fact an arbitrary range (independent of the actual power). You can for instance also use 0 and 100, so you can set the S-value as a percentage. The min and max value simply must match the GRBL Spindle Speed Minimum ($31) and Maximum ($30) that you have set for your machine. When you change these to 0 and 1000 for the laser: do not forget to restore the correct settings for your spindle motor when switching the machine back to spindle mode.

For the postprocessor:
Only one command is needed here, the command to start the laser mode: M4 S{S}. The laser does not need to be switched off for positioning movements as GRBL does so automatically. Just as it automatically reduces the laser power when the feedrate is reduced. To use this automatic mode the laser needs to be switched on using M4 (M3 will result in a constant laser power).
The S value in this command sets the initial laser power. In this command "{S}" is a placeholder, which will be replaced by the actual S-value while using DeskProto.
Laser mode will again be stopped by the M5 command at the end of the NC file (as set on the Start/End tab of the postprocessor). The M5 command is valid both for the spindle and for the laser.

The definition of a laser cutter contains in fact only one parameter: the beam width (Kerf). Graham Bland has tested a number of SainSmart laser modules, and found these Beam width values: Adjust the Maximum S-Value in each cutter definition to match your router's $30 setting (for Maximum Spindle Speed). And when you check the option to automatically set the speeds you can adjust the Feedrate and the S-Value according to your needs. Graham: thanks for sharing these results !

You can find more information in the SainSmart laser instructions