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  • Author Author: ralphjy
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Trying out my laser

ralphjy

Santa brought me a laser for Christmas and I finally picked up the last piece of required safety equipment - a CO2 fire extinguisher.  So, I finally get to give it a try image.

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I have a SainSmart Genmitsu 3018 Pro CNC router that has provisions to swap the spindle for a laser module.  I am using a SainSmart 445nm 5.5W laser kit.  There are less expensive modules available, but I've found that it is difficult to get a good set of specifications on these units and decided it was better to try one that is known to work with my CNC controller.  The SainSmart unit did not come with any documentation and the online "instruction manual" was marginal at best.  I've submitted a request to their support group for a schematic.  I know they have a Facebook group, but I don't do Facebook and I've found their Wiki pages difficult to navigate.  Hopefully their support is responsive.

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The CNC controller board has two connectors for lasers, a white Laser A connector and a red Laser B connector.  It turns out that the circuits behind these connectors are not the same.  Some YouTube videos indicated that the control signals (PWM) are inverted between the connectors.  At least the wire harness has a red connector on it so I could deduce which connector to use (they are not keyed differently).

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Another difference that I noticed between this kit and other modules that I've seen is that there is what appears to be a driver board between the CNC controller and the laser module.  The board has a jack for an external 12V supply, a power switch, and what appears to be a thermal protection circuit (temperature sensor signal from laser module).  Hopefully I can get a schematic for this board also.  I am not using the external supply (there was no documentation saying that was required).  I had to mount this board on the side opposite the CNC controller to allow for the X axis movement because the wires were too short to put it on the same side.  I guess that makes sense since I could put a holder for the laser module on that side when it was not in use and wouldn't have to de-cable it.

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Here is the laser module mounted in the spindle holder.  The loose connections are the spindle power wires (also disconnected at the control board).

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SainSmart recommends using LaserGRBL to control the laser operation.  LaserGRBL is a freeware program that converts images to GCode and acts as a GCode sender to control the laser and the CNC operation.  If the laser is enabled then the spindle speed codes are used to represent the PWM values.  LaserGRBL does not have Z axis controls so I'll need to add that to allow focusing using the GUI.  Fortunately, LaserGRBL allows you to add custom control buttons to send GCode.  Link: http://lasergrbl.com/

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Here is a video from the overhead IP camera that I use to monitor my workroom.  There is quite a bit of reflection when the laser goes to higher power.  Good news is that it is not apparent through the laser glasses that I got from Edmund Optical.  The laser always appears as a small dot.  I am not using the green glasses provided with the kit as they don't have a specified OD (optical density) and they do not do a good job of suppressing the reflections.  The glasses from Edmund have an OD of 7+ at the 445nm wavelength of the laser.  The playback speed of the video is 8X to reduce the overall video length.  With the default speed setting in LaserGRBL this engraving took over 20 minutes to complete.

 

Here is the end result.  I'm happy with it as a first attempt.  I guess I had some debris in the image that I encoded (although I don't see it in the image) and I've also got a lot of fine tuning to do (speed, power and focus).  I have found that it's not easy to adjust the laser focus visually.  I think I'm going to do a bunch of calibration runs and when I determine the correct spacing - I'm going to print some calibration blocks (that's what they use with the CO2 cutters at the community college).

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The next thing that I'm going to work on in my setup is fume extraction.  I won't try any cutting until I get that working properly as it will probably generate a lot of smoke.

 

And I want to add some additional safety features:

  1. Lighted warning sign to keep people from entering the room while the laser is on
  2. Power interlock and EMO (emergency off) button
  3. Removable filter to protect the camera sensor

 

The adventure begins........

 

 

Here are links to some of my related blog posts:

Genmitsu CNC 3018-PRO

Genmitsu CNC 3018-PRO - becoming useful

CNC - First Try at Engraving

Preparing to add a laser to my CNC router

Laser for Christmas

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