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Laser welding protocol: MOST

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This page describes how to use this: Open source laser system for polymeric welding located in the MOST lab. Our primary interest in it is making Expanded microchannel heat exchangers for all kinds of energy efficiency applications including solar water disinfenction.


Wijnen (talk): I'm editing this page to add all the steps that are required now. I am not cleaning this page, so there will be a lot of obsolete information on it. Feel free to clean it up.



The Laser is composed by three main devices: LaserMount 264, TECSource 5300 and LaserSource 4320. The LaserMount 264 is a unit that integrates a Peltier cooler for precise temperature control and the laser itself. TECSource 5300 is a temperature controller that needs to be attached with the LaserMount. LaserSource 4320 is a Laser Diode Driver, it controls the laser behavior.


General Basic Precautions

When operating the laser make sure that the doors to the rig are closed and that you are wearing the laser safety glasses.

The LSO shall be notified of the purchase of any laser, regardless of the class. Such notification should include the classification, media, output power or pulse energy, wavelength, repetition rate (if applicable), special attachments (frequency doublers...etc.), beam size at the laser aperture, beam divergence and users.

No attempt shall be made to place any shiny or glossy object into the laser beam other than that for which the equipment is specifically designed.

Eye protection devices which are designed for protection against radiation from a specific laser system shall be used when engineering controls are inadequate to eliminate the possibility of potentially hazardous eye exposure (i.e., whenever levels of accessible emission exceed the appropriate MPE levels.) This generally applies only to Class IIIB and Class IV lasers. All laser protective eyewear shall be clearly labeled with optical density values and wavelengths for which protection is afforded.

Skin protection can best be achieved through engineering controls. If the potential exists for damaging skin exposure, particularly for ultraviolet lasers (200-400 nm), then skin covers and or "sun screen" creams are recommended.

HANDS - Most gloves will provide some protection against laser radiation. Tightly woven fabrics and opaque gloves provide the best protection.

ARMS - A laboratory jacket or coat can provide protection for the arms. For Class IV lasers, consideration should be given to flame resistant materials.


The Template, and all other files are uploaded in SourceForge,

  1. Hydra – MMM modified for the Laser Welder --- *Java JRE required.
  2. Processing -- (If using source code).
  3. Inkscape --
  4. GCodeTools for Incscape ---

You can also get the template file here

Gcodetools Installation

  • Windows: Unpack and copy all the files to the following directory Program Files\Inkscape\share\extensions\ and restart Inkscape
  • Linux: Unpack and copy all the files to the following directory /usr/share/inkscape/extensions/ and restart inkscape.

Loading Samples

  1. Open the safety doors.
  2. Carefully remove the aluminum and glass plater.
  3. Remove the top layer glass.
  4. Place the plastic layers on the bottom sheet of glass (two the first time and adding one per weld routine if more than 2).
  5. Stretch the plastic layers flat and hold in place with magnets at the four corners. Make sure as many wrinkles are removed as possible.
  6. Put top sheet of glass on top of plastic.
  7. Slide the plater back into the laser rig.
  8. Close the box and put on the safety glasses.

Powering up and communicating with the device

  1. Turn on computer and log in
  2. Make sure the Arduino and LaserSource USB cables are connected to the computer
  3. Turn on the motor power supply
  4. Turn on the TECSource 5305 temperature controller using the "Power" switch
  5. Wait until it boots and then press "Output". The blue light next to it should come on.
  6. Wait until it stabilize at the temperature set point (Currently 25 Celsius)
  7. Turn on 4320 LaserSource controller using the "Power" switch.
  8. Open firefox and use the bookmark in the bookmarks toolbar to go to https://localhost:8080/
  9. Make sure "Show tweak settings" is selected
  10. At the bottom of the page, select "Import settings from file" and choose Desktop/Laser System for Polymeric Welding/Test/000_Laserwelder.ini
  • If localhost:8080 crashes, and the page becomes blank enter:
    • sudo service franklin restart
    • Password

Ready for use!

Note if the MOST RepRap printer interface crashes and persists, make sure your USB cords are plugged into the computer. If problem persists then type

  • sudo service franklin stop

enter password

  • sudo service franklin start

into a terminal This will restart the server manually

Also if there is still a problem type "franklin" into a terminal and this will show all the error messages.

Drawing on Incscape and Exporting to gcode

  1. After installing Incscape and Gcodetools, run Incscape
  2. Open the file TEMPLATE.svg, it has the working area limits and other things necessary to generate the gcode correctly. "Save As" you file under a different file name to preserve the template
  3. Draw weld pattern - select the line and press Ctrl+Shift+C (this converts it to a path and keeps it selected)
  4. Go to Extensions>>Gcodetools>>Path to Gcode
  5. On the tab Preferences, you can change the File name and Directory
  6. Click Apply. The GCode should now be generated to the Directory folder
  7. If you want to make any changes, first undo with ctrl-Z to get your original paths back

Laser Welding

  1. Close and latch the enclosure doors and put on the safety glasses.
  2. Turn the LaserSource enable key to "On"
  3. In the firefox page you opened, select the file to add to the queue and click upload (Usually located in Desktop/Laser System for Polymeric Welding/Test)
  4. Click "Print selected at center"
  5. Turn the "Enable" switch on the LaserSource to the "Off" position.
  6. You can now open the enclosure and remove the platter from the welding rig.


The settings below were written here; I have no idea what they mean. You'll have to figure out what works. To change things, you'll want to set the feed rates from inkscape and/or change the feedrate scaling factor on the web site. The power can be adjusted by changing the value near the top of /usr/share/franklin/ (you must be root to edit that file; don't touch it if you don't know what you are doing). After that, restart it with "service franklin restart" (also as root).

Just in case it helps anyone, I left the old information in here.

For welding heat exchangers the best settings are as follows.

For dots:

  • Current - 5500mA
  • Exposure - 120ms
  • Arduino code - Desktop -> Laser System For Polymeric Welding -> GCode_Interp_by_Rodrigo_dots -> GCode_Interp_by_Rodrigo_dots.ino

For lines:

  • Current - 2500mA
  • Speed - 20 RPM
  • Arduino code - Desktop -> Laser System For Polymeric Welding -> GCode_Interp_by_Rodrigo_V3 -> GCode_Interp_by_Rodrigo_V3.ino