Background information

This laser cutter/engraver utilizes the same electronics as a RepRap style 3-D printer for the motion and can be operated identically to a 1-layer high 3-D printer using Cura to create toolpaths from STL files and pronterface to run the gcode generated from Cura.

Although any diode laser could likely be used, a jtech photonics 2.8 Watt diode laser and 2.5 Watt driver kit was used and can be found here. They have in depth instructions on the connections to a RAMPs board, and other common 3D printers should you want to adapt your current 3-D printer to add laser functionality as well.

The printed files, bill of materials, and other information for the laser cutter can be found on youmagine here

What is different between the laser cutter and a 3-D printer?

Three-dimensional printers have an extruder, which uses plastic filament to print 3-D objects. However, the laser cutter has no extruder. In its place, it has a laser diode (comes bundled as a kit with the laser driver board), and the laser driver is connected to the fan output, which is adjustable in power from 0 to 255. Because the laser detects the fan, the strength of the laser can be set between 0 and 255, or from 0-100% in 0.39% increments.

The laser can either cut/engrave lines using typical 2D drafting software such as Inkscape and the jtech laser plugin. Additionally, the laser can easily create fill patterns using typical STL to gcode slicing processes commonly used with 3-D printers while having the laser act as a one layer 3-D printer.

INTERFACE SETTINGS FOR THE OPEN-SOURCE LASER CUTTER

Open build lab aluminum frame
Extrusion rods
Motor mount
Printed part

Connecting the Laser Cutter to Its Power Supply

The power supply powers the RAMPS board (board on which the fan is mounted).
A separate power connector attaches to the laser driver [board]. Once the power connector is attached, you must insert the key on the back side of the laser driver and turn it to the right. Then, you must flip a switch and push the red reset button on the laser driver. The fan on the driver board will turn on as well as the LED nearest the mode switch on the board signaling the laser is ready to use. As an aside, the red wire loop on the back of the laser driver board can be connected to an emergency shut off.

Operating the Laser

To operate the laser, you will need three programs installed on your computer: OpenSCAD(or Inkscape or Adobe Illustrator), Cura, and Pronterface.

Homing the Laser

Before beginning a laser-cut project, you must return the laser to home position—a process called homing.

Open Pronterface. You will see three sections in the interface: a circle diagram [detail - name for this], a grid, and a command box.
Click on the home button, the white button located at the bottom left of the circle diagram.

Preparing your design for cutting

Now, launch OpenSCAD (alternatively, you may choose to use Adobe Illustrator or Inkscape). This will be the interface you will use to create the STL file, in which you will define the surface geometry of your three-dimensional object. The standard OpenSCAD interface is divided into two sections: a command section and the image canvas.

Create a simple square etch design using the following code: cube ([20,20,0.2]). The last numeric coordinate indicates the depth to which the laser will etch.
Export the design as an STL file [need more specifics on procedure in the interface].

If using a 2D file in inkscape follow the instructions for the laser plugin here and learn more about the settings within the plugin here

Creating Slices

Cura is a slicing program that applies settings between designs, created in OpenSCAD, and the 3-D printer or laser cuter. Launch Cura; open the STL file in Cura. The Cura interface has two sections: the command section, which contains four tabs, and the graphic rendering in relation to the laser area.

The machine settings should be: 0, 240 mm, 240 mm, and a maximum of 0.25. [where in the interface?]
Position the cube in the graphic rendering section by estimating its corresponding screen location to how your wood is placed on the laser cutter board.

To create a basic square etch:

input the following coordinates in the Basic tab:
1. Layer height: 0.2 (a 0.2 height creates a one-layer etch; 0.05 layer will result in a 4-pass etch for a 0.2mm thick part)
2. Shell thickness: 0
3. Fill density: 100%
4. Print speed: n 20-40
5. Temperature: 0 (the temperature input in Cura typically controls the temperature of a 3-D printer extruder, therefore no temperature adjustment is needed)
input the following coordinates in the ‘Advanced’ tab:
1. Nozzle: 0.2 – 0.22 (e.g., 0.21)
2. Retraction: 40.0/4.5
3. Quantity of initial layer thickness: 0
4. Remaining options can be left as the default settings
input the following coordinates in the ‘Expert’ tab:
1. Under the Skirt section
  - Line count: 0
  - Start Distance: 0
  - Minimal Length: 0
2. Cool settings – Fan full on at height: 0 (this setting will start the fan when the laser cutter starts)
3. Cool settings – Fan speed min/max: 50 (this setting dictates the strength of the fan)
4. Strength – Adjusting this number affects [what?]; so, for example, a 50% strength [does/means what]
At this point, save the settings in a G-code file using the [option] in the [drop-down menu]

Printing Your Laser Cut

Pronterface is the print host.

Open Pronterface and load the G-code file.
Apply the following commands in the dialogue box on the right of the pronterface window
1. M106 S10
  - This will turn on the laser at a very low strength to allow focusing
Now, very carefully, adjust the focus of the laser using your fingers (focus is a ring at the end of the laser that twists, much like focusing a camera lens).
Set M to 107; this turns the laser on at full strength and turns off the fan.
Click ‘Print’, which is located in the ‘Print’ tab [Yes?]

Code to Create a Cube

Type the following code into [WHICH PROGRAM…and why?]. The last number in the string of three numbers specifies the layer thickness or, with laser printing, the depth to which the laser will cut. The ‘center-true’ command dictates where the item is placed on the laser cutter board.

Difference ( )

{ cube ([20,20,.2] center-true);

  Cube ([19.5,19.5,.25] center-true)}

Which program has a ‘First layer speed’ control?

Open-source laser cutter

Contents