Laser cutter

From Katy Makerspace Wiki
Jump to: navigation, search

Overview[edit]

The laser cutter at Katy Makerspace is a model known as a K40, sold by many different resellers on eBay and Alibaba. Out of the box the laser comes with a controller that does raster engraving, we've replaced ours with one that uses LinuxCNC. It can cut thin wood, some plastics, leather, paper and cardstock. It cannot cut metals or glass.

Her name is Lizzy.

Safety[edit]

Aside from the obvious risk of blinding (a class 4 laser can deal permanent vision damage in less time than the human blink reflex; if the beam shines in your eye you will lose that eye), lasers also come with a risk of fire, and fume inhalation. The laser should always be watched while running, and should never be run with the lid open.

No materials containing chlorine should ever be cut with a laser: PVC, Lexan, ABS plastic, will all release noxious and corrosive fumes when burned. Aside from harming anyone breathing them, the fumes can damage the focusing lens of the laser.

Safe materials include wood (including plywood), leather, paper, cardboard, and acrylic plastic (plexiglas).

Approved materials[edit]

The makerspace has a stock of 3mm thick, 12" square plywood sheets. These are by far the best material for laser cutting, balancing safety, quality of cut, and price.

3mm acrylic sheets can also be gotten in various colors and transparent. These cut very well, but cost a little more.

Operation[edit]

Toolchain[edit]

The general toolchain is, create a DXF file using LibreCAD (or the CAD tool of your chioce), turn that file into GCode using CamBam (or the CAM tool of your choice), edit the GCode some (because CamBam was designed for a CNC mill), and move the file to the laser.

Turning it on[edit]

To turn on the laser, turn on the power strip on top of the shelf to the right of the machine. You should hear the cooling pump and fan activate, and be able to see water moving in and out of the bucket. Never run the laser without the cooling pump active!

Then, turn on the big power switch on the top of the laser. This turns on the laser itself; to turn on the LinuxCNC controller board, lift up the right side of the laser's lid, and there is a stack of several connected-together circuit boards mounted in the machine. On the front-most board (a BeagleBone) on the top right side, there are two very small (you probably won't be able to see them but you can feel them with your finger) tactile buttons. Push the one on the bottom and a blue LED will turn on, the controller board is now booting up.

Controls[edit]

There are four controls on top of the laser: a power switch, a laser enable switch (functions as a kill switch in that it will cut power to the laser, although not the stepper motors), a test fire switch, and a power knob.

The power knob should be at about the 4:00 position. You should aim for 12-15 mA power usage (as measured on the power gauge) when firing. Using more power puts more stress on the tube, so try to use the lowest power setting that will cut your material.

The laser enable switch must be "in" to fire the laser. You can test this by tapping the test fire switch.

Material positioning[edit]

The laser work area is a little more than one square foot. The focal length of the lens is 2 inches, so you should adjust the height of the table (using the screw legs at the corners) so that the bottom of the cutting head is 2 inches above the material. You can test the focus with the test fire button; a single tap should leave a pinhole-sized burn on the material.

GCode[edit]

The laser needs some modification to the GCode before it will actually fire the laser:

  • In order to fire, the current Z coordinate must be below 0, so "G0 Z-0.1"
  • You must set the "spindle speed" to something. The actual value is ignored, but it must be set to something: "S1000"
  • To actually fire and stop the laser, use the codes M3 and M5 respectively.
  • 600-1200 mm/minute feed rate will reliably cut 3mm plywood.

We're working on a tool that will generate laser-compatible GCode from a DXF file.

Accessing the laser, using LinuxCNC[edit]

The laser is accessible over VNC at the IP address 10.1.10.200 (printed on the laser itself). Most of the machines in the space have VNC clients installed on them. There's an icon on the desktop to launch LinuxCNC.

Once it's running (it will take a couple minutes to start up), press the red power button in the upper left of the toolbar to open a connection to the machine, and then home both axes. Position the cutting head where you want it with the arrow keys, touch off both axes, open your file, and press the green "play" button to start the cut. It may be a good idea to do a dry run with the laser enable switch "out" to make sure everything's working.

Maintenance[edit]

There are three mirrors and a lens that need to be cleaned periodically: one in the back left corner of the machine, one on the left side of the gantry, one on the cutting head, and a lens on the cutting head. To clean these, put a small amount of rubbing alcohol on a q-tip or kleenex and gently wipe off any soot or debris. Generally, the closer to the cutting head an optical element is, the more often it needs to be cleaned. The lens can be cleaned by unscrewing the cap on the bottom of the cutting head; when reinstalling it, the curved side goes up.

Periodically, the mirrors may need realignment. To do this, there are adjustment screws on the back of each mirror assembly. Align mirrors in the order the beam hits them: place a piece of paper or tape over a mirror, and test fire the laser (on very low power) while adjusting until the beam hits the center of the mirror. Then proceed to the next mirror. Check the alignment with the cutting head in various positions in the machine.