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Laser Cutter

Purchased in 2015, the water-cooled CO2 laser cutter will cut material up to 20×12 inches, 1/4 inch thick, and can engrave on thicker material. The laser cutter is a wonderful piece of tech, and we continue to find new uses for it. The laser cutter requires a special introductory course before members can use it. Shawn is most familiar with the laser cutter. Any questions or concerns about it should go to him.

This is the cutter: It uses RetinaEngrave software.

As a general rule of thumb, you can cut non-chlorinated plastics (no vinyl, no pvc), leather and wood. Metal can't be cut or etched. This page is a good guide to what can and can't be cut:

Cutting plastics with chlorine in them can release chlorine gas which is highly toxic to you (known as mustard gas in World War 1!) and can corrode the laser components.

Preparing Your Files

The laser cutter mounts as a printer, so in theory any file that can be printed can be cut or engraved. In practice, we usually use the freeware Inkscape for cutting or engraving.

To prep your file with Inkscape you'll need need an SVG. Some tips:

  • It should be as simple as possible, with objects like dynamic offsets converted to paths. Ideally, you'd only have paths in your file. But the software will recognize some simple objects like circles and rectangles.
  • Filters should be removed.
  • All colors and layers should be 100% opacity.
  • All layers should be 100% opacity.
  • The page size should be less than 20×12 inches.
  • There should be some white space between the page border and your paths. The laser cutter software will strip out all the white space.
  • All paths should be within the page borders.
  • Stroke styles should be solid.
  • The laser recognizes red, green, blue, cyan, yellow, magenta and black strokes, and will treat them separately. So if you're cutting a doughnut, you might want to make the center blue and the outside red. When you cut it, specify blue before red to make sure that the doughnut doesn't shift at all before the center is cut. Or if you're designing a wood box that will have an acrylic window in it, make the wood and acrylic lines different colors so you can choose not to cut one or the other.
  • The laser will “snap” path stroke colors to a color it recognizes (pink, salmon and rose will all snap to red). Any colors or lines it doesn't know what to do with will snap to black. For that reason, it's best to avoid black on any lines you want to cut (so you can turn black cuts off).
  • You can make SVGs from any number of programs. However, there's a bug in Adobe Illustrator that will alter the size of the SVG by 20 or 25%. Watch out for this. See below for a fix.
  • The laser cuts along the path. So the stroke width is irrelevant to the laser when it's cutting along a path (vector mode). Stoke width, however, is relevant when in engraving (raster) mode.
  • Engraving (raster mode) is determined by a black and white value slider (everything darker than the slider value is engraved). As such, it will really only do on/off or black/white. It doesn't do “gray”. While importing bitmapped images like JPGs and PNGs into an SVG is legal, it often produces alignment issues. It's best to convert these to vector using something like Inkscapes “trace bitmap” tool.

Pre-Cutting Checklist

  1. Ensure you won't need to leave the cutter to deal with a phone call, bathroom, or any other reason for the estimated time of the cut/engraving (indicated at the bottom right of Retina Engrave).
  2. Ensure your power and speed settings are correct for the material you're cutting/engraving.
  3. Clean the mirrors and lenses with Q-Tips and rubbing alcohol.
  4. Set the height of the lens using the aluminum cylinder marked '2.0'.
  5. Ensure your work won't be in the way of the gantry.
  6. Ensure your work bounding box doesn't exceed your material area.
  7. Ensure the water pump is circulating water. You should be able to hear it and no air should be visible in the laser tube.
  8. Ensure the vent blast gate is open.
  9. Ensure the vent fan is running. With the lid closed, you should be able to feel air being drawn into the front vents of the laser cutter.
  10. Ensure the compressor has been recently drained. How to drain the compressor
  11. Ensure the compressor is on and air is coming out near the lens by feeling it with your hand.
  12. If there are any problems, stuff doesn't sound right, etc., don't run the job. Ask someone about it. As of this writing, Shawn, Marcel, Adam and Jim are among the most experienced with the laser.

Post-Cutting Checklist

  1. Turn off the laser cutter.
  2. Turn off the blower, water pump, compressor, and if you're the last one, the laptop.
  3. Close the vent gate above the cutter.
  4. Clean up inside the cutter. If it looks like it hasn't been done in awhile and if you have done it before, vacuum out the really small bits.


I want to cancel my job, but the stop button in the ReginaEngrave software isn't working! If it's an emergency, pound the physical red emergency stop button on the laser cutter. Otherwise, hit 'C' on the computer to cancel. RetinaEngrave for some reason disables the stop button a lot, only giving you brief periods to click it.

Why is it making an awful racket? Sometimes the software gets confused and tries to push the gantry past its limits. Check to make sure there are no physical obstructions to the lens assembly or on the tracks/rollers, then re-home it.

Why won't it jog when I hit the arrow buttons? Mostly likely, it's off or the gantry is unlocked. Unlocking allows you to move it by hand (slowly), but you'll have to hit the lock button to home it.

Why does my Illustrator file come out 20% smaller in Inkscape than it should? Somewhere in the conversion process, Illustrator makes an assumption that everyone will use 72dpi. Inkscape uses 90dpi. The solution is to edit the SVG in a text editor, and change the height and width (or add them) to the last two values in the “viewBox” attribute, followed by “pt”. for example, width=“1296pt” height=“432pt” viewBox=“0 0 1296 432”


We've installed a nodeMCU on the wall which is monitoring the temperature in the vent tube and the position of the blast gate. The recent temperature may be available on its web server at, within the HMS LAN only.

You can also subscribe to hmslasermonitor on Telegram to receive notifications on the state of the cutter. If the temperature becomes suspiciously low or high, a Telegram message is sent to subscribers. A cold temperature may mean someone forgot to close the vent, and the water cooled laser tube is in danger of freezing and breaking. A hot temperature probably doesn't mean anything. Or it's on fire. There seems to be some EMI from the motor of the vent fan, which messes with the temperature sensor.

There are various commands you can send to the bot, including one to get an update of the current vent conditions.

There's also a small LCD display on the monitor. Feel free to join the project to hook up more monitoring or activate the display. Current code for the nodeMCU is at

laser_cutter.txt · Last modified: 2019/12/11 19:15 by glassgiant