Notes on Using the Laser Cutter
These notes written Friday, March 9, 2012 by Tony (email@example.com), adapted from demos / classes given by the famous Robert Rayce (firstname.lastname@example.org).
First, have your art ready. There is currently only one laser cutter at Noisebridge and it is sometimes in high demand. It can take a great deal of time to print a single image on the Laser Cutter, particularly at the High (1000dpi) setting. Email your art or image files to yourself so that you can download them to the Laser Cutter computer. Most all image formats are usable – JPEG, GIF, PNG, TIF, etc. I typically use TIF files since they are higher resolution, print quality files, whereas JPEG and GIF are less so.
The computer currently attached to the Noisebridge Laser Cutter seems to save files as MAYA type by default. The program GIMP2/GNU can be used to edit those images as necessary (it's among the desktop icons). Open your art / image files with Retina Engrave (that's the Laser Cutter software program – also on the desktop). If they don't look right you can try adjusting the settings as detailed below, or else re-open them with GIMP2 or similar image editing program (Photoshop, Illustrator, Quark, etc.) to adjust before proceeding with laser cutting.
In Retina Engrave (RE), click on File > Open at the top left to select & open your art files. They'll most likely be in Documents > Downloads unless you saved them to the Desktop or another specific directory. Be sure to change the “Type of File” to “All Files” because the default file search is .XPS, and the directory window will only show files with that extension. (This is how it was at the time these notes were taken, anyway.)
RE automatically changes color art to black & white (this is not printing, it's engraving) and resizes the image to conform to an existing template. The file size you see on screen will not necessarily be the size of the printed image. You can zoom in or out on the image to see it in greater or less detail using the Zoom buttons on the upper left. (Rayce says not to use these – they don't work. It seems to me that they work for viewing on the screen, but don't affect the final print, which will be of the entire image.) You should already know the size from working with it in your image program previously. The maximum printable area that the NB Laser Cutter can accommodate is 9.5” high by 15” wide. It is advisable to keep your image slightly smaller than the maximum: a safe threshold for maximum image size is 8.5” or 9 “ high and no more than 14” wide.
There are two main Laser Cutter settings, depending on the type of image or engraving you're making: Raster (lighter, for general etching & engraving of images) and Vector (deeper cutting, more heavy duty - makes a stencil). They are the inverse of each other. The parts Raster etches away are the parts left by the Vector, and vice versa. (Unless I misunderstand this....)
Use the Trim button to crop the image, getting rid of white space or other empty areas of the image not necessary for the final product.
Adjust the Speed as you desire – Rayce says slower speed and less intensity is generally advisable for higher quality.
Threshold is like Contrast. Play around with it until your image looks the best to you.
Clicking Invert will make a photo-negative of your image: white areas turned to black and vice versa, as in Gimp and other image editing programs.
Be careful with the Quality setting as this will affect the time it takes to Laser Cut your image. High (1000dpi) can take a very long time – the better part of an hour to engrave a single large image. You would use this setting for intricate artwork, small text, anything where fine detail & clarity are key. Medium (500dpi) will work for average images, and Low (250dpi) ought to be fine for simpler artwork such as logos consisting of large letters, basic geometric shapes, that sort of thing.
Alan thinks that anything over 250 DPI is just wasting time and does not add to the quality or precision of the final piece.
The Jog controls on the upper right in the RE display control the movement of the cutter. They are like the Spacebar, Return, and Arrow keys on a keyboard, with the cutter being like the cursor on a computer screen. It's OK to use the Jog functions when the Laser Cutter lid is open, but don't ever activate the laser at such a time, or you can hurt yourself. This is a laser, and it cuts.
Open the lid of the Laser Cutter and place a piece of paper or other disposable material on the honeycomb platform for testing. Always leave a margin of at least one inch on the left side of the platform, otherwise the Laser Cutter can go offline or damage itself – you'll hear a loud ugly noise if this happens, warning you.
Now look at the knobs and controls on the right hand top of the Laser Cutter. The Current Regulator is the one you will use most during cutting. The Ampere Meter measures the current. It should never go above 15 millamps; doing so is equivalent to going “into the red” when recording music, and in this case, you don't want to be Iggy & the Stooges. Prior to printing, test by simultaneously pressing both the green buttons below the Ampere Meter and Current Regulator knob. The current won't engage unless both are pressed at the same time. Once engaged, the Ampere Meter should automatically jump up to a point between 0 and 15 millamps; this is the amount you should try to keep it at during cutting. It varies somewhat from image to image. Pay attention and adjust the Current Regulator as necessary during cutting, trying to stick close to the indicated level – 5 millamps is a typical amount.
Whenever you switch substrates (the material you engrave on, whether it be paper, mat board, plexiglass, wood, or anything else), it is necessary to focus the laser using the [ name of square-shaped metal thing ] and focus lever beneath the Laser Cutter. This lever lowers the cutting platform when turned to the Left, raises it when turned to the Right.
Be sure to check with Rayce or another knowledgeable Noisebridger if you aren't sure that a particular material is safe to print on. We want to use materials that are ROHS compliant - i.e. environmentally safe. Some materials can contain toxic compounds like lead, halogen, etc that should not be used in this way. There should be crates or bins near the Laser Cutter, very obvious to the eye, containing paper, wood, plastic and other scrap materials ready for use with the Laser Cutter. More technical info on this topic is available.
Attend the Laser Cutter during use to ensure safety - it's possible for the laser to ignite materials and cause a fire!
Be sure to do a test print, if not several, when you are first acquainting yourself with the use of the Laser Cutter. Play around with the Current Regulator knob during cutting, turning it all the way to the left in order to reduce cutting to zero (no mark on the surface of your printing substrate), then increasing it by turning to the right (but not past 15 millamps!) for maximum penetration. If you are printing on a single sheet of paper or other thin substrate, the high current level will cut straight through, creating a stencil type image.
On the computer screen, in the Retina Engrave window, use Go and Cancel to start or stop the Laser Cutter.
The section below is in progress / draft form:
You can create etched images from which to make prints, if you have a flatbed roller press. Coat the etched image with ink, scrape off excess, leaving the etched areas filled with ink which will then be printed (via the force applied by the print rollers) onto printmaking paper or other material of your choice. This is similar to the process used for linoleum block printing, copper plate etching, and other traditional printmaking techniques.