Laser Cutters

This page is about general laser-cutting tools and tips. For the laser cutters at the Maker Nexus makerspace in Sunnyvale, CA, see MN Laser Cutters.

What do laser cutters do?

Laser cutters used focused energy beams to literally burn away materials like paper, cardboard, plywood, leather, metal tumblers, and laser-safe acrylic. When done right, you can barely etch the surface for rasterized designs, or you can cleanly cut through the material without setting it on fire. (The art of the laser is basically controlled burning.)

Safety considerations

There are more safety considerations than what's listed here. But these are some things we have learned:

In general

• Safety should be the most important priority. Always look at the machines and the work area. Don't distract people when they are actively cutting. If something doesn't feel right, stop. If you need help, ask someone or a staff member.
• Do not walk away from an active cut. If a machine is running, stay close to it.
• Fires happen very fast. Always have the spray bottle of water near your hands, and know how to pause/cancel the job. Don't play with your phone or turn your back on the laser.
• Don't rush or work when tired. You may miss safety checks.
  • Stay hydrated
  • Stay focused
  • Plan your restroom breaks

Hazards from laser energy

You can't actually see our lasers---they use infrared light. When the machines are operating you must keep the lids down because the high energy can be harmful. (It is safe to look at the laser through the lids.) However, there is a visible locator dot created by a second laser pointer.

Hazards from fire

This section should really be named "hazards from too much fire". (Laser cutting works by setting things on fire.) It is totally expected that the material you are cutting will emit a small flame, but the flame should be extinguished almost immediately.

A fire that is allowed to burn uncontrolled risks damaging your work, destroying the machine, or putting the facility (and its people) at risk.

• If the flame doesn't go out you must put it out, even before running for help.
  • Have a water bottle in your hands at all times so you can extinguish the flames.
  • If the flames don't go out, stop the cut immediately on the control panel.
  • Failing that, grab the emergency smothering blanket and throw it over the whole bed to snuff the flames.
  • Failing that, grab the fire extinguisher, pull the pin, shoot the base of the fire (not the flame part).
  • In all cases where the flame became large, immediately contact the MOD!

Hazards from smoke

Smoke is the visible burned particles thrown into the air. Do not breathe the particles in.

• After you are done a cut, leave the lid down so the air filter can clean the chamber for a few seconds.
• Too much smoke in the chamber can coat and damage the equipment including the laser lens, the mirrors, and the motors.
• Be sure the compressed air is functioning so smoke doesn't enter the lens head.

Hazards from fumes

Fumes are the gasses you can't see. All materials when cut will emit some gasses. In a maker space such as ours we have strict rules on "bad gasses" that can cause a lot of harm to your health or the equipment.

We have air filters on the lasers, but they cannot filter out many "bad gasses" and there's only a certain amount of fumes the filters can handle at any one time.

• Never cut a material you aren't absolutely sure about.
  • Ordering cheap materials through online stores sometimes results in them sending you a material that looks like what you wanted but is actually made of things we don't allow.
  • Check the Supply Sources page for reputable suppliers
• Never cut painted materials since those plastics and pigments can release toxic gasses.
• Don't cut glue. MDF is mostly glue!
• Only cut laser-safe acrylic; other plastics can emit toxic or corrosive gasses.
• Only cut polyethylene foam you are sure is pure PE foam. Polyurethane (PU) foam will create hydrochloric acid which will eat the machine from the inside. And your lungs.

Hazards from small parts

Be careful when cutting small parts. They may not separate in the cutting process and create a fire hazard.

Hazards from shiny materials

Anything reflective can bounce the laser beam back up into the lens which will overheat and destroy the lens. Lens are hundreds of dollars.

Hazards from warping materials

Thin materials like paper may get blown around the chamber. Cardboard tends to warp and pull up.

• Tape or weight down materials so they don't move. Blue painters tape works fantastic.
• A material that tips up can get caught in the mechanism.

Hazards from the bed being too high

The laser head can literally crash into the bed rails. Be sure to focus and align the laser beams, which usually keeps a good gap off of your materials. If the head does run into the rails it can bend the mechanisms or damage the bed.

Laser over plywood with a metal weight

Hazards from non-flat materials

Anything that pokes up can catch the head. That can misalign the head or the mirrors.

• Make sure the head will cleanly pass over your material
• Watch for long pieces you cut out that might tip up to the head
• When using weights, doing a "framing pass" and place weights outside the cutting boundary. Do this more than once.

Different Machines

Laser Manufacturers list (and associated equipment) with any notes we have.

Technology

An interesting explanation of the optics involved in laser cutters.

Parallax Technology offers a collection of tips and info about laser cutting physics.

How To

• Test to determine the correct focal distance for your laser video

• A YouTube channel with a lot of videos. Specializing in board game enhancements.

• Create 2D files for laser cutting from a 3D model in STL format.

• Better engraving in wood by using Borax

• Make the design for a box with a free online tool

• A very flexible Python program to make all kinds of different boxes, hinges, the scope of what it will do is really interesting Boxes.py

Techniques

Wood Staining

Use Minwax Water Based Wood Stain to color the wood before cutting. Available everywhere, including Ace Hardware stores. They add tint just like they would with a paint. I ignore the colors in the samples on the shelf. I asked to see the colors in the tint machine, there are about a dozen. For my red, I use the red tint straight, no other colors. The stuff works great. I brush it on with a foam brush, then wipe it with a cotton rag.

Cut for Vacuum_Forming

I cut a 3 inch medallion positive to use in laser forming. I cut it out of 6mm Baltic Birch plywood. I set the 3d Stamp mode in the driver to Shoulder 45, Widening 0. This gave great relief. On the 120w laser I used 400 DPI, speed 40, power 90, Stucki, bottom up. I did two passes.

Fitting Parts to a Sheet

SVGNest

Sometimes you have a lot of irregular shapes you want to cut. Maximizing the use of a piece of material can be tough. The demo on this site is pretty cool: http://svgnest.com/   It's open souce, source found here: https://github.com/Jack000/SVGnest

I haven't tried SVGNest yet, but the sample images on his page are impressive.

Joints

Mortise and Tenon on a laser cutter

Rotating joint idea

Sudo 3D

This web site shows a technique to create nice 3D chess pieces. He cuts the front profile then a bounding box. Then he rotates the piece 90 degrees to cut the other profiles. The results are very interesting. http://imgur.com/a/Rt8kz   Thanks to Bruce for finding this.

Working with Inkscape and the Epilog Helix

The basics

• "Objects" in Inkscape can be created in several forms:

1. Object "primitives" (my term) -- the objects that you can draw using the tools on the left hand side of the Inkscape window -- these include rectangles, ovals, polygons, and text strings;
2. "Stroke" objects -- the objects that you create when using the pen tool -- either lines or Bezier curves; and
3. "Path" objects. As far as I know, you cannot create path objects directly, but you can convert other objects to paths using "Path | Object to Path" and "Path | Stroke to Path". If you use "Path | Trace Bitmap" to convert a pixel (raster) image to a vector drawing, the result is a stroke object.

• KEY CONCEPT: you MUST convert all objects that you want the Epilog laser to cut/engrave into "Path" objects.
  • Select the object and use "Path | Object to Path" or "Path | Stroke to Path", as appropriate. If you don't perform these conversions, the objects will be ignored by the laser cutter!
  • You can test that the object has been converted to a path by using the node editor tool (on the left toolbar below the select pointer). You should see a whole bunch of nodes that represent the path around the selected object. Another good test is to select "View | Display Mode | Outline" to clearly see the defined paths.
  • After converting all of your objects to paths, use "Object | Fill and Stroke" to designate vector cutting/engraving (no fill, stroke line width = 0.001") or raster engraving (fill the object with black color and no stroke or stroke greater than 0.001").

Techniques

To vector cut/engrave an object or text: place the object in the workspace. Select the object with the arrow pointer. Then: "Path | Object to Path". Next, select "Fill and Stroke" and make sure that there is no fill and that lines are solid and 0.001" wide. The difference between vector cutting and vector engraving is in the driver settings and not the Inkscape file.

To raster engrave an object or text: place the object in the workspace. Select the object with the arrow pointer. Then: "Path | Object to Path". Next, select "Fill and Stroke" and make sure that there is a solid fill and no stroke (or stroke greater than 0.001"). The depth of the raster engraving is in the driver settings and not the Inkscape file.

To align objects inside of other objects (e.g. to center vertically): Select both objects and use "Object | Align and Distribute"

To both vector engrave and vector cut within one project, select different colors for the cut objects and for the engraved objects. Make sure to note the full RGB settings for your color(s). In the Epilog driver, use the Color Mapping tab. Make sure to check the box to enable color mapping, select the color (double check that the RGB for the selected color are exactly what you set for the object in Inkscape), enter the settings and use the right arrow by the settings to transfer the settings into the color table. Each color can have different settings for the laser. The per color settings of raster/vector/both do not specify that the entire color will be rastered or vectored - that is determined by the width of the line in your Inkscape file. Any color that is not set in the color settings will use the default vector/raster settings on the main driver tab.

Settings that work well with 3 mm birch plywood are:

• Raster engraving: raster speed = 30%, raster power = 75%.

• Vector engraving: vector speed = 50%, vector power = 50%, vector frequency = 2500 Hz.

• Vector cutting: vector speed = 20%, vector power = 90%, vector frequency = 2500 Hz.

Making a box with the Inkscape TABBED BOX extension. See the document on the MN Member Google Drive, at: https://drive.google.com/file/d/1btpuTFqOBQuDYE213z-sIyOjfjcpTbVC/view?usp=sharing

Air Assist

Why do you need air blowing on the lasered area? Air assist is just a steady flow of air to blow smoke and cutting residue away from the beam path and optics of a laser cutter. It’s simple, but critical; without it, smoke can obscure and reflect the laser beam, foul lenses and mirrors, and severely degrade cut quality. An interesting test of different air sources.

Materials

Ponoko has a fun list of 10 great materials to laser.

Baltic Birch Plywood

It comes in 5x5 foot sheets 3mm (1/8th inch) for about $18. I have them cut the boards into 24 inch strips so that they fit in my car. I then cut the strips into 24x18 panels at TechShop. The price per panel is about $2.50. It also comes in 6mm sheets. These prices are from 2014 at the now defunct Southern Lumber. We've found a supplier on the web: Ocooch Hardwoods I've found that the glue in this plywood makes it harder to cut than plain wood. There are also some hidden hard spots in the plywood. I have to cut at a slower speed or else I'll have some places that do not cut through.

• Settings for 3mm 45watt: speed 8, power 90, frequency 500. If the laser is really clean then speed can go up to 12.
• Settings for 6mm

Another source for Birch Ply is Mayan Hardwoods In Paso Robles. http://www.mayanhardwood.com/ Mayan carries a full line of hardwood plywood and regular hardwood lumber by the board foot. They do not have a cutting service for sheets of plywood. They do have a chop saw to cut board down. They have the Baltic Birch in 5' X 5' sheets in both 1/8" (3 mm) and 1/4" (6 mm).
They also have Birch Plywood in 4' X 8' sheets. The 5 X 5 sheets are a much better quality than the 4 X 8 sheets.

They offer contractor prices

• Birch 1/8" 5 X 5 sheets for $17.77
• Birch 1/4" 5 X 5 sheets for $21.45

Mayan also has Oak 1/8"; and 1/4" plywood in 4' X 8' sheets.

Acrylic

Also known as Plexiglas. It comes in several thicknesses; usually specified in English units (1/8, 1/4) but actually manufactured in metric (3mm, 6mm). It is easy to laser cut with a nice finish on the cut edges. Etching also produces nice effects. While extruded is cheaper, we highly recommend cast acrylic for your projects.

Cast Acrylic

Has a paper protective layer stuck to it with rubber cement. You can etch and cut through the paper. Has a very consistent thickness across the sheet. Superior etching results. It can warp if left in the sun on the dashboard of a car.

Extruded Acrylic

Has a blue plastic protective layer. The protective layer is reported to be laser safe but etching through it may not be ideal. May have slight thickness variation across the sheet. If precise thickness is important to your design, you may want to work in smaller pieces, measuring each with calipers and adjusting your design before cutting. Goes soft at a lower temperature than cast acrylic. Is 15% cheaper than cast acrylic.

Mirrored Acrylic

Mirrored acrylic has a thin reflective layer on one side. The mirror is seen when looking through the acrylic, the other side is a dull matte finish. You cannot cut or etch mirrored acrylic with the reflective side up (towards the laser). You can, however, cut mirrored acrylic with the dull side towards the laser. You can also get some interesting effects by etching the dull side, which removed the mirrored layer from areas.

Cement

While many glues may hold acrylic for some time, by far the best option is acrylic cement. This is a very thin liquid that wicks into a joint between two pieces of acrylic and dissolves the two pieces to form a very strong molecular bond. The bond requires that the two pieces have good contact between them; the cement does not fill gaps. You should search YouTube for a video on how to use acrylic cement - it is filled with good tips.

You can also use double sided tape or other similar methods.

Cardboard

Generally safe to cut. Use weights in known open spaces to hold down against warping/cupping.

C flute corrugated, single wall

Suggested settings

• Boss Laser, Red Laser
  • Cutting
    • 65mm/sec, 45% upper power, 35% lower power

Mat board, thick pressed fiberboard

Suggested settings

• Boss Laser, Red Laser
  • Cutting
    • 65mm/sec, 35% upper power, 30% lower power

Foam

Be very careful with foam:

• Use only the foams we have tested below
• Watch for fire very carefully
• Stop immediately if unexpected smells happen
• Check with Mods the first time you cut a specific piece

Polyethylene (PE, Expanded PE)

It's one of the safer plastic foams because it's carbon with some hydrogen. It feels pretty solid.

_Remember to check the packaging. When ordering online some stores use polyurethane and polyethylene interchangeably._

Suggested settings

• Red Laser
  • 35 mm/sec, 25% power, 2 passes, max 1" thick

Polyurethane (PU)

_DO NOT CUT._ Heating it will release toxic chlorine gas and our filters can't deal with that. It feels spongy.

Sources

Tap Plastics is a well known supplier of acrylic. They will cut sheets to size while you wait. They also have a scrap bin that is often filled with cheap pieces of acrylic. The scrap bin will also have pieces of other plastics that are not laser safe. If you have a question about the material, ask their helpful staff if the piece you want to by is acrylic.

Paper

Cuts super easy on our lasers unless it's dark paper.

Plain paper

Suggested settings

• Boss Laser, Red Laser
  • Cutting
    • 65 mm/sec, 10% power

Linen/thick paper

Suggested settings

• Boss Laser, Red Laser
  • Cutting
    • 65 mm/sec, 15% upper power, 10% lower power

Worbla

Feels like plastic, but is laser cutter friendly. One side is sticky. You can heat it with a heat gun and form it like clay. Works great to make costume parts. An internet search for warbla will show a plethora of cool examples.

Worbla activates at 90 C.; I dipped in almost boiling water and was able to easily work it by hand. This is great stuff.

You can buy it at CosPlay Supplies.

You can also make your own Worbla

Supplies

Also see the general Supply Sources page.

LaserBits

http://www.laserbits.com/
I have not purchased from this company yet. Full line of engraving supplies.  They have Color fills and seals. Engrave a piece of acrylic and then use this stuff to fill the engraving with a different color.
http://www.laserbits.com/laser-supplies/laserbits-pro-color-fill-sealer.html

Marking metal and glass

Learing

Video testing different techniques

Thermark

You spray this product onto a metal or glass surface, laser it, then wash off the part that was not hit with the laser. I saw this used at TSMP on metal and the result was very good. The woman using it recommended it. I got a 6oz bottle of the spray on Thermark Laser Marking Material LMM14 Black from the manufacturers web site Thermark for $62 plus $11 shipping UPS. Not cheap. My settings: 60W laser, 600 DPI, Stucki, speed 5, power 90.  Anything with less heat left the image susceptible to scratching off.

Dry Moly Lube

(From Evil Mad Scientist web site) A can of "CRC Dry Moly Lube" sells for about $10. Clean your metal with isopropyl alcohol. Spray lube on your metal, let dry. Do this three times. They etched with 20-30% speed (laser power unspecified) which showed a big difference. Clean off the excess lube with alcohol. They say the finished image seems tough. I haven't tried this yet.

Sawmill Creek also has a riff on this technique. He used "Sprayon LU200", 2 coats from 4 inches high. 600 DPI, 3% speed and 100% power, air assist and two passes. He cleaned it by spraying with Krud Kutter and letting it sit for a few minutes.

And... one commentator says that Cermark is so easy to use (one coat, water clean up) and fast to laser that the cost of the good stuff is not significant.

Interesting Projects

Things found on the web that would be interesting to try.

Self locking joints of all kinds. Good seeds for brainstorming.

Highly detailed wood inlay. Stunning results.