Laser-cutter-user-guide

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Shop Area: Rapid Prototyping

Tool: CO2 Laser Cutter

Requires in-person training: Yes 

Procedure Number

UG 120-02, Rev. 1

Date

1/28/2021


GENERAL

This guide is for the 100W ShenHui and 150W Boss CO2 laser cutters. 

These CO2 lasers cut leather, non-synthetic textiles, acrylic, wood, and other non-metal materials. In a CO2 laser cutter, the laser beam is created in a tube filled with CO2 gas. Next, with the help of mirrors and lenses, the laser beam is directed to the laser head and focused on the material surface. Electronically controlled motors move the laser head to cut or engrave the desired shape into the material of the workpiece. The shape is defined by an input file which can be a vector or raster image. When the laser hits the material, a very small area is heated in an extremely short period, causing the material to melt, burn or vaporize.

In general, there are two tasks that a laser cutter can perform: Cutting and Engraving.

We use LightBurn as the software for controlling the laser. The general workflow is to draw something in a program like Inkscape or FreeCAD, save the drawing as an svg or dxf file, then import the svg or dxf file into LightBurn. Lightburn is then used to control power, speed, and cutting operations before sending the job to the laser cutter. Simple designs can be created within the LighBurn software, skipping the Inkscape/FreeCAD step.

SAFETY

  • The lasering process may generate smoke and gasses that can harm you and damage the machine. Note that materials such as PVC and Vinyl create a corrosive chlorine gas and are prohibited.
  • Lasers are a fire hazard. Keep extinguishers close and NEVER leave the machine unattended.
    • All materials are flammable, don't walk away mid cut.
  • Close the lid before sending your file to the laser. The lid is not meant to be leaned on and cannot support body weight.
  • Do not lean on the honeycomb bed platform inside the machine. The honeycomb platform is not strong enough to support body weight.
  • Do not remove material from the cutting bed before it has cooled.
  • Clean up clutter, debris and flammable materials in the laser cutter after use. 
  • Do not look directly at the laser beam.
  • The high intensity laser beam can produce extremely high temperatures and significant amounts of heat as the substrate material is burned away while cutting.

REFERENCE

PROCEDURE

  • LightBurn is the software for controlling the laser.
    • Draw an item in Inkscape or FreeCAD.
    • Save the drawing as an svg or dxf file.
    • Import the svg or dxf file into LightBurn.
    • Lightburn is then used to control power, speed, and cutting operations before sending the job to the laser cutter.
  • LightBurn is setup to read dxf files in units of inches (select inches when exporting from the design program).
  • The three most important settings of the laser cutter are power, speed, and focus distance.
    • Power: Defines the output power of the laser. Typically can be set from 0 to 100% (maximum power). High power is used for cutting thick materials and lower power is used for engraving and cutting of thin materials such as paper.
    • Speed: Determines the movement speed of the laser head. For engraving and cutting of thin material, the speed is usually set (close) to the maximum (recommended max = 250mm/s).
    • Focus: The focus point (where the laser beam is thinnest) should be on the material surface or slightly below, for most applications. See panel on left side of machine and use focus gauge to adjust the distance of the laser nozzle from work piece.
  • Use a sample piece to test to get the correct power and speed settings. Start with a light cut, you can always reprint/recut multiple times over the same area with increased power as needed to get the desired cut.
    • Each type of wood is going to be slightly different. A slightly thicker sheet of Acrylic might need a slower speed and/or a higher power.
  • The laser speed determines how fast the laser will travel while cutting. The slower the speeds, the longer the laser sits in a spot, which yields more heat and the deeper the cut or engraving will be.
    • Acrylic etching - high speed, low power (easy to cut). High power has the potential to distort the acrylic.
    • Acrylic cutting - low speed and high power.
    • Anodized Aluminum etching - high speed and low power.
    • Painted Brass - high speed, low power will get rid of the paint at the cut zone.
    • Glass - medium speed, high power (experiment as there is a wide range of glass)
    • Plastic - experiment on type of plastic
    • Wood - experiment and figure out for each type of wood separately.

Materials that can be cut or engraved with a laser.

Material Cut Engrave Comment
Wood x x  
Plywood x x Lasers can struggle to cut plywood sheets with exterior glue. Use plywood with interior glue.
MDF x x  
Cork x x  
Cardboard x x  
Paper x x  
Leather x x Use vegetable-tanned for best results
Felt x x  
Cotton x x  
Acrylic (Plexiglas) x x  
Delrin (POM, acetal) x x  
High-density polyethylene (HDPE) (x) (x) Edges melt badly. Watch closely – easily catches fire.
Polypropylene (PP) x x Melts somewhat
Granite   x  
Marble   x  
Slate   x  
Stone tiles   x  
Ceramic, Porcelain   x  
Glass   x  
Stainless Steel   (x) Can be marked
Aluminum   (x) Can be marked

 

Materials that should NOT be cut or engraved with a laser.

These materials include (but are not limited to):

  • Artificial leather that contains chromium (VI)
  • Carbon fibers (Carbon)
  • Polyvinyl chloride (PVC)
  • Polyvinyl butyrale (PVB)
  • Polytetrafluoroethylenes (PTFE /Teflon)
  • Beryllium oxide
  • Any material containing halogens (fluorine, chlorine, bromine, iodine and astatine), epoxy or phenolic resins

Two different cutting techniques: “Vector” and “Raster”.

  • Vector is much more adept at cutting things out, while Raster to be used for engraving.

Vector

  • Vector is a straight line cut.
  • When cutting material with vector, there is an additional setting beyond the power and speed. The frequency setting controls how many laser pulses are applied to the piece being cut.

Raster

  • In raster mode, laser acts similar to an inkjet printer, and prints thousands of dots per inch (dpi). Depending on how dark the area you want etched is the more dpi will be needed.

Rotary Engraving

The laser cutter can perform rotary operations using the U-axis. The general procedure is as follows:

  1. Plug the rotary engraver into the inside, right wall of the laser.
  2. Navigate to Tools > Rotary Settings. Click the Enable Rotary button and set either the Object Diameter or Object Circumference to match your part's dimensions.
  3. Use ‘Start from current position’ in Lightburn
  4. Jog x and y on the control panel to move the laser to the required starting point on the work
  5. Press ‘Origin’ button on the control panel
  6. Send job (not start) from Lightburn to laser
  7. Load file from control panel by pressing File -> filename. Then run job by pressing start button on control panel.
  8. DO NOT FORGET to disable rotary when finished. Tools > Rotary Settings, deactivate Enable Rotary. Otherwise the machine will not work for the next person.

TROUBLESHOOTING

  • If your parts are dimensionally inaccurate, LightBurn is setup to read dxf files in units of inches, so make sure to select inches when exporting from your design program.
  • If regular shapes are being engraved or cut as irregular (i.e. circles are coming out as ovals), there's likely something wrong with the drive belts, probably tension
  • If laser performance is poor, the lens may need to be cleaned:
    • Ensure you have all the proper cleaning materials:
      • Lens Cleaning Paper
      • Cotton Swab
      • Liquid Lens Cleaner
    • There are two mirrors and one lens that direct the laser beam. One of the mirrors and the lens are located on the part that moves around and cuts, the other mirror is on the far right end of the arm.
    • To clean the lens, fold some Lens Cleaning Paper, do not touch whatever part of the paper you intend to clean the lens with. One or two drops of a liquid lens cleaner on the paper, and wipe the lens off. If the paper comes out dirty, get a new piece of paper and repeat the process. When the paper is no longer dirty, the lens is clean.
    • Use a cotton swab for the mirrors. Brush off your mirrors with it, and check the swab for dirt. If you see dirt repeat the wiping until no more dirt/dust comes off.
    • The mirror that's far away from the lens doesn't need to be cleaned as often, as it's not in direct line of the cloud of material smoke being created by the laser.
  • If smoke is not venting out through the back of the machine, the exhaust hose may need to be cleared:
    • At fan unit near window, remove wooden cap from Y shaped exhaust port.
    • Use provided brush to clean out exhaust port.
                                             END OF THE PROCEDURE