Laser-cutter-user-guide

Shop Area: Rapid Prototyping Tool: CO2 Laser Cutter Requires in-person training: Yes

Procedure Number UG 120-02, Rev. 0

Date 8/31/20

 

GENERAL

A guide for using the130W ShenHui CO2 laser cutter. It cuts leather, cloth, wool, fur, acrylic, wood, and other non-metal materials. The bed is roughly 4 ft wide by 3 ft deep.

A CO2 laser cutter machine, 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 three tasks that a laser cutter can perform: Cutting, Engraving and Marking.

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.

 

SAFETY

• Make all machine adjustments or maintenance with the machine unplugged from the power source.
• 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.
• Lasers are a fire hazard. Keep extinguishers close and NEVER leave the machine unattended.
  • Acrylic, Wood, Paper, and Plastic are flammable, don't walk away mid cut.
• Never 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.
• When cutting reflective things, never have the reflective side facing upwards towards you and make sure you don't use too high a power.

REFERENCE

• LightBurn Video Tutorial

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 four most important settings of the laser cutter are power, speed, frequency, 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.
  • Frequency (Hz, PPI): The frequency parameter specifies the number of laser pulses per second. Frequency depends completely on the material used. For example wood cuts best at around 500 to 1000 Hz and for acrylic 5000 to 20000Hz to achieve a smooth edge.
  • Focus: The focus point (where the laser beam is thinnest) should be on the material surface or slightly below, for most applications.
• 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):

• Leather and 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.
• The frequency can be set between 10 and 5000 pulses per inch (ppi). Since these pulses are traveling along the same line as the laser, they end up creating a straight cut in which the laser is on for the entire duration.
• The higher the ppi is set, the hotter the material gets. Cutting wood use a lower the ppi. This is also useful for lessening the charred/burnt look.
• Cutting acrylic for sharp corners use a low ppi. For rounded corners, and a smooth edge, a higher ppi will help achieve that look, by melting the edge of the acrylic where the laser is cutting.

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.

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
• LightBurn is setup to read dxf files in units of inches, so make sure to select inches when exporting from your design program. Otherwise, the size of your part will likely be wrong.
• 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. Need to clean all of these after each use or the laser will not keep in good condition, and won't cut as well each consecutive time.
  • 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