Laser cutting

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Draft

1 Introduction

According to Wikipedia (March, 2017). Laser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to be used by schools, small businesses, and hobbyists. Laser cutting works by directing the output of a high-power laser most commonly through optics. The laser optics and CNC (computer numerical control) are used to direct the material or the laser beam generated.

(to be done)

In the meantime, see other articles in the Category: laser cutting

See also:

2 Typical workflow

(1) Create a 2D vector model and follow the conventions for defining objects that should be engrave and others that represent cutting lines

(2) Test the settings

(3) Engrave and cut.

3 Materials for CO2 lasers

A small CO2 laser cutter can cut or engrave a wide variety of materials, e.g. (some) plastics, wood, cardstock, textiles, cork, Delrin, Depron foam.

Never cut anything that includes chlorine. Its gas can badly damage your lungs and the machine. Without ventilation it even could kill. Other materials like ABS or HDPE can catch fire and/or melt.

Read more:

3.1 Acrylic (plexi)

Acrylic, better known as Plexiglas and also known as Plexi, or Perspex is probably the easiest material for cutting. There are two different types of Plexiglas – cast and extruded. Cast acrylic seems to work better.

It is best to place the sheet on some pieces of wood as opposed to directly putting it on the honeycomb (i.e. there will be less reflection that could cause little damages to the plexi).

  • Chemical name: PMMA, (in french): polyméthacrylate de méthyle

Cast acrylic (Plexiglas GS)

  • Presents a nicer surface
  • Cutting is more precise
  • becomes white or mat after engraving, i.e. you get a better contrast

Extruded acrylic (Plexiglas XT)

  • is cheaper
  • remains clear
  • doesn't cut as nicely and sometimes even badly.

In other words, extruded Plexiglas is cheaper but results (both for cutting and engraving) are not great.

3.2 Cardstock, cardboard and paper

All cut well and engrave well enough.

  • Cardstock is "thick paper", e.g. like birthday greeting cards.
  • Ondulated carboard a very good prototyping material, since it is free (you always can find shipping boxes that you can tear apart) and it has a similar thickness as poplar plexiglass and plywook width (i.e. about 3mm). Make sure to use less power for cutting and single pass engraving or there could be a risk of fire. In any case, ventilation should be on.
  • Thick paper that one can use with a laser or inkject printer can be engraved and cut. Cutting power should be low and engraving power rather high.

3.3 Wood

We had very nice experience with Wood from Wine boxes (7mm). Easy to cut in two passes, nowhere near as smelly as MDF or Plywood. Produces very few ashes compared to other two.

3.4 Engineered composite wood

Various variants of "engineered woods" are popular materials in education, since it they cheap and stable. However, they contains glue and other ingredients and may not cut as nicely as solid (non resinous) wood. In addition, these components may represent a health risk.

3.4.1 MDF (Medium density fiberboard)

According to Wikipedia (10/2016), “edium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure. MDF is generally denser than plywood.”

There exist variants. Again, according to Wikipedia, MDF is typically made up of 82% wood fibre, 9% urea-formaldehyde resin glue, 8% water and 1% paraffin wax and the density is typically between 500 kg/m3 and 1,000 kg/m3.

3.4.2 High-density fiberboard

High-density fiberboard (HDF), also called "hardboard" is, according to Wikipedia (10/2016) similar to particle board and medium-density fiberboard, but is denser and much stronger and harder because it is made out of exploded wood fibers that have been highly compressed. Consequently, the density of hardboard is at least 500 kg/m³ and is usually about 800–1040 kg/m³. It is used in the furniture industry and construction.

HDF works well with laser cutters

3.4.3 Plywood

Plywood (contreplaqué in French and Sperrholz in German) includes at least three rotated layers of wood. Plywood boards are cheaper to produce than wood and keep their form. However, unlike wood, it is difficult to sand plywood to make it look again once it starts aging. According to Wikipedia (10/2016), Plywood is a sheet material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another.

There exist many different types, e.g.

  • Softwood plywood, typically used for construction
  • Hardwood plywood “is made out of wood from angiosperm trees and used for demanding end uses. Hardwood plywood is characterized by its excellent strength, stiffness and resistance to creep.” (Wikipedia)
  • Aircraft (or high-strengh) plywood is usually made from mahogany and/or birch.

For laser cutting, there are three challenges:

  • Avoiding defects (e.g. hard nodes) in the inner layers
  • Cut a larger sheet in a single passage (smaller lasers like ours cannot do that) and avoid too much "burning". Good quality plywood (e.g. birch) seems to be hard to cut (much harder than wood from wine boxes or MDF)
  • dealing with (sometimes) rather toxic glue.

Usually, more layers (multi-ply) wood means better quality. According to the nervous system blog, multiple layers may include more opportunities for "bad" spots to exist and contain more glue and therefore are not more suitable for laser cutting. As result they decided to have their own three layer version built from high quality wood.

There are companies that sell plywood designed specifically for lasering.

3.5 Foams

Various foams can be cut, but tend to melt and produce somewhat toxic gases. Special safety measures must be taken (ventilation on) and the lens should be cleaned after each job. Also strictly avoid anything that includes PVC (see further below).

According to Trotec (10/2016), Foams made of polyester (PES), polyethylene (PE) or polyurethane (PUR) or Neopren® are well suited for laser cutting, laser engraving and laser marking. (in french: polyester (PES), polyéthylène (PE) ou polyuréthane (PUR) ou Neopren®)

Polyester

Polyester are mostly used for clothing, but some kinds of foams also seem to exist...

Polyurethane (PU)

Is the kind of foam that one can find in packaging and matresses. Typical brand names are: PUR, PU, Cellasto®, Elastocoat®, Elastoflex®, Elastofoam®, Elastolit®, Elastopal®, Elastopan®, Elastopor®, Lupranol®, Baydur®, Bayfill®, Bayflex®, Baylit®, Baymer®, Baytherm®, Desmodur® (according to Eurolaser)

Different densities exist (measured in kg/m3) and the material is rather cheap. E.g. on Amazon.fr 200x60x3 14kg/m3 white is 6 Euros on Amazon.fr. Denser material is a bit more expensive, e.g. 200x120x3 is 16)

Polystyrene (PS)

Foams made from Polystyrenes are mostly semi-ridid, i.e. use in architectural models or publicity. Seems to be very inflammable

Some brand names are PS, Hostyren®, Vestyron®, Styropor®, Hostapor®, Vestypor®, SMART-X®, Elmer.

For example: Elmers is sold in carft stores and online, e.g. here. Elmers foam is probably OK if you have a good ventilation system. It does not contain chlorine, see the MSDS

Polyethylene

Seems to melt a lot.

To sort out

  • Adams
  • DTFB

3.6 Cloth

Most "natural" fibers like felt, hemp or cotton cut well.

Warning there is a danger that the print head will grab some piece of floating textile and then displace the whole thing (remember 3D printing). To avoid that, make sure that the cloth is very flat, e.g. wrap it around a sheet of metal or even better tape it down with some double sided tape.

Some synthetic fibers also do well, but be very careful (in particular never use dangerous PVC/Vinyl)

Engraving is a bit more tricky. Fleece or felt jackets are probably best. For these, try 100% and 100% speed. Doing thinner materials without cutting out too much is difficult. Maybe use two passages with lower power ?

Anyhow, cutting and engraving textiles is fun, but always try first with a same or very similar material before you thread your new blue jeans...

3.7 polyvinyl chloride (PVC)

According to Wikipedia, The terms "PVC", "vinyl" and "PU" tend to be used interchangeably by retailers for clothing made from shiny plastic-coated fabrics. These fabrics usually consist of a backing woven from polyester fibers with a surface coating of shiny plastic. The plastic layer itself is typically a blend of PVC and polyurethane (PU), with 100% PVC producing a stiff fabric with a glossy shine and 100% PU producing a stretchy fabric with a silky shine. A manufacturer's label may say, for example, 67% polyester, 33% polyurethane for a fabric that contains no PVC; or 80% polyvinyl chloride, 20% polyurethane with mention of the polyester backing omitted. To add to the confusion, the plastic layer is often textured to look like leather ("leatherlook", "pleather"), as opposed to smooth ("wetlook", "patent").

  • Very dangerous. It will both damage the laser (e.g. the lens) and your lungs. You will have to particularly careful with unlabelled textiles. Do never use Vinyl sheets made for the cutting plotter.