Principles and technology of laser cutting

The way the laser cutter machine works is as follows: a tool moves along axes (XYZ) to cut, mark or engrave 2D shapes in a previously chosen flat material.

In this case, the Z-axis is only used to focus the laser on the chosen material and this is done before the work starts (we will see this later). The laser cutter only operates along two axes (XY) and therefore only in 2D and only on flat material.

For your information, laser means light amplification by stimulated emission of radiation. Hidden at the back of the machine, a laser tube emits a powerful laser beam. A series of mirrors directs the beam vertically downwards through the tool head and focused through a lens onto the surface of the material which melts or burns. This material extraction cuts, marks or engraves your material according to your design and the predefined settings.

A laser cutter project starts with a 2D vector drawing. These drawing is then converted by computer aided manufacturing (CAM) software. This generates toolpaths which are a compilation of commands and XY coordinates. This allows the machine tool to be moved and operated to make your object as desired.

CAM software is often linked to the machine, as it contains machine-specific parameters: tool type and properties, predefined parameters for available materials, etc.

Why & when to use laser cutting

(Source: https://www.stephencoorlas.com)
A fluid shape cut and fabricated using a three-dimensional grid of laser cut plywood shapes

(Source: https://makezine.com/)
Laser cut and CNC Panel Joinery Notebook.

And more :

• Curved laser bent wood
• Joints for lasercut assemblies
• Makercase

How it works

As we have seen in the 2D Design unit, designs must be drawn in vector format, raster images must be vectorised to be processed.

The extension of your file depends on the CAM software of the machine you are working with. You may need to export your design in the desired format.

To cut, engrave or mark material with the laser cutter, the material must be flat. Then, the two factors to be taken into account are the thickness and the nature of the material.

For engraving and marking, the only restriction on thickness is that the material must fit into the machine. But for cutting, laser technology does not allow more than 1 cm depending on the material. Tests must be performed beforehand.

As the laser burns the material, any material that produces toxic fumes should be avoided.

The materials commonly used with a laser cutter are:

• Plywood

• Cardboard

• Acrylic

• Leather

• Textiles

• Biomaterials

The following materials should be avoided as they produce toxic fumes and/or can damage the machine:

• Leather that contains chromium (VI)

• Carbon fibers (Carbon)

• Polyvinyl chloride (PVC)

• Polyvinyl butyrale (PVB)

• Polytetrafluorethylenes (PTFE/Teflon)

• Berylium oxide

• Any materials containing halogens (fluorine, chlorine, bromine, iodine and astatine), epoxy or phenolic resins

Depending on the chosen material —its properties and thickness— three main settings have to be set:

• Power and speed: These two go hand in hand. The laser needs to work at the right power and speed so that it can cut, mark or engrave as desired without over-burning the material. Depending on the model of your laser cutter, you will find settings online or supplied with your machine according to the material you are working with. Most fablab or makerspace have their reference settings as well. It is however necessary to test these settings on your material beforehand via a small cut, mark or engraving on a corner of your material. To adjust your settings, it is always better to lower the speed before increasing your power. Good settings are those that mark, engrave or cut as desired without over-burning / destroying the material.

  It is possible to work with different settings in the same design. It is for example possible to cut a shape and engrave a text on the same file. You just need to choose different settings for different actions. You can assign these different settings to different colours / layers and assign these colours / layers to different elements in your design.

• Focus: The gap between the material and the laser head must be set to the correct distance (depending on the machine) so that the laser lens is in focus. Otherwise the laser will not be accurate and its settings will be wrong. These will mean that your work will either not be cut through, or not marked enough if the laser is too high or it will be burnt too much if the laser is too low. If it is set too low, flames may appear and a fire hazard may arise. So be attentive!

The laser cutter is an extractive machine, which means that it removes material by burning or melting your material to create the desired shapes.

The kerf is the width of the material removed by a cutting process, as if it were a saw cut. The laser always burns a part of the material when it cuts it. It varies from 0.08 mm to 1 mm depending on the material.

The notion of the kerf is very important to take into account when doing precision work. Without considering the kerf you will get wrong measurements.

This involves adjusting the dimensions of your design so that they have the desired final dimensions when cut.

Now that we have an overview of the principles and possibilities of laser cutting, let’s go back to the case study we started to analyse in the 2D Design unit. This will be useful for understanding and demonstrating the practical exercise that follows.

So Tattie Toys is a bioplastic fossil making kit for children that raises awareness about the plastic waste issue. We chose this case study from the Distributed Design PlatformTalents because it uses different ways of using 2D design through illustration design, typography and layout to create different tools such as moulds, cards and packaging. We particularly appreciate the fact that designer Daniel Lockhart has used different materials and different techniques for cutting and engraving these materials with the laser cutter to produce a simple but elegant maker project with educational value.

Through this case study we will analyse how to use the laser cutter in different ways to create the set of cards or signs that you have designed as part as your practical exercise of the 2D Design unit.

When you have several actions in the same design, as in this case, it is important to run the engraving and/or marking actions first before the cutting action. This is because cutting will detach the part from your material and it may then move slightly out of position. This means that if you engrave or mark after instead of before cutting, the marking or engraving may not be in the right place. The same logic is to apply with the inside cut and the outside cut.

So for example here in the wood board we will define as a first action the engraving of the text in the bottom left, then the cutting of the inside shape of the dinosaures and finally the outside cut of the cards themselves. We then have 3 layers / colours to apply in our design in the CAM software of the laser cutter. Let’s say yellow for the texts, red for the dinosaures and blue for the cards. However, the cutting parameters for blue and red will be the same.

(Source: https://distributeddesign.eu/)

What is interesting in this case study is that Lockhart has created a layout design that you can overlay. The layout work is also done in 3D. He plays with the different materialities of the surfaces chosen to make his boards. He has used plywood for the illustrations and cardboard for the informations. In your 2D designs, you can already think about the superposition of elements that will bring relief when you will assemble the different elements fabricated.

If you work with text, it is important to vectorise it when you are satisfied with your design. This is because only vectorised text can be seen as points and lines and therefore used on a fabrication machine.

The first square is cut, the next two squares are marked and the last 3 squares are engraved. The different settings used are listed underneath.

In this case, the text seems to have been engraved on the cardboard while the little pictogram on the top right has been marked.

What is interesting about this case study is that Lockhart has created cards that play with different materials and levels. He has simply layered different elements to give them more texture and elegance. He has used plywood for the illustrations and cardboard for the informations. We invite you to play with different materials to explore the laser cutting technique from different perspective but also to give your object a more sophisticated look.

(Source: https://www.instagram.com/danlockhart.design/)