4. Computer Controlled Cutting#

A laser cutter is a computer-controlled machine that uses a high-power laser beam to cut or engrave materials.

The LabLab has two laser cutter, the Lasersaure and the Epilog.

This laser cuter manual is a must before using one of the two machine.

Materials#

The manual will be not replicated in this documentation except some materials as I have some things to say about theses after testing them.

material	descrition	Fab Lab recommended	comment
Acrylic (PMMA/Plexiglas)	transparent	recommended	Ideal for laser cutting
Wood		recommended	Difficult to pass through. Nice to engrave.
MDF	Easy to cut and engrave. Between wood and hard cardboard	not recommended	Not recommended by the laser cuter manual, but everyone uses it anyway. A shop at proximity (Brico) sells it.

kerf#

Kerf of a laser is essentially the gap left by the laser beam after it has cut through the material. The size of the kerf is influenced by:

• The power of the laser : if the material burn due to a hight power, the kerf is whidth.
• The type and thickness of the material being cut.
• The focal parameter : some cutter, like the Epilog can calibrate itself but the Lasersaure has to be calibrated by hand.

If the kerf width is not taken into account when designing an object, they may end up slightly smaller than intended.

To measure the kerf, we can make a sample like this one and measure the height after cutting and divide it by the number of line to retrieve the average width of the kerf.

We tried on a piece of wood but the laser cuter was not powerful enough to cut it. With a piece of Acrylic, we calculated a total height of 0.9mm. Kerf = 0.9 / 11 = 0.08. The Lasersaur has a kerf of 0,3mm for MDF.

Drawing#

The laser cutter work with two types of drawing: matricial and voctorial.

• Vectorial: The laser follow the vector curves
• Matricial: Like pictures and hand drawing. The laser cutter cannot cut with matricial drawing but will engrave like a printer does.

Softwares#

Finding a good software for vector drawing was quite difficult. The majority of the vector drawing software don’t support constraint like sketching in fusion 360 or SolidWorks. It means that we can’t make “technical drawing” with theses¹ as they are made primarily for web designer. Here I will introduce some software.

• Inkscape: Visibly the default for vector drawing in the FOSS community. Inkscape supports embedding of raster graphics and allows for operations such as moving, scaling, rotating, skewing and 3D transformations. It is widely used for creating graphics such as logos, diagrams, maps, web graphics, and icons.
• Boxy SVG: Supports a wide range of SVG features, including paths, shapes, text, markers, clones, and more. It also offers a range of tools for transforming, grouping, and arranging elements, and it includes support for layers, gradients, patterns, and filters. Boxy is available in browser mac and Flatpak (linux).
• LibreOffice Draw: Editor and diagramming tool included in the LibreOffice suite. It provides capabilities to create both simple and intricate layouts for a variety of applications including technical drawings, brochures, posters, and flowcharts.
• SolveSpace: It has many of the usual capabilitys of a CAD software. It also includes constraint-based modeling capabilities, which means you can specify geometric relationships between parts in your design, such as “these two parts must always be parallel and 5mm apart”, and the software will automatically adjust the rest of the model to maintain those constraints as you edit.

drawing a 3D object#

We will desing a house in Fusion 360 and export each bodies in DFX format for laser cutting. This project has been realized for the group project of this course.

The drawing has a parameter “t” defining the thickness of the material. With this, all body of the project are made in 2D with the same thickness adjustable is accordance with the future material. Each panel has to be an independent body. When two bodies collides (interferences), the functionality “combine” can accelerate the design process of assembling parts.

Here we can see two perpendicular pannel interfering with each other. One has joins (tool bodies) and the second has none (target body). With this, parts of the project can be mounted without glue.

An extension “save dxf for laser cutting fusion 360” allow to select a face of a body and generate a .dxf file out of it.

.dxf files can be opened with Inkscape and pieces be positioned on a panel corresponding to the dimensions of the laser cutter platter.

Warning: from dxf to svg to laser, cutter can modify the scale of the drawing. Verify at each software migration that the dimensions are correct.

The final result of the project:

To be sure that the assembly work, we can go to utility tab of fusion 360 and select the interference tool. This tool allows to select bodies and verify if they are superposed in the 3D space. For example in the image above, the top part of the roof has some interferences that we can’t see easily without the tool.

If no interferences, assembling the model is pretty satisfying.

The final project:

The plexiglass is too clean to be seen in this image. The material is a pleasure to cut with the laser cutter as its edges are smooth and transparent.

There is also plenty of sites with interesting model for laser cutting. Mine come from here. This site allows to generate objects who take in account the kerf and the width of the material used.

To laser cut an object, we have to take into account the kerf so that the assembly can hold in place. The Epilog one has a kerf so thin that we can practicaly ignore it.

Here is the generated svg with exaggerated lines to better visualize it.

With Inkscape, I added a nice pattern on top. The idea is to print this matrix drawing and then cutting it.

We can see the box line under the pattern. Notice How the two have different color. The laser cutter can’t cut and engrave in color of course. But this has its importance in the next step.

Cutting the 3D box#

The practical part can be done by following the laser machine tutorial as it is a complex procedure that can’t be easily documented due to the reservation system who is pretty strict and limiting for people who want to make some experiment with a reserved machine.

Settings#

In the Epilog software, who’s accessible only on the computer of the machine, these settings where used:

• Black and blue: These are the line to cut through. It has to be en the last steps the cutting machine proceed so that the piece stay in place during the pattern engraving.
  • mode: vector
  • power: 80%
  • speed: 20%
  • frequency: 100%
• Red: the matrix pattern.
  • mode: matrix
  • speed: 50%
  • speed: 50%
  • frequency: 50%

Result#

The FabMan (the reservation system of the fablab) stoped the machine at 16h50 although the schedule allow the use of the machine until 17h. The Laser cutter had almost finished the pattern and was on the verge of cutting the box.

Analysis#

We can see that the power for the patter could have been a little higher.

files#

Here is the svg file of the box.

What I learned#

I didn’t even know what the principle of vector drawing so we can say that I knew nothing of what was discussed in this module.

Here is a list of what I learned:

• Security measure of the laser cutter
• Laser cutter manipulation
• Software to manipulate vector. (and the fact that I didn’t find technical drawing software to my tastes)
• I discovered a world of possibility and possible project to make where laser cutting can be of use.
• To estimate the power parameters of a laser cutter depending on the material.