Computer-controlled cutting

So in Our Group we look at our two different lasercutter. The GS System (150 Watt) and the Epilog Zing (50 Watt).

Safety check

But first of all it is important that everything works at the lasercutter and there is a fire extinguisher nearby.

Always make sure that the air filter is operational

Make yourself familiar with the emergency stop button

Check if the laser is in focus

GS System 150 Watt

Focus test

We made a focus test for the GS System lasercutter because in the past we were not quite sure how well its auto-focus works.

We came across a really good tutorial from Lisa Schilling from the Kamp Lintfort FabLab Click here for Lisa Schilling’s lasercutter tests

At first, we made a cut using auto-focus and placed some poplar wood at an angle, then performed a laser cut from one position along a long line.

Next, we checked which part of the line came out the best. We moved the laser to that position and measured it. By the way, the perfect position was not the auto-focus; the optimal position was at 34.4 mm.

Then we placed the poplar wood on the base and performed a normal auto-focus cut. Afterward, we cut a line at the new distance, and finally, we cut another line using the acrylic cube distance (a 10 mm offset).

We discovered that the laser cutter did not have the correct distance with either the auto-focus or the distance cube so we manually adjusted the focus to 34.4 mm.

Engrave and Cut

For the GS System 150-watt lasercutter, we created a DXF file to test the speed (mm/s) and power (%).

This allowed us to determine the best speed for the laser cutter. Our instructor informed us that the laser cutter speed must stay below 300 mm/s because, if it went any faster, the machine would vibrate too much, which can cause the sensor to shift into an incorrect position.

Before learning this, we had already noticed that the sensors sometimes causes issues when cutting at high speeds. This insight was an important lesson for us.

Usually, we worked with RDWorks, but there weren’t enough colors for the different settings. So, we switched to LightBurn. This is an open-source laser cutter settings software.

LightBurn offers 29 different colors. This is not enough for a single cutting process, but we divided it into five cutting steps: three for the settings test and two for text engraving and board cutting.

We also intentionally tested the power at slightly higher levels to understand potential dangers for future use.

Through this experiment, I learned that maximum power and speed are not always necessary. Instead, conducting proper tests allows us to find the optimal settings for safe and precise laser cutting.

Kerf

In order to determine the kerf for our later cuts this week, we designed a simple test file in Fusion360. This basically consists of just five cutouts, each of which has a width of 1, 2, 3, 4 and 5 mm in the design. In the interests of minimalism, I did not engrave the respective laser cutter when creating the file. Kerstin created this for the GS laser in LightBurn when transferring the file.

After cutting out the test file, we measured the cutouts with the caliper, as shown in the example in the picture. The kerf did not deviate significantly regardless of the width used and ranged between 0.26 and 0.28 mm, with the caliper having a measurement deviation of +- 0.03 mm.

Joints

Inspired by the joints presented by Neil, I created four different connections, for which I also used Fusion360. Because the joints showed different problems, I actually did the whole thing twice. Starting from the left with the designs shown below, I will go into the error images.

The typical finger joint works well, but was not yet adapted to the kerf. This problem existed with all joints, which is why I ended up making them twice. With the second joint, the chamfer joint, I made a mistake with the depth of the cut the first time, so the parts could be pushed further into each other than originally planned.

The third joint was much more complicated and at the same time deviated from the joints presented - the inspiration for this came from the following document:

There it is called a rotary snap-fit joint. The missing dimensions were complicated because I only recreated the connection based on a photo. As you can see better in the photo below, only a thin strip of material remains in the middle of the round cutout. In the first draft, I created an offset for this, i.e. a material width of 1 mm. Unfortunately, the connection broke there when plugging it in. With 1.5 mm, it held on the second attempt. A very cool connection, different to the other two for a connection on a surface. Still very delicate, and I wouldn’t want to subject it to great stress unless you experiment a lot with both the standing strip of material and the bevel of the plug.

The fourth connection works like the previous one as a connection on a surface. In contrast to the previous connection, I would consider it to be stronger, but here too you should experiment with the width of the two pins on the plug side. Here you have to find a good mix of flexibility and stability in each individual case. Nonetheless, it is a cool connection that sometimes clicks nicely - without the wood breaking. In the first attempt I also created a width of 2 mm here, but here the clicking when plugging together worried me because it sounded more like a cracking noise. So in the second attempt it became 3 mm. All connections work, have fun trying them out!

Finger

snap

press fit

Epilog Zing 50W

The laser cutter available in our lab is the Epilog Zing 50W, a high-precision CO₂ laser system that allows for both engraving and cutting on a variety of materials. Below are its specifications:

• Workspace: 610 x 305 mm
• Engraving Speed: 14.45 min (varies based on material and settings)
• Resolution: Adjustable from 150 dpi to 1000 dpi

To work with the machine you need to turn it and its ventilation on. You can find the button at the lower part of the laser cutter. For the airflow you can find this small manometer with a small handle mounted at the wall.

To operate it, you can use one of the computers you see next to the machine. Just open your file in Inkscape and press the button Open in VisiCut, to open the software for the settings of the parameter. When you’re done with your setting you can send your file to the laser cutter and start your job.

But don’t forget to set the focus depending on your material strength! You can find the focus button on the panel at the right. Press focus and raise or lower the bed by pressing the arrows up or down depending on the material strength.

Once you have set the correct distance between the pendulum and the material it should look like in this video:

Engravable Materials

The laser cutter is capable of engraving a wide range of materials, including:
- Stainless steel (with marking spray)
- Laminate-based plastics
- Acrylic/Plexiglass
- Painted metals
- Anodized aluminum
- Wood, plywood, MDF, and veneer - Leather, rubber, and cork
- Paper, cardboard, and paperboard
- Fabrics and textiles
- Organic materials such as food (e.g., apples or bananas)

Cuttable Materials

While some materials can be engraved but not cut, the following materials can be precisely cut using our laser cutter:
- Laminate-based plastics
- Acrylic/Plexiglass
- Wood, plywood, MDF, and veneer
- Paper, cardboard, and paperboard - Cork
- Thin foils
- Leather and rubber
- Fabrics and textiles

Power and Speed

Power refers to the amount of laser energy delivered to the material, typically adjustable from 0% to 100%. Higher power settings result in deeper cuts or engravings but can cause charring or excessive melting if not properly managed.

Speed determines how quickly the laser head moves across the material. Slower speeds increase exposure time, leading to deeper cuts, while faster speeds result in shallower cuts or surface markings.

Balancing Power and Speed: The interplay between power and speed is crucial. For instance, cutting thicker materials may require high power combined with slower speeds to ensure a complete cut. Conversely, engraving delicate patterns on sensitive materials might necessitate lower power and higher speeds to prevent damage.

For our tests, we used 3mm plywood and used fields with the different parameters for Cut Speed and Cut Power.

Here you can see our template, that we adjusted for our laser cutter.

Here you can see the different colors in visicut that belong to different settings of the cut power, cut speed, engraving speed and engraving power.

On the bottom of our test card we have demonstrated the different values for engrave speed and engrave power.

From our laser cutter test card, we can clearly observe the impact of power and speed settings on both cutting and engraving results.

In the cutting section of the test card, we can see how different combinations of cut power and cut speed affect the ability of the laser to penetrate the 3mm plywood. Higher power levels combined with lower speed settings result in cleaner, more defined cuts, while lower power or higher speed settings leave incomplete or shallow cuts. The burn marks around the cut holes also indicate that excessive power at lower speeds leads to charring, which might require post-processing like sanding or cleaning.

In the engraving section, the differences between engrave power and engrave speed are particularly noticeable. Higher power settings produce darker and deeper engravings, while lower power results in lighter surface markings. Additionally, at lower speeds, the laser has more time to burn into the material, causing deeper and darker engravings, whereas at higher speeds, the engraving appears lighter and more subtle. In our test, this is especially evident in the middle row, where excessive heat buildup at certain power levels resulted in overburning and uneven coloration.

Frequency

Frequency pertains to the number of laser pulses emitted per second, measured in Hertz (Hz). In vector cutting mode, adjusting the frequency influences the smoothness and quality of the cut:

• High Frequency: Produces a continuous cut with smoother edges but can generate more heat, potentially causing charring on materials like wood.
• Low Frequency: Results in a series of closely spaced pulses, which can be beneficial for cutting heat-sensitive materials by reducing thermal accumulation.

The frequency range goes from 0 - 5000Hz. For the illustration, we worked with 2%, 10%, 20%, 50% and 100% of the frequency (which is 100, 500, 1000, 2500 and 5000 Hz) and used a power / speed of 70 / 30 and 30 / 70. You can see from the result that the row with power 70 was cut completely. On the row with the lower thickness of 30, you can see that the cut lines are perforated and the material has therefore remained in place and has not been completely cut out.

Kerf

Kerf is the width of material removed by the laser beam during cutting. It is influenced by factors such as laser power, cutting speed, material type, and focus. Accurately accounting for kerf is essential for designing parts that fit together precisely, especially in press-fit assemblies.

From our measurements, you can see, that the kerf lies between 0.09 and 0.17mm. This means that this value would have to be subtracted when designing a press-fit kit in order to produce accurately fitting parts, as this part is removed during the laser cutter’s cutting process.