Week 3 - Computer-Controlled Cutting
Published on: February 11, 2025
This week, we are exploring computer-controlled cutting using a laser cutter and a vinyl cutter. The focus is on understanding how digital designs can be precisely cut into different materials.
In the group assignment, we go through safety training and test different laser cutter settings, such as focus, power, speed, and kerf, to understand how they affect the final result.
For the individual assignment, we create a parametric construction kit, which allows us to design interlocking pieces that fit together without glue. We also get hands-on experience with the vinyl cutter, cutting out custom designs.
By the end of the week, we will have a better understanding of how to prepare files for cutting, how material properties influence the cutting process, and how to create precise and functional designs.
Parametric Construction Kit
This part of the assignment is the design of a parametric construction kit designed for laser cutting or CNC milling, allowing for modular and tool-free assembly. The design consists of interlocking vertical panels that fit precisely into slots in a circular base plate, enabling various configurations and heights. The use of parametric constraints in Fusion 360 ensures that the kit remains flexible, allowing adjustments to dimensions such as slot width, amount of slots, panel height, material strength and kerf without requiring a complete redesign.
1. Designing the Base Plate
The first step in creating the construction kit was to design the base plate, which serves as the foundation for the interlocking vertical panels. To begin, a new sketch was created on the XY-plane, where the overall shape of the base was defined as a circle with a diameter parameter (diameter_bottom). This parameter allows the base size to be easily modified at any stage of the design process.
Once the base shape was set, slots for the vertical panels were added. The slot was assigned a slot width parameter (slot_width) to ensure that the vertical panels would fit snugly, and a slot depth parameter (material_strength - kerf) to determine how deep each panel would sit in the base.
To distribute the slots evenly around the circular base, the "Circular Pattern" tool was used with the parameter "amount_of_slots", making it easy to modify the number of slots if needed.
With the slot pattern complete, the sketch was finished and negatively extruded to the defined thickness parameter (material_strength), which was set based on the material intended for fabrication (initially to 3mm). The use of parameters ensured that any changes to the material thickness could be applied instantly to all related components and the cut-outs for the slots.
2. Creating the Interlocking Vertical Panels
Once the base plate was finalized, the next step was to design the vertical panels that would fit into the slots. First a side profile was created in a new sketch on the XZ-plane. To ensure that the base and vertical panels would fit perfectly together, the slot geometry from the base plate was projected into the new sketch using the "Project" (P) tool.
Extruding and Expanding the Slots
Next, I extruded the slots and widened them at the top of the plate. To create a curved and visually appealing effect, I used an arc and set its height to the parameter plate_distance. After that, I modeled the counterpart with the corresponding dimensions of the slots.
The Circular Pattern tool was again used to arrange the columns according to the slot positions.
Designing the Upper Plate
Next, I constructed the upper plate in the same way as the lower one but assigned a different parameter for its diameter, giving it a larger value.
Just like the lower plate, I extruded the upper plate and drew the slots, arranging them using the Circular Pattern tool.
After this step, the model looked like this:
Parametric Adjustability and Expandability
One of the key requirements for the parametric construction kit was that it should be adaptable and expandable in multiple ways. This was achieved by designing the model with an even number of slots, allowing half of the columns to be mounted upwards and the other half downwards.
To visualize this, I mirrored the upper part in Fusion 360 to demonstrate its feasibility.
As shown in the following images, the design allows for adjustments such as the number of slots, the diameters of the plates, and the distance between the plates.
Fabrication of the Parametric Construction Kit
Preparing the Model for Laser Cutting
To manufacture the model, I adjusted the parameters accordingly and exported the individual sketches as DXF files.
Setting Up the Laser Cutter
Since we were advised to use cardboard, I placed a large piece of cardboard into our 150W GS Laser Cutter and opened the DXF files in the laser cutter's software.
Before starting the cut, the Autofocus needed to be set on the laser cutter. Using the Origin and Frame functions, I adjusted the position of the design to fit correctly on the material.
Laser Cutting the Parts
After determining the appropriate settings for the cardboard (Speed: 26, Power: 50), I arranged the pieces efficiently and started the cutting process.
Laser Cutting Video
Here is a video of the laser cutter in action. I explained how I compressed the video in Assignment 2.
Assembling the Parts
Once all parts were cut, the exciting part began – assembling the pieces and checking if everything fit together properly.
Successful Assembly
Relief! The pieces fit together perfectly without any issues. The small cardboard table was even strong enough to support objects.
Final Thoughts
I was extremely happy that my first attempt worked flawlessly. Seeing my own 3D design turn into a real, tangible object was a truly rewarding experience.
Downloads
Vinyl Cutting
This part of the assignment focuses on using a vinyl cutter to create custom designs. The process involves selecting an image, converting it into a vector format, and preparing it for cutting. Vinyl cutting is useful for making stickers, labels, or custom t-shirt or hoodie-designs.
1. Selecting and Preparing the Design
The first step in the vinyl cutting process is selecting a design. I chose an image that I wanted to cut and downloaded the file. Once the image was ready, I opened Inkscape by pressing Ctrl + O and selecting my file.
2. Converting the Image to a Vector Graphic
Since vinyl cutters require vector files, the next step was to convert the image into a vector format. In Inkscape, I used the "Trace Bitmap" function to generate a vector graphic from the image. This step is crucial because it transforms the pixel-based image into a scalable vector file that the cutter can follow precisely.
After tracing, I removed the original non-vectorized image. A quick tip to distinguish between the two: the non-vectorized version typically has more white space around it. Deleting the original image ensures that only the clean vector graphic remains in the file.
3. Saving the File in SVG Format
Once I had the vectorized version of my design, I saved the file in .svg format. This format is widely compatible with vinyl cutting software and preserves all necessary vector information.
4. Preparing for Cutting
With the SVG file ready, I imported it into the vinyl cutter software (Cricut). At this stage, I adjusted the cutting settings, including blade pressure and speed, depending on the type of vinyl. Usually we use the settings "Every-Day Iron On" for foil used for t-shirts or vinyl for stickers.
The design was imported into the Cricut Design Space software, where it was prepared for cutting.
The design was resized and positioned correctly on the virtual cutting mat within the Cricut software.
The correct material type was selected, ensuring the blade pressure and speed settings matched the chosen vinyl.
The vinyl sheet was placed onto the cutting mat and loaded into the Cricut machine.
The cutting process was started, with the machine precisely following the vector paths.
After the cutting was complete, the excess vinyl was carefully removed (weeding process).
Transfer tape was applied to lift the vinyl design from the backing for easy application.
The vinyl design was applied to the final surface, completing the cutting and transfer process.
Group Assignment
Characterizing Our Laser Cutter
Safety Training
Before using the laser cutter, all team members completed the required safety training for our lab. This training covered important aspects such as fire prevention, proper ventilation, handling of materials, and emergency procedures. A key takeaway was the importance of always monitoring the machine while it is operating, as well as understanding material safety to prevent hazardous fumes from materials such as PVC. A more detailed description can be found at the designated part of the group assignment.
Overview of the Epilog Zing 50W
The laser cutter available in our lab is the Epilog Zing 50W, a high-precision COâ‚‚ 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. The power button of the Airflow Control is located at the lower part of the laser cutter and the power button in the right side.
For airflow control, there is a small manometer with a handle mounted on the wall.
To operate the machine, use one of the computers next to it. Open your file in Inkscape and press the "Open in VisiCut" button to adjust the laser settings.
When you're done with your settings 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.
Before starting the job, set the correct focus based on material thickness using the panel buttons.
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
- 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.
And here are the different settings visualized in VisiCut:
The engraving section shows the impact of various power and speed settings. 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.