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Week 3 : Computer-controlled cutting

Computer Aided Manufacturing (CAM) are technologies that uses softwares (see week 2) to control machines, such as laser and vinyl cutter, to automatically manufacture parts based on digital design.

Week 3 assignment could be categorized as follows:

  • Group assignment (including health and safety, and machine specification)

    • Laser cutter tolerance test
    • Image and video sharing to the group repository

  • Individual assignment

    • Laser cutter press-fit construction kit
    • Vinyl cutter design

Group assignment

Laser cutters were highlighted during the start of the week as a powerful tool that can easily catch fire if not used safely. A code of practice is in place at the makerspace and its content is summarised below :

  • Training and qualifications : Only authorized users may operate the laser cutter; new users must be supervised
  • Personal protective equipment : Wear safe clothing
  • Preparations and operating rules : Never leave the machine unattended while running and ensure everything is working properly before starting the work at the laser cutter
  • Emergencies : Familiarise with the emergency stop button. Use fire extinguisher if condition is deemed safe, else evacuate
  • Cleaning up after operation : Everything should be switched off and cleaned for the next work
  • Reporting and maintenance : Report any unsual behaviours to the makerspace's administrator

Smoke and fumes

During the cutting process, if excessive smokes could be seen, then exhaust is not working properly. After cutting, do not remove the materials immediately. Wait at least 2 minutes to allow smoke and toxic fumes to dissipate before handling the pieces.

The CMA 1610 laser cutter by Yueming is available at the makerspace. The detailed specification of the machine could be found in their website under products and then the CMA series - process to turn it on and a summary of its specification is shown next :

Turn on cooling system so that the laser cutter doesn't overheat.

Turn on exhaust management system so that it filters and removes the fume.

Turn on the laser button, else the nozzle will move without the laser.

  • Type : CO₂ laser cutter and so longer wavelength (10 μm) than other machines, thus its energy is not well absorbed by metals (i.e. not suitable to cut). Suitable for non-metal materials such as wood and acrylic. Suit
  • Focus : No details were found in the available specification sheet. This could possibly be due to translation issues, as the original document is in Mandarin. It is worth to note that materials that are available here are 3mm basswood and 3mm acrylic and several tests have been carried out in the past. An experimental data reference sheet (i.e. setting of laser power, strength percentage, speed, and expected result) could be seen further below.
  • Laser power : 30-150 W
  • Cutting speed : 0-36000 mm/min or 600 mm/s
  • Cutting thickness : 0-25 mm (depending on material)

Once a CAD model is finalized, it can be further adjusted for cutting using the machine’s software, SmartCarve 43. More documentation on it could be seen at the individual assignment section.

Laser cutter tolerance test

The width of material removed by the laser beam during cutting is basically the kerf. If the kerf is determined to be 0.1 mm and a user wants to obtain 3 mm, then an adjustment of 3.1 mm (i.e. 3 mm + 0.1 mm) at the CAD needs to be made for a single line.

The comb test with slot gaps ranging from 2.5 mm to 3.2 mm in 0.1 mm increments was designed to test the fit with the 3 mm basswood. It was then exported and cut on the laser cutter using a single fixed setting, with power ranging from 75% (minimum) to 95% (maximum) and a cutting speed of 20 mm/s. Results could be seen here :

The design dimensions are shown above and the actual measured widths are recorded. The kerf is determined by calculating the difference between the two, average of it (mean and median appears to give similar numbers, and so confirming the accuracy), and dividing by 2, since material is removed from both sides (i.e. focus is amount of material removed from 1 side). This results in a kerf of 0.11 mm.

Slot (from left to right) Original (mm) Actual (mm) Difference (mm)
1 2.5 2.63 0.13
2 2.6 2.80 0.20
3 2.7 2.87 0.17
4 2.8 3.01 0.21
5 2.9 3.19 0.29
6 3.0 3.32 0.32
7 3.1 3.37 0.27
8 3.2 3.43 0.23
Average difference 0.22
Average kerf (average difference / 2) 0.11

Additional visual documentations of the group work could be found at the following links and the next section describes the details of the process.

Image and video sharing to the group repository

The goal of this exercise is to upload pictures and videos from the group work to the makerspace's GitLab repository. Users need to navigate to the repository of interest, click the fork button, and change the project url to determine where the fork should be stored. That repo could then be cloned to be edited locally.

Fork vs Clone

A fork is created to provide a personal copy of the repository on GitLab. Forks are used when changes are intended to be made and later submitted back to the original repository through a merge request. This approach is recommended when collaborating on group projects.

A clone is performed to copy a repository (either the fork or the original) to a local machine for development. Cloning by itself does not permit changes to be pushed to the original repository unless write access has been granted.

Summary: A fork should be created first if contributions are intended, followed by cloning the fork to a local machine for development.

A simple analogy: A repo is a cookbook, a fork is a copy of the cookbook, cloning is taking the copy home to actually cook from it.

Source: ChatGPT by OpenAI, February 2026

The group website is built using Docusaurus, which is similar to MkDocs with perhaps more interactive features ; and so similarly, to run and develop website locally, Node.js, npm, and Yarn (a package manager analogous to miniconda ) are required which is built based on JavaScript. Installation documentations are readily available online. The "live preview" or "mkdocs serve" equivalent is :

yarn start

Using the image and video compression techniques applied in week 2, the files are then ready to be "uploaded" by a merge/pull request (push request by user, but pull based on the perspective of the reviewer) which will then be reviewed by the Gitlab repository administrator.

Once the administrator approves the request, the status should change from "Open" to "Merged".

Individual assignment

This section builds upon the laser cutter tolerance test through the development of a personal press-fit construction kit. In addition, a design created using the vinyl cutter is presented.

Laser cutter press-fit construction kit

Some joint types were presented during the introduction call, including press-fit, chamfer, and snap-fit. Therefore rather than focusing on specific design, the exercise conducted here explores how these joints perform in practice. The components were designed with the combination of the parametric spreadsheet - including the kerf determined from the group laser cutter tolerance test - and constraint features in FreeCAD.

Where :

  • Slot

    • length: The length/width of the slot used for a press-fit connection, excluding chamfers or rounded snap features.
    • lengthsnap: The length/width of the slot including the snap-fit feature. If lengthsnap equals to length then the snap-fit feature could block the insert of the mating part.
    • height: Height of the slot — how far the mating part inserts into the material.

  • Joint

    • distance to slot : The minimum linear distance between the edge of the slot and another specified edge (e.g., the outer material edge or another slot).

  • Material (basswood 3 mm in this case)

    • thickness: Thickness of the material.
    • averagekerf × 2: Average kerf multiplied by two.
    • averagekerf: The average width of material removed by the laser cutting process, based on the settings used in the laser cutter tolerance test.

  • Chamfer

    • diameter: The diameter of the circular feature used to create the chamfer.

No joint clearance or intentional gap added to the design and so the fit should be exact or potentially tight.

The images below provide a visual context of the results. There were three attempts in total and the piece illustrates the incorrect scaling (from deepnest), correct scaling but wrong height from the original design itself, while the piece on the right shows the final version version.

Since measurements in millimeters were used, labelling the different joint types with text was added to facilitate easier identification. This also served to test the laser cutter’s engraving feature.

However, in FreeCAD, text is a collection of individual nodes rather than a single solid shape. This makes editing or copying text more time-consuming because each node is treated separately. When changes need to be applied, all nodes must be highlighted to ensure the modification affects the entire text and so operations like copying multiple any objects that includes the text can take longer. This appears to be an issue also for onshape.

From experience in Week 2, it was found that Inkscape can convert text into a single continuous path. Therefore, the DXF files of each joint type designed in FreeCAD were first imported into Inkscape and the corresponding text labels were added. Using the Object to Path function, the text are finally converted into vector outlines (i.e. single continous path) and is then ready for the laser cutting.

The scaling from FreeCAD to Inkscape was confirmed to be correct here.

Deepnest - a software that could optimize placement of 2D shapes on a (cutting) layout - was also tested to minimize waste. The scaling of the parts however was later realized to be wrong after the import to the tool. This might be due to specific import or unit settings and further testing would be needed to understand the cause. Since this is only a test and the shapes of the pieces are not yet complex, the issue will be explored in more detail another time.

It is better to cut a few pieces first before starting the full job. This helps to identify errors early and prevents material waste

Finally, the design is exported from Inkscape as a DXF file and transferred to the control software, Smart Carve 43, for the laser cutter. By default, the software applies a single set of laser settings to all parts, but users can assign specific settings to individual objects, such as cut-through or engraving. In this case, the engraving settings (color coded as red and blue at the software) were configured with lower laser power and slower cutting speed compared to the cut- through (black). The former is selected for the text and the latter for the outer boundary respectively to ensure that the pieces remain stable during the process.

Pro tip

The cutting order is important. Always cut the inner parts first before the outer boundary to ensure the pieces remain stable during the laser cutting process.

And voila.

The chamfer and the slot joint fit together very well as expected. It is interesting to note that these fits though degrades after several inserts and so perhaps actually having joint clearance would actually reduce its degradation.

Due to small radius, the effect of adding chamfer is not so clear and the snap feature breaks easily. Nevertheless it is clear that flexibility is indeed the primary advantage of latter compared to the other two.

Vinyl cutter design

It was pointed out during the introduction session that the vinyl cutter is frequently underestimated, even though it could actually be used for different applications including heat-transfer graphics on fabrics and even circuit mask. Nevertheless, for the current experiment, a pragmatic solution was chosen: creating a design with a name on a sticker. The failed and successful product can then be used to identify one's own tools/materials in the makerspace.

The design was inspired by the idea of that the user's development is supported by the collaboration between Fab Academy and the makerspace. Fortunately, the Chaihuo Makerspace logo was already available at the template sticker and so only some adjustments need to be made to incorporate the other desired element into the final design. However, it was realized that since the logo is originally a picture - and so grouped objects and has a rectangle outline- the respective parts need to be break apart in separate vector shapes first which can be seen in the video below :

The "trace bitmap" function converts the raster image into vector paths. No manual masking is needed! Without this, the vinyl cutter will see the design simply as the following because the outer layer :

The Cricut X1 was used for this exercise. The installation and setup process is well documented online and a successful installation is indicated when the Cricut Design Space opens correctly :

Clicking a new project and blank canvas would then bring the user to the upload image option (either in the form of SVG or DXF), as shown below :

Clicking “Make” prompts the user to review the layout and select the appropriate material and cutting settings. At this stage, adjustments such as blade pressure (turning the knob at the vinyl cutting machine) and mat positioning can be configured before starting the cut.

It probably would have been easier if the Chaihuo logo had been designed together with the rest of the layout from the beginning, as that would have allowed better alignment and positioning. For now, the result works, but the optimal settings and alignment can be further refined in the future.

Files