Week 3: Computer Controlled Cutting

This page covers the fundamental principles of parametric design and operational workflow for both laser cutting systems and vinyl cutting machines, focusing on basic modeling logic and parameter control.

Desing

This page is linked to the group documentation page, where complementary technical information is provided, such as kerf characterization, joint and press-fit strategies, and material behavior during digital manufacturing processes. Additional practical details such as machine calibration parameters, test cuts, and fit validation methods are documented there to avoid redundancy and keep this section focused on the individual design and workflow implementation.

Parametric design in SolidWorks is defined by parameters, dimensions, and mathematical relationships. Instead of creating fixed shapes, the model is based on variables that automatically update the sizes, proportions, and behavior of features as they change.

Parametric design is a practical application in the development of snap-fit kits made of MDF, where all parts must automatically adapt to the material thickness, cutting groove, and scaling factors.

Equations menu

The Equations menu enables dimension linking and global variables, allowing fast design iterations, scalability, and precise change control. By designing parametrized parts, many issues can be avoided. This is possible because parametric modeling defines geometry through variables and mathematical relationships, so when a value is modified, all dependent dimensions and features update automatically throughout the model.

Global Variables

Global variables are parameters that store numerical values and can be referenced by multiple dimensions and features of the model. They are defined in the Equation Manager or directly when assigning a dimension, by typing "=" followed by a random word.

Operations

The operations section lists the model features whose dimensions are being driven or referenced by equations. From here, you can identify which extrusions, cuts, patterns, or other features depend on parametric relationships.

Equations

Equations establish mathematical relationships between dimensions, variables, and feature parameters. They allow proportional scaling, dependency rules, and constraint logic.

Import

The import function allows external equation and variable sets to be loaded into the current model. This is useful for standardized parameter libraries, repeatable part families, and collaborative workflows where predefined parametric rules are reused across multiple designs.

Export

The export option saves the current set of variables and equations to an external file. This facilitates documentation, parameter backup, and reuse in other parametric models, enabling scalable and replicable design workflows.

Insert curves

The insert curve tool allows you to import external geometric data, such as text files containing airfoils or guide curves, directly into a sketch or 3D space as reference geometry. These curves can be constrained, dimensioned, and linked to global variables within the Equation Manager, thus ensuring their parametric control.

Scale entities

The Scale Entities function resize the selected sketch geometry according to a scale factor, which can also be determined by a variable or equation.

Outer airfoil profile

Using a scale factor of 100 (assuming the original NACA0015 airfoil definition was normalized to a 1 mm chord), the resulting chord length becomes 100 mm, which is defined as the primary driving variable of the model. This parameter controls the global size of the section and is referenced by sketch equation D12, which positions the structural frame that supports the wing spar. Because it is equation-driven, any modification to the chord variable automatically propagates to the frame location and related features. Considering a material thickness of 3 mm also defined as a variable, the spar slots are dimensioned as material thickness minus two times the kerf (Equations 9 and 16), ensuring a press-fit after cutting. These base parameters generate the remaining dependent equations and dimensions in the sketch.

Inner airfoil profile

With the same global scale, material thickness, and kerf compensation, the inner profile—being a hidden structural support element—allows controlled material removal to reduce overall wing mass. Non-critical lightening holes (such as central circular cutouts) can be left unconstrained or weakly constrained, while structural frames and spar interfaces continue to follow the compensated-fit rule (material − 2× kerf) to maintain proper assembly tolerance. All tabs intended to connect with the spar or other interlocking components are dimensioned as slot width = material thickness + 2× kerf to ensure proper engagement after laser cutting.

Structural stick

The spar is responsible for carrying wing loads and resisting aerodynamic forces at a basic structural level. Although full structural sizing can be derived from beam and bending calculations, this prototype uses seven ribs (two outer and five inner) as a practical approximation. The outer ribs interface directly with the airfoil profiles, while intermediate ribs are distributed along the span using a pattern feature. Connection cutouts are positioned at a chosen offset and dimensioned using the same compensated-fit formula based on material thickness and kerf. Then just need to replicate the slots with controlled spacing.

Living hinge

For detailed hinge pattern design, refer to the Fab Lab Puebla 2025 documentation.
For detailed hinge pattern design, refer to the Fab Lab Puebla 2025 documentation. Functionally, this component must flex around the airfoil contour, requiring an approximate wrap angle on the order of 190–200°. This bend angle (θ) is defined as a design parameter. Material thickness influences slot spacing and hinge compliance; for tighter curvature requirements, a slightly denser cut pattern is selected. Mounting holes and tabs that interface with the profiles follow the compensated rule (material − 2× kerf for slots), and repeated features are generated using a pattern operation.

DXF export

To export fabrication, go to File → Save As → DXF.
Here just select the specific view or reference plane that represents the 2D cutting geometry (typically the front view or sketch plane). Confirm the selection and verify in the preview dialog that the correct contours are included before completing the export.

Here almost the same workflow is followed to generate a vectorized image for Week 2.

3- The document or canvas size is adjusted to match the design boundaries and intended fabrication scale.

4- After configuring the tracing parameters as required, the result is exported as a vector path file suitable for vinyl cutter workflows.

Laser Cutting Workspace

SmartCarve is used to prepare and execute jobs on a laser cutter. It allows the user to import vector designs, assign cutting or engraving parameters (such as power, speed, passes, and order of operations), and generate the machine toolpath. In conjunction with the laser cutter, SmartCarve acts as the interface that translates the digital design into precise cutting and engraving instructions for fabrication.

On the left side of the interface there is a tool panel that provides object manipulation functions such as move, rotate, scale, align, and arrange. These tools are used to position parts efficiently on the work area and optimize material usage before machining.

On the right side, the layer manager and process parameter controls are located. Each layer can be assigned independent machining settings such as laser power, speed, and operation type (cut, engrave, mark). This allows you to process different features of the same design with different parameters. Below this section is a process menu, where you can export files for the slicer or even manipulate them directly.

Based on previous group tests and calibration runs, the parameters selected for this working configuration are:

Finally, click on file save to export the file with the parameters to the USB drive.

The machine used was the CFL-CMA1080K laser cutter, which is composed of and operates with the following subsystems:

Chiller is responsible for maintaining a stable temperature inside the machine.
IMPORTANT: Check if it is turned on

Turning on the Automatic Voltage Regulator is the second step in turning on the machine

Next, you need to turn on the switches located on the side of the machine.

With this activated, all that remains is to open the emergency system and enter the security key to turn on the machine.

For the laser to work correctly, the z-axis must be set to 5 mm from the material, as this is the distance at which the laser focuses.

Enter Udisk+, then select Read Disk to access the files stored on the USB device. Browse through the directory until you locate the job file to be cut. Once selected, press Enter and copy the file to the machine’s RAM memory. After the transfer is complete, press Esc repeatedly to return to the main controller menu, where the newly copied file will appear in the local job list, ready to be configured and executed.

Vinyl Cutting Workspace

The vinyl cutter used was the STM ROBOTICS; to turn it on, simply plug it into the power outlet and it will turn on automatically.
Next, insert the vinyl into the machine from the front. To secure it, simply lift the rear clips.

To set up the machine, press the Manual button. This sets the origin. The printhead pressure is adjusted using the arrows. To lock the origin, press the button twice to confirm the initial position.
To modify the speed and cutting pressure, press the reset button and adjust with the arrows.
Finally, you need to do step 4 in the Inkscape menu, which is to click the plot button.

Transfer the vinyl:

First, remove the excess vinyl surrounding the cut design (weeding process).

Then place a piece of transfer paper on top of the design; use a flat tool (such as a scraper or card) to press and rub the surface to ensure all elements adhere properly to the transfer layer.