Week 3 — Computer Controlled Cutting¶
This week I explored FreeCAD and LightBurn to understand the workflow of computer-controlled cutting.
I also learned how to prepare and configure the laser cutting machine before fabrication.
Group Assignment¶
This week, I worked together with Ani as part of the group assignment.
At the beginning, we explored the laser cutting machine, focusing on its structure and safety rules before starting any practical work.
To understand how accurately the machine works, we checked the laser beam position using a transparent acrylic sheet. This helped us clearly see where the beam hits without creating smoke.
We avoided using paper because it could burn and produce smoke that might damage the mirrors.
After observing the marks, we analyzed how the beam behaves across different positions.
Mirror Adjustment¶
Next, we adjusted the mirrors of the laser system.
By carefully tuning the alignment screws, we ensured that the laser beam travels through the center of the optical path and reaches the working head correctly.
We repeated this process several times until the beam consistently hit the correct positions.
This step was important to make sure the machine is properly calibrated and ready for accurate cutting.
Engraving and Cutting Tests¶
We then created test samples to explore how different materials behave during laser cutting and engraving.
We tested both cardboard and plywood, since each material reacts differently depending on the machine settings.
After these tests, we moved on to kerf calibration to understand how much material is removed during cutting.
Kerf Test¶
To measure kerf, we designed a parametric test model in FreeCAD.
The model included slots from 3.00 mm to 2.50 mm with a 0.05 mm step, allowing us to test different joint fits.
The design was exported as a DXF file and imported into LightBurn.
We assigned cutting and engraving parameters and executed the cutting process.
Result¶
After cutting, we tested the joints by fitting them together.
The best result was achieved at around 2.75 mm, which provided a good balance between tight fit and easy assembly.
From this test, we estimated the kerf of the machine to be approximately 0.25 mm.
This value later helped me improve my parametric design in the individual assignment.
Parametric Design¶
During this stage, I created a parametric model in FreeCAD using Spreadsheet parameters.
Steps:
- Created a Spreadsheet
- Defined material thickness
- Added kerf parameter
- Defined joint width as a formula
Joint width was calculated using:
joint width = material thickness − kerf
Laser Parameter Testing¶
I performed laser parameter tests by varying speed while keeping power constant.
The goal was to understand how laser speed affects material cutting behavior and surface quality.
Calibration Test (11 Rectangles) — Group Work¶
During group work, Ani and I designed a calibration test consisting of 11 rectangles (10 mm each), cut as a single continuous geometry.
Expected total length:
110 mm
Measured result:
107.77 mm
Problem Detection¶
The measured dimensions showed significant deviation from the design.
We realized that the issue was not only related to laser kerf.
The results suggested a possible machine calibration problem, especially related to X/Y axis scaling.
The dimensional deviation indicated a machine calibration issue rather than only kerf loss.
Temporary Adjustment¶
To continue testing, we applied a temporary scaling compensation in LightBurn to correct dimensional deviation.
A correction factor was calculated using the formula:
Scale factor = 100 / 98.058 ≈ 1.0198
This adjustment improved dimensional accuracy but was considered a temporary solution rather than a final machine calibration.
Kerf Calculation¶
After improving dimensional accuracy, we calculated the laser kerf.
Expected total length: 110 mm
Measured total length: 107.77 mm
Total material loss:
110 − 107.77 = 2.23 mm
Number of cuts between rectangles: 10
Kerf estimation:
Kerf = Total Loss / (Number of Cuts × 2)
Kerf ≈ 2.23 / (10 × 2)
Kerf ≈ 0.11 mm
This kerf value was later used to improve parametric joint design.
Result¶
After compensation and kerf integration into the parametric model, cutting accuracy improved significantly.
Press-fit joints behaved more predictably and dimensional consistency increased.
Parametric Design Development¶
After calculating the kerf, I created a parametric geometric model in FreeCAD.
The goal of this design was to develop a flexible structure that can generate different forms by simply modifying parameters in the Spreadsheet.
By adjusting values such as material thickness, kerf, joint width, and number of joints, the geometry automatically updates, allowing rapid exploration of multiple design variations without rebuilding the model.
This approach significantly improved the efficiency of the design process and ensured higher accuracy in press-fit joints.
This parametric workflow demonstrates how digital fabrication shifts design from static geometry to adaptable systems, where a single model can produce multiple outcomes.
Reflection¶
This week helped me understand that digital fabrication is not only about design, but also about machine calibration and measurement.
I learned that:
- machine accuracy must be verified
- kerf directly affects joint fitting
- parametric modeling simplifies iteration
- measurement is essential in fabrication workflow
The iterative process (design → cut → measure → adjust) shifted my approach from simply using machines to understanding and calibrating fabrication systems.