WEEK 03 Computer-Controlled Cutting

LASER:

At Fab Lab Benfica in Lisbon, Portugal, we have the Fabulaser Mini, a compact and powerful open-source laser cutter designed for Fab Labs by Fab Academy alumnus Daniele Ingrassia. You can find more details about it here.

SETUP & COMPONENTS

• On the right side, there's a fume extractor, which can be connected to an air filter.
• Under the table, a water cooler keeps the laser at the right temperature.
• On the left side, there’s a computer running two key software programs:
  • VisiCut – Converts .dxf files to .nc g-code.
  • UGS – Controls the laser during operation.

KEY SPECIFICATIPNS

Laser Source and Power:

• Equipped with a 40W CO₂ laser tube, the Fabulaser Mini.

Cutting Area and Resolution:

• Offers a generous cutting area of 600 x 400 mm, accommodating sizable projects.
• Achieves a resolution of 0.05 mm, ensuring precise and detailed cuts.

Maximum Cutting Thickness:

• Capable of cutting up to:
  • 8 mm acrylic
  • 6 mm MDF
  • 8 mm plywood

Speed:

• The maximum cutting speed is 400 mm/s, allowing for efficient processing of projects.

Focus:

• Proper focus is crucial for achieving clean cuts. The Fabulaser Mini includes a coaxial laser pointer to assist with calibration, ensuring the laser beam is accurately focused on the material surface.

Additional Features:

• Equipped with air assist to improve cutting quality by reducing heat and removing debris.
• Safety features include double interlock switches, an emergency stop, a water flow sensor, and a fully enclosed design to ensure user safety during operation.

Kerf and Joint Clearance:

• The kerf (the width of material removed by the laser) and joint clearance can vary based on material type, thickness, and specific cutting parameters. While exact kerf measurements aren't specified, the high resolution of 0.05 mm suggests minimal material removal, leading to tight and precise joints. For optimal results, it's advisable to conduct test cuts on your specific material to determine exact kerf and adjust designs accordingly.

SAFETY

This is the only machine in the lab that must never be left unattended.

• In case of an emergency, there’s a big red STOP button.
• I have also learned the locations of all fire extinguishers in the lab.

TESTS

Unfortunately, our Fabulaser Mini is quite old and doesn’t work properly. Some areas (dead zones) don’t cut well, and engraving is not recommended.

I tested cutting speeds on different materials without adjusting focus or cutting strength:

Materials Used

• 3.3 mm hardboard
• 4.5 mm wood
• 2.7 mm cardboard

Test Process

1. Designed a simple square (wireframe) in FreeCAD.
2. Saved it as a .dxf file (VisiCut requires this format).
3. Selected different cutting speeds in VisiCut:
   • 100, 50, 20, 10, 5, 1

Results

• For wood, only the speed of 1 fully cut through, but it caused a bit of burning, I’ll try 2 next time.
• For cardboard, even 10 cut through, but the edges were wavy.
  • A speed of 5 or maybe 6 seems best.
  • Surprisingly, even 100 cut through in some places.

*back side

STEP-BY-STEP CUTTIN PROCESS

1. Open the .dxf file in VisiCut.

   • Select the objects to cut (in this case, everything).

   

2. Choose a material setting.

   • We use MDF just to adjust the speed settings.

     

3. Save as g-code and open UGS software.

   • Connect to the machine, upload the file, and press PLAY.

   • The g-code appears in the bottom window.

     

     

4. Final result:

   • The cut was successful, but I think some wavy lines appeared due to vibrations.

     

     

TESTING KERF

For my construction kit, I’m making a miniature version of my final project’s treadmill. To test the kerf, I designed a parametric comb that, when cut twice, can be tested in multiple ways.

Designing the Comb in Fusion 360

1. I started by creating a simple outline shape in Fusion 360.

   

2. After refining the sketch, it looked like this, and it was time to add parametric constraints:

   

   

3. I removed the original dimensions and replaced them with parameters and functions instead of fixed values.

4. Apart from the comb height, all other values were set using functions.

   • The middle section has no kerf at all.
   • Moving to the right, the kerf increases (+1 kerf value).
   • Moving to the left, the kerf decreases (-1 kerf value).
   • By adding only one kerf per cut, I can have more precise kerf check

   

   

5. Next, I added extrusions and chamfers for easier assembly.

   

Preparing for Laser Cutting

To arrange the parts for laser cutting:

1. Go to MODIFY > ARRANGE, select the object, and choose a plane for placement.

   

2. Create a new sketch, then go to CREATE > PROJECT/INCLUDE > INCLUDE 3D GEOMETRY.

   • This projects the shape onto the plane as purple lines.

   

3. Right-click the sketch and export it as a .dxf file.

   

Fusion 360 File Download:

• COMB_kerf.f3d

LASER CUTTING

First Test: 3.3 mm Hardboard (Speed: 2)

Result: It did not cut through. Possibly, a speed of 1 would be better.

Issue: A strange error appeared in the cut, but I will continue testing on a different material.

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Second Test: 4.5 mm Wood (Speed: 1)

Result: Did not cut through again.

Plan: I will reduce the speed to 0.7 next time.

Repeated Error: The same cutting issue appeared, but only on the first comb.

Next Step: Open the file in FreeCAD, duplicate the second comb, and try again.

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Final Results & Observations

Error persists – No clear reason why.

Cutting burns the material – Even at lower speeds, edges are overburned.

Possible causes:

• Old machine
• Laser misalignment
• Step and focus calibration issues

Best Fit Measurement

Despite the burns, the best fit was:

• -2kerf = -2 * 0.05 mm = -0.1 mm

While doing the documentation, I realized that my comb didn’t make any sense. I should have made the base size equal to the material thickness and then only decreased the values by the kerf size or by double the kerf size (to account for kerf on both sides of the cut).

Well, what’s done is done, but at least I didn’t burn the lab!😅🔥

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Also bonus:

I learned how to use a vernier caliper. It’s a measuring tool used to determine precise internal, external, and depth dimensions. It consists of a main scale and a vernier scale, which allows for more accurate readings than a standard ruler. The vernier scale, invented by Portuguese mathematician Pedro Nunes and later refined by Pierre Vernier, enhances measurement precision by enabling readings to a fraction of a millimeter or inch.

How to Read a Vernier Caliper

1. Close the jaws and ensure the caliper is zeroed.
2. Read the main scale – Note the measurement just before the zero of the vernier scale. This gives the whole number and first decimal.
3. Read the vernier scale – Find the line on the vernier scale that aligns exactly with a line on the main scale.
4. Add both values – The main scale reading plus the vernier scale reading gives the final measurement.

Example:

• Main scale: 10.2 mm
• Vernier scale: 0.06 mm (where lines match)
• Final measurement: 10.26 mm

VINILCUTTER:

Machine I'll be using is Called SHILOUETTE CAMEO 3. You can download Silhouette Studio in their website https://www.silhouetteamerica.com/software

Applying the Vinyl

1. Lift up the lever on the right side.
2. Place the vinyl sheet on the cutting mat.
3. Mark the limits and distribute supports evenly.
4. Close the lever and press "Load" on the touchscreen.

5. The vinyl sheet will be pulled in, positioning it under the blade.

   

File Preparation in Illustrator

Silhouette Studio does not keep the scale when importing files so I’ll prepare the file in Illustrator before importing.

Steps in Illustrator

1. Set the artboard to the same size used in Silhouette Studio (A4 in my case).
2. Draw a rectangle the same size as the artboard.

3. Export the file as .DXF.

   

   

   

Importing to Silhouette Studio

1. Open the .DXF file in Silhouette Studio.
2. The scale will not match the original design.
3. Group all objects and resize them to A4.

4. Remove the frame (to avoid cutting it).

   

   

Cutting the Vinyl

1. Go to the SEND panel.
2. Select the material type (settings adjust automatically).
3. Generate a test shape to check the cutting settings.

4. Start the cut!

   

Final Application

1. Repeat the process for different colors.
2. Use transfer tape to layer and apply the vinyl design.
3. Carefully place it onto the final surface (in my case, my laptop).

TREADMILL MINATURE PARAMETRIC:

Since learning parametric design in Fusion, I decided to create my own treadmill model.

In our lab, we recently got new 3D printer filaments, but since they come in 2kg spools, none of the existing supports can hold them. They're also quite large, so I designed a miniature version of my treadmill’s base to serve as a sturdy filament holder.

Here’s how I structured the functions, and later, I adjusted the values to fit the filament size (30x7.5 cm).

Fusion 360 File Download:

• Tredmill_Parametric.f3d

CHECKLIST:

Group assignment:

• Do your lab's safety training
• Characterize your lasercutter's focus, power, speed, rate, kerf, joint clearance and types.
• Document your work to the group work page and reflect on your individual page what you learned.

Individual assignments:

• Design, lasercut, and document a parametric construction kit, accounting for the lasercutter kerf, which can be assembled in multiple ways.
• Cut something on the vinyl cutter.

Learning outcomes:

• Demonstrate and describe parametric 2D modelling processes.
• Identify and explain processes involved in using the laser cutter.
• Develop, evaluate and construct a parametric construction kit.
• Identify and explain processes involved in using the vinyl cutter.

Have you answered these questions?

• Linked to the group assignment page.
• Explained how you created your parametric design.
• Documented how you made your press-fit construction kit.
• Documented how you made something with the vinyl cutter.
• Included your original design files.
• Included hero shots of your results.

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WEEK PLAN:

DAY	WED	TH	FR	SA	SU	MON	TU
PLAN	-12:00 LAB with Andre
-14:00 Global evaluation
-15:45 Neil’s class	-10:30 Andre online class	-10:30 LAB with Andre	-15:00 Global time
	-10:00 LAB alone	-10:00 LAB alone
-12:00 Regional review
INFO	Plan the strategy for the week	Prepare a logo (2 colours) for vinyl cutter
Prepare parametric joints for laser cutter	Group assignment	Mk docks + week01 documentation catch up		Blender animation + video compression + week02 documentation update