Computer Controlled Cutting

Task

I have this week worked with computer controlled cutting in the three following areas:

• Vinyl Cutting
• Laser Cutting a Parametric Press Fit
• Characterize our lasercutter Group Assignment

Vinyl Cutting

The video to the left shows how i used the vinyl cutter to create a small multi color logo. I've tried various options for aligning the different colors of vinyl, but have not yet found the perfect method. I used the entire width to cut multiple parts - so I am in a great position if the perfect alignment is just a matter of practicing my craftsmanship skills.

From Fusion to PDF

I created my parametric press-fit design using Fusion 360 and used following steps to prepare the .pdf-fil for out lasercutter:

• Right click on sketch and select Save as DXF.
• Right click on DXF-file and select Open In... Inkscape.
• Press OK (or use different scaling options).
• Delete undesired lines (ie. Construction Lines) from the import.
• Move the import to the top left corner of the document.
• Change stroke color to RGB red, and widht to 0.025mm.
• Create Cloned Tiles (Edit > Clone) with enough spacing.
• Save as PDF.

Vinyl Cutting 101

I used a GCC Expert 24 Vinyl Cutter with the accompaning SignPal-software.
The machine was setup for vinyl cutting, so I didn't do a lot of experimenting with it before cutting.
I am however aware that wrong settings can cause a range of errors when using a vinyl cutter:

• Cutting too deep vs not cutting deep enough.
• Cutting too fast may rip edges.

Laser Cutting 101

I used a Universal Laser with the accompaning Universal Control Panel (UCP).
The laser can operate with various settings depending on the color of the drawing.
I played around with various settings while cutting / engraving smaller parts, but came to the following personal guiding settings:

Cutting

• Stroke color: RGB RED.
• Set Z to material height, unless there is a need to unfocus.
• 3mm MDF: Power: 100%, Speed: 8%, PPI: 100
• 3mm Acrylic: Power: 100%, Speed: 6%, PPI: 100
• 2mm Cardboard: Power: 100%, Speed: 70%, PPI: 100

Engraving

• Fill/stroke color: RGB Green.
• Set Z to material height, unless there is a need to unfocus.
• 3mm MDF: Power: 100%, Speed: 20-80%, PPI: 100
• 3mm Acrylic: Power: 100%, Speed: 20-80%, PPI: 100
• 2mm Cardboard: Power: 20-50%, Speed: 100%, PPI: 100

Comb = Short Cut for Tight Fit

I initially laser cut a comb piece of MDF with different gap sizes ranging from 2.4 mm to 3.4 mm in increments of .1mm. The intention of this comb is to esablish tap width for - allowing for the kerf - for a press fit construction.

Kerf Meassurement

I the created a large rectangle, which was subdivided in 19 smaller rectangles. These 19 rectacgles where cut using 20 vertical cuts. So the kerf (the amount of material lost by laser cutting) could afterwards be meassured by placing all the small rectangles in the large rectangle, meassure the gap and divide the gap by 20. Based on:

• Laser setting: Power: 100%, Speed: 10%, PPI: 100 & Z: 3mm.
• Material: 3.0 mm MDF.
• Meassurement of gap: 2.19 mm.

I calculated the kerf to be (2.19 mm / 20 =) 0.1095 mm

Applying Kerf

I now transfered meassured / calculated values of both material thickness and kerf to the parametric design in Fusion 360. I further more reduced the side of the box in order to reduce the use of material.

The first laser cut box with based on 3.0 mm thickness and 0.1095 mm kerf resulted in an exact fit construction without suficient press to make the parts stay nicely together.

I thus made three additional sets by adjusting only material thickness to respectively 2.9 mm, 2.8 mm and 2.75 mm.

The latter design file had a gap (2.75 mm + 0.1095 mm = 2.8595 mm or aprox 95.31% of the material thickness) which created a really nice and snug press fit.

My conclusion about measuring and applying kerf in order to create a press fit construction is:

• It is important to make a parametric design.
• The "press" is dependend on the material used.
• Press-fit-construction will allways required manual adjustments.

Press Fit Construction

My Press Fit Construction was originally intended to be used to subdivide the storage compartment in the table top of my original proposed idea for the final project.

I really enjoyed the challenge - and stated by sketching and playing with pieces of paper. I then created the first lasercut version which I refined by:

• Creating parametric design.
• 100% apadtable to size, kerf and material thickness.
• Meassuring, calculationg and applying knowledge about the kerf.
• Making manual adjustment to obtain press fit.

Design Files

• Comb Test SVG-file (6 kB)
• Kerf Meassure SVG-file (47 kB)
• Press Fit Design in Fusion 360 (Online)
• Press Fit Design Exported af DXF (2 kB)
• Press Fit Design Exported af PDF (1 kB)

Work from other FabAcademy Students

• FlexWood Generator by Nicolas De Coster
• Kit Piece Generator by Nicolas De Coster