Week 3, Computer-Controlled Cutting¶

Assignment¶

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 assignment¶

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.

Group Work¶

For our work at Fab Lab Reykjavik (FLR), we split tasks for the overall group. My work was to characterize effects of power and changing DPI. My characterization of power relied upon changing grey scale levels in a created image.

See my contribution in the “Power and DPI test” on our Fab Lab Reykjavik group page.

Vinyl cutting¶

For this work, I used the Roland GS-24 available at Fab Lab Reykjavik.

Aspect	Value
Product name	GS-24
Drive System	Digital control servo motor
Cutting Widths	50 to 700 mm
Cutting area (max)	584(w) x 25000(l) mm
Cutting blade	Roland CAMM-1 series
Cutting speed	10 to 500 mm/s
Cutting resolution	0.0125 mm/step
Software resolution	0.025 mm/step

Specifications for the GS-24 vinyl cutter. Source

This work begins from the image used last week.

For this I only wanted to cut out the blue (fist) layer on the vinyl cutter. I am making a t-shirt with the pattern.

To make the path needed for the vinyl cutter, I limited the image to the B&W version. To that image, I used the “Trace Bitmap” command. I did a single scan with “Edge Detection”. The default settings results in a good trace from this image, which can be seen in the preview.

This results in in a path which I put in a separate layer. For the vinyl cutter, the path needs to be red and with a width of 0.02 mm (forgive the typo in the screen shot).

This file was exported as an PDF, which was transferred to the computer connected to the vinyl cutter.

For the cutter the knife needed to be adjusted for the vinyl I would be using. By hand, I traced out circles with the knife looking to cut the vinyl without cutting the backing material. The knife depth is adusted by turning the cap holder.

The cutter needs to detect the vinyl piece size. For a piece, one hits the menu button is at “Piece” and then enter. This will detect the size of the piece. If one is using a roll, the same should be done with “Edge” not “Roll”.

“Print” the PDF from the computer, and the vinyl is cut. Once done, take the piece. The areas of the vinyl not to be on the t-shirt need to be removed.

In my cut I can see that the bottom of my arm did not have cut line. This is because the area to be traced went to the edge. In the future, I need to ensure that the path is fully enclosed. This wasn’t a big deal in this case. I could cut with scissors as this would be a straight line.

To transer to a t-shirt a heat press is used. The heat press needs to be heated to 160C. After putting that setting, it takes about 10 minutes on to heat up.

The sticker needs to be aligned on the t-shirt. and put on the heat press.

Laser Cutting¶

Learning the laser¶

While I had i little experience using a Epilog laser cutter several years ago, I needed a refresher. Leading to my group work above, I based my inital work on a material test file found at Thingiverse. This includes a raster test.

For this work I used an Epilog Laser Mini for the work.

Aspect	Value
Model	Epilog Laser Mini 24
Work Areas	24” x 12” (610 x 305 mm)
Laser Wattage	40W

Specifications for the laser. Source

To start, I learned how to adjust the start position. To set the laser home position start:

Turn on laser (reach down back right)
Turn off X/Y
Hit go
Turn on pointer
Move laser to desired position
Push home button to set
Hit reset button to ensure home properly set

It is also critical to focus the laser. To do this.

Insert the material to be cut
Put the metal piece over the laser carriage
Use up/down on the control panel until the metal piece just touches the material
Remove the metal piece

When running the laser, it is important to have the air pump running. On the laser I was using (named Luke), there is a pump which manually needs to be turned on.

Safety is paramount when using the laser, as the materials can catch on fire. Therefore, there are two critical rules. First, always stay with the laser and watch the cutting. Second, never run the laser when alone in the lab. Should a fire start, stop the laser, and ensure that the fire is extinguished.

I started with cardboard and adjusted the laser position

I loaded a start PDF, which had been slightly edited from the original download. This was loaded on the computer, and printed from Adobe photoshop.

Parameters were adjusted, and printed as combined

For the raster:

Speed: 80%
Power: 100%

For the vector:

Speed: 10%
Power: 100%
Freq: 500 Hz

(Need to check the parameters in the lab. Suggested cardboard values were used.)

Note that cardboard is not good for raster testing. The top layer is just burnt away (with enough power). Also, the vector cuts were not done. This is because the red cut lines were not set at 0.02 mm. I edited the file for those lines, and tried cutting 4mm timber.

Cardboard and timber versions side by side

Note that the card printed better, but the card was not cut out. I hadn’t noted the cut line to surrond the entire card, and that was then edited to 0.02 mm red. This updated file was then run, and printed as expected.

This gave me confidence to initiate work from my custom file. This proceeded by group work.

Parametric project¶

Learning Fusion 360¶

To get started on making a parametric project, I first needed to better learn Fusion 360. To do this, I followed a tutorial to make a Lego block found online. This is the top hit when searching on Google for “fusion 360 tutorial”

I followed the tutorial, and made a lego block.

As a short video, here are the steps.

Creating toy block

This DXF file is the result of this tutorial work.

Interlocking circle and square¶

I then moved onto making a circle and square with slots that can be joined together.

I modeled a circle and added slots at each 90 degrees. The starting circle was 75mm, though I used paramters for adjustment.

Based on recommendation from my instructor, I heavily used parameters in my circle design. This proved invaluable, because my original drawings assumed a ply of 3mm, though I eventually cut on 4mm. It was easy to open the drawing and modify one parameter to fix this.

I subsequently made a square with similar logic. Again I used parameters. It was critical to use construction lines, as that kept objects aligned when changing parameters. For example, the slots are 1/4 the length of the diagonal. The parameter dialog has functions, and I could use the sqrt function to find the appropriate length. While I worked as square, further adjustment would be needed for proper calculations if the square is adjusted to an arbitrary rectangle.

Video for steps creating the square

The file for laser cutting was made by the following steps.

Select the body
Create a new sketch
Use the project (P) command to make the sketch of the desire side (top)
Export as DXF
Import the DXF into Inkscape
Change all the lines to 0.02 mm in red
Save as PDF and use on the laser printer

These pieces were cut on the laser cutter with the parameters 11%/100%/500Hz (Speed/power/freq).

The first iteration had 3mm slots. I adjusted to 4mm (via the ply parameter) and recut. Here are the pieces put together. In the image, a circle with 3mm slots sit beside a pair with them put together.

These pieces would certainly be improved with addition of a chamfer. Going forward, these will be added to my work.

The circle and square DXF files from my design work.