Week 3:
Computer-controlled Cutting

Mission objectives:

Make lasercutter test part(s), varying slot dimensions using parametric functions, testing your laser kerf and cutting settings (group project).

Cut something on the vinylcutter.

Design, make, and document a parametric press-fit construction kit, accounting for the lasercutter kerf, which can be assembled in multiple ways.

Explain how you designed your files.

Include your design files and photos of your finished project.

Vinil and Laser cutting

During week 2 I started to create 2D and 3D parametrical tools for parabolic shape fabrication. It is optical element that creates heat for my solar cooker final project.
This curved mirror will be covered with reflective material which can not be cutted in laser cuter but vinyl cuter can deal with it.
That means I need to create cardboard parabolic surface and supporting structure for it in laser cuter and also to cut the reflective mylar in vinyl cuter. Different machines requires different files to prepare.

Group assignment

As a group we managed to make several materials cutting tests in our lab and we documented in table the limits by parameters like: kind of material, its thickness, cutting speed, laser power minimum and maximum.

The cardboard scale shows the connections/joints test were we found the best pressure for parts interlocks. To create the best results we needed decrease the scale from the material thickness size as the widest option to smaller cuts.
The steps we took were -0.05 mm each from the previous one. From 1.20mm, 1.15mm,… to 0.90mm.
Cardboard is soft/forgiving material but it has its limits also, were the joint is too tight and it smashes itself and defects its edges and structure.

Logo preparations in Inkscape

1. Open new document

2. In File menu - define Document Properties - orientation, size and units, shortcut: Shift+Ctrl+D

3. In File menu - Import PNG file, shortcut: Ctrl+I

4. Select and locate the image at the format page with Select and transform objects tool, shortcut: F1

5. In Path menu - select command Trace Bitmap, shortcut: Shift+alt+B

6. Select and delete the PNG image

7. Select the Trace that PNG left

8. In Path menu - select command Stroke to Path, shortcut: Ctrl+Alt+C

9. In Fill and Stroke menu - remove fill in Fill section, shortcut: Shift+Ctrl+F

10. In Path menu - select all and command Brake Apart, shortcut: Shift+Ctrl+K

11. Select and delete double lines and points

Reduce extra points from sketch lines with Simplify command:

12. In Path menu - Simplify command, shortcut: Ctrl+L

Fix lines and corners, combine lines that fits, make dots/points connections with Edit paths by nodes tool, shortcut: F2

13. In Path menu - select all and command Combine, shortcut: Ctrl+K

Select the final structure of the sketch and define line color and thickness:

14. In Fill and Stroke menu - select Stroke paint section - flat color black RGB, shortcut: Shift+Ctrl+F

15. In Fill and Stroke menu - select Stroke style section - Width 0.01 mm, shortcut: Shift+Ctrl+F

Select all the lines/objects

16. In File menu - Save as command, shortcut: Shift+Ctrl+S. Make it DXF file for vinyl cutting machine

Vinyl cutted stickers

Vynil attachment sticky process video

Combined back in to 3D spheric shape.

From 3D software I've got 2D files, converted the drawings in to vectors and exported them as dxf files. 0ne for Laser cut base from cardboard 1.5 mm and another one for Vinyl cut cover from reflective mylar.
Laser Cutting process in video

Supporting ribs made from cardboard. Constructive shape in minimum material.
3D model animation video in Fusion 360

Ribs for laser cut - cardboard - srtucture

Slices in one piece for vynil cut - reflective mylar - top cover

Here are more ideas about how to make the transition from 3D model to 2D machining process that will allow the material assembly back of the 3D shape. I like the idea of light weight parabolic reflector and it brought me to use Pepakura Designer. . Software that many paper pop-up and mask makers have in use and it gives compete control of the 3D model transformation in to 2D layout. The cutting edges, parts nesting on the paper format and the gluing flaps shapes and sizes - all those processes are maximum adjustable with Pepakura.
Flapless version - one piece

This version fits to material that has some thickness. It is possible to to stich it back in to 3D shape with the glue tape. The Red line is cutting and connection guide line. The dash line is the folding sign.

1. Print the image.

2. Cut the black circle and the red line.

3. Fold lightly all the dash lines in same direction.

4. Attach back together the red lines with tape or/and glue.

Separate slices with flaps

This version fits cutting thin materials, like paper or mylar film. It has flaps to attach with glue.

Here all the peaces are similar. It is one modular slice replicated 12 times. The flaps fits to the opposite side of each slice. The right side always has only middle flap and the left side always has top and bottom flaps. The sharp corner of slice is the center of the structure and the opposite side is the outside diameter of the parabolic dish.

1. Print image and cut out the slices.

2. Fold lightly all the dash lines in same direction.

3. Then put glue on the flaps and points marked 3,4,5 and attach them together. Leave marks/flaps 1 and 2 to the end.

4. Keep gluing slices to the first couple in one direction until you close the shape. You will need only 10 pieces. The rest are spare or for test.