3.Computer-Controlled Cutting

This week we explore the process to do computer aided 2D cutting.

Assignment

• Group assignmnet:

  • 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.

Group assignment

Link to this week's group assignment page.

Parametric construction kit: Wang Tile Map Tiler

Wang Tiles

Wang tiles is a concept originates from the question - Given a set of square tiles with a color on each tiles, arrange them side by side and with matching colors, whether they can fill the whole plane or not. It turns out that there exists the sets of tiles that can tile the plane aperiodically, and such concept can be used to generate non-repetitive patterns with a predefined sets of tiles, which is very useful in many applications.

Below is a tile set that is proven to be the smallest set that can tile the whole plane, which consists of 11 tiles and 4 colors.

I want to explore with this concept, so I decided to cut a set of tiles that can be connected on the edges with joints in different ways, together they form a seamless pattern, which utilizes the property of Wang tiles.

Below is a set of tiles I found on opengameart.org, the tiles can be connected on the sides seamlessly in different ways to form a non repeative pattern.

Parametric 2D design in FreeCAD

To make the tiled map based on Wang Tile, I need to make serveral square-shaped tiles and join them on the edges. I decided to go with basic press-fit joints between the tiles but make them relatively small to show the patterns on each tiles.

The image pattern of the tile set is often defined in the form of an image containing an array of every pattern, just like the one I picked. So I need to arrange the cutting path into the same array as the image. So I just need to parametize the row and column count of the tile set image, the size of the tiles and the size of the joint, then overlay the tile set image over the cutting path to make the tiles.

So I start off creating a 2D sketch in the Sketcher workbench. First create a square in the XY-plane and set a length constraint on the side to control its size.

Then open up the Spreadsheet workbench, click Create Spreadsheet and select the spread sheet in the Model Tab. Select one cell in the sheet and edit its alias field on the top-right corner, the alias will then be used to link the value of the cell to other part of the drawing. I first set the alias "tile_v_count", "thie_h_count" and "tile_size" for 3 cells and set their values.

Now go back to the sketch and double click the constraint, select the Expression button to enter the constraint value as an expression, set it to "Spreadsheet.tile_size", and the constraint will use the corresponding value aliased in the spread sheet. Now the size of the square is controlled by the value in the spreadsheet.

Then I start sketching the joints on each size of the square and added constaint for the lenght and the width of the joint. I added the "kerf", "board_thickness" and "joint_depth" to the spreadsheet and the value of the constraints are computed from those values. Specifically, the width of the joint is set to "Spreadsheet.board_thickness - Spreadsheet.kerf".

Then go to the Draft workbench and select the Array tool, then go to the Property Tab and adjust the Interval X, Interval Y and Number X, Number Y properties, set their values to the expression in the spreadsheet acclordingly. The X and Y axis intervals are set to "Spreadsheet.tile_size" and the X, Y number are set to the "tile_h_count" and "tile_v_count". Now the drawing can be adjusted by the parameters in the spreadsheet.

Then open the TechDraw workbench and create a new drawing, select the array in object on the left in the Model tab and click the 3D gimbal to switch the view box to the top view. Then click Insert View to add the view to the drawing and right click to export it as DXf file.

Then I import the generated DXF file into the Lasercutter controller program - Lasermaker and import the tileset image, scale it can put it over the path of the tiles to make the engraving of the pattern.

Adjust the speed and power, then just start the cutting. On the first time, the plywood material bends heaveliy because of the engraving and is pushed to the side. So I taped the back size of the board and used the line tracing functionality of the software to chang the engraving to line drawing, and the tiles were cut cleanly this time.

Then make the joints using the same approch, and cut them. The connections are very good.

Vinyl Cutter

Currently everybody is on holiday during the Spring Festival and we cannot get access to the machine, will add the cutting process later.

I want to cut a sticker of Ecology and Cultures Innovation Lab that I'm a member of.

TODO: add the vinyl cutter