Laser cut wooden block tower – final design_part 1

 in Get Inspired by

PLUGNMAKE FABLAB DELFT·THURSDAY, JANUARY 18, 2018

Maaike Kok
I have finally started printing my first prototype of the wooden block tower (see my former blogs here). Only the three smallest cubes of the block tower (ca. 50x50x50mm, 70x70x70mm and 90x90x90mm) could be printed during this Open Day (within the half hour time span). Next time, in part 2, I will print the remaining 3 cubes of the wooden block tower.

This article will elaborate the first results of this prototype and further study the engraving method for a new image I designed, this image will be located on one side of each cube. As a reminder: the final goal of this project is to create a block tower for children, which consists of 6 cubes, increasing in size. Each cube is built out of five plywood panels, so the cubes function as boxes. The five wooden panels are connected to each other by means of finger joint. This blog does involve content which is already described in the earlier blogs on the Wooden Block Tower, in this way you can understand this blog independent from the earlier blogs.

Design software: Rhino 5 (Windows)
Material: 3mm plywood
Laser cutting settings (in RD Works V8) :
Scheme of the laser cutter' settings

Laser cutting settings on the 100 watt laser.

Original dimensions

Originally the wooden block tower was designed in Rhino 5 with a finger joint connection of exactly 10mm. For the smallest cube of 50x50x50mm this resulted in the dimensions as shown in figure 1.
measurements of the box' sides

Fig 1: Dimensions of the smallest cube. From left to right: 1. Front- & back panel. 2. The two side panels. 3. Top lid.

However, in the laser cutting workshop (done prior to this studies) it became clear that the above mentioned dimensions for the finger joints were not optimal. The box did not hold together on its own and felt apart immediately. It was very difficult to get the cube standing upright, so glue was needed to construct the cube. As the laser beam has a thickness of its own, it cuts away more than anticipated. The dimensions I had drawn, where not the exact dimensions as printed.

My first prototype

As mentioned earlier I printed just three cubes (cube 4, 5 and 6) of the designed wooden block tower. Each with different and decreasing dimensions: The exact design and dimensions of each cube are shown in figure 2 and 3. In order to connect the wooden panels without the need for glue, an offset of 0.095mm is used from the original dimensions.
design screenshoot

Fig 2a. Design and dimensions of cubes 4, first prototype. This cube is biggest cube out of three (cube 4). Grey = Engraving type 1. Red = Engraving type 2. Black = Cutting.

Design' screenshoot

Fig 2b. Design and dimensions of cubes 5, first prototype. Grey = Engraving type 1. Red = Engraving type 2. Black = Cutting.

design screenshoot

Fig 2c. Design and dimensions of cube 6, first prototype. This cube is the smallest (cube 6). Grey = Engraving type 1. Red = Engraving type 2. Black = Cutting.

Disassembled boxes

Fig 3. Printed result of cubes 4 till 6, first prototype. Top cube is biggest cube out of three (cube 4). Bottom cube is smallest (cube 6). Grey = Engraving type 1. Red = Engraving type 2. Black = Cutting.

Study on engraving type

All side panels of the cubes are provided with an image. For one panel of the cubes I recently designed a new image, consisting of the count 1 till 6 accompanied by the same number of butterflies (see figure 4). The butterflies drawn on the smallest cube (ca. 50x50x50mm) are so little that I wasn’t sure if these could be suitably printed by the laser cutting machine. But if they could, I wanted to find out which type of engraving I should use to get the best finish. Figure 4 shows the two different designs I made for the butterflies and the engraving options I tried for these designs. The printed result is shown in figure 5. The first butterfly design consists of an inner and outer line with an offset of only 0.165mm (see figure 7). The second butterfly design is a simplified version of the first, the butterfly is drawn with a single line (see figure 6). The first design is performed with both vector- and raster engraving, the latter is only performed with vector engraving.

side n6

Fig 4. Design variations for engraving. Grey = Engraving type 1. Red = Engraving type 2. Black = Cutting. Left: Butterfly with double line (offset 0.165mm), vector engraving (see figure 7). Center: Butterfly with single line, vector engraving (see figure 6). Right: Butterfly with double line (offset 0.165mm), raster engraving (see figure 7).

Fig 5. Printed result of the design variations for engraving. Left: Butterfly with double line (offset 0.165mm), vector engraving (see figure 7). Center: Butterfly with single line, vector engraving (see figure 6). Right: Butterfly with double line (offset 0.165mm), raster engraving (see figure 7).

Butterfly design

Fig 6. Butterfly image variation single line.

Double lined butterfly design

Fig 7. Butterfly image variation double line (offset 0.165mm)

Positioning of the design on the laser bed

The pieces to be printed were positioned in the top left corner of the laser printer, see figure 8. In this way I estimated that the laser beam would be the coolest and cut away the least amount of material.
Scheme of the positioning of the design on the bed of the laser cutter

Fig 8. Positioning of the design on the laser bed

Result and conclusions

The first three parts of the wooden block tower are created. I am very happy with the chosen engraving methods for all sides. From the engraving study I chose to engrave the butterflies with raster engraving (see right element in figure 4 and 5). Vector engraving is not possible for this image, due to its small size the image becomes unclear. Fortunately raster engraving still works on this small scale. Connecting the wooden panels in order to form the cube was a little struggle unfortunately. With the taken offset of 0.095mm from the original dimensions and the positioning on the bed as shown in figure 8 the side panels could be easily attached to each other, however when attaching the top lid in order to form the box, cracking sounds were heard. For box 4 the top lid even got damaged. Either the design of the top lid should be changer, or the offset should be reduced. In the bottom pictures the result is shown of the first three cubes of the block tower.
See you next time for the rest of the block tower!
picture of the final blocks

Fig 9. First prototype

Back side of the final boxes

Fig 10. First prototype

Front of the final boxes with the eyes

Fig 11. First prototype

the boxes from 4 to 6

Fig 12. First prototype

picture of the boxes as a 'Matrioska'

Fig 13. First prototype

a close picture of the boxes one inside the others

Fig 14. First prototype

side of the boxes representing buildings

Fig 15. First prototype

different configurations of the boxes from the 'building' side

Fig 16. First prototype