Computer-Controlled Machining - Shopbot

Designing the Meditation Pod in Rhino

This was my second time designing in Rhino. Unlike in the previous week, I had a clear vision of what I wanted my project to look like. I enlisted the help of Jacob to learn more about how he sets up and interacts with Rhino as a frequent user. Jacob was superbly helpful in showing me how to create custom prefences and shortcut keys to enhance work flow. Some of the settings we added included a gradient background and shortcut keys to quickly move between views. The most helpful setting Jacob showed me was a feature called Gumball, which allows you to easily rotate and move selected objects. As we designed the shell we created circles and used the loft command to link them together. We used a trim command to cut a 45 degree angle from all of the circles for the openning of the pod. For the side panels we created a curve along the circles. Once the first S curve was complete it was time to find the intersections with the circles. When I continued to design the pod I learned about the usefulness of the arraypolar command, which allowed me to evenly distribute the S curves along the circles.

Creating Puzzle Pieces

Next I had to pin the different pieces onto a flat plan so they could be ready to explort. I tried to arrange the pieces to minimize the number of sheets I would use. The big thing that threw my design off was the fact that I thought I was designing for a 4 x 8 sheet of OSB, however, when I got to the shop I found out the Harvard Shopbot only supports 4x4 sheets. I quickly tried to scale the pieces to reflect this change.

Using the Shopbot

I spent all day on Friday adjusting my designing and assisting others as much as I could with Shopbot useage. I was excited, all be it tired, when it was my turn. First I created the toolpaths on V Carve Pro. I made sure to measure and remeasure board thickness. Rob and I decided the little notches in my design would do best with a 1/8 bit. Next I got the board ready. I had learned from watching others that it was important to note how the board naturally bowed. You wanted the bow of the board to be on the machine so that when you nailed down the edges the board would naturally come to neutral. I carefully drilled down the edges. Rob and I decided that for the S curves we may need to pause the bot and add more nails to prevent too much bowing as they were positioned close together. After preparing the board I zeroed the machine and zeroed the Z. After turning on the dust collector and following the prompts on the screen, it was ready to cut. I watched eagerly as the tool made its first cut - the long S of the panel. It was beautiful to see the curved shape coming out of the stiffness of the board. The of the first panel took some time because the 1/8 bit does 4 tool passes. After the first curve was done we paused the machine and extracted it. Rob and I noticed something odd. The notches in the panel seemed really thin. When we measured them they were .2 inches wide instead of .44 inches as I had planned.

Confronting the Issues

Hacking the problem took me quite a bit longer than I expected. I started trying to figure out the problem on Friday evening at the shop and only found a solution on Tuesday afternoon. In between I tried countless of hacks and read lots of online tips, but I found that I hit a wall in my understanding of Rhino. The first thing I went back to investigate were my dwg files. The odd thing I found was that in both Rhino and the dwg file my notches were calculating as 2 1/2 inches. If look carefully at the picture to the left you can see the distance reading. I tried exporting the file into 123D Make as I know you can account for board thickness when you make radial slices. However, when I imported it there it showed up as a series of tiny lines. I went back to my Rhino file and tried to export it as different types of files: dwg, dxf, stl, png, etc. I couldn't understand why the notches calculation was inconsistent while the lengths of the panels and the diameter of the circles remained consistent.

Starting Fresh-Pod 2

Part way into the weekend I got frustrated with the fact that I couldn't figure out how to fix the problem. I emailed a few folks I knew were comfortable with Rhino along with my files to see if they could shine some light on the situation. Nathan suggested I double check the units of my file. Sure enough the file template was set in feet and I wanted it in inches. I used the units command to change it to inches. Next he suggested I scale the geometry of the design. i tried a few methods to approach this, but I did not seem to follow what he was describing. Once my frustration reached a certain point, I openned a new file and started again. This time I used the polyline tool to draw the curve and then the revolve tool in surface creation to create a more cylindrical shape. I created a box to intersect at a 45 degree angle to trim the difference.

123D Make Issues

I hoped that since I got a shape I liked in Rhino I would be able to import the file into 123D Make and easily create radial slices. However, the picture to the left shows you what I saw. Some googling told me this occurs when there is an issue with the mesh. I then went back to the Rhino file used the mesh commands and the OffsetMesh commands as one forum suggested. Lastly I selected the solidify option from the OffsetMesh pop-up window. I was hoping this would solve the issues, but it did not. I felt like I was again back at square 1.

I see the light!

Finally a breakthrough. After some emailing back and forth with Nathan we were able to find a solution. After realigning and completing the intersections again, I was able to successfully export the design into 123D Make. There I set a new template for our machine settings and OSB thickness. The final product is ready for new toolpaths and to have it's day on the Shopbot. I am so excited to see how this will look completed!


I was finally able to get some time on the Shopbot to mill my pieces. Even though this prototype is not as large as an adult-sized model I hope to build it still took up nearly 5 sheets of OSB. This was due to the large C curves. If I make an adult version I will need to cut it outside of the Harvard shop as the bed only accommodates 4x4 pieces. I got quite quick at the Shopbot process after the first two boards so in all this took about 1 hour and 15 minutes to go through the all the steps.