11 Week
Build a Machine:
This week I was involved in three groups to build the chocolate extruder: Camera team, fabrication team and Chocolate extruder team. For the most part I was involved in the machining of parts in the Shop Bot and running parts on the 3D printer. I found it was very helpful to work closely with the design team who were able to follow up with us when one of the parts failed in the cutting process. Divided into 3 teams: Design, Fabrication and Assembly, with team members moving in and out of the teams to hand off or relay information in the different stages of the process.
The fabrication team took turns to design tool paths, watch over the shop bot and trouble shoot any errors. We encountered the following issues and solutions while cutting:
Tool Path Design and File Prep
Initially, the design team was having issues with the flat pack plug in, since they were mostly working on OS platform. They were able to flat pack some of it, but for the most part each piece was manually imported into the V-carve file. That took some time to figure out and laying it out in the most efficient way possible.
Following the online tutorial we were able to get most of the settings right but we did encounter some issues. We believe the strange translation between programs and operating systems was causing some issues with joining vectors even after we did the Join/Close vector command. We went back and forth between the tool path calculations to make sure all the vectors were closed, so we had to do that manually as well.
Selecting each individual circle for pecking tool path was a pain in the butt, but we found the most efficient way is to drag the mouse in the circle pattern and collect all around it while holding shift button. Someone please invent a plug in or function to detect circle vectors in V-Carve.
Something that helped optimize the cutting was to separate inner cuts from outside cuts, so we had tool paths total (in order) Pecking, Inner path, Outer path.
Cutting:
We hadn’t done pecking on the shop bot before so we weren’t aware that the pecking depth didn’t need to be more than 1 or 2 per hole. Our initial setting for the peck depth was .75 mm which for a 12 mm cut depth was around 16 pecks per hole. That took about 4-5 hours of cutting. For the later cutting we set it to be 6 mm per peck and that helped significantly
We had several pieces that did not survive the first run, due to faulty tab settings and some dog bone errors. They weren’t appearing on the tool path at all since the material is 9mm thick, while our cut depth is 12. We had initially set them to 1 mm, which did not appear to make a difference at all. Then 3 mm, which only appeared on a few of the pieces. 4 mm seemed to be the ideal since it left Just enough material for the pieces to not move, but also snap out very easily without the need of external tools. Basically for tabs it would be:
Cut depth (12mm) - Materal thickness (9mm) + 1 or 2 mm. See below for the resulting tab.
Several pieces of web started to wobble due to tension form the machine and the very narrow amount of material between them did not provide enough support. This is the resulting cut in the web:
This also created some warping in the sheet which caused some of the outside and inside cuts in the smaller pieces to not be deep enough. We fixed this by doubling the spacing between the webs in V-Carve which provided enough support and adding the tabs correctly.
Re-Cutting:
A useful way to keep track of Re-cutting on the same sheet is to save several versions of the VCarve file. Each new version contains all the previously cut vectors, for reference, but you delete the existing tool paths every new version. See below:
Just remember to delete them under the toolpath settings and start fresh so there won’t be any confusion or doubling of tool paths during the cutting process. Ideally this is all done in the same session so that you don’t lose your Z-axis if the shop bot is turned off. In addition this is very helpful while working on the assembly as it will allow you to quickly edit and cut pieces as needed. Below is an example:
In addition, I helped Oceane with creating the casing for her raspberry PI camera module, this is also great because It will help me learn how to do this for my own final project as well!
