Using the CNC in the Build Lab

For my street seat project I decided to learn how to use the CNC in the Build Lab. The Build Lab is behind Cowgill in the basement of Bishop-Favrao hall. To sign up to use the CNC you just talk to one of the students that work there, tell them about your project, and then they can schedule a time for you to come in. If it’s a large project like mine, they’ll schedule the whole day for you. If it’s your first time using the CNC, make sure you talk to Daniel, he’s the only one that really knows how to use the machine, and he can probably come in during your scheduled time to teach you how to use it.

If you’re using full sheets of plywood like me, you can store them right outside the build shop on one of the sheet carts. Make sure you grab an orange name tag, fill it out, and tape it to your material. Before you come to the lab, make sure you have your file on a flash drive in the form of a .dxf and .pdf in case one of them doesn’t work with the machine. Include small tabs in your line work so that the material doesn’t come completely loose while cutting.

The first thing you need to do is load the .pdf into the program that sets up your toolpaths. It’s a long and tedious process to select all the paths and apply the correct toolpaths so I would recommend bringing a mouse so you don’t have to use the trackpad the whole time. Then you save the toolpath file onto your flash drive and then setup the machine to run. There is a CNC instructions word file on the CNC laptop that you can open and it will walk you through all the steps to turning on the machine and running your program. Make sure you are very precise when zeroing the bit to the corner of the material. If you have to stop halfway through because the shop is closing like me, then you’ll have to re-zero the machine the next time you come back because the machine loses its zero when it shuts down.

The whole process of troubleshooting and setting up the machine to be just right for my project took about 3 1/2 hours so I’ll let you know some of the problems I ran into in case you run into the same ones. The first problem I ran into was that we accidentally resized the linework file will orienting it in the toolpath program. So be careful when rotating your selections. The next problem really annoyed me; one of the tools that was named “0.25 in” was actually programmed to be recognized as .125 inches in diameter. So always double check that the diameter is set correctly. Another big problem that I kept running into at the start was that the CNC was cutting my paths on the inside of the line instead of the outside. It turned out that since the paths weren’t closed paths, what the program thought was the outside was actually the inside. All I had to do was change the toolpath to cut on the “inside” and it worked perfectly.

The troubleshooting process ruined a small section of my plywood but luckily I had plenty of duplicate parts so it wasn’t a problem. Also, a note about the time it takes to cut out a project. You can see in the picture above that my linework was pretty dense so the CNC had a lot of work to do. Half of the sheet took about 3 hours. As I’m writing this, the machine is still cutting my project so I don’t know the final time but it’s taken me two sessions and I won’t even have time to cut my second sheet. So if you have a large project, make sure you come in early and are ready to work until the shop closes.

I hope this post will be helpful to someone who wants to use the CNC in the coming years. Ask me if you have any more questions about using the CNC in the Build Lab.

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