This semester I’m taking 2.72, in which groups of 5-6 design and build a desktop lathe that can machine a part accurate to 50 microns. It’s an awesome class and a great way to end a mechanical engineering degree, as it forces us to revisit some of the basics we learn right off the bat (shear and moment diagrams, anyone?) and use them in intelligent ways.
One of the things I’m working on is the fatigue analysis for the spindle shaft — the part that transfers torque from the motor to the part you’re trying to cut. It’s pretty fun and super interesting, but probably a bit too detailed for a blog I want to keep mostly as pictures. However, one of the things that can affect the endurance stress of your shaft is temperature. So today I got to play with a thermal camera. 🙂
Basically we turn the lathe on and let it run for about ten minutes, then look at how hot it got.
The first is: you’re not really looking at the spindle shaft. The shaft is inside the housing, we’re just looking at the ends which poke out. The ends look to be at about the same temperature as the housing. Problem! The shaft inside is probably hotter. And we weren’t really able to disassemble the lathe that fast to get a look at the shaft once we stop spinning it.
The second is: the belt drive gets super hot! But it doesn’t actually transfer heat to the shaft, probably because the pulley is plastic and gets a lot of air flow around it.
So overall the experiment wasn’t a huge success. After doing it once, though, I feel like I could go back and do it much better (i.e. disassemble the lathe quickly enough) and run the whole experiment in half the time. We had issues with starting up the lathe correctly and getting the camera to work.
Another fun thing about thermal cameras: The heat of your body can easily reflect off of a metal surface. So if you image something while standing right in front of it, you’ll get artificially high readings due to the fact that you’re standing there. Awesome. 🙂