Robotics 2010-08-16

I should have started a robotics diary prior to now, but I didn’t, and yet it has to start somewhere. So we’re starting with an entry about a band saw. It has a happy ending.

A few weeks ago I purchased a Ryobi 9″ band saw. Then I procrastinated about using it because I needed to get an MRI and I had heard that metalworking could cause MRI related issues. So, with the MRI behind me, I plowed forward today.

First, however, some context… In the last couple of years I’ve been spinning up on doing some robotics tinkering in fits and starts. I bought the book Insectronics and decided to use it as a template for a project. I didn’t want to do VisualBasic, so instead of using the PIC micro-controller they suggested, I settled on an Atmel that would allow me to use a Linux tool chain and the C language. I got such an MC on a prefabbed board, acquired some servos, wrote some simple code to apply differing pulse width modulated signals, and got the servos to dance. Later I acquired all kinds of other tools, e.g. a signal generator, a digital oscilloscope, a regulated variable voltage power supply, a drill press, and so on. I flailed a little bit trying to find metal for the chassis but eventually discovered through a friend of a friend and got rolling. Then I got me a band saw.

I read through the band saw’s instruction manual. “This saw is intended only for cutting wood.” Oops… Well, kinda “oops”, but it’s OK. The saw, an el cheapo $100 model, has a non-variable speed drive train running at 3K FPM. Even with a metal blade (which I acquired separately) you would not want to cut most metals with this saw, but apparently aluminum is soft enough that it’s OK (though 3K FPM is the upper end of recommended). A for realz metal cutting band saw is quite a bit pricier, the extra large tag affording you such niceties as variable speed as well as liquid cooling. But hey, I’m just cutting aluminum, and not too much, so it’ll be fine. And if it isn’t then the worst I’ll (hopefully) do is wreck blades a little too fast or possibly clog up a $100 machine. Whaaaaatever…

Fastforward back to today… I unplugged the band saw, popped open the case, removed the table aligning bolt, took off the blade guard, and pulled out the table extension so I could take out the blade. Then I goofed and thought I could release enough tension by undoing the knob on the top, which I turned too far and had fall off, totally releasing tension on the blade. I was supposed to use the lever on the side for gross adjustments. Live and learn… Also, I thought I might have caused more serious problems with the top wheel, but then realized that its apparent lack of alignment was simply the result of the blade not putting it in tension.

Carry on! I put the metal cutting blade on the wheels, turned up the tension until the blade sang with a musical-ish note, then hand turned one of the wheels while fiddling with the blade alignment knob until the blade rode the center of the wheels. It looked good, so I reassembled the rest of the system, plugged it in, put on goggles and gloves, and got ready for the moment of truth. On it goes! No horrible grinding noises or scraping sounds… Now for a test cut… I had my brother standing nearby ready to dial 911 in case it turned out I had done something stupid. But I hadn’t… I fed a bar of aluminum through the blade, no blood went flying, and the bar separated in two. WIN! I even had the presence of mind to put a wastebasket by the saw’s exhaust port. In the future I ought perhaps hook up a wet/dry vac as recommended.



Leave a Reply