In an earlier post, I briefly discussed building the Hobby CNC driver board. In the following photo, you can see the board on my bench while I test it with the power supply and tune in the vref for current control.
By some fluke, the entire kit ‘n kaboodle worked on the very first try! Now, Monstro The Stepper is NOT a fast motor. My initial attempt to run it at a reasonable speed failed quite conclusively. At very low speeds, it does just peachy. While testing, I noted that the stepper driver got very warm. When I came back and did some testing later I used a clothesline clip to fasten a piece of aluminum to the driver. You can see it in the following video. The chip seemed to remain quite cool with this very small amount of heat sink. Just to be safe, I plan on putting large heat sinks on all four drivers.
Once I recovered from the initial shock of seeing the motor moved, I wasted little time affixing it to the mill. It took a while to solder the hookup wire and get the motor physically attached, however it didn’t have any trouble driving the Z axis without any load. Swell! The motor worked great without a load! Now, the real test would be to attach the head and try again. If I were to guess, I would say the head weighs between 60 and 80 lbs. Getting it wrestled into place is generally not pleasant, but since I was very excited it seemed a lot easier this time. The results can be seen in the following video.
Now, time for a couple of interesting notes. First, the motor was originally set to a very low speed. Stepper motors have much more power at low speeds. Even at the low original speed, the motor sometimes stalled when coming out of low current idle mode. I slowed it down even more to counter this effect and it worked very well. I’m happy with the results for two reasons. First, the speed is still reasonable. Remember that movement along the Z axis is normally limited to less than an inch so slow isn’t a big deal. Second, I’ve got a gas spring kit that I have not installed yet. If I want, I can install the spring and then increase the stepper speed. I may not do this, however, since heavy is usually better for milling. The spring would actually take away force that the machine can use when plunging.
In the above picture, you can see that the stepper motor is completely covered by the factor electronics enclosure. Also, note the block of wood under the quill. I had a very pleasant and unexpected surprise when I turned off the power to the stepper driver. The head didn’t crash! It would not have been a surprise for the head of the machine to crash once power to the motor was turned off because steppers only have a strong hold while powered. Even when I leaned on the head, it didn’t move. This means that I can use the machine like a drill press when I’m not milling something. A drill press with a 1” capacity! If this works out, I may even put my current drill press in storage. If you’ve seen the Secret Laboratory, you know exactly how much space it doesn’t have.