In the last post I started covering the installation of the glass scales on my Grizzly G0463 (AKA Sieg X3) mill. You might recall that I got the scales loosely mounted on the mill but didn’t have a controller to use them with. I didn’t want to tie-up the unit I’ve been using for testing, so before going any further I had to build a new one. This weekend I got some free time to finally build the controller and [mostly] button thing up.
|DRO interface ready to go into the garage|
The scale interface uses the MSP430 firmware for the glass scales, but the level shifter board is a bit different. Since I know what scales the controller will be used with, I was able to cheat. Instead of the LM339 comparators I opted for a set of voltage dividers. Using two resistors [per line] with a ratio of 33 KOhm to 20 KOhm reduces the 5V coming from the scales to a bit under 3.2V, which is pretty close to ideal voltage. The quill will use an AccuRemote scale that works well at MSP430’s native voltage, so it can be connected directly to the Launchpad input lines.
|DRO interface mounted to the wall|
The DRO controller is mounted next to the mill and ready to go. The board is wired for three glass scales and an iGaging or AccuRemote scale for the W axis. I haven’t made the bracket for mounting a scale to the quill, so the last port is not plugged in yet.
|The W axis is not used as the scale mounting bracket|
is still not done
Since the new DRO looked so much nicer than my “duct tape and bail wire” setup, I decided to mount the tablet more permanently as well. That is, if you call a piece of aluminum sheet zip-tied to a large screw hook “permanent”.
|A more permanent mounting bracket for the tablet|
|[Almost] finished setup|
The last step was to align the scales. To do this, I loosened the mounting screws on both end so they were just snug enough. Then I moved the scale to one end of it’s travel, tighten the screw, move the scale to the opposite end and tighten that screw.
Side note: I’ve heard from several sources that the glass scales being uber-sensitive to misalignment. In practice I found that this is not necessarily the case. The reading head rides the glass strip on a set of miniature ball bearing and is connected to the carriage via a spring, allowing for a fair amount of misalignment.