The AM Forum

Working on my current project, a 3X 3-500Z amplifier, inspired me to do something I have been meaning to do for years: install a digital readout on my milling machine.
   The readout can display two axis, but for now, I installed a linear scale only on the X-axis. Due to the configuration of my machine, installing a scale on the Y-axis will require a bit more work.
   As it was, a bit of creative fabrication was required to install the scale on the X-axis. To avoid the need for drilling holes in my machine, I used the existing T-slot on the front vertical surface of the table to secure the two mounting blocks for the scale. I machined the blocks from UHMW plastic, a very versatile and durable material. To help locate the blocks securely, I made them with a protruding key that engages the T-slot, while the usual bolt threads into the T-nuts inside the slot.
   The third plastic block, to which the optical read-head is mounted, is machined with a lip which maintains its alignment with the machine, and the thickness of this block brings the mounting surface for the read-head out to the same plane as that of the scale itself, to ensure that the read-head travels along the exact center of the scale, necessary for accuracy and also to prevent the read-head from coming in contact with the delicate markings on the glass bar inside the aluminum extrusion.  A length of heavy aluminum plate and a cover of aluminum angle stock protects the scale from metal chips, dirt, and incidental impacts.
   The readout and scale are Chicom stuff, from Amazon, but I think they will do the job. After installation, I checked the accuracy against my favorite Mitutoyo dial indicator, and it was flawless.
   For the next improvement, I would like to find a suitable zero-backlash ball screw to replace the original acme-thread lead-screw. A project for another day.

Very nice! I would have thought you would have needed something more mechanical like an LVDT to report position. Your display has large digits which is good for those of us with 'seasoned' eyes!

Thanks. It was a fun project. Although it is a cheap Chinese thing, it is capable of some cool tricks. For example, if you have both X and Y scales installed, the microcontroller in the readout unit can prompt you to bring the quill down at the proper coordinates to make a series of holes in a perfect circle. Sort of like a CNC machine, except the operator is providing the motion.
Yes, LVDT's are cool things. I worked with them a lot, years ago, in aerospace. I think they're used more often for shorter movements, though. This sort of linear scale is basically similar to an optical computer mouse that slides along a glass scale marked with very fine increments. The "mouse" generates a pulse every time it passes over one of the markings, and the readout does the rest.
I will eventually install a Y axis scale, but the configuration of my machine will make it more involved. When I get to that point, I'll post pictures, assuming I can get into the site again. I can't believe it's up right now. at 10:45 in the morning.
I would love to have a full-sized, modern CNC milling machine, but that's way beyond my financial means at this point in my life.