Several people asked me to post pictures of my DRO setup. Today I started installing a new DRO unit on my Grizzly G0463 (A.K.A. Grizzly Small Mill/Drill or Sieg X3) mill and decided to take advantage of this opportunity to take some pictures and post the progress.
I’ve been itching to get a set of glass DRO scales for a while but the cost has kept me off. Last July I randomly emailed a seller on eBay and asked if they would happen to have a returned or blemished unit they’d sell to me for experimenting. Surprisingly the guy replied that he is discontinuing the Easson scales and has two units [8” and 16”] that he’d sell at a steep discount. Additionally, he had one with a broken reading head that he’d throw in if I wanted it for parts. He wanted $200 for all three of the scales, including shipping. Needless to say, I jumped at the opportunity. When the scales came, I took the broken unit apart to see what’s inside and right off the bat found the problem. The Vcc line was broken and the exposed wire was shorting to the case. Five minutes later I had three working scales: one 8” long, and two 16”.
In early October I finally got some free time to play with the scales and finish the firmware for the MSP430-based DRO interface. Until now the scales were attached to the mill with a set of clamps and some 3M double sided tape (so I could take them off easily.) Now that the firmware is done and I don’t need to keep taking the scales to the “office” for troubleshooting, I can finally install them more permanently. Before installing the scales, though, I had some “remodelling” to do.
The iGaging scale for the Z axis was mounted to the column shroud but this setup felt pretty flimsy. Since glass scales are much heavier and more sensitive to misalignment, I didn’t want to risk it, and decided mount the scale directly to the column. Initially I planned to cut out a piece of the shroud just large enough to make space for the scale, but then decided to get rid of it altogether. This mean that the electronics and the controls had to be moved, but I was going to do that anyway [eventually] because reaching to the back of the mill to switch it on and off was pretty inconvenient, and seemed a bit dangerous at times.
The new control box came from an old speaker amplifier and a discarded shower hose provided a nice flexible conduit for the wires.
|Old speaker amplifier made for a nice control box|
with space to spare for future additions
While at it, I mounted an Ikea LED light and added 12V outlet for a ring light. All in all, the whole project took only a few hours and set me back a bit over $20, as most of the parts came from a local Goodwill store.
|Ikea LED lamp will provide a convenient work light|
If don’t know if these scales are supposed to come with mounting hardware; mine came without any brackets, etc. so I had to make them. Digging through my box of odd bits and pieces I found a piece of wide aluminum U channel, which, once cut lengthwise, provided enough material for both brackets.
|Finished brackets for X (left) and Y axis scales|
With that out of the way it was time to tackle the scales. Mounting the X axis scale was pretty easy. All I had to do was to drill and tap two M5 holes on the back of the table. The scale was almost the same length as the casting and the mounting holes lined up with the thick part of the table. I didn’t even need to redrill the saddle because the old holes lined up pretty well.
|The X axis scale was a prefect fit for the table|
The Y axis turned out to be a bit more tricky, though. The eight inch scale was a bit too long to fit next to the saddle ways. Moreover, I was told that the recommended way to mount glass scales was with the opening facing down, so there is less chance of oil and dirt getting into the inner workings. After a few dry-fittings I ended up mounting the scale on its side at the very edge of the base, barely missing the column. Even though the slit isn’t facing down, at least it faces away from the spindle, so hopefully it will be fine.
|8" is much too long for the Y axis and barely fits on the edge of the mills base|
|X scale's bracket in place|
The braket for the Y axis scale had to be a bit longer, since the scale was mounted more than an inch away from the carriage. To make sure that the bracket clears the scale's body I milled out a few hundreths of an inch off it's bottom.
|The bottom of the Y scale bracket had to be milled out to clear the scale's body|
|Both scales mounted on the mill and the cables routed and tied down|
My initial plan for the Z scale was to use two 0.75” steel spacers to mount the scale off the column so the head bracket could slide under it. Unfortunately that didn’t work at all; the end caps on the scale appear to be “hand made” and their mounting surfaces aren’t parallel. This was putting more stress on the scales than I felt comfortable with so I ended up machining two blocks of the same cross section as the endcaps. This did the job well, and after fiddling with the bracket for a few minutes the scale was ready to go.
|Z scale bracket and two standoffs|
|Z axis scale installed on the mill's column|
All in all the whole project, including relocation of the controls, took a bit over two evenings. A quick test looked good, so now I get to built myself a permanent version of the controllers as I’m still using the “bench” unit shown in the few recent for testing of the mixed scale firmware. If I get to it (i.e. pre-Chrismass “honey do” list doesn’t get in the way), I will post the update next weekend.