A week or so ago, a shiny new DRO unexpectedly(ish) arrived at my workshop.... OK, not that unexpected really; it's for my old Edgwick lathe. It's also not the story for this thread - I'll document the fitting, and some of the hoops I had to jump through, elsewhere, when it's closer to being done.
My original plan, before the Chinese manufacturer (Ditron - via AliExpress - good crowd, based on my experience) heavily discounted the DRO readout for me, was to just buy the scales, and use an Arduino to read them. Initially, I'll be using the supplied DRO head, which is actually surprisingly usable.... but long term I still want to make my own, with the features I want in it...
Also - due to impending arrival of first child - I'm about to lose most of my workshop access privileges (and time!), which means much more time sat around at home with a relative paucity of tools... so I plan to fall back to plan "B" and use my software skillz to write the DRO head software for the DRO
I want. And it also occurred to me, that you, gentle reader, might have some ideas of what makes a good DRO for you that I haven't thought of....
So, the overall plan looks like this:
- Each axis will be connected to a cheap Arduino clone (Mini Pro, probably, as I have a bag full of them). One per scale, because with the 1 micron scales I've bought, they can't reliably keep up with more than one - and also, the system needs to track both A & B channels fully, in order to get the 1 micron resolution.
- Each axis will communicate its scale position to a Raspberry Pi, which will be running the DRO software
- A 7" touchscreen will provide the primary interface.
- I may also add some real buttons, if it turns out that regularly jabbing a touch screen with oily fingers doesn't work too well...
So far, I've "built" (the word is massively over-used in this regard) a one-scale reader, which appears to work fine. Yes, you can trick it if you move the scale too quickly.... the only part of a normal lathe/mill I can see this potentially being a problem is on a quill-mounted DRO, where it's possible to move it faster (I think - haven't tried) than the Arduino can count. I'm wondering about the carriage too, I can move that pretty quickly on the lathe. If it is an issue, there are faster boards out there than the Arduino.
Anyway.... with the basic principle established, now's the time to start designing the features. So far, I have:
Readout:- Obviously, the basic "N" axis readouts are essential. In addition to the usual switchable decimal inches/metric; I think I could display both simultaneously (primary and secondary, secondary being smaller). Not sure how useful that would be.
- For our American friends, I wonder, would an inch fractional readout be useful? Maybe down to 64ths, with the secondary readout showing the usual thousands or tenths.
- Ability to re-name/move around each axis in software. So if you don't like the conventional "Z-Y" on a lathe, you can rename them "Carriage" and "Cross-slide", for example. Or "Tailstock". Or whatever Tailstock is in your first language.
- Nice big numbers that are easy to read. Actually, the Ditron scale is excellent in that regard, I will shamelessly copy it. But also allow the user to configure the colours.
- All-axes reset from a single button (with undo). Again, the Ditron partly does that (you can undo a zero press), but to zero all four axes requires four button presses. And really, who has the time for that, eh?
Features:Some ideas below for things the DRO can do.
- The usual Chinese DRO functions: Bolt pattern, 1/2 function being the two that instantly spring to mind.
- The ability to combine two axes. e.g. on a mill, the Knee/column "Z" axis, could be paired with the quill "z" axis, to give a unified read. So now, move either the table/column OR the quill, and your "Z" reading moves as appropriate. On a lathe, you could combine the main carriage + compound slide axes so you can accurately bore to a certain depth using the compound, even if you accidentally moved the carriage last time you measured it (don't ask me why I bring THAT specific example up!). It also occurs to me that, with a smidgeon of trigonometry, you could accurately cut a depth even if the compound is at an angle, if you can type that angle in somewhere. Or have a rotary encoder on the compound slide too!
- Targeting with audio alert: By which I mean... let's say you want to bore a hole exactly 1" deep. Rather than watch the DRO, wouldn't it be nice if it beeped at you as you got close to your target depth; the beeps getting faster & eventually becoming a solid tone as you reached depth. Almost exactly the same as reversing sensors work on cars... Just means you don't need to keep watching the DRO instead of the workpiece.
- Switchable diameter/radius mode (for lathe cross-slides). No more having to remember to half the depth of cut to hit a specific diameter.
- Tool library (I think most Chinese DROs implement this in some form. I've watched This Old Tony going through his DRO functions, and I reckon I can make it an order of magnitude easier to use). This won't be much use on my lathe, as my toolpost is not particularly repeatable. Plus I don't have anything like enough tool holders.
- Angular readout: If I ever find a cheap dividing head on eBay (or maybe make one?) that I can experiment with fitting a rotary encoder to... it would make gear cutting a more straightforward operation. That said, if one is going to that much trouble, maybe it'd be easier to just make an "cnc-esque" dividing head with a stepper motor & remote control. Still, it'd be cool if the DRO could control it, wouldn't it?
That's all I can think of right now... but I should have a decent amount of time to incorporate any scope-creep that might come along; and if there's any feature you can think of that I could sensibly add.... feel free to suggest it.
I'm also happy, once the basic principle is proven out & the software is at a point where it could be considered useful, to build a DRO unit for any madmodder, for the basic cost of the parts & postage. i.e. no labour & no fee for the s/w, if anyone is interested? Note that at this time, I have pretty much zero idea how much the parts will cost! Although I do expect the screen to be the most expensive bit, at around £45.
PS: I'll also do a proper (and I mean, proper) write up of the plans and designs for all the parts (except the scales themselves), so you could build your own from the plans if you preferred). The S/W I will make freely available under one of the open source licences.
