Lathe DRO question
Lathe DRO question
I'm rolling my own DRO for a 7x10 mini lathe and hatched another one of my harebrained schemes for implementing it, figured I'd throw it out here before I take the plunge
Initially I planned on just a a DRO for the cross-slide as that's where I believe I need it most. As I got to thinking more about it, I figured out a way to also include a carriage position DRO using just the one sensor. The sensor in this case is a draw wire optical encoder; think of it as a precision tape measure.
If I do this, the sensor will indicate the total wire draw from BOTH the carriage (Z) and the cross-slide (X). This seemed like it might be a bad idea at first but, I found myself being more interested in relative movement rather than absolute movement, and in no case have I felt the need to accurately track more than one axis at a time. So lets say I just finished a turning operation and want to advance the tool in by 0.002", I don't really care what the absolute reading of the DRO is, I just want it to tell me when I'm 0.002" more (or less depending on direction) from where I am now. Similarly, if I'm using a boring bar and want to plunge it 3/4", it doesn't matter what the current reading is on the DRO, just tell me when it's 3/4" more than the current reading, from there I can set a carriage stop to finish the hole.
Since the encoder is connected to a computer with a monitor, a value would be prominently displayed which indicates the current movement from the last waypoint, no need to play the differential algebra game.
There are at least a couple reasons I'd do it this way. 1) It saves money, each encoder with an interface is about $175. 2) There's not a lot of left over real estate on a 7x10 lathe, keeping the parts count down means less things to get in the way.
So team, shows promise, certain to flop, consult a medical doctor?
Initially I planned on just a a DRO for the cross-slide as that's where I believe I need it most. As I got to thinking more about it, I figured out a way to also include a carriage position DRO using just the one sensor. The sensor in this case is a draw wire optical encoder; think of it as a precision tape measure.
If I do this, the sensor will indicate the total wire draw from BOTH the carriage (Z) and the cross-slide (X). This seemed like it might be a bad idea at first but, I found myself being more interested in relative movement rather than absolute movement, and in no case have I felt the need to accurately track more than one axis at a time. So lets say I just finished a turning operation and want to advance the tool in by 0.002", I don't really care what the absolute reading of the DRO is, I just want it to tell me when I'm 0.002" more (or less depending on direction) from where I am now. Similarly, if I'm using a boring bar and want to plunge it 3/4", it doesn't matter what the current reading is on the DRO, just tell me when it's 3/4" more than the current reading, from there I can set a carriage stop to finish the hole.
Since the encoder is connected to a computer with a monitor, a value would be prominently displayed which indicates the current movement from the last waypoint, no need to play the differential algebra game.
There are at least a couple reasons I'd do it this way. 1) It saves money, each encoder with an interface is about $175. 2) There's not a lot of left over real estate on a 7x10 lathe, keeping the parts count down means less things to get in the way.
So team, shows promise, certain to flop, consult a medical doctor?
Re: Lathe DRO question
'Sounds to me like you are more interested in having fun with a complicated non-measurement system than in getting machining accomplished.
I believe that simplicity is always the best solution to complex situations.
Each to their own.
RussN
I believe that simplicity is always the best solution to complex situations.
Each to their own.
RussN
- Bill Shields
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Re: Lathe DRO question
Ditto on that
If you enjoy diddling with electronics -. Have at it
If you are interested in making good parts with the help of a plug and play DRO -> then suggest you go a different direction.
If you enjoy diddling with electronics -. Have at it
If you are interested in making good parts with the help of a plug and play DRO -> then suggest you go a different direction.
Too many things going on to bother listing them.
Re: Lathe DRO question
I'd just as soon buy a P&P DRO, I can't find one for a mini lathe. The one LMS sells is really a dial gage, tracking the lead screw and is subject to backlash.
What do you all use for DRO with a mini lathe? Pictures would help too.
What do you all use for DRO with a mini lathe? Pictures would help too.
- Bill Shields
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Re: Lathe DRO question
As I mentioned earlier, 7x10.
- Bill Shields
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Re: Lathe DRO question
OK, fair enough, I'm very interested in having fun, I don't have much time left on this earth, I plan to enjoy every day to it's fullest.
It seems you believe what I asked about is complicated and a non-measurement, that's fine, I don't agree and that's fine too. Extrapolating that to me being more interested in the means rather than the end is fine too.
The essence of my question concerns the importance of being certain about the position of more than one axis at a given point in time, what are your thoughts on that?
Re: Lathe DRO question
Well there are lots of situations where that's important. But you could get there by becoming certain of one axis's position, and then (without moving the first axis) becoming certain of a second axis's position. If I understand what you're proposing, it could work.dml66 wrote: The essence of my question concerns the importance of being certain about the position of more than one axis at a given point in time.
I'm gonna guess that you're thinking about mounting the sensor on the headstock, running the line around a pulley on the saddle and then attaching the free end to the cross slide, something like this (looking from above):
Is that about right? If so, I have thought of a couple of things you might need to watch out for. If not, can you supply a sketch of your idea?
-- Russell Mac
Re: Lathe DRO question
I'm getting the same impression.
I believe that simplicity is always the best solution to complex situations.
Ditto. There are scales available that will fit a small lathe. I would take a look at that first.
I'd expect that your scheme would work, but would be a PITA to use on a regular basis. For one thing, you would not have a reliable reference point, since both coordinates would simultaneously change with carriage and/or cross-slide motion. Also, the draw wire for the encoder would be easy to mess up or break. The people who make scales for machine tools go to quite a bit of trouble to make their product difficult to disrupt. You wouldn't have that reliability, in my opinion.
If you are mostly in it for the challenge, have at it. As much as I like working with electronics (I scratch-build single-board computers for fun), I would not do what you are thinking. I don't think it will be trustworthy.
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Music isn’t at all difficult. All you gotta do is play the right notes at the right time!
Music isn’t at all difficult. All you gotta do is play the right notes at the right time!
Re: Lathe DRO question
dml66:
True, I do not clearly understand what you are proposing, mostly due to lack of illustrations.
I have difficulty understanding text string descriptions of technical things. My brain mostly processes visually.
One of my "challenges" I live with, and a major reason I strive for simplicity.
Although I do build steam locomotives...
Thanks for your response.
RussN
True, I do not clearly understand what you are proposing, mostly due to lack of illustrations.
I have difficulty understanding text string descriptions of technical things. My brain mostly processes visually.
One of my "challenges" I live with, and a major reason I strive for simplicity.
Although I do build steam locomotives...
Thanks for your response.
RussN