Lathe DRO questions

[ching0n]

Anyone running a DRO on their lathe? I've got a few questions.

I figured I'd want a 3 axis unit, can the third axis be used for rotation of the spindle? Am I wrong in understanding this or will it only interpret linear motion?
Do most DROs have a lathe function? Can I set tool or material functions as targets?
Can I set DRO to do surface feet per minute w/some math logic using the cross feed & RPM signal? I was considering a separate unit that does this but figured if I did a DRO it may be built in.

Thank you,

 

[Firebrick43]

Anyone running a DRO on their lathe? I've got a few questions.

I figured I'd want a 3 axis unit, can the third axis be used for rotation of the spindle? Am I wrong in understanding this or will it only interpret linear motion?

They will not work with the rotation axis. I am not sure what you would even expect to do with that data on a lathe if you could get it

Do most DROs have a lathe function? Can I set tool or material functions as targets?

I don't know about the cheap chinese but all the good ones I have used and installed have a lathe mode, where you can measure/set offsets based on tools, and also material subtracted (double the actual cut)

Can I set DRO to do surface feet per minute w/some math logic using the cross feed & RPM signal? I was considering a separate unit that does this but figured if I did a DRO it may be built in.

Thank you,

I have not seen that functionality yet in any I have used. I still don't understand how it would help. The DRO cant control anything unless its a software DRO that is part of a CNC controller. IF feeding by power on the cross slide what are you going to do with the information of knowing SFM at that very moment. If you plan on hand feeding the cross slide to maintain an SFM number, its highly unlikely you will be smooth enough to rival the surface finish of the power feed even though it doesnt maintain constant SFM in an x axis cut

 

[paulsomlo]

I have a DRO for just the longitudinal axis - the crossfeed sensor got damaged during transport. It would be nice to be able to zero out the cross with the push of a button, but I can live with it. Don't worry about spindle speed - your eyes and ears will tell you what's right and what's not.

 

[ching0n]

They will not work with the rotation axis. I am not sure what you would even expect to do with that data on a lathe if you could get it

I don't know about the cheap chinese but all the good ones I have used and installed have a lathe mode, where you can measure/set offsets based on tools, and also material subtracted (double the actual cut)

I have not seen that functionality yet in any I have used. I still don't understand how it would help. The DRO cant control anything unless its a software DRO that is part of a CNC controller. IF feeding by power on the cross slide what are you going to do with the information of knowing SFM at that very moment. If you plan on hand feeding the cross slide to maintain an SFM number, its highly unlikely you will be smooth enough to rival the surface finish of the power feed even though it doesnt maintain constant SFM in an x axis cut

The information would be a "manual feedback loop" of sorts. My understanding is there are tables of established feedrates (in SFM) for best surface finish based on material, tool, and diameter. You wouldn't adjust on the fly but you would after x number of passes before beginning another cut. These tables would in theory live in the DRO and you'd just input your material # & diameter (or from cross-slide). I get that this is something gained from experience but the tables are basically a cheat code and a collection of industry experience.

The device I had looked at was this:

Trexon Tachulator Digital Tachometers

www.mkctools.com

And per some research, DRO seems to be a 'maybe', here's one discussing it but I had figured it may be standard on industrial DROs:

More New Features in TouchDRO

Blog dedicated to DIY digital readout TouchDRO and other hobby machining and engineering subjects.

www.yuriystoys.com

TouchDRO - Touchscreen Digital Readout (DRO) for Lathes and Milling Machines

TouchDRO is a touchscreen digital readout for manual mills and lathes. Designed, assembled, tested, and shipped from Portland, Oregon, it supports most common DRO scales and has been trusted by machinists since 2012.

www.touchdro.com

 

[GeoBruin]

TouchDRO is pretty cool. The best part is if a feature doesn't exist yet, it might in the future. It's just software that interprets inputs from the sensors and it's always improving. I'm going that direction for both my mill and lathe when I get around to installing a DRO

 

[Firebrick43]

Ok i understand where your coming from now.

Let me lay out what i know about commercial DRO.

I have installed mitutoyo and acu-rite DRO's as in complete replace of an older one maybe half a dozen times. Every time but one it was physical damage and replacements of the old NLA. I have replaced quite a few more glass scales than that from damage and piss poor cleaning on newalls and heidenhain. Installed hundreds of replacement scales on CNC machines over the years, mostly heidenhain

Many 3 axis DRO can display position of a spindle with a rotary encoder. We had a lot of multi insert cutters and our insert setting stations had DRO's with rotary axis but it was slow speed, moved by hand. The information of a powered spindle would be unreadable to a human across the DRO. Even a lot of CNC lathes don't have spindle encoders, just a speed (hall effect) sensor unless they have live tooling.

The main issue with what you want to do is DRO's need to be really robust and usually are really dumb. For the most part all they do is count, zero the count, and remember a few tool offsets from zero.

Machinist when i would install a new one would get giddy because the new one could remember 40 tools and have multiple zero points stored in memory(datums). Go back in a few weeks and not a single one would be using those options.

I have seen some newall lathe DRO's with RPM built in but I never saw a SFM calculator built in.

Almost all CNC lathes from the last 30 years have what you are wanting to do built in.

I was going to mention Touch DRO but you were talking about commercial units. Its tablet would have the processing power to run programs if anything could. I have not physically messed with one yet but I looked into one a few years ago for a friend before he decided to just go with a commercial unit for durability's sake.

 

[Firebrick43]

A little reasearch shows that heidenhain makes an odd DRO/controller? that could possibly do what you are asking. The ND 7013. It actually controls the spindle speed via a VFD analog input.

Its 2500 dollars for the head unit and then you need to buy compatible scales that are likely to exceed that number. It also needs switches to know what gear its in to do so which would be very complicated in a lot of lathes to impossible with a viable speed lathe with reeves drives as it doesn't actually have a speed encoder as I read the documentation (very quickly so I may of missed it) but calculates it via the programmed ratios of each gear. I don't know how you would do it either with a belt drive lathe so it knows which belt position you are in?

I guess you could set up programable IFM distance switches to see or have a manual set of switches that you select when you change belts? Of course that would be rife with the possibility to make a mistake.

 

[ching0n]

A little reasearch shows that heidenhain makes an odd DRO/controller? that could possibly do what you are asking. The ND 7013. It actually controls the spindle speed via a VFD analog input.

Its 2500 dollars for the head unit and then you need to buy compatible scales that are likely to exceed that number. It also needs switches to know what gear its in to do so which would be very complicated in a lot of lathes to impossible with a viable speed lathe with reeves drives as it doesn't actually have a speed encoder as I read the documentation (very quickly so I may of missed it) but calculates it via the programmed ratios of each gear. I don't know how you would do it either with a belt drive lathe so it knows which belt position you are in?

I guess you could set up programable IFM distance switches to see or have a manual set of switches that you select when you change belts? Of course that would be rife with the possibility to make a mistake.

I'm not doing close loop for the motor, I'm currently using a brushless and the controller does a good job of maintaining speed; that has built in hall sensors. All I'd be doing would be manually ramping up or down the motor speed based off a SFM display. Look at the tachulator I link above, basically I want that in a DRO . That one uses an optical sensor so you just paint lines on the headstock spindle and it's enough. It's real simple math so figured a DRO could handle it....even if I need to enter the diameter manually (though it'd be nice if it just updated based off the cross feed signal).

The other option of course is just run a DRO + the tachulator, it's inexpensive but wanted to avoid cluttered redundancy if able to.

 

[Firebrick43]

I'm not doing close loop for the motor, I'm currently using a brushless and the controller does a good job of maintaining speed; that has built in hall sensors. All I'd be doing would be manually ramping up or down the motor speed based off a SFM display. Look at the tachulator I link above, basically I want that in a DRO . That one uses an optical sensor so you just paint lines on the headstock spindle and it's enough. It's real simple math so figured a DRO could handle it....even if I need to enter the diameter manually (though it'd be nice if it just updated based off the cross feed signal).

The other option of course is just run a DRO + the tachulator, it's inexpensive but wanted to avoid cluttered redundancy if able to.

I looked at the link already. I fully understand what you want but you know what they say about wishing in one hand and what goes in the other.

It looks like the tachulator to me is out of production and only a few parts are still available.

 

[PopcornSutton]

I do a lot of barrel work on my lathe. I had a DRO once, and for my work I took it off. I tried to watch those numbers while threading to a shoulder, not for me. Turning to diameter is easy with the dials. I use a 2" travel dial indicator on a mount on the ways to control X travel. And a digital on the tailstock for feed.

Now for a mill, DRO all the way!

 

[ching0n]

I do a lot of barrel work on my lathe. I had a DRO once, and for my work I took it off. I tried to watch those numbers while threading to a shoulder, not for me. Turning to diameter is easy with the dials. I use a 2" travel dial indicator on a mount on the ways to control X travel. And a digital on the tailstock for feed.

Now for a mill, DRO all the way!

I was going to take the plunge on these which are basically dial indicators slides w/a remote display:
https://www.ebay.com/itm/166618386236

but now I'm changing my mind....honestly don't see much difference between dro and mounted dial indicators (except having to look up & making the math a little easier.) Accuracy & resolution on the ones I link seems kind of garbage.

 

[PopcornSutton]

I have a 14x40 Acer that came with a tach readout, since it also has a VFD. So there is no gears to change for rpm which would tell you what rpm you selected. While I occasionally mount a barrel full length, it is seldom I utilize the full length of the bed. Maybe in some line of work, the need to have a readout 36-40 inches long, my work is done up at the chuck. I haven't run across needing more than the 2" travel of the dial indicator. And the cross feed, mounting the scale is usually done on the tailstock side which might not let the tailstock get as close to the carriage.

But, there are many lathes with DROs and people love them. It's your choice. I went a long time before putting a DRO on my mill, and kick myself every time I use it for not doing it years ago!

 

[paulsomlo]

What lathe is this going on?

 

[ching0n]

What lathe is this going on?

6x18

 

[Firebrick43]

6x18

It’s not the size but how you use it.