DRO for dummies (aka .... me)

[Bradells]

I didn't want to derail the https://canadianhobbymetalworkers.com/threads/need-a-dro-what-one-to-get.2193/ thread...

But (for now).... Can a "big boy" DRO display take input from say digital callipers directly (matching up the data pins) or other magnetic strip reader?

Or, can the above work, but needs an adapter box in-between because they may be different protocols (that already exists)?

Glass scales are too big for my current machine.

I've looked at the TouchDRO system (have an android tablet in the shop for quick CAD "math" and tunes), but looking to 'future proof' a little more with an actual physical DRO display ... Thoughts?


Brad

 

[YYCHM]

You have Digital Callipers have an output port?

 

[Bradells]

You have Digital Callipers have an output port?

I have a bunch of 6" that do ... sadly the 8" ones I just got today don't (back to Amazon for some more 'expensive' ones that look like they do ... same body style as my 6")

Brad

 

[Dabbler]

Ok - one answer is "it depends"... There are slimline DRO scales that fit almost anywhere.

A lot of people mount a digital caliper-type display on their lathe tailstock, and mill quill. They are very handy and help get you to good work faster.

Now that I am used to using a DRO on a mill I almost couldn't work without it. Really the most valuable place for a DRO is on a mill. Assuming your gibbs are reasonably tight over the range, it is easy to do very precise work, even with a worn lead screw.

I've never used a DRO on a lathe, but I'm tempted.

The short answer is that you can make digital calipers work, but you get the same function using a travedial** in X and Y for a lot cheaper, and less hassle to set up.

** a Travedial is a 2" or 3" plunge indicator on a magnetic base with a reference surface so you can make the direction of plunge parallel to the direction of the carriage or knee.

All this depends on the accuracy you need. If you are +/- .003 or so, using the dials is usually good enough.

 

[Johnwa]

Short answer is no.
The port on the digital callipers is a serial port. The output is the actual reading of the display. There are many Arduino projects that adapt them to a custom display.

The “big boy” DRO scales output a Quadrature signal, two sinusoids or square waves that are 90 degrees out of phase. The display unit counts the transitions, determines direction and calculates the reading. The electronics of a digital calliper do the same thing by the way.

I think @Dabbler is referring to the igaging type of DROs that use a Caliper type mechanism but have a remote readout (I’m not happy with mine)

I have clamped a regular digital calliper to my lathe and used it as a “travel dial”. That works quite well.

 

[DPittman]

"I think @Dabbler is referring to the igaging type of DROs that use a Caliper type mechanism but have a remote readout (I’m not happy with mine)"

What don't you like about them John? I have some on my lathe and have really liked them but the one display does freeze up initially quite often and has to be repowered on/off to reset. There are black faced models that are not as accurate as the " absolute" model that I have. The scales of mine are nice and narrow...basically a digital caliper style. Here's a picture of mine on the cross slide of a 10x22 lathe.

 

[Tom Kitta]

I am with Dabbler again - a DRO on a mill is addictive - I cannot work without it now. On a lathe I am thinking of a DRO but I can do work within 0.001 without a DRO on a lathe with relative ease - I did it yesterday. Lathe and mill are quite different - on a mill you do many multiple passes to same location or multiple fix locations - without DRO it would be a pain to do it accurately especially knowing of a backlash.

On a lathe you usually do very few passes or maybe even only one pass to dimension.

 

[Dabbler]

@Johnwa I was referring to Sony's slimline magscale and another brand of glass scales that have a very small footprint. The usual offshore ones are a bit larger, I think.

My DROs are a Mitutoyo glass scale accurate to half thou, and a Sony magscale accurate to 2 tenths. They perform very well for me, and I love using them.

I have always heard great things about the offshore DROs. Only in a couple of instances have I heard about scales or displays going out. From a pragmatic perspective, they are so inexpensive relative to their genuine value, that owning an extra display unit is a cost effective version of self-warranty.

-- electronics geek suggestion on this, though. If you buy an extra head, don't just leave it in the box. A very common and necessary component regularly used in electronics is the electrolytic capacitor, which ages badly if it isn't charged and discharged at some interval. So plug it in, and turn it on for an hour every month, and it will be a 'hot spare' in case you need it. --

(cheaper than buying an extended warranty from a big box store or memory express)

 

[Johnwa]

@Dabbler Do you have any use for a 300mm Mitutoyo scale. I have one that I was thinking of putting on my z axis. However, Mitutoyo uses a sinusoid signal which is more difficult to adapt than the common ones with TTL signals. I’m thinking it might be more trouble than it’s worth trying to make it work.

 

[Johnwa]

I also have a 750mm TTL scale that I will trade for a 450-500mm scale. I hate the thought of cutting the long one down.

 

[Dabbler]

I don't think it will fit my older Mitutoyo. If I want to use a newer scale, I have to buy an adapter costing as much as the scale itself. Thanks for the very generous offer, but I'll have to live with what I have (which still works thank goodness)...

 

[PeterT]

I've often wondered why 'micro DRO' systems aren't available for small machines. Supply & demand & custom fitting issues I suppose.

Sherline has a system for their equipment. I didn't watch the full video but it almost looks like the encoder works off the turn handles... which... I'm not entirely clear how that would mitigate backlash compared to linear systems that are reading direct displacement. Maybe I'm out to lunch. I just happened to land on it googling
https://www.sherline.com/product/82008260-2-axis-lathe-digital-readout/

In typical DRO's one has to consider both the linear scale and the encoder/reader head as an assembly. If you have a small section, compact scale but a bulky encoder, it may still not fit.
Example Shooting Star scale (red arrow) is a ~0.25" steel rod with teeth cut down the side. The cover (orange arrow) is just one of those wire shrouds maybe 0.5" diameter. The reader head (purple arrow) is somewhat compact as far as systems go but they all seem to be bigger than a match box. (ps I'm not advocating the company, there are pros & cons including price, just mentioning 'systems')
http://www.star-techno.com/INFO.HTM

This site is kind of useful for reference because they show glass & magnetic scale systems, general info & more importantly some installation pics & dimensions of the scale/reader assembly.
https://www.dropros.com/

Newall has a system with small diameter 'tube' scales. Very reliable but $$. Notice the reader head still occupies some volume though.
http://machinetoolsforsale.com/Newall.htm

Something like this (which is offered under different names) might be the closest match, but the lengths still ave to match your machine.The scales cant be cut
https://www.accusizetools.com/3-axis-dro-display-unit-scale-not-include-1104-0110/

These are kind of generic. Some people use them for downfeed on bigger mills or tailstock for regular lathes
https://www.accusizetools.com/electronic-digital-dro-scale-unit-horizontal/

Before I had a DRO on my lathe I just used a dial indicator with a magnetic back. Attach to lathe bed & plunger makes contact with the carriage or some convenient stop. If you get a cheap digital dial, you essentially have a re-settable digital scale. This wont give you the full range like a caliper base system though.

 

[Bradells]

Yeah the sherline system is based on the handwheels, and you tell it what the backlash is... not a fan, but it is ‘clean’ on the machine though... compared to making a direct reading one...


I’ll check out those links.


Thanks!

Brad

 

[Bradells]

The other thing, is the lathe bed is also my mill bed .. so while it may be overkill to dro the lathe, it makes up on the mill side of the setup

Brad

 

[YYCHM]

Lots of mini machine DRO options here https://littlemachineshop.com/products/search.php?tabName=Products&term=DRO

The ones I had on my 7X12 counted screw revolutions and left a lot to be desired.

 

[Johnwa]

I don't think it will fit my older Mitutoyo. If I want to use a newer scale, I have to buy an adapter costing as much as the scale itself. Thanks for the very generous offer, but I'll have to live with what I have (which still works thank goodness)...

@Dabbler How old is yours and do you have the manual for the head? My scale has a round 8 pin connector that I haven’t been able to find the pin out for. I have found the pin out for the Dsub15 connector.

 

[Bradells]

Next dumb question ..

5micron ~= .0002 inch?

So if I was looking for a +/- 0.0005 readout, 5micron is enough and not need to get a 1micron scale/reader?


Brad

 

[Dabbler]

It takes very special techniques and tooling to do work in the .0002 range, let alone 1/5 of that. .0005 resolution (12 micron or so) is also fine. I have no problems with my mill and half thou.

 

[DPittman]

I've heard from others that too fine of a resolution and it gets frustrating because you are trying to hit the same number and it fluctuating all around when in reality that sort of precision is either not needed or unobtainable in many cases.

 

[Bradells]

I've heard from others that too fine of a resolution and it gets frustrating because you are trying to hit the same number and it fluctuating all around when in reality that sort of precision is either not needed or unobtainable in many cases.

Just would like to see 0.0005" as that's what I can measure ... So I guess I won't worry as much about 1/5micron.


Brad