DRO advice for lathe?

[JimDawson]

You might take a quick look at my installation. My preference is magnetic read heads.

Lathe DRO

Last weekend my son informed me that it is time to put a DRO on the lathe. I guess he hasn't figured out what all those little numbers are for on the dials. :rolleyes: He has a short production run for a product he is developing so figured it would be easier to do it with a DRO. I suggested...

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[Winegrower]

Looks like that $190 is just for the head display? Not the magnetic sensors as well.

Correct. Except that some scales have different pinouts, as I've discovered empirically. I just finished wiring up some DB9 connectors to adjust for magnetic scales. One D80 notes "magnetic scales" on a rear sticker, the other doesn't, and needed the conversion. Maybe there's some way to check that before ordering. Both DRO and Scales are RS422, but who knows why the pinout is different.

 

[mksj]

I do not move my compound except to cut a taper, so all the coordinates stay fixed. The absolute position needs to be set when you power up the DRO, they are not absolute reading scales. If you have an assortment of tool holders you can index them all off of an absolute position in the tool datum file, one of these days I may get around to doing that. If you want summation of the compound and X and Z movements, you need something along the lines of an EL700/750 (the MX200L only has 2 axis), you need to accurately put in the angle of the compound and it will calculate the movement in the X and Z. The ES-12B does not have this functor or axis summing. in lathe mode it is pretty basic. The Ditron DRO's seem particular to the magnetic scales used as to their accuracy, so more hit or miss. My point with the Easson 12B package with magnetic scales, is that essentially you are getting the DRO display as an extra when buying the scales which sell by themselves for $150-200 a piece.

Ditron with magnetic scales, you still would want a 1 micron scale on the cross slide and the length you need, make sure you get Ditron magnetic scales as opposed to some no name brand. I only see the Ditron Official Store through Amazon, service/support in general is disappointing and warranty they say contact the seller. So kind of a revolving door on that one.

Amazon.com

As far as installing, I always prefer to do my own and almost never use the stock brackets which are usually cobbled together. A lathe 2 axis DRO install is pretty straight forward, and magnetic scales you do not need to be spot on. You save $300, good learning experience. Lots of information in this forum on the install on the PM lathes. Warranty and support are both important if you have any issues, but for others its just rock bottom cost. All I can say is to know what you are getting, and not be disappointed down the line.

 

[tjb]

You might also look at the Easson, I use the 12B on my lathe and it works very well, no issues with glare. Quite a few people have ordered them from Machine DRO in the UK, ships by air and arrives within a week. The display has 3 axis inputs, so I use the 3rd scale on my tailstock (Z1), but you can also get it with 2 scales. The magnetic scales are an easier install as to alignment and bulk, and the price is not much more than glass. If ordering you will want to upgrade the X axis to a 1 micron read head, the scales are all the same. The exchange rate is very favorable, and you do not pay VAT, shipping is about $70, the 1 micron head upgrade is around $30. So £550 works out to around $500, so figure around $600-650 for a 3 axis with magnetic scales. You can download the manual for features, it has soft keys which change based on the menu, you can change the display colors to your preference.

Universal Lathe Digital Readouts DRO Kits - Easy Fitting - Machine DRO UK

Wide Range of lathe Digital Readouts DRO Packages with Magnetic Encoders

www.machine-dro.co.uk

Easson ES-12B LCD digital readout package including 3 linear magnetic encoders

3 Axis Easson ES-12B LCD graphic digital readout package with three magnetic encoders. The encoders offer a very compact profile size and can be cut to length to custom fit the machine being installed. The package is suitable for mills up to Bridgeport 42" sized machines or 30" between centre...

www.machine-dro.co.uk

View attachment 415028

About a year ago, I followed mksj's advice on the Easson packages on both my mill and my lathe. I replaced glass scales on both pieces of equipment and have been thoroughly satisfied with both. It's a little more money but well worth it in the long run. This strikes me as one of those areas where the axiom, "buy it cheap, buy it twice; buy it right, but it once" is most relevant. I was beginning to have issues with my glass scales, and magnetic is much better. All the features you're looking for are on the Easson packages, and I use them regularly.

Regards

 

[skcncx]

This strikes me as one of those areas where the axiom, "buy it cheap, buy it twice; buy it right, but it once"

And that is the crux of my waffling on which lathe and which dro, etc ... Sounds like the PM-1236T with magnetic DRO scales is the way go to for me. I've even thought the 1340GT but then another $1k overall cost.. never ends and the 1340GT is even a longer wait.

I've already purchased my atlast 618 and I'm replacing pretty quickly... but still a good investment to "know" what I'm getting into before spending the nearly $10K on a PM-1236T outfitted with DROs and a couple extras.

Sounds like glass scales are good, but given the option, most prefer the magnetic.

As far as having a scale on the compound so it can affect both x and z would be a luxury. It seems most of the time you lock down the compound and only use the carriage and cross feed (x/z) movement. My main "thought/revelation" on that was, if you take the time to setup all your various tool offsets and such and either swivel your QCTP or move your compound (angle or lead screw)... your offsets and DRO is off and therefore you have to reset everything or return the QCTP/Compound back to where it was when you cataloged everything... and that must be very precise. Having a scale on the compound would allow travel and the system would track it... but you still cannot adjust it's angle or change the QCTP angle and assume the DRO knows where everything is at in space... so, it doesn't seem like the cost/benefit to have that feature is there for me... maybe I'm missing something. And it's one less wire dangling around.

I'll do little extra reading on the Easson and Ditron DROs you guys have pointed out... great input and exactly what I'm looking for. Though, if I can buy from a reputable reseller that provide support... that's a big benefit to me, even if it's a bit more.

If I stick with PM... it's either the MX-100L or the MX-200L... both magnetic... but the MX-200L is LCD screen and likely easier to navigate w/out manual... is that worth the extra $200... I don't know .

 

[Winegrower]

I notice the second Ditron D80 has added some new features...a feed rate computation that can be set quickly to any axis, a visual indicator of getting close to a setpoint and the ability to sum together either X+Y or X+Z axes. There's no ability to set a compound angle, as far as I know, but there are a bunch of features I haven't looked into yet.

 

[skcncx]

The absolute position needs to be set when you power up the DRO, they are not absolute reading scales.

That didn't register in my head... but now I understand the meaning of "absolute".. and most magnetic scales (at least in my price range) are not. Seems like the primary/critical axis for this is the X axis.. Do you insert tool #1 (which all other tools are offset by), turn something and measure to get back to resetting your absolute position?

Not sure if I'm asking/stating that right... I guess what's the process to "reset" the absolute position when you turn your DRO back on and it has or hasn't moved when it was off?

If you have an assortment of tool holders you can index them all off of an absolute position in the tool datum file, one of these days I may get around to doing that.

I'd imagine, I'd only do this for the 2-3 most common tools I use and switch between.

 

[skcncx]

I notice the second Ditron D80 has added some new features...a feed rate computation that can be set quickly to any axis, a visual indicator of getting close to a setpoint and the ability to sum together either X+Y or X+Z axes. There's no ability to set a compound angle, as far as I know, but there are a bunch of features I haven't looked into yet.

Having the spindle RPM input to calculate SFM on the fly based does seem like a nice feature. I think the TouchDRO has input for that.

Seems like the "distance-to-go" feature is pretty common, though likely better visual on an LCD screen.

With all these "fancy" features, the LCD screen (assuming it's done well) is a huge advantage, a requirement really.

Funny how all this works... I put cheap IGauging read outs on my Atlas 618 just so I didn't have to stop and measure as much, at least not until I get close to my target dimensions... those are nothing more than built in calipers.... and now that I'm planning on a DRO system for my to be lifetime setup.... I want all the extra bells and whistles.

 

[JimDawson]

Not sure if I'm asking/stating that right... I guess what's the process to "reset" the absolute position when you turn your DRO back on and it has or hasn't moved when it was off?

Turn it back on? You turn it off? I keep my electronics on all the time. Unless you have a fixed location to set a tool/carriage to, its not possible to set an absolute position. A DRO is normally used as an incremental device, however you might set a 0,0 as a work coordinate per the job. You are not going to have a home position like on a CNC machine.

 

[mksj]

If indexing all your tools off of absolute position, there are a number of ways to set the the absolute position. One is simply use a dial gauge in a holder with a known diameter stock and have a calibration point, you could also setup a touch probe in a holder to do the same. You can buy a cheap one for a mill put it in a holder and touch off on a known diameter stock. What I typically do is to measure the diameter of my stock, touch off with the tip of the reference cutter (insert), do a test cut, remeasure and then enter the diameter if different. Then all your other tools would be indexed off of that known diameter, you would calibrate the others by doing a test cut in the same material measuring and entering the value.

With a lathe the amount of material removed and the final diameter of the work, often requires some fine tuning if doing work in the sub 0.001" range. I recently turned some tapping O1 steel blanks and needed one to be +0.0010" of a given diameter, I remove the bulk of the material with 0.1" DOC (0.2") diameter, then 0.050" and when I get down close to target will do a smaller increment measure and then compensate for the indicated DRO reading and the actual diameter cut on the pass. You need to remove enough material which is about 1/2 the nose radius of your cutter and you have some movement of the piece being turned relative to the cutter. You also have thermal expansion from cutting the piece. Below is an example of a series of replacement pins I needed to make that all were within 0.0002" diameter spec.

I agree with buying with a dealer that offers support and a warranty. I have a EL700 DRO (purchased years ago from Dro Pros) on my mill which is essentially the same as the MX200, the latest model is the EL-750 which has some software changes/new functions. The display and menu system is great, it is a touch screen so you do not have the tactile button feel and they can get a bit finicky if your fingers are greasy/wet. The other issues they need to be resolved with the MX200 DRO's is that the feed rate is not accurate and the display refresh rate is painfully slow (at least reported recently). I do not have those issues with my EL700. The latter refresh rate is not acceptable in my opinion. Use of a DRO on a lathe, is more basic functions and reading the numbers, so they will all get you there for the most part. Being able to read the numbers and ergonomics is what is important for me, one reason why a I prefer the vertical screen so the axis buttons are aligned along the left side of the ES-12B. If they where horizontal or on the right side of the screen they would be more awkward to use. On my mill I use a horizontal screen and it is mounted on the right side of the head, the axis and keypad are on the right side of the display.

PM’s new MagXact MX-200L DRO?

I can try mine today and see if I get the same behavior.

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