Cross Slide Rotary Encoder

[Speedy Builder5Participant @speedybuilder5]

Living in metric land with an imperial machine, has anyone come across small rotary encoders that would fit onto Boxford / Myford lathe cross / top slides which would then be used to indicate the slide movement.

Linear slides etc seem to be the preferred method of measurement, however they are relatively bulky. A small rotary encoder would be out of the way of swarf and cutting fluids but would have to rely on the accuracy of the feed screws – the same as the existing hand wheel dials.

Just an idea ?

Bob

[Speedy Builder5Participant @speedybuilder5]

[Michael GilliganParticipant @michaelgilligan61133]

Many years ago, WolfCraft offered a primitive version of such a thing

[ I was about to write ‘cheap and cheerful’ … but it was neither of those ]

MichaelG.

[JasonBModerator @jasonb]

You would still get backlash with a rotary one as it does not give slide position like a linear scale does. And I think you would only get angular rotation so still have to do maths to work out how many turns needed for a given length

Need not be bulky, a magnetic strip can be fitted inside a Myford topslide and possibly the cross slide too

Sieg do the readouts for their machines that may retrofit but I think they have the ability to convert the metric leadscrew into a metric length readout so would need a metric screw to start with.

[Joseph Noci 1Participant @josephnoci1]

Bob, I made such a device for my Emco V10P lathe – I did a posting on this forum, not in great detail, but the concept is clear. I have seen other strap-on implementations – a underhang mount of the encoder with a toothed belt drive, etc – all iffy WRT swarf and such. I made mine inline with the leadscrew and the result is compact and well protected.

Backlash needs to be accounted for in the conventional way of course, but once used to using lathe dials, it comes naturally.

I interfaced the pulse output to an existing FAGOR readout system, with a bit of software translation in the way by means of an Arduino type do-alike.

It's not easy to find specific posts on the forum software, but I think this may work –

X Axis encoder post

I may have more detailed photos somewhere , but it was in 2017…

Joe

 

Edited By Joseph Noci 1 on 17/10/2022 07:07:29

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 17/10/2022 07:04:03:

You would still get backlash with a rotary one as it does not give slide position like a linear scale does. And I think you would only get angular rotation so still have to do maths to work out how many turns needed for a given length

[…]

.

Those WolfCraft ones that I mentioned embedded that calculation and displayed directly.

They also did one for the Z axis, which took account of the rack & pinion gearing.

They were small and self-contained … but not really up to the job.

MichaelG.

[YouraTParticipant @yourat]

Perhaps something like this system:

http://www.bwelectronics.co.uk/

would work for you?

Although I second the comments about the magnetic scales being very unobtrusive and easy to fit – I've used one at the back of the table on my milling machine (I didn't want to use the front as the useful auto feed stops are there), and didn't loose any travel.

Edited By YouraT on 17/10/2022 09:00:52

[YouraTParticipant @yourat]

Also there this posting from a while back:

https://www.model-engineer.co.uk/forums/postings.asp?th=139332

Y.

[IanTParticipant @iant]

When I first saw this post, I assumed it was with regard to a rotary encoder with a spooled 'wire' (attached to the moving part) – not a direct readout of the handwheel movement.

There is/was a company that used to sell such devices at shows pre-covid. They measure the actual slide movement of course, so account for any backlash too. I doubt they would be quite as accuate as a commercial scale but would probably be much less expensive as a DiY project and possibly much easier to fit in some cases.

Regards,

IanT

[BazyleParticipant @bazyle]

If it is just to 'go metric' it would be less effort to change the screw and that would give you the chance to reduce backlash too.

[Clive FosterParticipant @clivefoster55965]

YouraT

Interesting link to BWElectronics. I thought the proprietor retired some years ago and that the design had become obsolete due to some parts no longer being available. Either outright or at a sensible price.

My experience is that they work well but, like all pull wire sensors, are sensitive to wire vibration. To my mind the killer app was neatly adding a digital readout to a Bridgeport or similar machine quill. It fits nicely just under the bulge in the head casting above the depth setting micrometer device. The wire doesn't get in the way of anything unlike the capacitive scales (Quillstar et al) which cover the depth setting device and the common optical scales which have to be clumsily mounted off to one side.

As Jason says the ability to fit magnetic tape inside with low profile read heads have pretty much made other solutions for cross slide readout on smaller machines obsolete.

Roll your own is a nice project but don't kid yourself that it will be up to commercial standards.

Possibly the best implementation of the leadscrew readout was that offered by ArcEurotrade to fit a couple of models of Seig lathe for a short while some years back. It sat between the handle and the slide with a digital display. Neat and effective but it just didn't catch on. No real advantages over a dial to justify the cost.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

It should, of course, be possible to do this purely mechanically, by making a geared dial for the screw.

Quite common on milling machines, but might be ‘interesting’ to build at a size to suit Boxford or Myford slides.

MichaelG.

[Ady1Participant @ady1]

None of the hobby lathe people do them because they are not really accurate

I tried with arduino and LIDAR modules but the same problem arose

If you want good repeatable accuracy DRO is the only way

[JasonBModerator @jasonb]

Lack of accuracy may well be why ARC now sell the "upgrade kit" to replace the Sieg Factory fitted readouts which you can see in the second photo are also quite bulky as I imagine any wire system would be too.

Machine DRO do an embeded cross slide kit which just has a bit sticking out the back so you avoid the often seen glass scale down one side. Also possible to make your own up, there was a thread doing it to a Warco 280 for not a lot of cost. I think the New Myfords also have this option of hidden scales.

[Douglas JohnstonParticipant @douglasjohnston98463]

I fitted a magnetic scale under the cross slide of my Myford ML 10 lathe a few years ago and I find it a superb addition to the lathe. It is hidden away and does not get in the way like fitting scales in other ways. It has worked perfectly and no swarf can get to it. I have some photos of it in my album if anybody wants to see it.

Doug

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 17/10/2022 09:39:27:

It should, of course, be possible to do this purely mechanically, by making a geared dial for the screw.

.

In the unlikely event that the idea appeals … there is some useful information in this thread: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=168312&p=1

MichaelG.

[Bob WorsleyParticipant @bobworsley31976]

Still here, but rarely make a readout now. I still repair them, right from the very first ones I sold in 1992, and keeping the software so it does still work was quite difficult at times. Still using the same 486-25 computer from then, even the same disc drive, PIC firmware in assembler.

I have been slowly going through all the software with the intention of putting on the web site so when I pop my clogs, 67 now, others can work out how to re-calibrate the sensors. Bigger problem is brain fog, simply can't remember things now and have to be careful when re-calibrating so it does work properly.

If you want to make your own, then use the Tensator constant torque springs, SR02 I think, ball bearings and the very soft aircraft cable with the 7×7 construction. My first sensor used fishing trace wire, and it is still working on my lathe so might not really be necessary. If you want to use commercial encoders then I used the HP ones from US Digital or the Bourns ones. Either uses a spring loaded wire or a toothed pulley with the belt running inside some 1/2" aluminium channel around some bearings.

I found that the sensors gave an accuracy of +/-2 thou, the errors were always cyclic so error didn't increase as the distance increased.

Going back 30 years and the design requirements were minimum cost, so the idea of moving the sensors between machines was very popular, as was a single axis self contained readout. Other very important idea was the minimal space taken up by the sensor, the Myford doesn't have much spare room.

[Michael GilliganParticipant @michaelgilligan61133]

Great input, thanks Bob

MichaelG.

[Clive FosterParticipant @clivefoster55965]

Bob

Great to hear that you are still able to repair your sensors. I've got a dead one that could do with fixing in case I ever use it. One of the special ones with direct digital output you made for me for an MoD project back when I was working for RARDE.

Yours worked better than mega expensive ones from a professional supplier, which annoyed my boss who wasted money on them. Having a readout on the machine instead of having to wander back to the computer screen made life so much easier.

Given to me along with a whole bunch of non ISO 9000 compliant kit when I got the redundancy/consultancy deal "provided you agree to look after all the non-ISO kit" contract.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Joseph Noci 1 on 17/10/2022 07:04:14:

[…]

It's not easy to find specific posts on the forum software, but I think this may work –

X Axis encoder post

I may have more detailed photos somewhere , but it was in 2017…

Joe

.

Was this the project you were looking for, Joe

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=167722

Your Album seems to have dates of 2017 and 2020

MichaelG.

[Speedy Builder5Participant @speedybuilder5]

Thanks all for the input. I wouldn't be troubled by backlash as that is what is inherent in all screw driven slides anyway. I was hoping that there was an encoder that could be "slipped" onto the slide hand wheel in a simple manner which could (A bit like the Vickers wheel) then be interfaced to an Arduino or similar.

As for the BW electronics readout, Mine is fitted to the Z of the Warco Economy Mill and is very useful – Thank you Bob.

Bob

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Speedy Builder5 on 17/10/2022 15:43:19:

[…]

I was hoping that there was an encoder that could be "slipped" onto the slide hand wheel in a simple manner […]

.

Although it probably wouldn’t slip onto a Boxford, there was … but they weren’t good enough to survive the process of ‘natural selection’ … The WolfCraft ones used Gray Code and mechanical wipers busily wearing-out the PCB tracks, and a tiny grey-on-grey LCD

With the increasing miniaturisation of electronics; it’s probably time someone re-thunk the idea and made a Bluetooth-enabled equivalent with decent resolution, which put the display on your ‘phone or whatever.

Meanwhile … we can but dream

MichaelG.

[YouraTParticipant @yourat]

>>

With the increasing miniaturisation of electronics; it’s probably time someone re-thunk the idea and made a Bluetooth-enabled equivalent with decent resolution, which put the display on your ‘phone or whatever.

<<

oh, so something like this perhaps?

https://www.yuriystoys.com/

[Michael GilliganParticipant @michaelgilligan61133]

Posted by YouraT on 17/10/2022 16:50:01:

>>

With the increasing miniaturisation of electronics; it’s probably time someone re-thunk the idea and made a Bluetooth-enabled equivalent with decent resolution, which put the display on your ‘phone or whatever.

<<

oh, so something like this perhaps?

https://www.yuriystoys.com/

.

Not quite

I know and love what you have done over the years, but unless I have missed it [in which case please forgive me] there is nothing of yours that does the bit that Speedy was looking for … a self-contained rotary device which slips nicely onto a feed-screw and counts parts of a turn.

MichaelG.

[YouraTParticipant @yourat]

Posted by Michael Gilligan on 17/10/2022 17:00:36:.

Not quite

I know and love what you have done over the years, but unless I have missed it [in which case please forgive me] there is nothing of yours that does the bit that Speedy was looking for … a self-contained rotary device which slips nicely onto a feed-screw and counts parts of a turn.

MichaelG.

Not me, although that names are similar

It was more a response to the bluetooth connection and on screen display than the leadscrew bit of the OP's request.

I do think though that using small format magnetic scales on the slide is a better approach than the rotary encoder option, as you will be measuring actual slide displacement rather than something one link removed from it.

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