Lathe Electronic Lead Screw

My lathe has come in very handy over the years but it has had a few drawbacks:

- Threading requires a lot of time spent finding change gears, installing change gears, meshing change gears and, most importantly, Cursing change gears

-If you need to thread different pitches on the same part multiply the above times the number of changes time a whole bunch more than the sum of each of the changes plus extra Cursing time

- It doesn't have a reverse feature for the lead screw; not used a lot but on the odd occasion when you would like to have it it's a real downer

- No power cross feed

-It's about 6" too short for my liking

-The turret tool post is a PITA​

It won't cure all the above but I've been thinking about a ELS for years however until the last couple of years or so there were only a few kits available that were absurdly expensive. But in the aforementioned last few years, with the falling prices on CPU power and motive devices, a few talented individuals have applied themselves to the problem and there's now some successful examples on the web.

I actually spent quite a bit of $$$ (Damn near a thousand bucks ) buying Phidgets robot parts to try this on my own, resigned to learning the CPU module programming language & a lot of experimenting, when literally days after the stuff arrived I stumbled across Cliough42's series on Youtube -

This was exactly what I was looking for

A year and a half later the Phidget's stuff is still in a box on the floor ​

Fortunately the parts for Jame's version are pretty cheap

This won't be a detailed how-to, for that you'll need to view the stuff on Youtube- not that that's fully detailed either. It's just a bunch of pictures I need to do something with but if you're thinking about this for yourself you might get some ideas.

In the beginning-​

Pretty isn't it? Ahhh to be young and have fresh paint again


The change gears, well four out of a couple dozen anyhow-​

They look innocent don't they?
They Aren't. Those little B@$#@&*$ cost me a fingertip. ​

Over the years the paint became pretty rough- apart from the dings & scrapes the finish deteriorated & it just would not clean up any more so obviously the first objective was to tear it all down & apply some fresh paint -

I actually had to paint it twice- the first attempt just did not like the thinner I used to spray it with, a year and a half later some of the things like the back splash still have not fully dried. Talk about watching paint dry​

The second attempt went a lot better -​

Ahhh- That's Better Note while I had everything apart I swapped in a quick change tool post; I like it- I Like It A Lot

I also re-located the power and direction controls- I never liked them down on the lead screw box- they just were not intuitive to grab for when you were in the middle of Something Going Wrong


Again while I had it apart I took the time to address an oil seepage issue- this model is infamous for oil coming out around the speed selector levers. I added O-rings to the shaft bushings & that seems to have fixed it. ​

TBC...

 

So with everything back together its time to make some changes

Before the teardown I noodled out a rough idea of how I could put the drive together-​

I did up a scaled drawing to nail it down a bit more & from that with the aid of a spread sheet to calculate required belt lengths I was able to figure the possibilities. I used the servo James tested here so I went with the 6:1 reduction with a 20 to 60 cog selection on the first stage and 20:40 on the second.​

The blue area represents the 'safe area" to place the intermediate cog gears- in reality it was not that large as there are spots in there where the belt ended up rubbing on either the motor mount casting or on the encoder mount.​

I drilled some holes in the gear cabinet and with some re-enforcing plates mounted the servo-​

I re-purposed the change gear support (intermediate gear mount) casting & shaft to hold the intermediate cogs.​

Well that came out pretty much right ​

Next is mounting the encoder. As it so happens the lead screw drive shaft is tapped on the end to accept a 6mm bolt, through one of those weird explainable coincidences the universe occasionally throws at us the encoder was made to fit on a 6 mm shaft.​

Hmmmm....

So I chopped down a 6 mm bolt, screwed it into the shaft, bolted the encoder onto the end & spun'er up to full speed.​

The darn thing was vibrating back in forth so hard i thought it was going to fly apart
​

WTF?

Long story short the end of the shaft where the gear mounts is off center by 4 thou and even worse the bolt hole is out by 16 !?!​

WTF ?!?

How the factory manged this one I'll never know but I think I now understand the root cause of the issue I was trying to understand the day I lost my fingy tip ​

I had to make an adapter to slip over shaft that would eliminate the issue. I chucked up some round stock , cleaned it up to round & bored a hole in the end to fit over the shaft.​

I flipped it around and adjusted the four jaw chuck to offset the thing, as is clearly visible in the pic, the aforementioned .016" & carved a 6 mm nubbin on the end.​

After some careful adjustment I have a 6 mm mounting post for the encoder that is off center by less than 1 thou. ​

The encoder mount is made out of HMW plastic -​

TBC...

 

And the Electronics...

For some reason people just love to gear up big'ol cabinets with DIN rails & whatnot & bolt them to the wall with cables running all over the shop to connect to their lathe.

I prefer things a bit more integrated. ​

This is everything that needs to be mounted & connected together-




Obviously the display/control goes someplace where you can see it; most people like to mount it in a separate box someplace but I put it in the change gear cabinet just above the direction control as you can see in the first post above. The encoder also went in the gear cabinet as previously discussed so that leaves me with the cpu, 48V supply for the servo & 5 V supply for the processor.

I went with a utility box that I had kicking around, found it in the trash at work These are most commonly seen being used for security systems etc.​

Mounted to the gear cabinet door-​

A bit tight but everything fit. I did add some vent holes in the back of the box.​

Note the green wires, discussion below.

Instead of a separate mains powered 5V supply I found a 5V convertor on Amazon for cheap that I ran off the 48V supply, also discussed below.


The interconnecting cables are shielded- the encoder came that way; for the control board connection I used shielded ethernet (again sourced for the junk at work) and for the servo controller link I twisted some wires together, slipped shielding braid over them and covered that in nylon loom to prevent inadvertently touching bare metal, strangely enough again discussed below. ​

​

Why all the worry over shielding? It seems some people have been having issues with noise getting on the wires- especially the ones running cables all over the room to wall mounted controller enclosures. Mostly it seem to be happening when there's a VFD in the room.


WARNING-

I suspect these folks are not bonding the cable shields to ground correctly resulting in current from improperly grounded/noisy equipment flowing over the ELS cables. I don't have a VFD and for testing I had the thing working quite happily using unshielded ribbon cables but hey- why not? I did make sure that my shields are only bonded (Green Wires!) at one end thereby prevent any current passing through them and that all grounds run to a single point where they connect to the lathe's frame & to the mains ground, again preventing current flowing through places it has no right being.

Now you might be saying- "There aren't supposed to be any currents flowing through ground to begin with" & you'd be absolutely correct but I suspect there's a lot of cheap crappy electrical stuff making it's way into home hobby shops (& if reports are to believed more than a few commercial establishments) that, if not outright Viciously Violating Code, then at least is poorly designed to the point it's inducing noise onto close by conductors.

It shouldn't be happening but it does.

In fact James recommends a separate 5V supply as he's afraid of noise from the drive motor making it's way from the 48V supply into the CPU but this seems a bit excessive to me. He also recommends leaving the 48 & 5 V supplies floating, i.e. no connections from the negatives to ground; I'm sure he has his reasons but leaving supplies floating can introduce a whole separate set of issues, especially if you have cables strung all over the room to a control cabinet. I expect at some point I'll at least hook a 1 or 10 K resister from the PSU to ground just to eliminate any possibility of static buildup if nothing else.

So it didn't come out too badly-​

Some little stick on cable clamps to keep everything organized & power separate from signal lines finish it off quite nicely


And the Money Shot-​

So that's it for the install. I've got to say it's a complete game changer for doing things, already ran off a few parts that would have taken five times as long if a had to mess with change gears. It also leaves a lot nicer finish on cuts than if I had made them by spinning the hand wheels myself.

 

Thanks Mike , always appreciate your comments on this stuff. Yes the QC toolpost is a real time saver as well.

 

I wish I could say I DID have a homemade Gingery lathe- that was the original plan but I just didn't have the time