Spindle Encoder solution for Hardinge lathes?

Hello, all.

I think I may have figured out a solution to my problem! Maybe this will help others, too. The problem was that I was having a tough time figuring out an encoder placement and choice on my old DV59 spindle. Turns out I can just remove the hand wheel and it will expose end of the spindle. That's about 1.75" in diameter and about an inch past the rear of the head stock. If I can fashion or find an encoder wheel that's got a hole'through the center that is as big as the spindle plus about 20 thou, I can machine a bushing to carry the wheel, that gets close to the flat machined vertical plane on the rear where the hand wheel covers. I can mount the encoder reader to the head stock, even with something like JB weld to test it. If it works, it's a direct spindle encoder and from what I understand it'll keep count minimum following errors. And if I'm not incorrect, even if the belt slips when the motor reverses in something like a tapping cycle, the encoder will still stay accurate.

It's a remarkably easy conversion and it can even be covered easy to protect it. The placement is perfect, I think.

I was planning on trying my hand at etching through a .015" thick piece of 304 stainless to see if I can make a fairly fine resolution encoder wheel and I was doing some studying about how it's done. Seems pretty straight forward if you have the right chemicals and disposal process.

So here's a question. Have any of you bright men done any chemical etching of stainless steel? If so, any resources would really help. I've searched the web pretty well and found some awesome leads for resists and etchants. I'd just like to hear any pointers or what someone experienced regarding process.

Thanks in advance,

Scot

every mashine is different
as well as the electronic needs
so make a image if you are happy with the solotion you found

the thing is clear encoder connected to Spindle direct is the best way to go
and as many lines as the electronic coudt handle for best use

around 500ppm is the standard

Andy Pugh pointed out on another thread that you can get hollow shaft encoders quite inexpensively from Aliexpress. For example for your 1.75" shaft a 45mm encoder will slide on, but I am not sure whether the collet style clamping will take up the half mm play.


www.aliexpress.com/item/32850293643.html...4,searchweb201603_52

If the link doesn't work, search for 45mm hollow shaft encoder.

You might be better off with a 50mm encoder and a split sleeve.
www.aliexpress.com/item/32986801220.html...4,searchweb201603_52

Mark

Thanks Mark. That is an option that I not only didn't see, but with this new idea of hand wheel removal, is much more viable than any other off the shelf solution. The fact that I don't have to fabricate anything other than an adapter bushing is very inviting. The PPR on those is great, too.

I'm going to pull that collet closer and then remove the hand wheel to see how it'll fit. I'm 100% sure I can adapt something like that to the lathe if there is enough spindle out of the rear. It's much less expensive than I imagined, as well.

So again, thanks. All that's left to do is the grunt work if this is applicable.

Scot

Thanks for the help, Andy. But I have to admit, I'm new to the VFD/encoder interactions in any system, let alone Linuxcnc. So this is a bit confusing to me. And I'm still learning as I go.

What I planned on doing was setting the spindle speed through the analog control it has now, to it's maximum with new belts. Then the plan was disconnecting all the analog controls with the cams and levers, leaving the motor at the maximum belted speed, then controlling it with the VFD to get the low rpm's, leaving the highs to be met with the 10volt max in the VFD, controlled by the computer. Does that make sense or am I missing something?

As for the encoder problem, I don't think I'll be able to get the gear on the rear of the spindle, off. So the slip-on type encoder probably won't work. Fortunately, I have the ability to machine a split bushing that can mount to the rear of the spindle, in front of the gear, then attach a home-brewed encoder wheel to it. So I think I can get the encoder built at roughly the same cost. It's just more time consuming.

So when you were speaking doing the mathematics, the only number I have to work with is the max RPM of 3500. Not to sound completely daft, but would a 100-500 PPR encoder work? That was the plan when I was considering buying the encoder, rather than building it.

Thanks again, you've been an amazing help.

Scot

This helps immensely! Thanks so much. Now to build it!

Scot

Buy a omron rotary encoder!
It have A,B,Z phases.