Servo Drive For a lathe Compound

[lkrestorer]

I'm looking for some constructive help with an idea. For a couple of different reasons I would like to come up with a design for a servo-type power feed for a lathe compound. I have a Grizzly G4003 12x36 lathe and what I am picturing is a small servo or stepper motor mounted on the top of the compound and driving the.screw with a cogged belt or gear train connected at the manual handle.

I would compare this idea to a standard power feed installed on a Bridgeport but on a smaller scale. I'm not interested in CNC type operation but as long as I'm dreaming the idea of adjustable travel limit switches could be a future addition. I would like to have it with a speed control and a forward/reverse switch - probably remotely mounted both for safety and convenience.

There is one YouTube video that shows the beginnings of this type of project but it doesn't take it much farther.

I am not afraid of this type of project. I worked as an industrial electrician for 43 years and I have replaced the Chinese motor (that went up in smoke) and the sketchy wiring on this lathe and have converted my Bridgeport clone to variable speed VFD operation and built a pneumatic power drawbar for it. My uses for this equipment have gone from making parts for old tractors and engines to building little steam engines and cannons and making custom modifications to wheels for my Corvette.

So much for the dream. What I am asking all you fine gentlemen for is to be pointed in the right direction. I need parts and pieces. Where do I go to determine motor type and correct size? Where do I get something to give me a smooth speed control? What about the proper gearing or belting equipment?

I have been slogging around the internet and finding a lot of brick walls so I assume I'm looking in the wrong places. I even tried looking for some sort of CNC retro-fit device that I could convert to this use without any luck.

Help? Anybody?

 

[lkrestorer]

I have to say I'm a bit disappointed. Since I posted my question There have been 65 people that have read it but nobody has replied to even tell me it's a crazy idea or to say "I dunno". I have been following HMEM off and on since 2009 and have found many good "how to" tips and have built an engine with another couple of them waiting for my attention. The people here have some great ideas and a lot of combined knowledge and experience. It has been very helpful. I had come up with a problem that I needed help with so I thought I would try to fit into the conversations. There are no amateur machinists in my area so the internet is my only real outside access to information.

I have been continuing my search and have found a couple of things. First, the idea of mounting a small motor on the compound is probably not going to work because of the lack of real estate. I did find another YouTube video showing a setup using a standard Chinese-made mill x-axis servo drive mounted to the compound. The drive is angled upward to clear everything so the handle and switches are on top. This would be fairly easy to accomplish but it is a large protrusion on that part of the operating area of the machine. I'm not sure if it would be too much in the way.

Am I being too impatient? Any comments?

 

[bdrmachine]

Try looking on cnczone.com. GeckoDrive (G201) and a nema 34 stepper motor maybe what you are looking for. The drive electronics for the Gecko could be as simple as a pulse generator, to a old PC running a program like LinuxCnc.
Are you close to the Duluth, Mn area?

 

[RonGinger]

Not a lathe, but I have a G0704 mill that has its Z handle up on the top of the machine, very awkward to reach. I mounted a stepper motor and built a simple Arduino board to control it. Instead of mechanical limits I made electrical ones. There is a button for up and one for down. When you have the axis at a place where you want a limit you press the limit button. A red LED comes on, and there after the control will not pass that spot. You can set a limit for either extreme. This has worked well for me. When I built the box to house the driver I added one for the X axis, but I never got a round to doing the mechanical work.

I see no reason it would not work on a compound,as long as you can mount a motor close enough without messing up other access.

 

[dazz]

Hi
I trained as a Weapons Engineer so I know about control systems. I am just finishing a VFD conversion for my Nardini MS350 lathe. I have been looking at CNC control of the cross slide on the 2 lathes I have. I have reached some conclusions that will probably help you.

You will need to know where the tool is on the Z axis. There are two ways of doing this:
The cheap crappy way is to put an encoder on the tailstock end of the lead screw. There are a number of reasons why this is a bad idea
The best option is to add a DRO to the Z axis. The value of the Z axis would set the X axis at all points.

The X axis position also needs to be known. This will be powered so it can be done with a stepper motor (not so good) or a DRO scale (much better).

You will also need to know the A axis position for thread cutting. You will also need control of the A axis position relative to the Z axis. The common method of using a single point (magnet) pickup typically seen with Mach 3 on micro lathes is crap. A hollow shaft encoder is the best, and most expensive option. It is the rotary version of a DRO. Another not so good option is to install a gear tooth sensor on the main spindle driven gear, most likely found inside the headstock.

Modifying any top slide for CNC is too restrictive. I think it is better to replace the top slide with a new power driven version. You suddenly have a lot more design options. On my Nardini, the cross slide has Tee slots that I could attach a powered version, much like a hydraulic copier. Alternatively, it would only take a few minutes to remove the manual top slide and replace it.

Basically I plan to build an electronic version of a hydraulic copier but without the noise and leaking oil. The stylus and template would be replaced by software. This type of setup will almost have the capabilities of a full CNC conversion. This concept has some similarities with the Electronic Lead Screw project that you have probably found. My concept is closer to a full CNC retrofit.

You will need software to drive all this. There are options but I favour LinuxCNC because it is fully programmable and I like doing that sort of stuff.

 

[lkrestorer]

bdrmachine,
Thank you for pointing me to cnczone.com. This is a new place to me. The first thing I noticed was that I've just stepped into a whole new world where I 'm not familiar with any of the jargon and standing on the outskirts of the rest. You guys sound very familiar with the design of these things - I'm not. My world revolved mainly around: "Here's a pile of parts. I know they will work together so now go figure out how to put them together and install them so they will do what they are supposed to do." I'm not well versed in the design part of this stuff.

I looked at the Gecko site and will have to take time to look through their information. It looks like they have wiring diagrams and other stuff to study.I also need to familiarize myself with the stepper motor world and the differences with the NEMA sizes.

I'm not very close to Duluth, I'm halfway between Hastings and Red Wing.

 

[lkrestorer]

Not a lathe, but I have a G0704 mill that has its Z handle up on the top of the machine, very awkward to reach. I mounted a stepper motor and built a simple Arduino board to control it. Instead of mechanical limits I made electrical ones. There is a button for up and one for down. When you have the axis at a place where you want a limit you press the limit button. A red LED comes on, and there after the control will not pass that spot. You can set a limit for either extreme. This has worked well for me. When I built the box to house the driver I added one for the X axis, but I never got a round to doing the mechanical work.

I see no reason it would not work on a compound,as long as you can mount a motor close enough without messing up other access.

This sounds like something else I'll have to look up. I'm not familiar with what an Arduino board is. I like the idea of the electrical limits and the method of setting them that you describe. Is this something that could be a stand-alone unit or is it dependent on a drive + motor combination to locate the positions ?

 

[lkrestorer]

Hi
I trained as a Weapons Engineer so I know about control systems. I am just finishing a VFD conversion for my Nardini MS350 lathe. I have been looking at CNC control of the cross slide on the 2 lathes I have. I have reached some conclusions that will probably help you. and I like doing that sort of stuff.

Whoops! You are taking my little idea too far into the CNC world. Your project will result in a computer controlled machine. I want a manually controlled, variable speed drive for the compound (cross slide). The only "automatic" controls I may need are limits so that if it catches me momentarily out to lunch I won't destroy the machine. Basically, I would like a SERVO drive that's miniaturized to fit on the compound and operate like the ones on my mill do.

The idea of adapting the full-sized milling machine x-axis unit to fit my compound would result in a bigger-than-I'd-like piece of hardware sitting where it might get in the way. I do like the idea of the electrical limits with a stepper drive setup - if I can get my mind around what pieces to use.

 

[Cogsy]

Just spitballing here, but how about something like a miniature axis drive as found on a mill? So a simple geared DC motor and small PWM controller for speed adjustment, then add a mechanical limit switch to each end of the travel for safety and a reversing switch. Very mechanical and shouldn't be overly difficult to mount up (depending on your machine). With a geared motor you wouldn't need belts or pulleys and could just drive the lead screw directly. Possibly make it 'quick change' where you remove the handwheel and slide on the electronic drive, so you can switch between the two systems as required.

 

[john_reese]

Unless you are cutting a lot of tapers with the compound building a power feed for it seems like overkill. I use my 1/2" cordless drill to drive the compound, or the rotary table, or the dividing head. You probably own a drill that would work.

 

[dazz]

Hi
As a professional Engineer, I make things complicated because I can. No problem is so simple that it can't be made complicated.

OK if you are looking for a simple variable speed feed, then a stepper motor would be simple to rig. Connect the stepper motor to a stepper drive output.

Connect a variable frequency oscillator to the driver input. I would use an Aduino but you might be able to find a kit or something off the shelf. If you haven't used an Aduino before, they have a relatively shallow learning curve.

The advantage of using a stepper motor is they perform best at slow speed. DC motors etc perform better at higher speeds. Steppers are also simple to drive.

 

[Wizard69]

I think you need to give people time to actually visit the site, especially over a holiday.

If you mean the compound and not the cross slide this is very doable. I would likely choose a stepper instead of a servo, mainly for compactness. The biggest problem is that you will need to fabricate and thus design a lot of parts.

As for steppers, I'm not sure which size would be a proper recommendation, you may be able to get by with a relatively small stepper. Maybe something as small as a size 17 stepper. If you purchase a stepper with a through shaft you can mount a handle on the other end of the stepper.

The biggest problem you will have is coming up with controls to drive the stepper. In this regard it is probably a bit easier to go with a stepper. However do realize that there are many Arduino solutions out there that would get you 90% of the way, with the balance being a bit of programming and electrical work.

There are dozens of ways to go about this so it is up to you to decide which path to take.

 

[john_reese]

I have no aversion to stepper motor drives. I will be installing one on the X axis of my mill. I, too, am a professional engineer (retired) but I do not share your philosophy of make it complicated. I am a firm believer in the KISS approach. Besides, I am old, grumpy and kind of lazy so I look for the easy way.

 

[StephenB]

I had a little bench top horizontal mill that had little handles that fit onto 3/8" squares on the ends of the lead screws. perfect fit for a bbq spit motor I had. It worked ok and was very small. It did burn out after a while, but the thrift stores always seemed to have a bunch of those...

 

[DJP]

I would like to go back to the beginning of this thread to ask why you need a motorized feed. Are you planning a high quantity production run? Why wouldn't a power drill take away any tedious effort much more simply while keeping you in direct control of the process? This is an hobby using old metal working machines as they were originally designed, right?

 

[ignator]

I am picturing is a small servo or stepper motor mounted on the top of the compound and driving the.screw with a cogged belt or gear train connected at the manual handle.

I to, have wanted this on my large lathe. Nice constant feed would give quality finish. But an installation that keeps it out of the way, as well an engage clutch mechanism limits the location and coupling drive.
I've seen the battery drills used, but don't like speed control that is not repeatable.
.
I just don't understand why this tread has to turn into a pissing match about the right way to implement, when the question is straight forward as to a machine mounted mechanism.
.
I would like to see Ron Ginger's milling machine feed photos.
I've found links in youtube, that are reconfiguration mechanisms, and not left on the machine.
I've been looking for a small diameter motor with axially in line gear reduction that could be mounted next to the feed screw in the hollow between the way's. I've not seen a hollow shaft motor that could be fitted on the crank end of the feed screw, but that solution would keep it clear of the work.
For reference, I've installed power tailstock feed using a milling machine after market table feed. This provides very consistent feed, that allows very deep holes and large drills to be used without grabbing. The only 'babysitting' is to clear the flutes in deep holes so the drill don't break.

 

[TimTaylor]

I would like to go back to the beginning of this thread to ask why you need a motorized feed. Are you planning a high quantity production run? Why wouldn't a power drill take away any tedious effort much more simply while keeping you in direct control of the process? This is an hobby using old metal working machines as they were originally designed, right?

Good question. My guess is to control consistency of the surface finish - same reason we use power feed to take a final cut on an OD. Any of the power drills I've seen don't have very accurate speed control, especially at lower speeds.

 

[comstock-friend]

Yes, we got the 'what' he wants to do but not the 'why', plus the confusion of 'compound (cross slide)'. If the compound, I would assume it would be for the powered cutting of tapers. I would think that a Grizzly G4003 already has a powered cross feed (my Enco 12" does, probably the same lathe with a different badge). If the need is power cutting of tapers, instead of hanging a motor on the front, why not built the taper attachment on the back and be done with it. I love the taper attachments on my 9" and 13" South Bends. For the occasional short and sharp taper, the drill motor deal is the way to go!

 

[TimTaylor]

A single, packaged solution might be hard to come by, or expensive...such as a power feed add-on for a mill.

That said, you could do it with a few parts......

This might be overkill, but it looks like it would do everything you want and then some - just add the stepper motor, driver board and power supply....such as driver shown in 2nd option....
https://www.amazon.com/dp/B011NJA38A/?tag=skimlinks_replacement-20

or these:

https://www.amazon.com/dp/B07B9ZQF5D/?tag=skimlinks_replacement-20
https://www.amazon.com/dp/B01J88T1AO/?tag=skimlinks_replacement-20

A nema-17 with reduction on the belt drive would probably have plenty of torque.

The first option directly supports limit switches, while with the 2nd it would take some additional interfacing, but nothing all that complex.......

All told, you're probably looking at around $75.00 or so

 

[stackerjack]

Have you thought about a washing machine motor?
You wouldn't need a separate power supply and an old washing machine would have all the control circuitry you need.