Servo Drive For a lathe Compound

Discussion in 'Tools' started by lkrestorer, Dec 31, 2018.

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  1. Jan 3, 2019 #21

    joco-nz

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  2. Jan 3, 2019 #22

    dazz

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  3. Jan 3, 2019 #23

    TimTaylor

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    Mechanical taper attachments work well and are easy to install IF your lathe has a telescoping cross slide lead screw. If it has a fixed screw, then you have to either remove the screw or modify it to be telescoping. Looking at the G4003 manual, from the parts drawing it looks to be a solid single lead screw, so modification or removal would be necessary to use a taper attachment.
     
  4. Jan 5, 2019 #24

    lkrestorer

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    I didn't have time to get back to this computer for a couple of days so I'm fascinated by the response it's gotten.

    First, I apologize for complaining about nobody responding. I guess I jumped the gun a little bit and didn't consider the holidays getting in the way. I do appreciate the comments. You guys do know your stuff.

    I am referring to the compound. The cross slide on the Grizzly is already powered. I made a gizmo to use my battery drill but the speed control stinks (meaning I can't maintain or repeat anything steady). The "need" for this was prompted by a few widely scattered taper projects with the latest being Brian Rupnow's "Crazy Joint". I really liked the style of pulleys that he shows in his set of prints so I wanted to duplicate them. It requires a concave side and a convex side to each pulley/flywheel with a 60 degree dish design. The setup on my lathe (to get the tool pointing the right direction) was to point the compound toward the operator at 60 degrees and feed the tool manually toward myself. I could have fed it away from the operator and ran the spindle in reverse but I prefer to run it forward. Note: "I prefer" just because it feels better to me. Other people will have other ideas but, understand, this is what got me thinking about a power feed. I enjoy making tools and modifying tools. It makes for fun exercises and makes me think above and beyond the normal. It's not a matter of need. It's a matter of want. Like I said above, I switched out my single phase motor for a three phase motor on my Grizzly mill (G9902) and hooked up a VFD so I would have the variable speed control and I built a power drawbar attachment because it was a nifty addition to my arsenal of tools. This is what I like to do.

    Turning these pulleys requires a lot of metal removal and quite a few passes. I realized that reaching over the top of the machine put me in an uncomfortable position and caused my hand to cramp up with all the repetition (yes, I'm an old guy!). I realized that I didn't need to worry about surface finish until I got to the final passes but I tried on each successive pass to attain the ideal finish as I figure this is good practice. If I couldn't do it on the preliminary passes then I wouldn't be able to do it when it counted. The smooth and repeatable control of a power feed would be ideal.

    Here is the video that shows pretty much what my machine would look like if I adapted a milling machine x-axis power feed to it:
    I was just hoping to find some way to put together something a bit more compact.

    I do appreciate what you folks have to offer but my design ability is very limited and most of these items that have been mentioned are foreign to me. I don't want to put anybody on the spot or hire a "designer" but what I really need is some honest soul to spec out the parts and sketch me a wiring diagram. I started this out in my first post by asking: 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've walked into a world that is slightly over my head. What I would like to do is sit down with a "buddy", share ideas and maybe build two of these things, one for each of us, but I don't have any "buddies" that share this hobby. I don't want somebody to do this legwork for me unless they enjoy the challenge.

    TimTaylor,
    Your parts list looks very interesting but I'm lost with how to put it all together.

    Ignator,
    Thank you. You hit the nail on the head. Take a look at the video I mentioned above and see if you think it would work without being a pain to work around. That tailstock feed idea sounds interesting, too. Drilling with that would be a breeze.

    comstock-friend,
    The taper attachments that I've seen won't work with as steep of an angle as 60 degrees. Granted, the compound travel on my lathe is only 3-1/4 inches but the items I have made are within this range of motion. (like morse taper shafts)
     
  5. Jan 5, 2019 #25

    Cogsy

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    Here's a link to a cheap Chinese PWM controller - LINK. With this thing, it has two sets of DC terminals, one set for input power and one set to the motor. You then have a push button for on/off of the motor and the control knob regulates the speed of the motor from 0 to 100%. I'm not sure what size geared motor you would need for your application, but for ease of wiring this thing can't be beaten. Wiring in a simple switch between the controller and the motor would give you simple change of direction too, so you could power feed in either direction. Adding in limit switches would also be a simple wiring job (as simple as adding in an on/off switch is) but mounting them in the right places would be more difficult. I don't see a solution getting much simpler than this setup, but I can't help with the required motor size. Sorry. Maybe have a search for geared DC motors on ebay and see what comes up.
     
  6. Jan 5, 2019 #26

    ignator

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    I've thought of putting a power feed just like that but it does appear to be huge and probably would be in the way. One of my projects is to repair the sleeve that came with my big lathe. The sleeve converts the lathe spindle taper to a #4 morse. Problem is the minor diameter of this adapter is .0045 inches too small, so it rocks in the spindle. I never noticed it for many years as it seems like it sits tight, and it has to be tapped out. So I want to mount the tool post grinder on the compound and dial in the correct angle for this 90mm metric taper. This milling machine power feed would be in the way of my tool post grinder. I've looked for a hollow shaft motor with a gear reduction, but no luck.

    This is a power feed on a 19 inch drill press. So originally I had the feed attached to the custom mounting stand, and it drove the pinion quill feed gear directly. The unit did not have enough torque. So I found a 10:1 gear box, and made some more conversion plates, and extension shafts. This works pretty good. And you still can operate the feed manually. The original gearing was 1 turn of the pinion, have 4 inches of quill. These power feeds are designed to drive lead screws of .1 to .2 inch pitch. So the original gearing was 4 inch pitch, just too much for the unit.
    upload_2019-1-4_22-44-47.jpeg

    A little better lighting of the drill press power down feed.
    upload_2019-1-4_22-48-54.jpeg

    My lathe is a 10x24 Jet. I added an extension to the tail stock and made a new quill that was much longer as the original only had 3.5" of travel, and some of that was the ejection of the #2 morse taper tool shank.
    upload_2019-1-4_22-51-54.jpeg

    upload_2019-1-4_22-52-14.jpeg
     
  7. Jan 5, 2019 #27

    TimTaylor

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    Sizing a motor is pretty straightforward:

    First you need to determine how much torque you need to drive the compound slide screw under load.

    If you choose to go the gear motor route as Cogsy suggested, just choose one that meets the torque requirements.

    If you want to go the stepper route, you need to calculate the torque multiplication required and that will determine the reduction ratio that gives you the needed torque. It's a simple calculation just divide the required torque by the motor rated torque to get the reduction ratio: For example, with a Nema 17 stepper rated for 50 oz-in, a 2:1 ratio would give you 100 oz-in, 5:1 - 250 oz-in, etc. Yes there are some minor losses at high speed, but sized with a little reserve it won't be an issue.

    The motor's steps per revolution, multiplied by the reduction ratio, gives you the number of steps per revolution of the feed screw. You can get fancy and calculate the pulse rates for given feed rates, but honestly you can eyeball the rate and do just fine - just like you would do in manually feeding.

    As far as wiring, look at the 2nd link in my original post - the 3rd picture down on the left is a typical wiring diagram.....

    Hope this helps!

    Tim
     
  8. Jan 5, 2019 #28

    lkrestorer

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    This brings up one of the points brought up previously. I call it the "compound" and that's what I've been searching for. This calls it the "topslide" and so did the YouTube video that I posted. I have to expand my searching.

    Paul's version looks very close to what I want. The diagrams from this site just show the "before" and I'd like to see the "after". I hadn't heard of this site before (it's a long way from Minnesota!) but I will take some time to check it out closer.

    I like this installation and I'll try to put all of this together. Some of you are going for the stepper and some are going to just a DC motor. I'm going to keep researching this and try to put something together.

    My brain may have a better time with a DC motor, a power supply, a pot for speed control, a reversing switch and a timing belt with a couple of gears to give it a bunch of torque (even though it shouldn't need a lot).

    The internet will be getting a workout and I'll see what I can dredge up.

    Back to the search.
     
  9. Jan 5, 2019 #29

    lkrestorer

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    You shouldn't have shown me that power fed tailstock. I'm going to have to put that into my "maybe-I-want-to-do-that" list. It looks like a very nice setup. My bag of gizmos that I like keeps getting bigger. I live by the idea that I can't die as long as there are still projects waiting.
     
  10. Jan 5, 2019 #30

    lkrestorer

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    This is an option for tapers of length and shallow angles and something that I have considered. However, I don't think it would work with the hardware on my lathe without major modifications.
     
  11. Jan 5, 2019 #31

    lkrestorer

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    This might be a simple approach to what I'm after. I'll look at it a little closer. Thank you.
     
  12. Jan 5, 2019 #32

    lkrestorer

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    Oops, they won't ship to the U.S.

    Searching again.

    One of the problems with all of this time spent researching is that it takes away from the time I could be in the shop making "glitter" as my granddaughter calls it.
     
  13. Jan 5, 2019 #33

    TimTaylor

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    If you use a DC gear motor you shouldn't need any additional torque....
     
  14. Jan 5, 2019 #34

    TimTaylor

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    try searching "DC PWM speed controller" and "DC gear motor" on Amazon - lots of stuff there......
     
  15. Jan 5, 2019 #35

    ignator

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    I've never finished the same mod for the large lathe (18x40, 450x1000mm), but the parts are mostly made.
    There are just too many other tasks to get done in retirement hell. Currently working on sanding 660sq.ft. of oak flooring.
     
  16. Jan 6, 2019 #36

    Cogsy

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    The link I gave was for eBay Australia but there would surely be identical units on the US or UK versions.
     
  17. Jan 6, 2019 #37

    ignator

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  18. Jan 10, 2019 #38

    Wizard69

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    Hey glitter is important to young girls.

    AS for the distraction of making machine modifications, fixtures and such; for many that is part of the journey into model engineering. For some it becomes the main focus of the hobby.

    Your interest in a drive assembly for the compound slide is not uncommon, ONE approach is to drive the cross slide with an external device. An electric drill or screw driver are very common ways of driving this slide at a smooth feed rate. Generally that is what most people are after - smooth feed rate to get a good finish. Battery operated, variable speed, screw drivers often are preferred here due to the relatively low operating speed. Find a way to key them to the compounds leadscrew knob and you are all set.

    Now I've plum forgotten which size lathe you have here, but on the smaller lathes if you want a bolted on drive it might make lots of sense to develop a completely new compound. I have a 9x20 and I do believe I could benefit from a longer compound slide that is frankly more rigid. The real advantage in length here would be the ability to put the motor on top of the slide and drive it with some sort of gearing arrangement. With your own design you could potentially design a mechanical drive that disconnects the motor for manual operation with the lead screw handles. This way changing for manual to electronic drive is as simple as throwing the gear system in and out of engagement.

    Another simple possibility is to use a stepper with a double ended motor shaft. Connect the stepper directly to the leadscrew on one end and put a handle on the other. This is why I mentioned before that there is likely hundreds of ways to put a motor on that compound. It is up to you to choose which one and how it should be designed.
     
  19. Jan 10, 2019 #39

    Wizard69

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    That would depend upon your lathe as you note. You can get a shallow taper mechanics like this to work on any lathe if you are willing to go through the mechanical design effort. There are a number of tapers though that would benefit from accurate feed rates on the compound which brings us back to your original question. I believe that your desire here is well founded as it can produce much better results off of the compound. However deciding on the right approach is not easy

    Which approach, that is between the taper slide attachment and a powered compound, should really be decided based upon your likely interests. It could make sense to employ both methods as needs demand.

    Whops for got to mention, such taper attachments can be used with most lathes. On some you need to remove the cross slides leadscrew. On some more drastic modifications are required. In any case the attachments can be made to work. The big problem is that the slides only cover a very narrow range of tapers. So depending upon your needs you may end up with needing a powered compound anyways. For the best quality on a low end lathe I would even go so far as to say that a taper attachment will be preferred (when used within its operating range).
     
    Last edited: Jan 11, 2019
  20. Jan 11, 2019 #40

    ignator

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    lkrestorer; I found this hollow shaft gear motor on eBay. But it's too big. In this case it's a 3 phase 220VAC motor, that could be powered with a VFD.
    I'm looking for something like this but 1/2 its size. This one is 90w, and has 4 ft-lb of torque. More then enough to crank the compound even under load.
    upload_2019-1-10_20-26-3.png
     

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