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CNC Mill Retrofit Idea - (Eureka!?)

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  • CNC Mill Retrofit Idea - (Eureka!?)

    I picked up a little retrofitted Taig mill the other day just to dip my toe back into CNC. Of course it's never enough, right? So been kinda casually pondering what comes next eventually.
    The Grizzly 0704 (?) is popular for retrofitting apparently - there are a ton of video examples on it. So I was kinda thinking that might be a good size for a machine quite a bit more capable than the Taig, but still easy to deal with, i.e. runs on 110V, doesn't take up a whole room, etc.
    Then (and you might not believe this, but it's totally true) I remembered that I already have something in the garage that might be close to perfect, and tons better than a Grizzly or the like.
    I bought it over 15 or so years ago and haven't used it much, and not a single minute for the past 8 years, so I just kinda forgot I had it.

    It's a Hardinge horizontal mill and lots of stuff came with it, including a vertical head and indexer.
    When I got it the condition was almost mint. It has almost zero wear on it. Sadly, it now has surface rust on it, but mostly on the handles which would come off in a retrofit anyway. Otherwise, the thing is still a gem.
    I always thought these particular mills were odd in that they are incredibly well-built but pretty klunky on the user-friendly side of things. It's a step belt pulley arrangement which you have to crawl on the floor to reach, etc. It's not at all as well designed as their lathes, so kind of curious.

    So I was thinking, here I'm sitting on this extremely well-built machine which is massive for its capacity, thus stable as a rock for its size. But it's not very convenient to use so I never do. So if I retrofit it for CNC it might end up being a true joy to operate. Of course it's got a small envelope, however about the same size as the Grizzly but so much more rigid and probably a magnitude better build quality.
    This build would warrant servo motors and all the proper conveniences available with CNC other than an automatic tool changer. But for garage fiddling, the lack of ATC would be a pretty minor inconvenience I think.

    I paid extremely little for this mill back when I got it and I don't think it would even cost more than $2K at the tippy tops (thanks AOC) to set it up in a pretty deluxe way. It might be half that. I'm thinking possibly an Acorn setup to go with the servos and attach a VFD and encoder to the spindle (motor is already 3-phase)

    What do you guys think of this? I guess I'm just wondering if I'm missing something, but it almost seems like a no-brainer.
    Last edited by tyrone shewlaces; 03-27-2019, 09:09 PM.

  • #2
    Sounds like a killer idea to me. I've been using manual tool changing for almost 20 years doing it as a business. Don't think that will be much of a problem for you.

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    • #3
      Hi,

      The only real fly in the ointment I see is weight of the knee, (I assume you intend to motorize the knee), it will probably take a much beefier motor to move than either the x or y axis. Or if you have a moving spindle,then it will be easier to size.
      If you think you understand what is going on, you haven't been paying attention.

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      • #4
        Yeah, I've considered that. I don't see it as much a fly in the ointment as much as just a variable to compensate for, i.e. it's just a matter of choosing a motor with appropriate power. But the table assembly is small enough to be several times lighter than plenty of milling heads I've used which are driven up & down all day long. There may be an efficient, cost-effective way to possibly "counterbalance" the mass to reduce the requirements of the Z-motor too. I'm not sure which way is most practical, but I'm just in the pre-planning stages at the moment anyway.
        Also, I've been alive long enough to know that my first iteration often misses the target and it might take a bit of trial & error before things are the way they ought to be. But I might get pretty close enough as long as I don't overlook big things and compound too many small ones, so I definitely thank you and appreciate and the input.

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        • #5
          Nice, I think a horizontal mill makes a better candidate for CNC as well, it's much more rigid and the chips will tend to fall away from the work area.

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          • #6
            Cnc'ing the knee has been done many times, I did it on a Bridgeport years ago. It is not without issues though, because of the weight it usually accelerates slowly and max speeds are limited. This really comes into play when doing things like peck drill cycles or 3d contouring. Counterweights or gas springs help but are not a cure all.

            Would it be possible to cnc the main spindle somehow? I have seen factory knee mills with the head mounted on linear rails with about a foot of travel. Alternately, a second sub spindle is a possibility, cnc controlled. The router guys make their own Z (spindle) axis mechanics all the time.

            All that being said, I have no idea what the mill you have looks like.

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            • #7
              Just another idea to perhaps sway you to the "yes " side. Put an encoder on the spindle, so that you can thread with it. Make up a block to take your lathe toolhoders, and you can make it double as a cnc lathe, albeit a short, and limited one, but for small repetitive parts it would be awesome.

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              • #8
                sounds like a fabulous idea, where are the pics??

                I also love the idea of forgetting a machine tool in the garage. I'd be either tripping over it in my place or cursing the fact that I have to move it to get to something else

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                • #9
                  Originally posted by tyrone shewlaces View Post
                  Yeah, I've considered that. I don't see it as much a fly in the ointment as much as just a variable to compensate for, i.e. it's just a matter of choosing a motor with appropriate power. But the table assembly is small enough to be several times lighter than plenty of milling heads I've used which are driven up & down all day long. There may be an efficient, cost-effective way to possibly "counterbalance" the mass to reduce the requirements of the Z-motor too. I'm not sure which way is most practical, but I'm just in the pre-planning stages at the moment anyway.
                  Also, I've been alive long enough to know that my first iteration often misses the target and it might take a bit of trial & error before things are the way they ought to be. But I might get pretty close enough as long as I don't overlook big things and compound too many small ones, so I definitely thank you and appreciate and the input.
                  The cheapo way is with gas springs. Problem is gas springs will fail. The luddite way is with cables and counter weights. Sort of in between is with a pressure relieving regulator, an air cylinder, and a couple gallon air reservoir.

                  That being said, I have three mills that came with gas springs on the heads. I've had 3 gas spring failures,, but none of the replacements have failed.
                  *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

                  Comment


                  • #10
                    My own mill is buried under stuff in a dark garage (so no pics of my actual machine), but since there were requests I figured I'd link to a couple just for conceptual reference.
                    Mine was this clean when I first got it but it's got some rust on it now. It's not as bad as I make it sound and really still looks pretty good. As I mentioned, it's worst on the handwheels and not much at all on anything else. I guess the handwheels are so prominent that the rust on them kinda jumps out. Anyway, here it is.
                    Oooh. I found a picture with the horizontal setup in front and the one behind has the vertical head attached.



                    I've run mine just a tiny bit in either configuration and one thing I can say is it runs really smooth and the spindle is quiet as a mouse.
                    The spindle has a 5C taper and the vertical head is 4C, which was a stupid call in my opinion and I don't know why they didn't just go with 5C on both, but it is what it is. They are like, what, 1/2" different in length and 1/4" in diameter? Whatever. If it gets to be a CNC machine I won't mind dealing with whatever I need to do for tooling.

                    I have the index head and spiral gearbox too. I won't need the gearbox for CNC, but the indexer might be a nice 4th axis addition. It's a 4:1 (not a typo) but adding a worm & gear in place of the crank would be straightforward enough.
                    Here's a pic of the indexer:

                    Last edited by tyrone shewlaces; 03-28-2019, 02:00 AM.

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                    • #11
                      Really! hahaaa. Love it, emm. Those both are yours? Ok, you suck. Two well equipt machines.

                      (I cant spell worth a darn by the way, lazy might be an issue. But I am well read and had to right for a living so? Solly for the mis-grammers)

                      Yanking our chain about converting one of these right? Ill come over and give you a "what for". Thats when yer friend socks ya in the face and you say "what for"

                      I wound not convert eight of those nice machines.

                      The vertical head on the other one is what I would CNC.

                      Ill Convert anything. I would not mess with those. JR




                      Originally posted by tyrone shewlaces View Post
                      My own mill is buried under stuff in a dark garage, but since there were requests I figured I'd link to a couple just for conceptual reference.
                      Mine was this clean when I first got it but it's got some rust on it now. It's not as bad as I make it sound and really still looks pretty good. As I mentioned, it's worst on the handwheels and not much at all on anything else. I guess the handwheels are so prominent that the rust on them kinda jumps out. Anyway, here it is.
                      Oooh. I found a picture with the horizontal setup in front and the one behind has the vertical head attached.



                      I've run mine just a tiny bit in either configuration and one thing I can say is it runs really smooth and the spindle is quiet as a mouse.
                      The spindle has a 5C taper and the vertical head is 4C, which was a stupid call in my opinion and I don't know why they didn't just go with 5C on both, but it is what it is. They are like, what, 1/2" different in length and 1/4" in diameter? Whatever. If it gets to be a CNC machine I won't mind dealing with whatever I need to do for tooling.
                      My old yahoo group. Bridgeport Mill Group

                      https://groups.yahoo.com/neo/groups/...port_mill/info

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                      • #12
                        Oh. I forgot to add the ways on the vertical are not meant for that ammount of movement. Its a Horizontal Thin ways compared to even a Rong-Fu copy RF-45 vertical.

                        Which is very easy to convert to servo, encoders, servo drive head, coolant and pressure oiling for ways. Its endless.

                        Not with the lil horizontal. You scored sometime.

                        Do you have the side drive? JR
                        My old yahoo group. Bridgeport Mill Group

                        https://groups.yahoo.com/neo/groups/...port_mill/info

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                        • #13
                          Dang JRouche! You seriously need to cheer up.

                          You would think so wouldn't you? I agree that they give the impression of being a very fine mill. But it's complicated. It is indeed a very fine machine, but actually using it doesn't ever seem to work out because of a few little details that just weren't designed all that great. So the build is great, but the design is kinda "meh". That's why I think it would be such a good conversion candidate.
                          By the way, just to be clear, those are just pictures I lifted off the net, not my own machine(s). Same machine though. Mine is well outfitted, but I only have the one.
                          And yes, I do have the spiral gearbox. I've never used it and honestly I don't ever see myself using it.
                          Also want to add, the scale of the machine doesn't translate from a picture. They look larger than they are. The top of the machine comes up to about chest-high.
                          Last edited by tyrone shewlaces; 03-28-2019, 12:30 AM.

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                          • #14
                            Why not sell the horizontal to someone looking for one and go buy what you want? When I was working, I considered a small horizontal just for cutting keyways in shafts. Never found the right deal.

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                            • #15
                              One more consideration: What is the max spindle speed on the vertical head? If its only something like 3000 you will not be very happy. Aluminum and small endmills want lots of rpms for cnc use, I have 6500 on my bridgeport and its still a pain at times.

                              Before someone says it, yes you can work with the lower rpms.... but many hours for a toolpath won't be unusual. Its the difference in possible and practical.

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