CNC Mill - Build or Buy?

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  • Tony
    Senior Member
    • Oct 2002
    • 1742

    CNC Mill - Build or Buy?

    howdy folks.

    I've come across yet another of life's crossroads.. and my Gcode
    is ambiguous on which way to go.

    I've been getting more and more into prototyping (plastic, aluminum,
    etc etc) -- curvy consumer product stuff. I do the design
    work and then it gets sent off to be (usually) rapid prototyped.

    I'd like to have the ability to mill some of these parts in house.

    So my requirements are:
    - around 250-300mm in X&Y
    - 300mm would be great for Z but 200 might cut it (pun intended)
    - 4th axis
    - fast spindle.
    - price range: $6-8k including 4th axis, tooling, etc.

    I built a CNC plasma a couple of years ago and, thought it works
    great, I don't know if I have it in me (time/energy) to build a mill.
    I'd love to, but I think I'd rather just jump in make some parts.

    Something to consider: I do have a (manual) Bridgeport. I could,
    in theory, throw a CNC kit at it -- but I don't know how agile it
    might be for small parts (think cell phones, hair dryers, etc) --
    anyone know what I'd be looking to spend to convert the Bridgeport?

    Anyway, I really like the Roland benchtop mills:
    http://www.rolanddga.com/ -- but their top of the line is pricey.

    I really like the Tormach too -- but again, out of my price range
    once I get all the bells and whistles.

    I remember some posts ago about the Taig/Seig X something or
    other -- are those around yet? and have they been burned in?
    I'd like something a little higher build quality -- but its not
    absolutely mandatory.

    So, if you had $6-8k to spend on a CNC mill -- which way would you
    go?

    Thanks,
    -Tony
  • Michael Moore
    Senior Member
    • Jun 2004
    • 721

    #2
    I paid US$5K for my used 325 Tree with 6000 RPM spindle.



    What do you consider a fast spindle?

    For the kind of Z travel you are wanting you'll need to go with a bed mill of some sort. The Tree has 6" in the quill and I wouldn't think that a powered knee is going to be the way you'd want to go.

    It seems like something like a Haas Superminimill or Fanuc Robodrill would be up your alley, except for the price.

    cheers,
    Michael

    Comment

    • MickeyD
      Senior Member
      • Jun 2004
      • 934

      #3
      If you have a bunch of free time you can cobble something together that works, but if I were in your shoes, I would go with the Tormach. I would get them to prewire it for the 4th axis, and then add sprutcam universal because it now supports a live 4th axis vs. just an indexer. Sprutcam for the Tormach is pretty solid and you are not going to find anything else out there remotely in your budget. Add the live 4th (or build one yourself) whey you can and you will be in business. If you have a lot of free time, you can always retrofit a machine (I am trying to finish up my old Hurco), but they alway take a lot longer than you think

      Comment

      • Tony
        Senior Member
        • Oct 2002
        • 1742

        #4
        MikeM -- wow. thats alot more machine than I had in mind.
        but sounds like you got a good deal.

        I'm not 100%, but I'm going to guess spindle speeds around
        the 20k mark for those itsy bitsy finishing mills.

        MickyD -- I keep turning back to the Tormach catalog. Its become
        my "benchmark" .... "400mm travel .. hold on, what was in on the Tormach"
        etc.

        I went full circle here, first starting with the cnc mills (&mach3) then
        looking at the newest 3D printers (but still too much $ for what they
        do .. at least at a 'reasonable' price) .. and, considering the raw material
        costs and maintenance -- right back to cnc mills.

        -Tony

        Comment

        • macona
          Senior Member
          • Aug 2006
          • 9425

          #5
          300mm is a lot for the Y axis. Maybe with something like a series II bridgeport.

          Dont bother converting your knee mill. Its a waste of money and will actually devalue your mill.

          Fine a used mill with a dead control. They are not all that hard to come by. Keep an eye out in CL.

          Comment

          • KiloBravo
            Senior Member
            • Sep 2007
            • 443

            #6
            This website is for sale! industrialhobbies.com is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, industrialhobbies.com has it all. We hope you find what you are searching for!


            Might be worth a look, not sure if it meets all your criteria, but
            they have a kit if you want to build it.

            Comment

            • Evan
              Senior Member
              • May 2003
              • 41977

              #7
              I wouldn't try building one unless you are willing to spend many hours, many many hours. I have no idea how long it took me to build mine except that it was probably above 500 to 1000 hours of shop time. Even though I work slowly on that sort of thing it was a long project. I don't mind long projects at all but for many people it's a good way to ensure it never is finished. You have to have more than a bit of OCD to keep focused on something that takes years to finish. I also didn't save any money over a factory made unit but I did get to have it MY WAY. I am very happy with it and some of the features have proven to be excellent. I haven't needed to adjust the gibs in about 6 months now as they are essentially self adjusting and stay adjusted.

              I wouldn't build such a machine again, but then I don't need to.
              Free software for calculating bolt circles and similar: Click Here

              Comment

              • Tony
                Senior Member
                • Oct 2002
                • 1742

                #8
                Evan, but now that you have one at your disposal, I'm guessing it'd
                be a heck of lot easier and faster to build another one.

                oh.. and how much would it cost me?

                Comment

                • Evan
                  Senior Member
                  • May 2003
                  • 41977

                  #9
                  oh.. and how much would it cost me?
                  Do you have a son?

                  Building another will be much easier and I have plans to make a stand-alone engraver from the bones of an old HP pen plotter. The parts are just waiting on my attention...
                  Free software for calculating bolt circles and similar: Click Here

                  Comment

                  • JoeFin
                    Senior Member
                    • Jul 2007
                    • 1732

                    #10
                    I’ll second finding a used CNC with a dead controller.

                    As long as the seller is willing to admit the controller is dead, and or out of date unserviceable / unsupported by the factory.

                    What a lot of folks selling older CNCs don’t like to admit is that the controller is out of date / unsupported. I went through this with an Anilam controller. The factory service reps basically told me they don’t support it, they won’t send me the electrical schematics, I can’t get new freshly programmed PROM chips, and basically it is a really nice hunk of junk. Just try finding a place to buy the replacement IC chips, - they are not available!

                    And this applies to most of the controllers more then 15 yrs old

                    I see some really nice looking CNC mills out there but I wouldn’t touch them because the guy is asking way too much money for a machine that needs a new $8000 - $10000 control system. And that does not include servo drives and motors!

                    Forget about the PC based stuff for any thing you would ever consider using in a production environment. Nice concept – good stuff, but as long as they are using some one else’s base operating system its not going to work quite right. You’ll want to find some thing using “Brushless – AC Drives” as most control systems have moved to that arraignment. Also an inverter drive for the spindle is a really good feature as you can adjust the ramp time to play nice with you RPC too.

                    So taking every thing into consideration $1500 - $2000 is what a used CNC with an out of date controller is worth. Sure I see a lot of folks trying to fetch $5000 or more for them, but I certainly would not touch them myself. Once a new or near new controller is installed, given your spindle and ball screws are in good working order, you’ll have a good working, reliable machine for about $10,000.

                    Compare that to the $40,000 to $60,000 price of a new Bridgeport CNC

                    BTW: there were a couple of +25 yr old Bridgeport Series II CNC mills that sold in auction for a couple of hundred bucks not too long ago.
                    Last edited by JoeFin; 07-03-2008, 09:11 AM.

                    Comment

                    • fasto
                      Senior Member
                      • Jun 2007
                      • 365

                      #11
                      Originally posted by knucklehead
                      So my requirements are:
                      - around 250-300mm in X&Y
                      - 300mm would be great for Z but 200 might cut it (pun intended)
                      - 4th axis
                      - fast spindle.
                      - price range: $6-8k including 4th axis, tooling, etc.
                      FWIW, I just bought a used (OK, well used) but working quite well VMC. 24"x16" with 20" Z. 6krpm CAT40 spindle, 24 pot tool changer, Fanuc control, 8000 pounds of cast iron, 8'x8'x8' footprint, $9900 delivered to my shop, installed, leveled, wired, 1 day of operator training. It wont be delivered until the end of the July because we've got to re-arrange the shop.

                      Granted, the machine is old, but I bought it for exactly the same reason you did, to make rapid prototypes.
                      I started investigating the tabletop CNC machines, then went to old knee & bed mills, then to something with a toolchanger, and eventually arrived at a full boat VMC.

                      For an extra $2k over the tormach I've got a huge additional amount of functionality. I made the space happen by rearranging the shop.
                      Maintenance of the old Fanuc control is an unknown, but ebay is full of Fanuc parts and I could probably design the thing from the ground up anyway.

                      Comment

                      • JoeFin
                        Senior Member
                        • Jul 2007
                        • 1732

                        #12
                        Originally posted by fasto
                        I could probably design the thing from the ground up anyway.
                        Not to deminish your skills but there is nothing like having 2 complete CPU/Mother-boards, (Input CPU and Output CPU) through putting to registers and latches controlling your servo drives, relay boards and reading the inputs at gigahertz speeds. I imagine writing the machine language and assembly code for that would not be child’s play.

                        Or you could deal with the results of “Hobby” orientated PC control systems and fight the PC’s “time splitting”, and "CPU throttling" results in your work,

                        No doubt the folks who made the capitol investment in a programmer work group to develop an OS specifically orientated to controlling their CNC Control system are asking a lot of money for their equipment. – But then again there just may be a reason for that.

                        Comment

                        • airsmith282

                          #13
                          I seen alot of vidoes of people converting mills to cnc and also building cnc stuff as well and over all i think given the choice id build or convert to a cnc my self .. its really not that complex to do but iam sure it takes a bit of time for sure ....my mini mill is going to eventually going to get a cnc mod done to it..

                          Comment

                          • fasto
                            Senior Member
                            • Jun 2007
                            • 365

                            #14
                            Originally posted by JoeFin
                            Or you could deal with the results of “Hobby” orientated PC control systems and fight the PC’s “time splitting”, and "CPU throttling" results in your work,
                            I actually design, specify, program, construct, and sell real-time control systems as a business. I would not dream of using any PC based system for such a product. We sometimes use a PC, but always use a separate CPU for the real-time operations relegating the PC cpu for graphics, operator interface, networking, etc. I've designed with QNX, a deterministic RTOS for PC hardware, but I prefer the flexibility of non-pc hardware for the real-time elements.

                            Regardless, what I meant by my somewhat ambiguous statement
                            I could probably design the thing from the ground up anyway
                            is that I can realistically troubleshoot to the component level, and perform board-level repair of the Fanuc control.

                            Comment

                            • DR
                              Senior Member
                              • Jan 2003
                              • 4783

                              #15
                              Buy a running mill and make parts tomorrow. Build one and (maybe) make parts in a year or so.

                              BTW, I have never seen any for profit shop that had a home built machine in it making money for the owner. I've seen a handful of shops where the build-it-yourself CNC project got started and was dropped in favor of buying a factory built machine.

                              I'm sure we'll hear from the crowd that feels putting Machx on a machine makes it the equivalent of a modern factory made machine. It just ain't.

                              Comment

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