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Yay! Bought a "real" CNC lathe project!

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  • Yay! Bought a "real" CNC lathe project!

    Yes, it's only a "training" lathe, a Denford Orac but its guts are very serious. It has good ballscrews on both axes with adjustable double ball nuts, double A/C bearings at both ends of the Z screw along with the spiral expanding chip covers, hardened ways and serious bearings in the spindle. I'm getting only the bed/headstock-spindle/carriage with ballscrews, etc and the sheet metal base carcass. I won't be needing the ancient steam powered tape drive electronics & steppers. It came (I'm told) from a university and has around 30 hrs. on it. It's perfect for the small production work I get these days and will fit in my shop with just a few minor shuffles.

    Here's a pic of it from a brochure:



    It's freaky how things work out sometimes. I've been collecting bits & bobs to scratch build or retrofit a more capable CNC lathe than the one I cobbled together last year from the Craigslist Denford MicroMill. I've looked at used 7x14's and read all the CNCZone retro's thinking I'd do one of those (yuck.) Thankfully, along comes this Orac at a fair (not gloatworthy) price and I pulled the trigger on it a couple days ago.

    After doing a little research and downloading the manuals, I find that under the hood it's an Emco Compact 8, the exact lathe my manual lathe is a very well-built clone of! So, the 3 & 4 jaw chucks, the ER-32 collet chuck, the tailstock (which the Orac is missing) the steady rest and other tooling is a perfect match! I couldn't be happier.

    Well, I guess I could be happier if coincidentally one of you guys just happened to travelling from the Detroit area down through east Tennessee or west AR this weekend and had some extra room in the back of your truck.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  • #2
    Nice score Milton!
    You have been doing some nice work on your home brew one. I look forward to your progress on this one.
    Dave

    Comment


    • #3
      I have an Orac (and an Avon mill. I wonder how much of a Blakes 7 cast it's possible to get in machine tool form).

      Mine is complete and working in it's original condition, but could really do with a Mach 3 upgrade.

      A bit of nostalgia for British forum members is the Orac promotional video on Youtube; http://www.youtube.com/watch?v=QV1bQeJ9tx4

      William Woolard was a Top Gear presenter back when it was a factual informational program!
      Paul Compton
      www.morini-mania.co.uk
      http://www.youtube.com/user/EVguru

      Comment


      • #4
        That's the other wierd thing in my life's ongoing twists & turns. I've **worked for British car dealers since 1971 and the 2 most recent machine tool purchases I've made were both built in the U.K. Who would'a thunk a guy in the middle of the USA in Tennessee would've ended up with not one but TWO machines built in Yorkshire, England. The other bit of irony is that I worked with a lad from Leeds for 16 yrs. Taught me the value of a dollar, I can guarantee!

        **"worked for British car dealers since 1971" Some might say that a guy that worked on 70's era British cars and still bought the 2 machines ought'a seek professional psychological treatment! (Just KIDDING, I love 'em.)
        Milton

        "Accuracy is the sum total of your compensating mistakes."

        "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

        Comment


        • #5
          Not many Americans would understand the naming of Denford tools. I'm glad you appreciate the strange humour of it. Now if they had made a Servalan grinder I would have been interested.
          Bill

          Comment


          • #6
            Milton,
            Got an identical one in storage somewhere but I think that one has got an air operated chuck on it.

            I did plug it in when I bought it but just errors out, it's been parked up waiting for a transplant.

            Probably move to EMC on this as Mach3 still cannot thread properly on machines with less than 10Hp spindle motors.
            EMC will support multi-line encoders.
            .

            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



            Comment


            • #7
              Originally posted by John Stevenson
              Milton,
              Got an identical one in storage somewhere but I think that one has got an air operated chuck on it.

              I did plug it in when I bought it but just errors out, it's been parked up waiting for a transplant.

              Probably move to EMC on this as Mach3 still cannot thread properly on machines with less than 10Hp spindle motors.
              EMC will support multi-line encoders.
              When I read about your one in storage my mind flashed on it sitting under a pile of [email protected] and it's little ATC plaintively crying out: "John...JOHN...JOHN...Put me in a sturdy wood box and send me to Milton over in Tennessee so I can live out my life being reverently used in a nice warm place!"

              Since I can barely use Mach, there's not much chance of me using EMC to cut threads. What little threading I might be doing is pretty small & short stuff so I assumed that Mach would work OK. I see lots of videos where it looks like it's working. Not true, eh?
              Milton

              "Accuracy is the sum total of your compensating mistakes."

              "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

              Comment


              • #8
                Originally posted by DFMiller
                Nice score Milton!
                You have been doing some nice work on your home brew one. I look forward to your progress on this one.
                Dave
                Oops, missed your kind remark...thanks Dave! May I send a link to SWMBO? She thinks I'm messed up in the head for doing all of this stuff...until the checks come in.
                Milton

                "Accuracy is the sum total of your compensating mistakes."

                "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                Comment


                • #9
                  Originally posted by DICKEYBIRD
                  Since I can barely use Mach, there's not much chance of me using EMC to cut threads. What little threading I might be doing is pretty small & short stuff so I assumed that Mach would work OK. I see lots of videos where it looks like it's working. Not true, eh?
                  It works if the spindle speed is stable under load. Mach 3 uses just one pulse per revolution, so it can't necessarily track speed changes accururately enough. A sensorless flux vector drive might do the job. I plan to have a play with an ordinary cheap VFD and an external speed feedback circuit.
                  Paul Compton
                  www.morini-mania.co.uk
                  http://www.youtube.com/user/EVguru

                  Comment


                  • #10
                    Originally posted by DICKEYBIRD
                    After doing a little research and downloading the manuals, I find that under the hood it's an Emco Compact 8, the exact lathe my manual lathe is a very well-built clone of! So, the 3 & 4 jaw chucks, the ER-32 collet chuck, the tailstock (which the Orac is missing) the steady rest and other tooling is a perfect match! I couldn't be happier.
                    Cute lil machine. I like it.

                    Not to nitpick, but to save a headache, the tailstock will need to be shimmed or ground as appropriate. They do not interchange between lathes perfectly.
                    "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

                    Comment


                    • #11
                      Originally posted by justanengineer
                      Cute lil machine. I like it.

                      Not to nitpick, but to save a headache, the tailstock will need to be shimmed or ground as appropriate. They do not interchange between lathes perfectly.
                      You're right and it will be checked and hopefully shimmed up to center if it's low and I really have a need for it. I'll have to cross that bridge when I get to it.

                      The work I have planned for the machine is pretty short so it probably won't be needed. The seller does have a tailstock but IMO wants too much for it.



                      Hey Paul, do you know what the max speed of the your original AC motor is? I see the max spindle rpm noted in the manual but not the motor speed.

                      I really liked that YouTube video you linked to, thanks. Definitely a blast from the past! Any idea how much they sold for when new? I'm guessing pretty high.
                      Milton

                      "Accuracy is the sum total of your compensating mistakes."

                      "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                      Comment


                      • #12
                        Originally posted by EVguru
                        It works if the spindle speed is stable under load. Mach 3 uses just one pulse per revolution, so it can't necessarily track speed changes accururately enough. A sensorless flux vector drive might do the job. I plan to have a play with an ordinary cheap VFD and an external speed feedback circuit.
                        Paul, that might not work as good as you think.

                        I have a prototype CNC lathe here from Sieg in China, it's powered by a 500 W brushless servo motor with encoder feed back, I know it's only a small motor but it's also only a small lathe.

                        If this was in manual format you set the speed say 800 rpm and start cutting, as the load goes on it senses the rev drop and the speed board compensates and steps the revs back up to 800 just as it's designed to do.

                        However in CNC format the revs drop, the spindle board compensates but as the revs drop the one rev encoder that's feeding Mach also senses the drop and tells Mach to slow down, however because of the one rev per pulse delay the speed is back up, courtesy of the spindle board. So the spindle encoder is fighting to motor encoder all the while.
                        You can't use the motor encoder as a spindle encoder because of gearing and belt slip.

                        This machine is probably the best test bed for threading because if anything can go wrong it will go wrong with this machine.

                        I have a friend with a similar machine but he's ripped the motor off and replaced it with a 1.5Kw AC motor and inverter but has no feed back via the motor and inverter, just a steady power output.
                        This threads up to a point before it starts getting out of pitch but he's moved onto EMC and it now threads OK.

                        My hands are tied in what I can do on this prototype machine, Sieg won't fit a larger motor because of cost, same as replacing it with a decent size AC motor but room is an issue here.

                        Milton, these motors on the Orac are rated at 1425 rpm but remember we are on 50 Hz so expect 1710 revs.
                        .

                        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                        Comment


                        • #13
                          Originally posted by EVguru
                          It works if the spindle speed is stable under load. Mach 3 uses just one pulse per revolution, so it can't necessarily track speed changes accururately enough. A sensorless flux vector drive might do the job. I plan to have a play with an ordinary cheap VFD and an external speed feedback circuit.
                          The code in Mach3 for threading is broken. Art has said after looking at it again that he dosnt know how it ever worked and Brian who controls Mach now has no intentions of fixing it. It works for some people some of the time. It was working for me, now it does not. And this is with a servo controlled spindle.

                          The solution to the problem is to use one of the external signal generators like the SmoothStepper or the KFlop. They run the threading routine internally skipping Mach3's bad code.

                          Comment


                          • #14
                            Thanks for all the info gentlemen. Sounds like I'll be learning Linux/EMC if I have much threading to do. I guess I could cut the threads and the nut with Mach and see if they'll screw together.

                            The specs show 2000 rpm max spindle speed and the pics I've seen looks like the motor pulley is smaller than the spindle so if the motor runs 1425, I guess they had some kind of frequency drive to overspeed the motor? Mine has no motor so I'm looking around for a 1/2 to 3/4 hp DC motor to go with my KBIC-120 controller. If nothing cheap enough turns up, I'll stick my trusty treadmill motor on it.
                            Milton

                            "Accuracy is the sum total of your compensating mistakes."

                            "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                            Comment


                            • #15
                              I would keep mach an run either a smooth stepper or the kflop. This allows you to use just about any pc with a usb port. Parallel works but it getting long in the tooth, i have intermittent issues on my mill with it depending on background processes and the like. Moving to an external motion controller eliminates this.

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