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Denford Lathe Toolchanger

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  • Denford Lathe Toolchanger

    Below is a toolchanger I made for my Denford lathe. It is similar to the orginal toolchanger. I spent most of the day
    getting to backlash out of the worm gear and worm wheel.



    The dial I made on my CNC Bridgeport.



    All I need is a coupler for the stepper motor. The shaft that drives the worm goes all the way through the mounting block
    I plan to put a hand wheel on the opposite side from the stepper motor for hand adjustments.

    I also included some ball oilers lubricating the toolchanger.

    Go to run
    Jim
    So much to learn, so little time

  • #2
    Jim, you got a ratchet it winds back onto ?
    The original Denford ones had loads of bag in the worm and wheel but it never mattered because it used to park up on the ratchet and the cutting forces kept it there.
    .

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



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    • #3
      John, I saw a picture of the original ratcheting toolchanger somewhere. You sent me a picture of your toolchanger. How does yours work?

      I'm not sure how well mine is going to work.

      Jim
      So much to learn, so little time

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      • #4
        Wow, heck of a project Jim. Lookin' good. Looks like your BP can move some metal!

        Here's a page out of the ORAC manual:

        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

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        • #5
          Thanks for the pic Milton.

          Will my toolchanger need some type of brake or locking system and if so I need some ideas on how to acheive this. I have a box full of air cylinders in the basement. I could make an air actuated shot pin to lock the dial in place or do I need to just bump the dial against the worm gear to be sure the backlash is gone?

          Maybe I'll try it the way it is.

          Jim
          So much to learn, so little time

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          • #6
            You could take a lesson from screw machines and use a hardened tapered pin in a hardened bushing, but instead of a cam you could use a solenoid to insert and retract the pin.

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            • #7
              Jim,
              In the Orac changer the motor which is a tiny 12v thing, 2332.912 11.151 000 [ the finned thing is just a cover to make it look bigger than it really is, so's the part number ] frives the worm thru a roll pin which is also not a good fit, this drives the worm wheel and the shaft with the ratchet wheel on, TR110/3.
              The ratchet pawl is just a piece of spring stel, TR110/7 held up by a spring and screw from the bottom, ML119/6 and TR110/8

              In use the motor drives the shaft past the next tooth on the ratchet and then the motor drops into 1/2 amperage mode and reverses and stalls.
              It stays in stall mode until it's need to select the next tool.

              This stall mode and the fact cutting forces are pressing onto the ratchet keep it in place.

              Also the ratchet is 8 position but only 4 tool slots, the other positions line up with the holes in the tool plate for boring bars etc.
              This is one of the prototypes we built that works the same way but uses a stepper motor.

              http://www.youtube.com/watch?v=5dvLbb-HNsE

              Another type but this requires an air supply for locking

              http://www.youtube.com/watch?NR=1&fe...&v=o-9J4KsXYwU
              .

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



              Comment


              • #8
                Hey Jim, I finally remembered where I saw this; hope it helps. Knowing you, you're probably finished with yours already!

                http://www.homemodelenginemachinist....-turret-18508/
                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
                  When I converted mine years back I designed the electronics to reverse onto the spring John mentions, hold it there for ten seconds, then reduce the current through the motor to quarter of normal. The original used to overheat and burn out as it was left stalled on full current.

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                  • #10
                    Don't mean to hijack, but since we're talking about spindle locks, what's the best CNC-controllable way to lock the spindle on a 4th axis so it won't slip under cutting forces? This is different from a tool changer because it has to be able to lock at any angle.

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                    • #11
                      High ratio worm and wheel, 40:1 plus works fine, they cannot be back driven.
                      .

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



                      Comment


                      • #12
                        Originally posted by alsinaj View Post
                        ...what's the best CNC-controllable way to lock the spindle on a 4th axis so it won't slip under cutting forces?
                        I hope this is the right thread: http://www.machsupport.com/forum/ind...c,22080.0.html It's quite a tome but somewhere in it he shows how he used a motorcycle disc brake (I think it was) to lock down his indexer. Apologies if it's the wrong one but I know it was simpson36. This guy's unreal.

                        Anyhoo, please take pictures and show us what you come up with.
                        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


                        • #13
                          Problem is under CNC is how can you lock it on a continuous move ?
                          If it's a job where it going backwards and forwards you need a low backlash method of driving that cannot be back driven.

                          Fortunately we have such a drive, worm and wheel which is fitted to virtually every rotary table and dividing head, why re-invent the wheel ?
                          The folk who need these brakes are the people who just drive a spindle of some sort on a simple belt drive arrangement.

                          OK on tiny low power machines but as soon as you start getting serious cutting forces soon make a mess of your work.

                          I don't mind admitting that years ago I made a massive rotary head, used the spindle off on old lathe with D1-3 fitting so i could swap chuck with the job still setup. Drove it via 1" wide toothed belt at a 5:1 ratio via a massive type 42 motor rated at 1800 oz / in

                          First job doing some splines you could see the spiral and it wasn't even.
                          On looking close you could see the belt cogging as cutting forces pushed the work away. I could have fitted a brake but how about continuous rotating jobs like cam tracks ?

                          Sorry to say it got stripped for the sum of it's parts and a HV rotary table put in it's place, that is still in use today.
                          .

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



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