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Automatic tool changer for my mill

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  • Automatic tool changer for my mill

    If you have a CNC mill and want to get all the juice from it, an automatic tool changer is a must. But before that, your spindle must be able to grab and release the tools on its own, that’s why I started by making my power drawbar. I you haven’t seen the post, make sure to check it!

    http://bbs.homeshopmachinist.net/thr...t-(TTS-system)

    First of all, my mill is the Weiss WMD30V, bigger than the most common benchtop mills (G0704, PM-25, etc). So if you want to make an ATC similar to mine, and you have one of those younger brothers, you would need to design a smaller ATC. I wanted to get the most tools possible in the carrousel, plus I want to use a stepper motor to drive it in full step. 10 tools were too little so I checked if 20 would fit. Luckily, 20 tools fit perfect on my mill, having enough space between tools to clear the spindle nose, and clearing the Z axis carriage. I wondered that if I could only fit 10 tools, I would make 2 ATCs, one on each side of the mill.

    Started the work by cutting the 2 bars that will act as bearing rails. I had some 20mm chrome shaft at home, expecting the hard chrome to hold the bearings. Lately found that I was wrong, the chrome surface with soft core wasn’t enough and it got quite marked, still functional but marked. I will change the bars with hardened ground shaft in the future. Then I machined the bracket that will hold the bars to the mill column.



    Then press fitted the shafts to the bracket. I was concerned about the saft flexing when all the tools were in position, but I did the math and the bending was very small. In fact once all is assembled it feels pretty solid.



    Machined another bracket, where the pneumatic piston will fit. Cut to length some aluminium profile to act as arm and installed on it a couple blocks where the linear bearings fitted.




  • #2
    As the plate I was going to use an aluminium plate, but my brother got a phenolic board to other project. The board was perfect and more than enough to make the ATC plate. This plate was too big for my mill Y axis travel, so I had to mill it in two setups, turned out pretty well. Also added the engraving for the tool numbers.



    You might be asking why so many holes. The idea is to insert set screws on some of them, to make a 5bit absolute encoder. This way I can use 5 input pins on my control to check if the ATC is on the right position before moving anything.

    Machined all the toolholder holders, someday may even get the mill scale out!



    Here are all the toolholders holders. Made them in two sizes, one for the standard TTS toolholders, and some other for bigger sizes.



    A this point I think I have lost some of the pics. Machined the plastic clips to grab the toolholders, the bearing block, the pneumatic piston fitting, the shaft and the bearing block slider that can be adjusted in position (you know, If you can’t make something precise enough, make it adjustable).

    I was going to machine the pneumatic piston too, but I realized It was way cheaper to buy it than to buy the raw material. Also bought the stepper motor and driver. Last thing I made was to install the home switches. I spent 3 years avoiding this task, but they were mandatory for the ATC so…

    Here is the last current state. I have the toolholder grooved too, lots of sparks.

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    • #3
      Love it. Can't wait to see it finished and hopefully video of it in action. I have a Series 2 BP with QC 30 spindle, but BT30 will work with a drawbar and allow a tool changer to be used....maybe someday.

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      • #4
        Pardon the criticism but I think you need a third bearing for stability. Stack two linear bearings on one Thomson shaft and a single bearing on the other will work.

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        • #5
          Linear bearings can withstand a momentum way better than deep groove bearings. Plus the distance between the center of gravity of the ATC plate full of tools and the centerline of the arm is just a few centimeters, so two bearings hold the system without problem.
          Last edited by DEVILHUNTER; 11-07-2017, 01:36 PM.

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          • #6
            Originally posted by DEVILHUNTER View Post
            Linear bearings can withstand a momentum way better than linear bearings.
            But, at the same time, they have their own drawbacks if compared with linear bearings.
            Mike
            WI/IL border, USA

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            • #7
              You are so goddam right The best are linear bearings!

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