• Another update on the CNC.

    The interfaceboards are etched, soldered and tested.

    IO / Control Boards

    IO / Control Boards

    Step- and directionsignals are generated by an ATmega32 which is controlled over RS232.
    This is only for testing purpose. In the final version a PC will control the movement.

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  • Mechanics 24.09.2008 No Comments
    CNC with notchplate

    CNC with notchplate

    Another part for the CNC router arrived today. I never expected it to be delivered so fast. I ordered it friday afternoon and payed saturday. I was not at home when the package arrived, but fortunately the DPD employee decided to give it to my neighbours instead of taking it back with him. Might have something to do with the weight of the package (ca. 9kg) ….

    And another order arrived today: 136 neodymium magnet spheres of 5mm diameter. They are so much fun to play with and even have educational value! You can visualise some basic materialsciences principles such as close-packing of spheres and edge dislocations.

    Even platonic solids can be constructed. Unfortunately I only have enough spheres for two pentagonal dodecahedrons (made of twelve pentagonal faces) and one decagonal dodecahedron made of twelve decagonal faces.

    Decagonal Dodecaeder

    Decagonal Dodecahedrons

    Pentagonal Dodecaeders

    Pentagonal Dodecahedrons

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  • While the mechanics are nearly complete, the wiring has just started.

    CNC Wiring (Z-Axis)

    CNC Wiring (Z-Axis)

    The light barriers are now all mounted but the metal sheets to trigger them need to be cut and attached.

    CNC Cabling (Z-Axis)

    CNC Cabling (Z-Axis)

    To shield the cableconnections from metal filings and such i placed a small plastic housing at the Y and X axis near the motor. All cables go into those housings through sealed holes. Inside they are connected by luster terminals.

    There will be 3 cables going to the z-axis. One for the motor, one for the 220V socket and one for lightbarriers and 12V supply. These cables are guided by a cable drag chain to prevent tangling.

    Next thing to do after the cabling is complete is to order the notch-plate and etch the interface boards.

    The coupling-problems are nearly solved. The 12mm holes for the motorshafts were misaligned, but the new holes look good. Maybe the holes in the frame for the couplings to go trough need some filing.

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  • CNC

    About a year ago, i decided to build a cnc router. First drafts were made in 3dsmax and the final drawings in CATIA.

    As I wanted to fabricate as many parts as possible by myself, i had to find a shop with adequate machinery which i could use. Fortunately there is a public shop with all the tools i needed in Munich. They offer use of their machines for 5€/h, but students only pay half of that.

    Raw aluminum parts

    Aluminium parts

    One of their employees recommended a firm where i could buy the raw aluminiumparts quite cheap.
    All parts i could not manufacture myself where bought from eBay. There are many shops which concentrate on cnc-parts, so i quickly found what i needed.

    At first i had planned to buy steppermotors and make the control- and driverboards myself. I already had ordered the H-bridges and layed out the boards, when i met a guy at the shop who had build a very big cnc-router in his basement and offered my to give me motors and controlboards for free.

    Motors and boards (a nice 19″ rack with slide-in cards) are from dismantled photomachines. The motors are, in contrast to the steppermotors you find in printers/scanners, 5-phase steppermotors.

    Control circuits

    Control circuits

    Two of them are 1.4Nm and one is 0.9Nm. The weaker one will drive the z-axis, which has a 1:2 transmission. The other two drive y- and x-axis. All axes have 14×4 trapezoidal screws and nylatron nuts.

    The z-axis is guided by four linear ballbearings on two 12mm steelshafts. 12mm might proof to be a bit sparse, but i think i can fit in 16mm shafts without major redesigns.

    The y-axis is also guided by four linear ballbearings, but on two 20mm steelshafts.

    The x-axis sits on four linear-rail wagons which run on two rails.

    The frame is made from aluminium profiles and everything is held together by steel screws.

    Due to exams in September/October 2007 and February/August 2008 (and my laziness) the progress was very slow.
    At the moment the mechanics are almost ready (only the couplings between the motors and the spindles are missing). Some of the limitswitches (light barriers) are mounted and the steelframe for the powersupplys and controlboards is nearly complete.

    Limitswitch at the x-Axis

    Limitswitch at the x-Axis

    The next step is to etch the interfaceboards, which distribute the signals from the parallelport to the motordrivers, and connect all the cables.

    I will try to post regular updates on the progress from now on.

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