week two Header Img

Week 2: Model your final project 3D

Week 2, much more relaxed than week 1.
Task: Model your final project in 3D, using 2D-,3D- and rendering-programs.
2D... hmm... The plan is to build a POV-Display, not much 2D-sketches to do.
So i decided to sketch a Name-plate for the Display. The plate will be cutted on the lasercutter,
so i choosed Inkscape to generate the sketch.
It is pretty straight forward:

  • write the text for the plate
  • convert the text into multiple paths
  • add a square around the text

  • If you have writen the text, you can do the positioning by two inputs in the upper row. Switch the display to mm!
    For the square i sketched a path and adjust the endpoints with the same tool.
    This came out:

    screenshot inkscape Img

    After InkScape i gave Adobe Illustrator a try.
    The look-a-like is quite similar, but you can feel that Illustrator is more a pro-app than Inkscape. Everything runs easier, smoother, faster than in Inkscape. Okay, you pay a lot of money for this. In the end i created almost the same file like before, and i can´t say that it was a big difference. I have the luck that i can use Illustrator for free. Without this i would take only Inkscape...

    screenshot inkscape Img

    Now the 3D-Part:
    I´m working since 8 years with SolidWorks so this is my favorite program for this. Sure, there are some other realy good Open-Source-Programs like SketchUp, but if you work normaly with some "professional"-software you don´t want to go back.

    First thing to model was the foot of the POV-Display. It will be a box of 30cm*30cm. Inside will the electronic for the lower Brushless take place, and the hole foot will be heavy. So it will get an bottom-plate out of steel or something similar.
    In the middle of the foot will be a 10mm shaft on which the globe will spin.

    Foot Img
    Rotor Img

    On top of the foot i will mount a brushless-motor with a hollo shaft. This way it can be placed concentrical to the main shaft, rotating around it. The rotating part of the motor will be directly connected to the rotor above it. The rotor itself has a ball-bearing on the top hole.
    On the bottom of the rotor will another brushless-motor take place. The rotating-part of this one will be connected to the middle-shaft, so it stands still while the part with the coils will rotate around the middle-shaft.
    This has two benefits: I don´t need a second ball-bearing at the bottom of the rotor, because the motor itself has a ball-bearing. The second benefit: There a a lot of coils spinning around a lot of very strong magnets.
    Due to the laws of physiks there will be some current on the leads of the upper motor...

    In the middle of the rotor will be some space for the rectifier and a UBEC. This will make 5V out of the 3 sine-phases of the upper motor.
    Next to the UBEC sits some self-produced electronics: an infrared-diode, a photo-diode and some OpAmps. This will be the assignment in a few weeks, but here is a little spoiler on that:
    The infrared and the photo-diode are isolated against each other, so the light can not get directly to the photo-diode. The reflecting light can...
    On the still-standing part of the upper motor will be a little piece of white tape.
    The tape reflects more light than the motor itself. This difference is used by a comparator to generate a 3,3V signal that can be used to synchronise the image of the POV to the rotating speed of the globe.
    The third device on the rotor will be a Beagle-Bone-Black. It will fire the OLEDs on the outer rotor with some data. Hopefully... ;)

    All-together Img

    And here is the full model:

    A few words about using SolidWorks (similar work with Fusion 360):
    Principal is it always the same workflow: first you have to decide if you will sketch your part additively or subtractive.
    If you want to make a bowl substractive you start with a sketch on the bottom layer.
    Then you create a feature out of this sketch. Now you´ve got a cube.
    Next step is to sketch a square on the top of the cube, a little bit smaller than the cube itself.
    Create a subtractiv feature out of your second sketch and define the height a little bit smaller than the height of your cube.
    And voila, you´ve got a very simple bowl :)

    I used this steps also on Fusion-360 to learn this new AutoCad-Program.
    Additionally i added fillets with 1mm diameter to every straight line to make the bowl more smoothie:

    Fusion 360 Img

    All in all Fusion-360 is a pro-app like SolidWorks. Fusion-360 is much more web-based than SolidWorks, your files are stored on an Autocad-Server if you don´t export the parts by hand. Some like this, some don´t...
    On my system (Macbook Pro 2015) Solidworks runs in a VM, and in runs smoother than Fusion native on Mac.
    In the end it is always the same: Coke or Pepsi? McDonalds or BurgerKing?
    Both Apps are very good and easy to use. I think i will use both in the future, but more SolidWorks. Something like 80% to 20%...

    If you want to download my files, here they are:
    The 2D-Plate (Inkscape SVG)
    The 2D-Plate (Adobe ai)
    The 3D-Parts (zipped SolidWorks files)
    The 3D-Bowl (Fusion-360 file)

    So far for this week, stay tuned ;)