-  Week 11  +

mechanical design and machine design

presentation slide

Tasks

  • MECHANICAL DESIGN (week 1 of 2)
    Make a machine, including the end effector, build the passive parts and operate it manually
  • MACHINE DESIGN (week 2 of 2)
    Automate your machine. Document the group project and your individual contribution

    • Idea

    We wanted to improve our documentation and make taking photographs easy and automatic. Hence, after a lot of brainstorming, we came up with this design for a camera dolly.

    We collectively finalized the design through a series of development sketches, this one made by Avishek covers most of what we ended up making.

    Team

    Avishek | Gautam | Dhruv | Me

    Work distribution

    We divided ourselves into pairs of two. I and Avishek were handling design, detailing and production. I specifically took care of entire production of the camera dolly. For the first week we made mechanical parts largely using laser cutting machine. And assembled all the components for seeing its working. Dhruv and Gautam handled electonics and programming.

    My thoughts and contributions

    • My contributions were mainly in design overview and validation and managing the design workflow. I also produced drawings for milling on the ShopBot and prepared toolpaths for the same and milled the frame/base.
    • I also did the assembly of the mechanical design.
    • In terms of learnings, we realized that system integration (bringing together different systems to compile the machine) requires a lot of forethought.
    • Taking this further, we must improve the camera mounting adapter design, replace the current belt with rubber GT2 timing belt
    • But my most important contribution was the fact that I made the demo video look good by being a good static model :D

    Design

    The frame is to be CNCed and hardware to be 3D printed where it can.

    The design was done as an assembly in Rhino to visualize the complete design.

    And then the profiles to be CNCed were compiled and worked on in AutoCAD.

    Fabrication and Assembly

    Onwards to CNCing, I was assigned this task which included toolpath preparation and CNCing.

    Doing the assembly was a group effort, the CNC frame is press-fit and the metal hardware was fastened in.

    Final Object

    The motors being firmly inset in thier grooves are essential, if they aren't the motors might rattle and expend energy wastefully.

    Process

    My understanding of the software workflow

  • This schematic was made in 'Google Docs - Drawings'

  • This is the screenshot of 'Marlin firmware' being uploaded to the Arduino MEGA

  • GOing through all the configuration options in Marlin

  • There was a lot of back and forth calibration between making test moves in Repetier and adjusting values in the firmware

  • this is the interface of the Repetier host, it can import some basic formats of geometry and control each axis through a gamepad like set of controls

    • The marlin firmware resides in the Arduino-mega
    • The RAMPS shield allows connections to upto 4 stepper motors, as it has 4 stepper drivers with heat sinks
    • The Repetier host provides the UI from a host computer

    Initial prototype of mechanism

    We fabricated a basic version of the mechanism to test the hardware's tolerances and gives., it helped us foresee problems we might face in the final CNCed version

    Us - trying to test the strength of the joint

    It also helped us in finalising proportions and key dimensions of the 2 axes.

    The assembly was coming together now.

    It was essential that these parts were as orthogonal as possible for smooth movement

    Components

    Component Origins
    CNC frame Digitally fabricated
    Hardware - Bearings / Smooth rods Local vendor, but accommodated in our digital designs :/
    Pulley Digitally fabricated (3D print)
    Timing belt local vendor

    Video

    Detailed documentation on Group page

    Links / Downloads / Code

    Week 9 and week 11 Documentation
    Machine-week.zip

    The above zip file contains the following-

    • DXF files for CNC machined frame
    • STL Belt holder to be 3D printed
    • STL Belt holder version 2
    • .GCODE for the same
    • .3DM files are Rhino designs

    Marlin firmware
    Repetier Host