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15. Mechanical design

This week I worked on tasks refered to Mechanical design in order to ‘work and communicate effectively in a team and independently; design, plan and build a system; analyse and solve technical problems; recognise opportunities for improvements in the design’.
This was the assignment:

  • Group assignment:

Design a machine (mechanism + actuation + automation), including the end effector, build the passive parts and operate it manually.
(Follow this link to see the group assignment)

SUMMARY

Have you?

  • 1. Explained your individual contribution to this project on your own website > DONE

On the group page, has your group

  • 1. Shown how your team planned and executed the project > DONE

  • 2. Described problems and how the team solved them > DONE

  • 3. Listed future development opportunities for this project > DONE

  • 4. Included your design files > DONE

  • 5. Optionally included an aprox. 1 min video (1920x1080 HTML5 MP4) + slide (1920x1080 PNG) > DONE

ASSIGNMENT | Mechanical design and test

The idea

First of all was to search for some ideas about machines made on previous years, or mechanisms intended to use.
After that, it was neccesary to find principles to decide what kind of machine was not possible to design:

  • Use translation/rotation (at least 2 axes)
  • Improve a previous machine/process
  • Justify the whole group work and tasks

Also, it was very important to put together all personal capabilities to agree in the way to work.

After some meetings and research process, and with the help of the instructor, Marta Verde, a Light-Painting machine was declared as the machine to work on.




Gianluca Pugliese’s work inspired the idea of doing 3D light-painted models. For that, a Scara machine will be modified to hold a light instead of an extruder. By taking photos with a high exposure time, with the lights out, the Scara could run a spiral job completing the 3D model made by light.

Gianluca‘s example

Scara example

Here is an example of the different brainstorming processes (and changes) with some ideas of the kind of machine to be made, and of the different behaviours disscused:

This is the final idea that was decided:

The ligh-painting machine (called Lighscara or Scaralight) has this main parts:

  • Base
  • Tower
  • Arm
  • Camera support (discarded)

Also, it has this other parts/components:

  • LED actuator (LED + board)

  • 4 motors:

    • Base rotation
    • Arm (Z movement)
    • Arm (whole rotation)
    • Arm (half rotation)

  • Spin ring (this component was finally discarded)

  • 3 shafts
  • 1 screwed shaft

  • Bearings:

    • 3 linear bearings (45x15x8)
    • 10 rotator bearings (7x22x5)
    • 2 rotator bearings (10x35x15)

  • Spacers

  • Arduino

    • Board
    • Board
    • Case

  • Screws and nuts

Project management

To accomplish this goal, the Trello platform was used to organize the work by defining:

  • The design and its parts
  • Bom and material ordering
  • Tasks and people assignments
  • Workflow
  • Platforms

This is the Trello in use, showing tasks, workflow and people in categories:




This is the bom made:

This is the Google Drive platform setup available to share different kind of files along the whole machine project development:

By this way, tasks were assigned to allow working on design before meeting again for the production process.

Design

These are the designs made based on the original one, using Rhino and Grasshopper, Fusion360 and Illustrator.

  • Base

  • Tower


  • Arm


  • Arduino case

  • Camera support (discarded)

Production

The processes followed to make the machine were 3D printing and lasercut:

  • Base


  • Tower

  • Arm


  • Camera support (discarded)

Results and problems

Once the different parts were bought, printed and cut, this was the assemby process:

  • Base



  • Tower

  • Arm



  • Camera support (discarded)

We had to make some changes, but, at the end, this was the final result:




And this is the manual testing process:

SLIDE
VIDEO LINK

base1:

base2:

arm1:

arm2:

machine1:

One of the problems founded was that the idea of using a slip ring for connections on a rotatory axis, was out of the bom plan; Adafruit is the only provider with high shipping cost and so much time to deliver the component.
Instead of that …

Another problem was that maybe the light would not be seen when the arm passes behing the tower, or if the LED holder hides the LED on some positions. One idea to solve this was to put the LED, extended with wires, at the end of the arm, while the controller board could be placed into the actuator piece near the tower.
Another solution for that is to use all the faces of the actuator to hold different LEDs

My participation on the assignment

I worked on this tasks along the machine’s development:

  • Idea
    I have participated on the research process to find a good idea to work on to make the machine.
    (reference pending)

  • Management


I have participated on all our meetings, taking group notes to make every important comment visible in order to clarify the target and to distribute the work to be done.


I have also participated on the platform management creating the repository directory (Google Drive), and working on Trello by putting down tasks, reviewing members, calendar goals and jobs descriptions.

I worked also on the BOM definition.

  • Design


I worked on the creative design of the whole machine, studying possibilities and making suggestions and sketches.

I worked also on the arm part. My idea was to make it light better than heavy and I decided to work with lasercut, so the design would just be drawed in 2D and cutted in a 20x20 cm MDF (3mm).

The idea was good but I had to consider the presence of gears instead of belts, so I had to reduce the friction as much as possible to help to the transmission process. For that I thought 2 main options:

  • hang the gears by their axis hole
  • quit material from the friction parts

So I had to draw 2 different but similar arms:

  • hanging gears








  • supported gears








I also had to consider the presence of bearings to put the on the main rotation axis.

  • Production and Assembly

I worked on lasercut, adjusting the design until the final one was done:

These are the 2 versions (again, some changes made by the group and by me):


For the final version, MDF may be substituyed by some kind of acrylic (crystal or black) make the slides easier, and to help the final light effect (with the lights out) to be more visible and gorgeous.

I have participated on the assembly process:

(sorry, no more photos of me working…)

  • Documentation

Finally, this week I was volunteer to put the machine info together, so I had to gather the group members info from the collective folder to write the Mechanical design process with the help of my partners.

Original design files