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Week 12

Mechanical Design and Machine Design

Assignment

This is a group week where the whole lab builds one machine together. It has two parts.

  • Mechanical Design: design a machine that includes a mechanism, actuation, automation and an application, build the mechanical parts and operate them by hand.
  • Machine Design: add the motors and the control so the machine actuates and automates on its own.
  • Individual: document the group project and my own contribution to it.

What I Did

As a team we designed and built a machine that moves on its own. It has a mechanism that turns motor movement into useful motion, motors that drive it, a controller that automates the motion, and a clear job that it does. We first built the mechanical frame and moved it by hand to check that everything ran smoothly, then we added the motors and the code so it works automatically. My own part of the project is described below, and the full group build is on our group page.

Link to the group project page

Tools & Software Used

  • CAD software: to design the frame and the moving parts.
  • Laser cutter and 3D printer: to make the mechanical parts.
  • Stepper motors and a controller board: to actuate and automate the machine.
  • Arduino IDE: to write the code that drives the motors.

How the team planned and shared the work

We started with a meeting to agree on the machine and split the work. We made a task list and each person took a part: the frame, the moving carriage, the electronics and motors, and the code. We met often to fit the parts together and kept one shared folder for the design files so nobody worked on an old version.

My contribution

My main part of the group machine was manufacturing the parts, and I also helped with the assembly and the testing. I took the team's CAD designs and made the mechanical parts on the lab machines, cutting the flat frame pieces on the laser cutter and 3D printing the smaller parts and mounts. I made sure each part matched the design before it went onto the machine.

After the parts were made I helped assemble them, fitting the pieces together and mounting the moving parts on the frame. Once it was built I helped test it, checking that the parts fitted well, refitting the ones that were too tight, and moving the machine first by hand and then with the motors to make sure everything ran smoothly without jamming.

Process

Step 1: Mechanical Design, moving it by hand

Before any motors we moved the machine by hand to check that the parts slide freely and nothing jams. This is where we caught most of the mechanical problems while it was still easy to take apart.

Step 2: Machine Design, actuation and automation

Once the mechanics were smooth we added the motors and a controller, then wrote the code that moves the machine on its own so it does its job without a person turning it.

Documentation

What I Learned

  • A machine only comes together when the parts are designed to fit each other, so the team has to agree on sizes early.
  • It is much easier to fix a mechanism by hand before trusting it to a motor.
  • Working as a team needs constant talking and one shared set of files.

Challenges & Solutions

Challenge 1: some parts did not fit together on the first try.

Solution: I checked them against the design, sanded the tight edges, and re-printed the parts that were out of size until they fitted cleanly.

Challenge 2: a laser-cut piece came out slightly the wrong size.

Solution: I corrected the measurement in the file and cut it again so it matched the rest of the frame.

Possible improvements.

Next time: add a small tolerance gap in the design from the start so the cut and printed parts fit first time, and label every part before assembly to make the build faster.