What the machine is

As a team we decided to build a small drawing machine that moves a pen across a flat surface to draw shapes. It has a mechanism that turns motor spin into straight line movement, motors that drive that mechanism, a controller that automates the motion, and a clear application, which is making drawings. So it covers the four things the assignment asks for: a mechanism, actuation, automation and an application.

For our application we picked pen plotting because it is simple to judge by eye. If the lines come out straight and the corners meet, the machine is working. If the carriage wobbles or a motor skips, you see it straight away in the drawing.

How the team planned, allocated tasks and executed

We started with a meeting where we agreed on the idea and broke it into parts. We wrote a task list on the whiteboard and each person signed up for a job. One small group took the frame, one took the moving carriage, one took the electronics and motors, and one took the control code. We set a daily stand up to check progress and fit the parts together, and we kept one shared folder for the design files so nobody worked on an old version.

1. Agreed on the drawing machine idea and the four required parts: mechanism, actuation, automation, application.
2. Split into four small teams: frame, carriage, electronics and motors, control code.
3. Set the shared sizes and the rail spacing early so every part would fit the others.
4. Met each day to fit parts together and update the task list on the whiteboard.
5. Built and tested the mechanical machine by hand first, then added motors and automation.

My contribution

My part was the moving carriage and the pen holder. I designed both in CAD so the pen can lift up and press down, and so the carriage slides smoothly along the rail without rocking. I printed and laser cut the parts, fitted them onto the frame, and adjusted the tolerances by hand until the movement was clean. I also helped wire the stepper motor that drives my axis and tested it with the team's control code. Where the rest of the team owned the frame, the electronics and the firmware, the carriage and pen lift were mine end to end.

1. Drew the carriage and pen holder in CAD, with the rail slots and the pen lift built in.
2. Printed and laser cut the parts, then fitted them onto the shared frame.
3. Adjusted the rail tolerance until the carriage slid freely with no wobble.
4. Wired and tested the stepper motor that drives my axis.

Part 1, Mechanical Design, running it by hand

Before any motors went on, we moved the machine by hand to check that everything slid freely and nothing jammed. This is where we caught most of the mechanical problems while it was still simple to take the machine apart. The four required parts were all present at this stage as physical hardware: the belt and rail mechanism, the motor mounts ready for actuation, the controller mount ready for automation, and the pen as the application.

1. Bolted the frame square and checked it sat flat on the bench.
2. Slid the carriage along each rail by hand to feel for tight spots.
3. Tensioned the belts and pushed the carriage through its full travel.
4. Pressed the pen down by hand on paper to check the lift gave even pressure.

Part 2, Machine Design, actuation and automation

Once the mechanics ran smoothly we added the stepper motors and a controller board, then loaded the control code that moves both axes together to draw a shape. Tuning the motor speed and the step count so the lines came out straight took a few tries, but when the machine finally drew a clean shape on its own the whole team was happy. At this point the machine was fully actuated by the motors and fully automated by the controller, with no hand needed once it started.

1. Mounted the stepper motors and connected the belts to each axis.
2. Wired the motors to the controller board and set the driver current.
3. Loaded the control code that moves both axes together along a path.
4. Tuned the speed and step count until the lines came out straight and the corners met.
5. Ran a full drawing start to finish with no hand on the machine.

Problems and how we solved them

1. The carriage wobbled because the rail slot was a touch wide. I reprinted it tighter and added a small bearing, and after that it ran straight.
2. One motor skipped steps because we drove it too fast. We lowered the speed in the code and the motion became reliable.
3. The pen pressed too hard and tore the paper. We added a small spring to the pen lift so it rests with gentle, even pressure.
4. The two axes started out of sync, so shapes came out skewed. We set a single home position both axes start from, and the shapes lined up.

Possible improvements

1. Add a second pen holder so the machine can swap colours during a drawing.
2. Make the frame stiffer so it can move faster without shaking.
3. Add limit switches so the machine finds its own home position at startup.
4. Feed it standard drawing files directly so we do not have to hand write each path.

What I learned

The biggest lesson was about working as a team. The machine only came together because the parts were designed to fit each other, which meant we had to agree on the sizes early and keep talking through the week. I also learned to always test a mechanism by hand before trusting it to a motor, because a problem is much easier to find and fix when nothing is moving on its own yet.

Design files and the global presentation

These are the machine design files, the CAD for my carriage and pen holder, the cut files, and the control code. For the global presentation the team also prepared a one minute video at 1920x1080 and a slide at 1920x1080.