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Design Phase 2

It has been a while since I visited my final project as school had been very busy. Right now, it is April 8th, 2024, and I am planning to do the following task in the upcoming months:

  • Get the electronics to work
  • Finish designing the project in fab, create a complete 3d render
  • Create complete electronic design in KiCAD
  • PCB milling + soldering
  • RP2040 code complete
  • Input, needs an on/off button that is NOT the powerline itself, integrated with the circuit.
  • Laser cut an enclosure: fill in the spaces between CNC a stand
  • sticker, ataraxy: state of serene calmness
  • Need a pvc pipe to transport tennis balls.
  • When documenting, I will use the new strategy of writing out the text first before putting in the images.

  • Include a Hall Effect Sensor to and an OLED display (0.96 inch) to display the RPM of the wheel (as required by Mr. Dubick).

  • OPTIONAL: if time, create a launch system controlled by a stepper motor that might adjust the angle of the wheels.

Right now it is June 1st, and I have around 12 days to finish my tennis ball machine before my big presentation on 6/12. Thank you to my dad, Yingming Tian for motivating and helping me to finish my project!

This is my ghantt chart for the next 12 days:

I began by going to Fusion 360 and re-modeling my ball machine, designing the parts that I have built in my CAD file as well as what I planned to do in the upcoming days. First, I imported a t-slot aluminum rail from Mcmaster Carr as a .sat file, and built the two sides of my machine:

To attach the motor, I first created a tab inside the aluminum rail:

I imported the motor attachment adapters from my other design files into the main file, and copied and pasted one on to the aluminum rail:

To attach the pieces together, I made all bodies within my file components and used the joint method to join their faces together, rotating and moving them as needed.

Then, I created a motor fixiation by drawing a rectangle and extruding the left 3mm part of it:

I created a circle on to the side of the fixation, drew tangent lines to the circle, and made a cut for the dc motor:

I imported a basic dc motor from McMaster Carr and adjusted it so that it fit the hole on the motor fixation component.

To make the wheel, I drew concentric circles and measured the diameter of my wheels. Then, I extruded a 10 mm hole through the wheel to make room for my 10 mm shaft:

I made the coupling for the wheel (from 5mm to 10mm), and attached the wheel to the motor side of my machine:

Then, on the right side (wheel terminal side), I imported a flange connector from one of my other files, and used the joint feature to connect it to a cylinder I made on the other rail. The point of designing what I built is to get a sense of scale and how the tube needs to be oriented. It was also to provide Mr. Dubick a somewhat complete visual of my project.

Then, I imported a flange (the piece that is the terminal side for the shaft, allowing it to spin freely) from MacMaster Carr and cut off most of it to allow enough space for it connect between the flange connector and the shaft:

I then connected it to the side of the wheel:

Now, one wheel is done.

I repeated the above process for the other wheel. Note that this wheel is mounted on the other side of the main frame and shifted downwards a bit (75 mm).

Then, I created a sphere to represent a tennis ball and tried to fit it in between the two wheels. I found that some adjustments were necessary in order for it to fit:

Originally, I tried to make the base out of aluminum rails so that the whole machine formed an “L-frame”.

But my dad and Mr. Dubick told me that I could just use wood for the bottom. Later, as I was testing the motors, I found that there was a lot of vibration coming out of them, so the base needs to be sturdy.

Next I created the tube for the box. I first created a midplane that is right in the middle of one of the wheels,and drew a “J” shape to model the tube. Then, I created a circle on an offest plane, and used the sweep function to create my tube. It was shelled at the end as well, and I want the thickness to be around 3mm (the tube will also be 3d printed).

I discussed with my dad about how to secure the tube, and we came up with the idea of creating an extension of beams from the top and making a frame out of it:

I measured the angle of the tube, which turned out to be around 75˚:

Originally, I was going to buy a PVC pipe for the tube, but it seems that that wouldn’t work because of the non-right angle that I have. So, I will 3D print the tube.

On the top of the machine, I created a box to hide the electronics in, and also to show the control panel consisting of 2 potentiometers and a control switch:

But after, Mr. Dubick told me to move the box to the bottom to hide the electronics better:

I plan to use the L-shape attachments I bought to attach the box to the rail:

At the bottom of the machine, I decided to CNC a box in order to store teh tennis balls, with the dimensions being 12 inch x 9 inch x 6 inch:

Here is the final design:

But Mr. Dubick told me I needed further reinforcements.

He told me that parallel wood planks are not enough because force from the motors would not be evenly distributed. Instead, I suggested that I build a square with a diagonal beam to secure the base. The base will be made completely out of wood. So, I reinforced the base:

Me and my dad also talked about further reinforcing the tube with aluminum beams coming out of the middle and having legs at the bottom for support:

Now, the beams are fully in position. I also planned to move the two side wooden beams (parallel) back a little bit so that the machine sits further out in front. This way, the box of tennis balls can sit further back without the tube getting in the way.

Hall Sensor Attachment

Per the requirement of Mr. Dubick, I needed to have one more input device, and so I incorporated a Hall Effect Sensor to measure the RPM of the wheels, whereby every time a magnet that is glued to the wheel passes through the range of the sensor, one cycle is counted.

To do this, I mounted the sensor at the bottom of the machine via an adaptor. I created a 2 piece design that fit together, and the wires will extend into the cap.

Here is the design file and layout:

Tube Design

To design the tube, I took an image from the side of the machine, and imported it into Fusion360. Then, I resized the image using the scale tool to actual size. I created parallel lines to model the cylindrical shape of the tube.

Then, the approximate angle was measured. I know a tennis ball’s diameter was about 68 mm, so I made the tube’s inner diameter 71 mm. Then, after the angle was made and the approximate position of the tube was determined, I used the sweep tool in Fusion to make a hollow tube from a 2D profile of a ring and the lines that I drew:

Then, to test that the tennis ball can fit inside it, I created a sphere and moved it inside the tube to see how it would fit, and it does!

Here is the final tube:

To attach the tube, I created a press fit tube attachment piece in Fusion360 as well. The idea is to tighten the tube through the use of a screw. I also added two slots at the back to attach this attachment to the aluminum rail of my machine. The idea of the rectangular holes is so that the distance between the tube and the wheels could be adjusted.

Electronics Management

I had a lot of wires and 2 motor drivers that needed to be hidden, both for aesthetics and for the safety of the user. I created a layout for the box, by creating cylinders with 3mm holes in them that would be used as attachments for the various electronics parts. I planned to use mk12 screws for this process:

Then, I extruded the various parts of the box according to the varying heights of the different electronic components, and the thickness of the box is 5mm.

Last update: July 1, 2024