Blog 7

Prototyping is essential for making a chemical product(just like how sleep is essential to my life) as it can prevent HIGH failure cost. Its better to fail early than failing late as we learnt from practical 4 and 5. Prototype is the cheapest and easiest way to visualise the product. This can make room for improvement and also open our eyes👀 to more ideas. 

Through a TED talk about the marshmallow challenge, it can be seen that kindergarteners won over business school students BECAUSE kindergarteners came up with multiple prototype compared to business school students who only focusses on one idea. Hence the way to success which is to have prototype and always have plan b,c,d. 

To start off, we need to specify our specifications. Specification table comes to use as it provides information they need to build out new features or functionality of a product.

Types of Specifications relevant to product Design: 

1. Material specification-Physical(dimension, weight, voltage required etc)

2. Functional/ performance specifications

3. Standard specification

4. Test standard

However, in the preliminary design stage, we will only focus on material & Functional/performance specification

Aspect	Specification Metric (or Quality)	Quantitative Value
Physical	Lightweight	< 100g
	Compact	Original(plaster) 7.3cm x 1.5cm(plaster) 2.5cm x 1.2cm (electrodes) Prototype 15cm x 5 cm (plaster) 5cm x 4cm (electrodes) Watch 21cm x 2cm
	Amount of voltage generated	Able to generate 4.2V
	Amount of power produced	3.9mW
	Amount of current produced	0.93mA
	Thin	0.1cm thickness Prototype: 0.5cm thickness
Functional	Water resistant	IP67
	Easy to use
	Operation time	48 hrs
	Minimal setup time	<10 sec
	Generating a total of 3mA	3 electrochemical cells=2.8mA
Others	Inexpensive	<$70

WEHHEE Now its time to sketch, Here is our design based on our CA part 5 report:

Our tagline for this product is: It gives you special power to charge your watch making you unique and giving off superior energy to stand out from the crowd

However, during our first prototyping lesson, Dr Noel told us we have to include at least one working mechanism 🤯hence we panicked. We decided to add watch as part of our product as it uses gears. Now, what type of gears? BEVEL GEARS 

So how does a bevel gear work and look? 

One side of the gear is vertical and one side is horizontal. The vertical gear is to turn the horizontal gear which is connected to a fastener to turn the clock hand on the watch face. 

However, we were not able to 3D print 😢and thankfully we modified our design and use 2 normal gear instead.

Here is a video of how it works, take a look at how it works:📹

Fabrication Process

Plaster:

1. Draw out the dimensions on cardboard and cut out the shape

2. Attach the rectangle piece behind the hole on the "tape" 

Watch:

1. Draw out the dimensions on cardboard and cut out the shape

2. Punch holes of equal distant at the bottom. 

3. Stick the bigger circle with the two strips as well as the rectangular attachment as shown below.

4. Take a sheet of parafilm and stick it onto the hole as shown in the above photo.

5. Cut a hole in the middle of the smaller circle. Take two zip ties and cut one of longer end and one shorter end.

Use wire tie and loop it over as it is much thinner than brass fasteners and secure it with a tape behind.

6. Attach the smaller circle on the bigger circle. 

Note: Do not glue the right side.

7. Beautify the watch by covering with masking tape. 

8. Slot in the other gear on the right.

CADD for our prototype (detailed CADD is below)

First part is the PLASTER

The layer of tape is overlaying the layer of electrochemical cells to hold the electrochemical cells in place while doing daily activities. 

Second part is the WATCH

Hero shot with the team(amazing team to be exact)📷

Demo on how our prototype works

Step by step guide for the PLASTER:

1. Click on "create sketch", and select a plane.

2. Click on "create", "rectangle" and key in 50mm by 150mm

3. Click on "modify", "fillet" then select the top and bottom part of the base

4. Click on "create", "line" then on the right toolbox, click on "construction" and create lines as shows below.

5. Click on "create" and "rectangle" 

6. Click on "modify" then "offset" and input a value of 5mm

7. Click on "finish sketch" and select the following layers and select "extrude" and input  10mm

8. Click on "create sketch" and press on the empty rectangle. Click on "create", "rectangle" then outline the outside rectangle.

9. Click on  "finish sketch" then "extrude" and select the rectangle and extrude by 5mm

Overall view, 

Step by step guide for the WATCH:

1. Click on "create sketch" and select a plane

2. Click on "create" and select "circle" and from the centre move outwards and input 50mm

3. Click on "finish sketch" then "create" and "extrude" and input a value of 5mm

4. Click on the top layer and press "create sketch". Then select "create" and "circle" and input a value of 48mm

5. Click on "finish sketch" then click on "create", "extrude" on the smaller circle and input a value of -1mm

6. Click on the outer ring and click on "modify" then "chamfer" and input 1mm 

7. Click on "create" then "create sketch" then click on the area outside the watch face.

• Click on "create" then "rectangle" and draw a rectangle of 20mm x 55mm on the top side
• Click on "create" then "rectangle" and draw a rectangle of 20mm x 100mm on the bottom side

8. Click on "create" then "arc" then select "3 point arc" then at the bottom strap, press the left point then right point then drag to the bottom  

9. Click on "finish sketch" then "create", and "extrude" by -2mm

10. Click on "create sketch" and select the bottom strap. Click on "create", "line" then on the right toolbox, change it to construction line and draw it down the centre.

11. Click on "point" then draw 4 points on the middle line.

12. Click on "finish sketch". Click on "create" then "hole" and input the height 3mm x 2mm

Repeat for the other 3 holes

13. Click on "create sketch" and select the top strap. Then click on "create" then "rectangle" and create a rectangle of 3mm x 1mm.

14. Click on "modify" and select "fillet" then select the two outer lines.

15. Click on "create" then select "rectangle" then create a rectangle at the end

16. Click on "modify" then "offset" and input a value of 0.5mm

17. Click on "finish sketch" then select the shaded area as shown below then click on "extrude" then input a value of 2mm

18. Click on "create sketch" then select the top face of the watch. Click on "rectangle" then change the rectangle type to "center rectangle"  and create a rectangle of 12mm x 0.8mm

Repeat on 3 more sides.

19. Click on "create" then "point" and add a point to the center of the circle.

20. Click on "finish sketch" then press "create" then "hole" and input a value of  4mm x 2mm

Although we felt that bevel gear is more suitable, due to time constrain, we decided to go with two normal gear side by side which can still adjust the watch hands.