Blog 5

 .Materials for design (Week 11)

During this lesson, we learnt about the qualities of the materials and what it meant. Most of the properties were already taught to us during our Year 1 Sem 1 module, Material For Design. However there were some properties that are new to me such as the fabrication properties. 

Properties

•  Tensile strength
• Young modulus
• Viscosity
• Thermal conductivity
• Ease of machining

After being taught these properties, we were tasked to work on our CA2 part 1. What we need to do was to select a material for a given device. The device my group was given was the inner layer of a Thermoflask.

 I thought to myself, how hard can it be, its just a Thermoflask, and boy was I wrong. The first thing i considered was the thermal conductivity, i feel that it should be low to reduce heat transfer. Then, i realized that there are more properties such as corrosion, low density and most importantly food grade. To me these properties are as important as each other so i had a hard time deciding which properties should weigh more in the COWS table. Below is the weightage we decided on.

This is the COWS table for the inner body

Function	To store water and to keep hot water warm for long hours
Constraints	Low thermal conductivity (heat won’t transfer out of the bottle) Corrosion resistant to mild acidity and alkaline Light weight (low density) High melting point  Food grade
Objective	Minimizing thermal conductivity

Criteria	Weightage	Reason
Low thermal conductivity	50%	It should be low thermal conductivity so that it can prevent heat transfer from the drink to the surrounding air or vice versa so it can keep the drink warm or cold
Corrosion resistant	20%	Some drinks such as coffee or tea are milk acidic hence it should be corrosion resistance to make the drink safe for the person
Low density	10%	It should be light weight as it will be too heavy for the user to carry around
High melting point	10%	It should have a high melting point so that it will not melt when in contact with hot fluids such as coffee or tea.
Food grade	10%	It is important as this will prevent the user from getting poisoned.

Criteria	Weightage	Materials
		Aluminium	Borosilicate glass	Stainless steel
Low thermal conductivity (W/m-k)	50%	165.01 Score:1	1.1 Score: 5	21.5  Score: 3
Corrosion resistant	20%	Excellent Score: 5	Excellent Score: 5	Excellent Score: 5
Low density (g/cm3)	10%	ρ=2.7 Score: 4	ρ=2.4 Score: 5	ρ=8.0 Score: 1
High melting point (℃)	10%	660.3 Score: 2	800 Score: 3	1400-1455 Score: 5
Food grade	10%	Excellent Score: 5	Excellent Score: 5	Excellent Score: 5
Total	100%	260%	480%	360%

Criteria	Weightage	Reason
Cost of material ($/lb)	70%	This is 70% as it will determine the cost of the thermoflask. The cost of thermoflask is usually not very high and so the cost of making it should be cold too
Ease of handling/ manufacturing	30%	Thermoflask are usually made in bulk quantity and so the ease of manufacturing it should be easy

Criteria	Weightage	Materials
		Borosilicate glass	Stainless steel
Cost of material ($/lb)	70%	0.4 Score: 5	1.4 Score: 2
Ease of handling/ manufacturing	30%	Poor Score: 2	Very good Score: 5
Total	100%	410%	290%

We then move on to decide on which material we should use base on the criteria using COWS and we decided on using would be borosilicate glass. By using COWS, we eliminated the use of aluminum as it has a high thermal conductivity which is unsuitable for the inner of the thermo flask which has to have minimal thermal conductivity. Since aluminum has the lowest score, we have narrowed it down to borosilicate glass and stainless steel. Through the COWS for economic viability, although borosilicate glass is harder to handle, however the cost is much cheaper than stainless steel hence borosilicate glass is more suitable.

This is the COWS table for the cap

Function	To prevent water from spilling out and to keep hot water warm for long hours
Constraints	Low thermal conductivity ( heat wont transfer out of the bottle High melting point High heat capacity (prevent user from getting burned)
Objective	To allow user to drink without getting burned

Criteria	Weightage	Reason
Low Thermal Conductivity	40%	It should have low thermal conductivity as the main purpose of a Thermoflask is to prevent heat transfer of the liquid stored.
High Melting Point	10%	The melting point is important as the liquid stored is often hot. The weightage is low as the liquid stored don't usually exceed 200℃.
High Specific Heat Capacity	40%	It has a high weightage because the cap is where the user drinks from. Having a high heat capacity means that more heat is needed to raise the temperature of the cap. This will ensure the user will not burn their mouth when drinking from the cap.
Food Grade	10%	This will prevent the user from getting poisoned.

Criteria	Weightage	Materials
		silicon	Polyethylene terephthalate (PETE)	High-Density Polyethylene (HDPE)
Low thermal conductivity (W/m-k)	40%	0.2 Score: 5	1.081 Score: 1	0.288 - 0.480 Score: 4
High specific heat capacity  (J/g-°C)	40%	0.713  Score: 1	1250 Score:4	1330-2400 Score: 5
High melting point(℃)	10%	1412 Score:5	250 Score: 2	118 - 137 Score:1
Food Grade	10%	Excellent Score:5	Excellent Score:5	Excellent Score:5
Score	100%	340%	270%	420%

Criteria	Weightage	Reason
Cost of material ($/lb)	70%	This is 70% as it will determine the cost of the thermoflask. The cost of thermoflask is usually not very high and so the cost of making it should be cold too
Ease of handling/ manufacturing	30%	Thermoflask are usually made in bulk quantity and so the ease of manufacturing it should be easy

Criteria	Weightage	Materials
		silicon	High-Density Polyethylene (HDPE)
Cost of material ($/lb)	70%	1.1 Score:1	0.55 Score: 3
Ease of handling/ manufacturing	30%	Excellent Score: 5	Good Score: 3
Total	100%	220%	300%

By using COWS, we eliminated the use of aluminum as it has a high thermal conductivity which is unsuitable for the inner of the thermo flask which has to have minimal thermal conductivity. Since aluminium has the lowest score, we have narrowed it down to borosilicate glass and stainless steel. Through the COWS for economic viability, although borosilicate glass is harder to handle, however the cost is much cheaper than stainless steel hence borosilicate glass is more suitable.

Material for design (Week 12)

So apparently the module coordinator feels that a week of material is not enough so he decided to have another week. During this week of lesson, we learn how to change the design of a product so a certain material can be used.. Dr Noel then talked about the evolution of hair dryers. Something along the line of, If a plastic casing is used, the heat produced cannot be too high as it will melt the plastic casing. We then went through another example on Coca Cola. I actually learnt that coke used to come in glass bottle and not plastic. It was apparently too expensive to produce coke in glass bottle so they changed. The difference they made to coke was so that it wont fizzle too much which will might make the plastic explode, From this lesson, i learnt that sometimes a certain material should be used and the designs need to be change. For example, if the material used before was not environmentally friendly but works very well, it is ok to change the material and make it work less well.

This actually brings us to the next part of the lesson, Sustainable design. Its pretty straightforward and all we learn is that the earth is sick and we should design our product such that it is sustainable. We were then tasked to change the design to fit a more environmentally material. We have decided to use the lunabrite to replace the scotchlite at the back of a bike. This is because lunabrite absorbs the UV rays during the day and glows in the dark. The disadvantages of using scotchlite is that the reflected light blind the driver by shining the light and might cause eye damage to the driver behind the bike. Another disadvantage is that scotchlite is only effective if light is shone on it; however, lunabrite can glow in the dark. When we use the lunabrite, the lunabrite does not reflect light but actually gives out its own warm light. It actually makes both the driver and the cyclist safer on the road.

We were then tasked to discuss

how a material can be used to enhance the functionality of an existing product through some changes in the design. Lunabrite can be used to replace acrylic for lampshades as it has night time visibility and user-friendly (e.g. babies), these features help to cut down utility cost and enhance the standard of living of the user as lunabrite only requires UV light to recharge it. Adding on, it can also absorb the light radiated from the ceiling light in the room at night meaning that it can share the same electricity  while saving utility cost. Furthermore, lunabrite is non-toxic hence it can be safely be used around children, water and pets making it very versatile.