Week 4

We were given a product where we have to choose the materials that are selected and how to use the material selection technique.

Our group was assigned to the product which is a disposable safety razor for men, where we were tasked to select materials for the blade and body. To make it disposable we decided to focus on the blade, as it will be the on that will be disposable, while the body however can still be reused.

To be disposable the metal of the razor must be environmentally friendly, means it can be either decomposed easily or recycled easily to produce other metal related products and will not end up in the garbage heaps. It must not be a toxin to humans when it is being used.

For the body, we would like it to be reused constantly while simply changing the blades for every use. Therefore, the body should be non-reactive to human skin and shaving cream. At the same time it should not corrode under water. 

However, since we are focusing more on the disposable part of the disposable safety razor, we shall just use the blade for material selection.

Functions	To shave a man/s mustache.
Constraints	Non-reactive to human (reactivity, does not produce toxins). Light weight (Low density, not so heavy) Able to corrode easily (low water-resistant, so that it can decompose, therefore environmentally friendly)
Objectives	Ensure that the shaver's metal can be decomposed easily, so that it can be called a disposable shaver.

Based on the description above, metal has been shortlisted as the possible materials. We shortlisted our choice of metals to five metals/alloys: Aluminium, Stainless Steel and Carbon Steel.

With reference to our constrains and objectives above, we will rank the requirements and assign a weightage based on their importance, for example the shaver's metal can be decomposed easily which is can be corroded easily, is the most important requirement.

Non-reactive is the second most important requirement, because even though the important requirement is corrosion, it must also be not able to react to a user human skin or the shaving cream applied so that toxins wont be produced which would affect the person using. 

Light weight is given a lower weightage as it is not very important compared to the other properties.

At this stage, the candidate materials are compared and ranked using a point of scoring of 1 (less likely meeting the requirement) to 5 (highly likely meeting the requirement). In doing this, we will need to check reliable references such as MatWeb to obtain the materials properties.

As for the handle, since it is not going to be disposed of, it shall be reused after every shave. We have shortlisted a few plastics such as polyester and silicones.

It is important that the handle must be corrosion resistant, non toxic and lightweight. The most important factor will be non-toxic as to prevent the user from any harm. The second important factor would be corrosion resistant, so that to ensure it can be reused without having the need to worry about it corroding.

Therefore, we decided to use the COWS decision matrix to decide on the suitable material.

 For blade：

Criteria	Aluminium Oxide	Stainless Steel	Carbon Steel
Corrosion-resistant	3	3	2
Non-Reactive	3	3	1
Light Weight	3	1	2

Criteria	Weightage (%)	Aluminium Oxide	Stainless Steel	Carbon Steel
Corrosion-Resistant	50	2	2	3
Non-Reactive	30	3	3	1
Light Weight	20	3	1	2
Total	100	250	210	220

For handle:

Criteria	Polypropylene	Polycarbonate
Corrosion-resistant	3	3
Non-Reactive	2	3
Light Weight	2	3

Criteria	Weightage (%)	Polypropylene	Polycarbonate
Corrosion-Resistant	50	3	3
Non-Reactive	30	2	3
Light Weight	20	2	3
Total	100	250	300

Overall, it has been concluded that Aluminium Oxide is the more suitable material for the blade as it has the highest score compared to the other materials. Conversely, Polycarbonate has the highest score compared to Polypropylene thus it is a more suitable material for the handle.

Reflection:

We have learned how to research on materials suited for different items. We also learned the importance of using COWS decision matrix to find the best suitable material among the other materials. We are now able to implement citation and decision making skills.

References:

Coleparmer.com. 2021. Chemical Compatibility Database from Cole-Parmer. [online] Available at: <https://www.coleparmer.com/chemical-resistance> [Accessed 13 May 2021].

Curbellplastics.com. n.d. Browsers and Using Curbell Plastics Website. [online] Available at: <https://www.curbellplastics.com/Research-Solutions/Chemical-Resistance-of-Plastics> [Accessed 13 May 2021].

Engineeringtoolbox.com. 2003. Metals and Corrosion Resistance. [online] Available at: <https://www.engineeringtoolbox.com/metal-corrosion-resistance-d_491.html> [Accessed 13 May 2021].

Matweb.com. n.d. Online Materials Information Resource - MatWeb. [online] Available at: <http://www.matweb.com/search/SearchProperty.asp?gclid=CjwKCAjwnPOEBhA0EiwA609ReQhOkoZdkpK8l33TqWSRFjQhkOkYXixgBmdvXm4qE4qzwfNJ8eNkWxoCkIwQAvD_BwE> [Accessed 13 May 2021].