WEEK 4

 HELLO👋! Welcome back to our blog. So this week was an asynchronous lesson and we were tasked to recap on our Year 1 module: Material For Design(MFD)🔗 so that we can use it to complete our given assignment. 

As we reviewed on the materials given, we realized that MFD is related to designing a chemical product as it involves specifying a shape, choosing a manufacturing process and the process of selection of a material which is most suitable for that particular product. This process is called COWS decision matrix. A brief introduction on COWS decision matrix is below so scroll down👇👇!!

COWS Decision Matrix🐄

It involves:

C - Criteria, develop a hierarchy of criteria, also known as decision model.

O - Identify options, also known as solutions or alternatives.

W - Assign a weightage to each criterion based on its importance in the final decision. 

S -  Rate each option on a ratio scale by assigning it a score of 1 to 3 based on each criterion. The final score is calculated as Rating x Weight for each material.

We also learn about material selection. More info down below!!👇👇

Material Selection🔧🔨

The aim of this process is to identify one or more materials with properties that satisfy the functional requirements of a product. Even better materials which can optimize performance objectives. The most suitable material is a trade off between requirements and numerous constraints. Material properties will include characteristics such as :

Mechanical properties💪 (E.g. density, young modulus, ultimate tensile strength, etc.)

Thermal properties🌞 (E.g. thermal expansion coefficient, thermal conductivity, specific heat capacity)

Magnetic properties🧲 

Fabrication properties🔧 (E.g. ease of welding, hardening ability, viscosity, etc.)

Environmental properties🌍💀(E.g. corrosion properties, polluting effects, toxic effects )

Therefore we were assigned to find a material for a certain object using the help of the material selection process as seen in figure 1.

Figure 1: The whole process of material selection.

we were assigned to select materials for the body and blade for a disposable safety razor for men. The object is seen below in figure 2.

Figure 2 : Disposable safety razor for men

To give you a clearer idea on material selection process, we have done the whole process to select materials for parts of our disposable safety razor. so scroll down below for our group's HARDWORK!!👇👇

STEP 1: MATERIAL REQUIREMENT FOR THE DESIGN.💭

function	Removal of body hair through the act of shaving
constraints	Less cost Light in terms of weight Good machinability High corrosion resistance Less ductile
objectives	To reduce the level of skill needed for injury-free shaving

STEP 2 : SELECT AND EVALUATE CANDIDATE MATERIALS.📂

CRITERIAS FOR BLADE💭

1. Cost 

 (Reason: For a disposable item, the item should come at a low cost to attract more people to purchase a large quantity of it. To be able to charge the item at a low cost, the manufactured material should also be at an affordable value.)

2. Weight

(Reason: Using a razor blade on your face requires control, hence, the material being light weight allows for better control of the razor and easier use. It also allows the item to be portable for easy travel use.) 

3. Machinability

(Reason: Good machinability allows the manufacturers to easily form the material into the desired shape for their desired purpose.)

4. Corrosion Resistance

(Reason: Razor blade will often be in contact with moisture and different chemicals from different shaving creams, hence, having corrosion resistance allows for razor blade to not corrode easily within one use.)

5. Ductility

(Reason: A lower ductility will prevent the material from stretching under higher tensile strength. This gives a lower chance for the blade to deform under stress, especially when it is being pressed onto the skin.)

CRITERIAS FOR BODY💭

1.Low density

(Reason: Having Low density will result in being of lighter weight. This will allow the user to have easier usage of the razor with better control due to its lightweight.)

2.Cost

(Reason: For a disposable item, the item should come at a low cost to attract more people to purchase a large quantity of it. To be able to charge the item at a low cost, the manufactured material should also be at an affordable value.)

3.Machinability

(Reason: Good machinability allows the manufacturers to easily form the material into the desired shape for their desired purpose.)

4.Ductility

(Reason: A lower ductility will prevent the material from stretching under higher tensile strength. This gives a lower chance for the body of the razor blade to deform under stress, especially when an excessive amount of force is applied on it.)

5. Waterproof 

(Reason: The body of the disposable razor blade will constantly be in contact with moisture in the process of shaving, hence, being waterproof will not affect the functionality of the razor blade.)

CHOICES OF MATERIALS FOR BLADE📋

1. Stainless Steel

2. Carbide Steel

3. Carbon Steel

MATERIAL PROPERTIES📌:

			Options
Criteria	Weightage	Stainless steel	Carbide steel	Carbon steel
Low density,(g/cc)(light weight)	30%	7.66 1 x 30%= 30%	6.45 3 x 30% = 90%	7.54 2 x 30% = 60%
Machinability	25%	0.38 1 x 25% = 25%	0.78 3 x 25% = 50%	0.70 2 x 25% = 50%
Corrosion resistant	25%	3 x 25% = 75%	3 x 25% = 75%	1 x 25%= 25%
Yield strength(Mpa)	20%	290 1 x 20% = 20%	350 2 x 20% = 40%	896 3 x 20% = 60%
Total	100%	150%	255%	195%

CHOICES OF MATERIALS FOR THE BODY📝

1. Polyvinyl chloride

2. Polypropylene

3. Polyvinylidene fluoride

MATERIAL PROPERTIES📌:

			Options
Criteria	Weightage (%)	Polyvinyl chloride	polypropylene	Polyvinylidene fluoride
Low density,(light weight)	40	=1.16-1.35g/cc 2 x 40% = 80%	=0.90-0.91g/cc 3 x 40% = 120%	= 1.78g/cc 1 x 40%=120%
Chemical resistant with shaving foam	30	B2 = Good  1 x 30% = 30%	A2 = Excellent 3 x 30% = 90%	A = Excellent 2 x 30% = 60%
Water resistant	30	B = Good 1 x 30% = 30%	A = Excellent 3 x 30% = 90%	A = Excellent 2 x 30% = 60%
Total (%)	100	140	300	240

Hence we will be choosing polypropylene and polyvinylidene fluoride to compare their economical viability since both of them meet the basic requirement of the body.

STEP 3 : CHOOSE THE MOST ECONOMICAL MATERIAL💰

BLADE💥:

Criteria	Options
	Weightages (%)	Stainless Steel 316		Carbide Steel		Carbon Steel
Cost($)	70%	$2000/ton 1 x 70% = 70%		$56.50/kg 3 x 70% =210%		$500/ton 2 x 70% = 140%
Ease of manufacturing	30%	1 x 30% = 30%		3 x 30% = 90%		2 x 30% = 60%
Total	100%	100%		300%		200%

BODY💣:

Criteria	Weightages (%)	Options
		Polypropylene	Polyvinylidene fluoride
Cost of material	70	0.532usd/lb (statista.com) 3 x 70% = 210%	10-12.5usd/lb (Made-in-China.com) 1 x 70% = 70%
Ease of handling/manufacturing	30	18 out of 20 (azom.com) 3 x 30% = 90%	16 out of 20 (azom.com) 2 x 30% = 60%
Total (%)	100	300	130

OUR CHOSEN MATERIAL FOR THE BLADE IS✔️:

Carbide Steel. Our results from using the COWS method have shown that carbide steel is highly corrosion and chemical resistant, light weight, comes at a reasonable cost and is easily able to be manufactured into its desired shape. 

Compared to the other two, stainless steel is shown to not be as light weight and is quite costly for mass production, and carbon steel is shown to not be corrosive resistant. Hence, we have come to the conclusion to have carbide steel as our chosen material for the blade of the disposable safety razor.

OUR CHOSEN MATERIAL FOR THE BODY IS✔️:

Polypropylene. Using the COWS method, polypropylene scores the best for both the property requirements and the economical table. It is the most suitable material selected to make the body part of the disposable safety razor, with all the properties of polypropylene, it enables a light weight, waterproof and chemically stable body yet it is also affordable when compared to polyvinylidene fluoride.

References📜

Coleparmer.com. 2021. Chemical Compatibility Database from Cole-Parmer. [online] Available at: <https://www.coleparmer.com/chemical-resistance> [Accessed 14 May 2021].

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Dotmar, EPP Pty Ltd. 13 Mar 2008. “Plastic machinability-machinability of engineering thermoplastics.” Azom. [online]. Available at:<https://www.azom.com/article.aspx?ArticleID=4097> [Accessed 14 May 2021].

Ian Tiseo. May 7, 2021. “Global price of polypropylene 2017-2021.” Statista. [online]. Available at:<https://www.statista.com/statistics/1171084/price-polypropylene-forecast-globally/> [Accessed 14 May 2021].

Material Properties. 2021. What are Costs of Stainless Steels – Price | Material Properties. [online] Available at: <https://material-properties.org/costs-of-stainless-steels-price/> [Accessed 13 May 2021].

Matweb.com. 2021. 316 Stainless Steel, annealed sheet. [online] Available at: <http://www.matweb.com/search/DataSheet.aspx?MatGUID=50f320bd1daf4fa7965448c30d3114ad> [Accessed 14 May 2021].

Matweb.com. 2021. MatWeb - The Online Materials Information Resource. [online] Available at: <http://www.matweb.com/search/DataSheet.aspx?MatGUID=ee25302df4b34404b21ad67f8a83e858&ckck=1> [Accessed 14 May 2021].

Metallurgy, M., 2021. Carbide price, 2021 carbide price Manufacturers & Suppliers | Made-in-China.com. [online] Made-in-china.com. Available at: <https://www.made-in-china.com/products-search/hot-china-products/carbide_price.html> [Accessed 13 May 2021].

Merriam-webster.com. 2021. Definition of RAZOR. [online] Available at: <https://www.merriam-webster.com/dictionary/razor> [Accessed 14 May 2021].

Process-controls.com. Chemical Resistance Chart. [online] Available at: <https://www.process-controls.com/Vissers_Sales/pdf/Chemical_Chart.pdf> [Accessed 13 May 2021]

scrapmonster,2021.#3 PVC Plastic Prices in the U.S.A. and Canada[online] available at:<https://www.scrapmonstoer.com/scrap-yard/price/3-pvc-plastic/453>[Accessed 14 May 2021]

Staff, R., 2021. Mixed news for recovered plastics pricing - Plastics Recycling Update. [online] Plastics Recycling Update. Available at: <https://resource-recycling.com/plastics/2019/02/13/mixed-news-for-recovered-plastics-pricing/> [Accessed 14 May 2021].

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