Question

Product Design and development

Figure 3 shows a plastic propeller used in a boat engine. During the setting of the final specifications, the development tean developed technical models for the propeller to predict the values of the performance metrics for a decisions. a) particular set of design Identify two (2) performance metrics that can be used to evaluate the customer needs. For each performance metric, propose value of the respective performance metric of the propeller a technical model to predict the i) List down at least three (3) independent variables for each technical model in Question 3a) i) which have significant effect on the respective performance metrics. il) State three (3) rapid prototyping (RP) techniques which are suitable to produce the prototypes of the propeller for investigating the above performance metrics. iv) Select any one (1) of the above RP techniques and provide three (3) reasons for your selection and explain the process with the aids of simple sketches. Explain three (3) advantages and three (3) disadvantages of the selected RP process in Question 3 a) ii). v) b) Discuss briefly the differences between Stereolithography Apparatus (SLA) and 30D Printing (Z Corp) in terms of the following: i) Surface finish ii) Dimensional accuracy iv) Support structure Figure 3: Boat Engine Propeller

Answer 1

a)

i) Two performance metrics to consider are speed and power needed. To find the required value we need the parameters of the boat like the weight, available engine specifications.

ii) Independent variables that affect the performance metrics majorly are the diameter of the turbine, number of blades, blade angles.

iii) Rapid prototyping is really important when developing new products to test and evaluate the performance of the products, 3D printing is now the way to achieve this, the following are the methods

1. FDM
2. SLA
3. SLS

iv) 3D Printing with SLA is the most viable operation for this product because,

• Has significant accuracy
• Better surface finish
• No need for support material

v) Advantages of SLA are the reasons why it has been selected now the following are the disadvantages,

• Not many materials to select from
• The material has a very bad odor
• Currently, the size of the print is very limited

b)

Property	SLA	Z Corp/Colour 3D Printing
Material properties/types	Uses liquid material (resins) and there are few varieties of it.	Similar to SLS, this is powder based and only colour absorbent powder made of gypsum is used.
Surface finish	A very smooth finish can be achieved and depends on the screen resolution at the bottom.	Since powder is used, the surface finish is not very smooth and achieving it needs extra processes.
Dimensional accuracy	The accuracy is really high.	Same as SLS, it is high.
Support structure	No support structure is needed in this method of 3D printing as the print is held at the top and printed at the bottom, unlike other methods.	In this method, the layers are printed independently of each other as the material is laid out separately s there is no such requirement.