CHAPTER 8: Concept Selections

​

​

​

SKMJ 1902

ENGINEERING PRINCIPLES

AND PRACTICE

UTM JOHOR BAHRU

Solution Concept

Concept Selection

Concept generation phase develops a number of concepts.

Hence, the next step is to select the final concept to be further developed.

​

Problems

• The criteria for selection may contradict to each other such as precision device may demand a higher cost in manufacturing process.

​

• Each concept may have good and bad features within a single design; however a perfect final design is having good features.

Selection Method

2 stage of selection

• Concept Screening : screening matrix
• Concept Scoring : scoring matrix

​

Or (if required)

Screening 🡪 Screening 🡪 Scoring

​

Evaluating conceptual alternatives

Based on comparing alternatives with the list of specification table

Matrix Selection: Criteria

Bad Criteria

Improved Criteria

Good Criteria

• Easy to compare (No of steps taken)
• Well understood by group
• Specific item is compared.

Datum

One of the concept or similar product in market

​

For each criterion, the concept will be compared with the same of criterion of the datum.

​

​

Range of mark depends on type of selection matrix

​

1. Screening (‘-’ , 0 , ‘+’) : worse, equal, better
2. Scoring (-2, -1, 0, 1 ,2 ): worst, worse, equal, better , best

Screening and Scoring Matrix

Screening Matrix: when the number of concepts is larger than 6.

​

Scoring Matrix: when the number of concepts is equal or less than 6.

​

​

​

​

​

​

Screening of Concepts

Screening of Concepts

Screening of Concepts

Screening Matrix

Screening Matrix

◊ Screen the concepts to be selected for concept scoring

◊ Proceed with at least half of the total number of concepts to the second level of selection

◊ Datum: existing product on market or one of the concepts

◊ Mark is given based : + 1: better than datum

0: equal to datum

- 1: worse than datum

​

Significance of the total mark

• Higher mark: better than datum
• Equal mark between two concept: indicate similar and may be can be combined to generate another new concept

Scoring Matrix

Scoring Matrix

◊ Scoring is used when increased resolution of the criteria

◊ Weightage on each criteria is set. PDS is referred

◊ Datum: existing product on market or one of the concepts

◊ Mark is given based :

1: much worse than datum

2: worse than datum

3: equal to datum

4: Better than datum

5: much better than datum

◊ Mark on each criteria for each concept = mark x weightage

​

Selection of criteria

◊ reference on selection criteria: PDS, sketch, discussion

◊ Cover from functional aspect to production and expected costing

◊ performance of the concept from their functional aspect or user perception (ease of use, ease of handling)

◊ Production and manufacturing aspect (ease of fabrication, material used, manufacturing processed required, etc)

◊ Monetary aspect (man-hours, costing)

if necessary, criteria in scoring is more specific from screening criteria, for instance

Material 🡪 Ease to get

Ease to cut

Price

​

​

​

Weigthage : scoring matrix

• The total weightage = 1.0
• You have to decide each criteria weightage.
• Different weightage yields to different final concept. If highest is set to cost, the final concept will be the cheapest one and you may sacrifice the performance

Dysfunctions of concept selection

• Fail to include the whole spectrum of criteria: refer back to your PDS
• Weight sets on each criterion can result a total different concept: discuss thoroughly and always refer to problem definition
• Only one person decides on the mark: all the team has to write the pros and cons on each concept before discussion
• Criteria set is vague: discuss the criteria and make sure each member has the same understanding

Overall Concept Selection

Concepts

Screening

Concepts after scoring

Scoring

Importance of weightage

Final concept: the best performance and may be very expensive and worst look

Final concept: very easy to manufacture but poor in performance and aesthetic

Final concept: very nice to see but may not working and cannot be manufactured

Therefore, the criteria may contradict to each other and to have best design, weightage is very important.

Detail of each criterion

Performance

Balls stuck in starting container

• When the balls fall into the contanier together

Balls bounce back from the container

• When the balls move in the container

Smoothness of flow out from the container

• This criteria is evaluate when the balls move out from the container into the runway

Accuracy of the balls to success according mechanism 1

• Ability of certain balls to sort according 1^st mechanism

Accuracy of the balls to success according mechanism 2

• Potential of sorting balls according 2^nd method

Collision of the balls

• Internal collision and external collision of the ball

Accuracy of the balls to bounce into other pathway

• Capability of the balls to jump into other path

Balls stuck in runway

• Ability of the ball to stuck before and after sorting

Balls stick together and move at the same time

• Possibility of the balls to stick together during the motion

Sensitivity of the regulators to recover

• Potential of the regulator to return to its form before working

Balls bounce from the final container

• Possibility of the balls to jump out from the last container

Example Criteria 1

Example Criteria 2

Example Criteria 3

Example

4.1 Criteria

4.2 Weightage

4.3 Screening Matrix

The datum used is Lego

4.4 Scoring Matrix

4.5 Final Concept

Final Design

The final design can be

​

• One of the proposed concepts with the modification during reflection of the final design

​

• The integration of two or more proposed concepts.

THANK YOU

univteknologimalaysia

utmofficial

utm.my

In the Name of God for Mankind