Sample Answers to Exercises and Thought Questions: Chapter 14
EX 14.1
A furniture manufacturer was considering a line of seating products to be fabricated by cutting and bending a recycled plastic product available in large sheets. Create a prototype of at least one possible chair design by cutting and bending a sheet of paper or cardboard. (You may wish to design the chair with a sketch first, or just start working with the sheet directly.) What can you learn about the chair design from your prototype? What can’t you learn about the chair design from such a prototype?
There is no "correct" answer to this exercise; it is a hands-on exercise. Some of the things you can learn about the chair are: geometric relations involving folding/unfolding, appearance of the geometry, stackability, and materials utilization. Some of the things one cannot learn from the paper prototype are: the projected weight, strength, and stiffness of the chair; and the comfort of the chair.
EX 14.2
Position the chair prototype described in Exercise 1 on the plot in Exhibit 14-5. For which of the four major purposes would a product development team use such a prototype?
A furniture manufacturer was considering a line of seating products to be fabricated by cutting and bending a recycled plastic product available in large sheets. Create a prototype of at least one possible chair design by cutting and bending a sheet of paper or cardboard. (You may wish to design the chair with a sketch first, or just start working with the sheet directly.) What can you learn about the chair design from your prototype? What can’t you learn about the chair design from such a prototype?
There is no "correct" answer to this exercise; it is a hands-on exercise. Some of the things you can learn about the chair are: geometric relations involving folding/unfolding, appearance of the geometry, stackability, and materials utilization. Some of the things one cannot learn from the paper prototype are: the projected weight, strength, and stiffness of the chair; and the comfort of the chair.
EX 14.2
Position the chair prototype described in Exercise 1 on the plot in Exhibit 14-5. For which of the four major purposes would a product development team use such a prototype?
The prototype is clearly physical and is more focused than comprehensive. The team would probably use this type of prototype for learning and for communication.
EX 14.3
Devise a prototyping plan (similar to that in Exhibit 14-14) for investigating the comfort of different types of handles for kitchen knives.
EX 14.3
Devise a prototyping plan (similar to that in Exhibit 14-14) for investigating the comfort of different types of handles for kitchen knives.
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Name of Prototype:
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Knife Handles
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Purpose:
(communication, learning, integration, milestones) |
What shapes are most comfortable for kitchen knife handles (learning).
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Level of Approximation:
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Shape and surface texture of handle are "production intent."
Knife blade is of approximately the right shape. |
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Quantity to Be Built (if physical):
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5 knives to be built based on most promising of the 20 "foamies" we have already built.
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Outline of Test Plan:
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Provide users with a variety of objects to cut (bagel, onion, tomato, celery) and ask them to rank order the handles in order of preference.
Use at least 30 experimental subjects with widely varying hand sizes from 10th percentile female to 90th percentile male. Measure hand sizes. Test hypothesis that preferred shape is related to hand size. |
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Schedule:
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10 May knives available from model maker
17 May basic functionality verified 24 May tests completed 28 May analysis of results completed |
EX 14.4
Position the prototypes shown in Exhibits 14-3, 14-4, 14-6, 14-7, and 14-13 on the plot in Exhibit 14-5. Briefly explain your reasoning for each placement.
Boeing wing prototype (Exhibit 12-3) -- physical and mid-way between focused and comprehensive. This prototype was intended to test only the structure, and therefore lacked avionics and other systems.
Bahco screwdrivers (Exhibit 12-3) -- physical and focused. These prototypes were to test only grip comfort.
Projector (Exhibit 12-3) -- physical and focused. The model was intended to communicate only appearance (and maybe heft/balance).
Bicycle in SolidWorks (Exhibit 12-12) -- analytical and somewhere between focused and comprehensive. A solid model can be used for many purposes even though
it is not completely comprehensive.
Urethane casting (Exhibit 12-13) -- physical and comprehensive. These parts were intended to be used in pre-production prototypes. They are fully "works like" and "looks like" prototypes.
TQ 14.1
Many product development teams separate the "looks-like" prototype from the "works-like" prototype. They do this because integrating both function and form is difficult in the early phases of development. What are the strengths and weaknesses of this approach? For what types of products might this approach be dangerous?
(Based on a solution by Paul Gallagher)
Some advantages of separate prototypes are:
Some weaknesses of separate prototypes are:
Two examples where the separation may be dangerous are:
In a high-tech computer system designed for military applications, prototype and test of separated prototypes may be dangerous. A functioning electronics component may survive a shock and vibration test on its own but when installed in a case, the response to shock is modified and the system as a whole may fail, requiring expensive re-design late in the development process.
Similarly chip design for electronic applications can be proved out in a working prototype but could fail completely in a production configuration due to electromagnetic interference between components when they are located in final configurations.
TQ 14.2
Over the past 10 years, several technologies have been developed to create physical parts directly from computer-aided design files (e.g., stereolithography and selective laser sintering). How might a team use a technology for extremely rapid fabrication of physical prototypes during the concept development phase of the product development process? Might the technology facilitate identifying customer needs, establishing specifications, generating product concepts, and/or selecting product concepts?
(Based on a solution by Philipp Borchard)
A product development team might utilize extremely rapid prototyping techniques to create physical prototypes of the concepts generated. These prototypes would allow the concepts to be effectively communicated to all members of the team. Physical prototypes could also be used for screening of the concepts, as potential problems may only become apparent through physical prototypes. Analytical designs sometimes do not reveal the limitations of a design as they cannot reveal phenomena which go beyond the underlying assumptions of the model. By discovering the limitations of a design through the building of a prototype the team can concentrate on overcoming these limitations or eliminating infeasible designs early in the product development process. The team could also show the prototypes to consumers and/or lead users and get more valuable customer feedback and possibly generate additional concepts from customer suggestions.
The technology could significantly facilitate identifying customer needs. The customer can be presented with different physical prototypes through which an assessment of the essential customer needs is simplified. By seeing and handling an actual physical prototype the user's real need can be more easily identified. Rapid prototyping during the concept development phase may pronounce the advantages and disadvantages of different concepts which are otherwise not readily apparent. Problems in certain designs may come to light which can then be resolved and improved upon or the concept can be eliminated from the concept selection list. By having a physical prototype the process of establishing target specifications is also simplified. The relevant parameters and their ideal magnitude are easier to identify than in a pure analytical model.
TQ 14.3
Some companies have reportedly abandoned the practice of doing a customer test with the early prototypes of their products, preferring instead to go directly and quickly to market in order to observe the actual customer response. For what types of products and markets might this practice make sense?
This practice may make sense for markets in which customer needs are changing rapidly and are difficult to evaluate with traditional market research tools such as interviews, focus groups, and questionnaire. Time is extremely valuable in such markets, and so it is often better to get something into the market and then iterate quickly based on the market response, than to take a lot of time to carefully conceive a product that may miss the mark. This situation can be viewed within the conceptual framework illustrated in Exhibit 7. The firm does not perceive that the probability of success is dramatically changed by building and testing a prototype and/or the cost of actually launching the product is low.
TQ 14.4
Is a drawing a physical or analytical prototype?
A drawing is a hybrid of the two types of prototypes. Clearly some aspects of a drawing are physical: the objects exist in (two-dimensional) space, they can be laid over one another to check for interference, objects can be placed on them to examine fit. Yet, the drawing also has analytical elements: it is a semi-formal, quasi-mathematical, abstraction of geometry, and it approximates only the geometric attributes of the product.
TQ 14.5
Microsoft uses frequent comprehensive prototypes in its development of software. In fact, in some projects there is a "daily build," in which a new version of the product is integrated and compiled every day. Is this approach only viable for software products, or could it be used for physical products as well? What might be the costs and benefits of such an approach for physical products?
This approach makes sense when the benefits outweigh the costs. In software, the costs of assembling the product each day are modest, and so the daily build can be a good strategy. For most physical goods, a daily build is not feasible. Just the costs of physically assembling most physical goods make the strategy infeasible, not to mention the time delays associated with such builds. However, the CAD files describing the product might be "assembled" each day. This strategy was adopted by Boeing in the development of the 777, and resulted in many of the same benefits reported by Microsoft.
Position the prototypes shown in Exhibits 14-3, 14-4, 14-6, 14-7, and 14-13 on the plot in Exhibit 14-5. Briefly explain your reasoning for each placement.
Boeing wing prototype (Exhibit 12-3) -- physical and mid-way between focused and comprehensive. This prototype was intended to test only the structure, and therefore lacked avionics and other systems.
Bahco screwdrivers (Exhibit 12-3) -- physical and focused. These prototypes were to test only grip comfort.
Projector (Exhibit 12-3) -- physical and focused. The model was intended to communicate only appearance (and maybe heft/balance).
Bicycle in SolidWorks (Exhibit 12-12) -- analytical and somewhere between focused and comprehensive. A solid model can be used for many purposes even though
it is not completely comprehensive.
Urethane casting (Exhibit 12-13) -- physical and comprehensive. These parts were intended to be used in pre-production prototypes. They are fully "works like" and "looks like" prototypes.
TQ 14.1
Many product development teams separate the "looks-like" prototype from the "works-like" prototype. They do this because integrating both function and form is difficult in the early phases of development. What are the strengths and weaknesses of this approach? For what types of products might this approach be dangerous?
(Based on a solution by Paul Gallagher)
Some advantages of separate prototypes are:
- Speed of prototyping for early prototypes.
- Existing size components and material can be used for function tests.
- Rapid prototyping techniques can be used for "looks-like" models.
- "Looks-like" models may be good enough for communication and some learning.
- Some integration of key components can be done in "works-like" prototypes.
- Early functional prototypes could remove working tests from the critical path (See Exhibit 9, wire wrap example in the text), which reduces overall development time.
Some weaknesses of separate prototypes are:
- Interactions between elements of the product can be missed until the final production stage, causing expensive redesign and delays.
- In any product where the function of the product depends on the physical geometry and materials, the true performance of the product will not be tested.
- Properties such as resistance to shock, vibration, thermal expansion, and electromagnetic interference are dependent upon overall configuration and materials.
- Problems with the fit of parts may arise at the production stage. Without complicated 3-D solid modeling, it can be hard to visualize and insure that all pieces of the final product will fit perfectly.
Two examples where the separation may be dangerous are:
In a high-tech computer system designed for military applications, prototype and test of separated prototypes may be dangerous. A functioning electronics component may survive a shock and vibration test on its own but when installed in a case, the response to shock is modified and the system as a whole may fail, requiring expensive re-design late in the development process.
Similarly chip design for electronic applications can be proved out in a working prototype but could fail completely in a production configuration due to electromagnetic interference between components when they are located in final configurations.
TQ 14.2
Over the past 10 years, several technologies have been developed to create physical parts directly from computer-aided design files (e.g., stereolithography and selective laser sintering). How might a team use a technology for extremely rapid fabrication of physical prototypes during the concept development phase of the product development process? Might the technology facilitate identifying customer needs, establishing specifications, generating product concepts, and/or selecting product concepts?
(Based on a solution by Philipp Borchard)
A product development team might utilize extremely rapid prototyping techniques to create physical prototypes of the concepts generated. These prototypes would allow the concepts to be effectively communicated to all members of the team. Physical prototypes could also be used for screening of the concepts, as potential problems may only become apparent through physical prototypes. Analytical designs sometimes do not reveal the limitations of a design as they cannot reveal phenomena which go beyond the underlying assumptions of the model. By discovering the limitations of a design through the building of a prototype the team can concentrate on overcoming these limitations or eliminating infeasible designs early in the product development process. The team could also show the prototypes to consumers and/or lead users and get more valuable customer feedback and possibly generate additional concepts from customer suggestions.
The technology could significantly facilitate identifying customer needs. The customer can be presented with different physical prototypes through which an assessment of the essential customer needs is simplified. By seeing and handling an actual physical prototype the user's real need can be more easily identified. Rapid prototyping during the concept development phase may pronounce the advantages and disadvantages of different concepts which are otherwise not readily apparent. Problems in certain designs may come to light which can then be resolved and improved upon or the concept can be eliminated from the concept selection list. By having a physical prototype the process of establishing target specifications is also simplified. The relevant parameters and their ideal magnitude are easier to identify than in a pure analytical model.
TQ 14.3
Some companies have reportedly abandoned the practice of doing a customer test with the early prototypes of their products, preferring instead to go directly and quickly to market in order to observe the actual customer response. For what types of products and markets might this practice make sense?
This practice may make sense for markets in which customer needs are changing rapidly and are difficult to evaluate with traditional market research tools such as interviews, focus groups, and questionnaire. Time is extremely valuable in such markets, and so it is often better to get something into the market and then iterate quickly based on the market response, than to take a lot of time to carefully conceive a product that may miss the mark. This situation can be viewed within the conceptual framework illustrated in Exhibit 7. The firm does not perceive that the probability of success is dramatically changed by building and testing a prototype and/or the cost of actually launching the product is low.
TQ 14.4
Is a drawing a physical or analytical prototype?
A drawing is a hybrid of the two types of prototypes. Clearly some aspects of a drawing are physical: the objects exist in (two-dimensional) space, they can be laid over one another to check for interference, objects can be placed on them to examine fit. Yet, the drawing also has analytical elements: it is a semi-formal, quasi-mathematical, abstraction of geometry, and it approximates only the geometric attributes of the product.
TQ 14.5
Microsoft uses frequent comprehensive prototypes in its development of software. In fact, in some projects there is a "daily build," in which a new version of the product is integrated and compiled every day. Is this approach only viable for software products, or could it be used for physical products as well? What might be the costs and benefits of such an approach for physical products?
This approach makes sense when the benefits outweigh the costs. In software, the costs of assembling the product each day are modest, and so the daily build can be a good strategy. For most physical goods, a daily build is not feasible. Just the costs of physically assembling most physical goods make the strategy infeasible, not to mention the time delays associated with such builds. However, the CAD files describing the product might be "assembled" each day. This strategy was adopted by Boeing in the development of the 777, and resulted in many of the same benefits reported by Microsoft.