204
CHAPTER
7 Concept Generation
Principle 10. Prior action a.
Carry out the required action in advance in full, or at least in part
b. Arrange objects so they can go into action without time loss
waiting for action This leads to the idea of having the clamp automatically move so the jaws come
into contact with the work prior action and then the grip force is translated into high clamping force with small motion. This is similar to the first idea, but the
prior motion is automated.
Principle 17. Moving to a new dimension a.
Remove problems in moving an object in a line by two- dimensional movement along a plane
b–d.
Others are not important here This leads to the idea of using a linkage to get a more complex motion than purely
linear. A linkage is used to get the jaws in contact with the work and then the small motion with high force is action as is typical with a one-handed clamp.
There are many other ideas to be discovered by working through the inventive principles and other TRIZ techniques see Section 7.11 for TRIZ information
sources.
7.8 BUILDING A MORPHOLOGY
The technique presented here uses the functions identified to foster ideas. It is a very powerful method that can be used formally, as presented here, or informally
as part of everyday thinking. There are three steps to this technique. The first step is to list the decomposed functions that must be accomplished. The second step is
to find as many concepts as possible that can provide each function identified in the decomposition. The third is to combine these individual concepts into overall
concepts that meet all the functional requirements. The design engineer’s knowl- edge and creativity are crucial here, as the ideas generated are the basis for the
remainder of the design evolution. This technique is often called the “morpho- logical method,” and the resulting table a “morphology,” which means “a study
of form or structure.” A partial Morphology for the redesign of the one-handed bar clamp is presented in Figure 7.21. This is highly modified from the morphol-
ogy done at Irwin to protect their intellectual property. A blank morphology is available as a template.
7.8.1 Step 1: Decompose the Function
The first half of this chapter details this step. For the one-handed clamp exam- ple, the function was decomposed in Fig. 7.11. The first four functions in that
figure are
7.8 Building a Morphology
205
Product: One-handed bar clamp
Organization Name: Irwin Tools
Morphology
Subfunctions Concept 1
Concept 2 Concept 3
Concept 4 One trigger
Jam plate
Move bar
Amplify force
Team Member: Team Member:
Team Member: Team Member:
Copyright 2008, McGraw-Hill Prepared by:
Checked by: Approved by:
Designed by Professor David G. Ullman Form 15.0
The Mechanical Design Process Short stroke
Long stroke Free sliding
2 speed system 2 speed system
Transform grip force and motion
to bar Two triggers
Ratchet Rack and pinion
Linkage Collect grip force
and motion from user
FH FH
FH
Figure 7.21 Example of a morphology.
■
Collect grip force and motion from user
■
Transform grip force and motion to bar
■
Move bar
■
Amplify force These functions were the focus of the new design effort, as Irwin wanted to
redesign these to make the clamp more user-friendly. Specifically, the functions “move bar” and “amplify force” are a contradiction. A mechanism that transforms
each handgrip cycle squeeze and release to move the bar rapidly will result in a lower applied force than one that moves the bar a short distance. As with any
other transmission system there is a trade-off between speed and force or torque in rotational systems. The user would like to be able to move the bar rapidly in
the position and then apply a high force. So, this effort focuses on rapidly moving the bar into position and then amplifying the force.
206
CHAPTER
7 Concept Generation
7.8.2 Step 2: Develop Concepts for Each Function
The goal of this second step is to generate as many concepts as possible for each of the functions identified in the decomposition. For the example, there are two
ways to collect the grip force and motion from the user, as shown in Fig. 7.21. The first is to use a single trigger as shown in Figs. 7.2, 7.3, and 7.4. This is shown
schematically in the morphology with a hand force applied to the trigger and the trigger pivoted someplace in the clamp body. Another option is two triggers,
shown as Concept 2 in the morphology. For this concept, both the force on the trigger and the reaction force on the handle are used to enable the clamp. The
concepts in the morphology are abstract in that they have no specific geometry. Rough sketches of these concepts and words are both used to describe the concept.
Four ideas were generated to transform the grip. These are not all well thought out, but the morphology is generating ideas, so this is all right. When the project
began, discussion centered on a two-speed system, fast to get the clamp in contact with the work and then slow so the force can be amplified during clamping. As
can be seen in the “move bar” row, an idea that evolved here is for more than two speeds. Although no immediate ideas were generated, this offered even more
possibilities to consider.
If there is a function for which there is only one conceptual idea, this function should be reexamined. There are few functions that can be fulfilled in only one
way. The lack of more concepts can be due to
The designer making a fundamental assumption.
For example, one func- tion that has to occur in the system is “Collect grip force and motion from
user.” It is reasonable to assume that a gripping force will be used to provide motion and clamping force only if the designer is aware that an assumption
has been made. The function is directed at how, not what.
If one idea gets built into the function, then it should come as no surprise that this is the only idea that
gets generated. For example, if “Transform grip force and motion to bar” in Fig. 7.21 had been stated as “use jam plate to transform motion,” then only
jam plate ideas are possible. If the function statement has nouns that tell how the function is to be accomplished, reconsider the function statement.
The domain knowledge is limited.
In this case, help is needed to develop other ideas. See Sections 7.5, 7.6, or 7.7.
It is a good idea to keep the concepts as abstract as possible and at the same level of abstraction. Suppose one of the functions is to move some object.
Moving requires a force applied in a certain direction. The force can be provided by a hydraulic piston, a linear electric motor, the impact of another object, or
magnetic repulsion. The problem with this list of concepts is that they are at different levels of abstraction. The first two refer to fairly refined mechanical
components. They could be even more refined if we had specific dimensions or manufacturers’ model numbers. The last two are basic physical principles.
It is difficult to compare these concepts because of this difference in level of