Formulator
This is the formulation of the problem.
Several problem statements of removing the screw from my femur were formulated using the Problem Formulation Process presented in Chapter 3 of Step-by-Step TRIZ: Creating Innovative Solution Concepts.
A network of relationships between desired and undesired events uses only four link words.
A provides B means A makes the good event B happen or B requires A
A causes B means A makes the bad event B happen
A prevents B means A reduces the problem of bad event B happen
A hinders B means A reduces the effectiveness of good event B
The problem formulation process identifies the following links:
[Screwdriver head slips in slot] causes [screw cannot turn out].
[Slot is rounded] causes [screwdriver head slips in slot].
(Large frictional force) causes [screwdriver head slips in slot].
(Large frictional force) requires (screw integrated into bone) and causes [screwdriver head slips in slot].
(Bone growth around threads and shaft) is required for (large frictional force).
(Heal crack in bone and fill hole) requires (bone growth around threads and shaft).
The structuring of this formulation yields the following network.
Ideas were recorded as they were conceived while reading the problem statements. The events are numbered and the problem statements are lettered for multiple problems for and event.
A flow chart depicting the function relationships (Figure 3-12) yields the following six problem statements:
1a. Find a way to enhance (heal the crack in the bone and fill the hole).
1b. Find an alternative way of (heal crack in bone and fill hole) that does not require (bone growth around threads and shaft).
2a. Find a way to enhance (bone growth around threads and shaft).
2b. Find an alternative way of (bone growth around threads and shaft) that provides (heal crack in bone and fill hole) and (large frictional force).
3a. Find a way to enhance (large frictional force).
3b. Find an alternative way to provide (large frictional force), which provides or enhances (screw integrated into bone), which does not cause [screwdriver slips in slot] and does not require (bone growth around threads and shaft).
3c. Find a way to resolve CONTRADICTION: (large frictional forces) provides (screw integrated into bone), and does not cause [screwdriver slips in slot].
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Concepts: lubricate, vibrate, reduce dimension of screw, soften bone, dissolve screw, dissolve threads. At this point, the patient became quite concerned as he pictured the application of each of these concepts—to his leg! Although someone working on a problem solution is not unusual so emotionally invested, this situation provided a dramatic example of the Voice of the Customer saying, "NO WAY." |
4a. Find a way to benefit from [slot is rounded].
4b. Find a way to prevent [slot is rounded].
5a. Find a way to benefit from [screwdriver slips in slot].
5b. Find a way to prevent [screwdriver slips in slot] under the condition of [slot is rounded] and (large frictional force).
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Concepts: use left-handed easyout, vice grip, glue, cut new slot, apply torque to tip of screw |
6a. Find a way to benefit from [screw cannot turn out].
6b. Find a way to prevent [screw cannot turn out] under the condition of [screwdriver slips in slot].
7a. Find an alternative way to provide (screw integrated into bone), which does not require (large frictional forces).
7b. Find a way to enhance (screw integrated into bone).
Notice the problem statements are a mix of those for future screw insertions and for the current removal. There are different level of difficulty. Concepts should be developed for each of the concepts for an exhaustive set of concepts.
The author found a surgeon who was both a mechanical engineer and orthopedic surgeon. However, the individual was not interested in studying the resonant frequency of bone and the effect on screw removal. The easyout was tried and failed because in was too short to work within the depth of muscle. Cutting, chipping and vice grips were finally used. This was a disappointment for me. After the screw was removed information for vibrations was found and a device. Too, late for me.
