Trimming rules

Trimming rule is an option for eliminating a component of an engineering system by either eliminating its useful functions or redistributing them to other system or supersystem components.

Overview

Trimming rules are scenarios according to which the process of trimming is conducted and they represent the key difference between trimming for devices and trimming for processes. For devices, there are three trimming rules that can be applied to functions of any rank (with some limitations for rule A). In the process, a trimmed operation comprises a set of functions with different ranks, and each function requires a distinct approach to be effectively addressed. Therefore, there is no universal set of trimming rules, but there are different sets of rules for carriers of function of a specific rank. Trimming for processes is usually more radical than trimming for devices. While for devices, component by component are trimmed, for processes, an entire operation is eliminated, along with its associated equipment, tools, labor, energy, raw materials, etc.

Trimming rules should always be selected considering the goal and constraints of the project, as well as the boundaries of the system.

Trimming rules for devices

When selecting a component of the device to trim, one of three trimming rules can be applied.

Rule A: Function carrier can be trimmed if the object of its useful function is removed too.

Rule A is the most radical of all the options for trimming – two components are removed at once. If the object of the function does not exist, the carrier of this function is no longer needed.

That rule should be used with caution. It is recommended that it be applied when the system is over-engineered and consists of too many components.

It is not recommended that Rule A be applied when the component being trimmed performs a basic function, because then the target must be also removed. Theoretically it is possible, but it does not happen often.

Rule B: Function carrier can be trimmed if the object of function performs its useful function itself.

Rule B, sometimes referred to as the self-service rule, is less radical than Rule A. However, remember that the component that is supposed to perform a new function on itself may have limited resources, and it might be challenging to “teach” it to do so.

Rule C: Function carrier can be trimmed if another component performs its useful function.

Rule C is the most frequently used scenario, since it is much easier to meet its conditions than for A or B. The system and its supersystem contain a number of components that gives a broad choice of new function carrier selection.

The new function carrier should meet at least one of the four conditions:

The component already performs an identical or similar function on the object of the function.
The component already performs identical or a similar function on another object.
The component performs any function on the object of the function, or it at least simply interacts with it.
The component has resources necessary to perform the required function.

Trimming rules for processes

Trimming for processes involves entire operations, but the sets of trimming rules apply to individual functions performed within them. According to some rules, performing a function may not be necessary, but this does not mean it is being trimmed.

There is no universal set of trimming rules here, but there are different sets of rules for carriers of functions of a specific rank.

There are five different sets of trimming rules, and each of them may contain a different number of rules. They are as follow.

Trimming rules for productive functions

When trimming the operation with productive function, the function can be handled the following ways:

Rule A: it can be eliminated if its object is eliminated from the system.

Rule B: it can be eliminated if the necessity to perform it is eliminated.

Rule C: it can be transferred to another operation.

Trimming rules for providing functions

When trimming an operation with providing functions, the functions are handled depending on the rank.

Supporting functions

Supporting function can be handled the following ways:

Rule A: it can be eliminated if the operation with the supported function is trimmed.

Rule B: it can be eliminated if the operation with the supported function is changed so that no support is required now.

Rule C: it can be transferred to the operation with the supported function.

Rule D: it can be transferred to another operation.

Transport functions

Transport function can be handled the following ways:

Rule A: it can be eliminated if its object is eliminated from the system.

Rule B: it can be eliminated if the entities between which its object moves are eliminated from the system.

Rule C: it can be eliminated if the subsequent operations are changed in such a way that it eliminates the need to perform the transport function.

Rule D: it can be transferred to another operation.

Measurement functions

Trimming rules for measurement functions direct us to the rules for other functions. They can be handled the following ways:

Rule A: it is handled according to trimming rules for the productive function if the measurement function is needed as the final output (for example, research, statistics, etc.).

Rule B: it is handled according to trimming rules for the supporting function if the measurement function is needed for the provision of another operation.

Trimming rules for corrective functions

When trimming the operation with corrective function, the function can be handled the following ways:

Rule A: it can be eliminated if the defect-generating operation is trimmed.

Rule B: it can be eliminated if the defect-generating operation is changed in such a way that the defect is not generated any longer.

Rule C: it can be eliminated if the defect-generating operation is changed in such a way that the defect is generated with another (safe) set of parameters; in this case the defect ceases to be a defect and the need for performing a corrective function is eliminated.

Rule D: it can be eliminated if operations which are harmed by the defect are trimmed.

Rule E: it can be eliminated if operations which are harmed by the defect are changed in such a way that they become insensitive to it; in this case the defect ceases to be a defect and the need for performing a corrective function is eliminated.

Rule F: it can be transferred to the defect-generating operation.

Rule G: it can be transferred to another operation.