6.4.1 Definition
It is difficult to give an extensive definition of agile manufacturing systems (AMS). Let us start with a common definition that will be refined by comparing AMS with lean manufacturing systems (LMS), see Section 6.6, and flexible manu- facturing systems (FMS).
An AMS is a manufacturing system that has the ability to manage market changes as a matter of routine. An AMS is able to quickly (that is with short lead times) produce low-cost and high-quality customized products in various volumes.
Note that market changes refer not only to changes in production volumes but also to changes in product characteristics and even in types of products.
A measure of agility is the time required to switch from one set of characteris- tics to another. A second measure of agility is the percentage of the initial invest- ment that can be reused when demand characteristics change: the greater this per- centage, the more agile the system. Figure 6.6 illustrates this second measure.
Agile manufacturing systems usually need resources that are far beyond the abilities of most companies. Therefore, AMS require a strong cooperation among several companies that, in turn, calls for a managerial structure to take care of the cooperation (resource sharing, contacts with clients, etc.).
204 6 X-manufacturing Systems
Reused percentage of initial investment Mass production
FMS
AMS Adaptation period
Figure 6.6 Adaptation to market changes
The aim of AMS is to combine organizations, people and technologies into a single structure able to manage quickly and at low cost a virtually infinite number of demand types. Obviously, these joint ventures will be successful only if they are supported by advanced information technologies and a collaboration frame- work that supports skilled people in their efforts to improve the production sys- tem. Knowledge is a major factor of success in AMS.
Another characteristic of AMS is their proximity to customers and providers in the sense that they organize common projects with them to improve the efficiency of the whole system. These projects are usually technical ones to improve the manufacturing processes and/or the characteristics of the products and/or the qual- ity, or organizational projects to optimize internal functions.
The importance of people in AMS is becoming increasingly apparent since they bring flexibility to the system. Several constraints must be satisfied to help work- ers to become as efficient as possible. The main constraints concern the involve- ment of employees in daily system improvement, ergonomics and training.
6.4.1.1 Provide Ergonomic Working Places Among other objectives, designers have to:
• Design working places that eliminate unnecessary effort.
• Make sure that information related to tasks to be performed is provided in due time and is easy to read.
• Assign a limited diversity of tasks to each working place (and thus to each em- ployee).
• Plan to include at each work place a sound alert in case of breakdown, quality deficiency, starvation, etc.
• Manage the system in order that components arrive at the work places on a just-in-time basis.
• Make sure that the communication with adjacent work places and the hierarchy is easy.
• Do your best to protect the health of the employees (low level of noise, optimal lighting, ergonomic seating, etc.).
6.4.1.2 Involvement of the Employees
Employees should be involved in the day-to-day improvement of the efficiency of the system. As a consequence, a system able to evaluate the performance of each workplace should be introduced.
6.4.1.3 Training
As mentioned before, knowledge is a major factor of success in AMS. Thus, train- ing the employees is of utmost importance, mainly in the following domains:
1. quality improvement;
2. identification and suppression of unnecessary tasks;
3. improvement of production processes.
6.4.2 Agile Versus Lean
While a LMS meets a given demand quickly with low cost, an AMS is able, in ad- dition, to adapt itself to changes in demand characteristics and even product types.
The principal difference between AMS and LMS is whether or not the market changes have been taken into account at the design level of the system.
6.4.3 Agile Versus Flexible
Let us now compare AMS with FMS. A FMS is able to rapidly switch from one task to another, but this is only possible if both tasks were foreseen at the design level, while an AMS is able to quickly respond to unanticipated market changes.
Thus the difference between FMS and AMS is that FMS covers a finite set of tasks while the set of tasks included in AMS is virtually infinite. AMS are proac- tive, the definition of which is “to act before a situation becomes a source of con- frontation or crisis”.
6.4.4 Cost Stability During the Life of an AMS
Real costs observed during the life an AMS are often different from those fore- seen. The main reasons for this observation are the following:
206 6 X-manufacturing Systems
• changes in the system such as, for instance, increase of capacity, introduction of new resources as substitutes for some old ones, etc.;
• evolution of demands;
• simplification of manufacturing processes;
• changes in characteristics of some products, which calls for changes in some processes;
• problems arising when starting the new system, which calls for changes in the manufacturing system design;
• a breakdown ratio that appears to be greater than foreseen, which also calls for changes in the design of the manufacturing systems;
• hidden costs (unplanned training of the employees, resource costs greater than expected, etc.).
This list is not exhaustive.
In an AMS, surpassing cost expectations leads to consequences that are less crucial than in mass production. The main reason is that adjusting an AMS to new conditions is much easier than in the case of mass production (or FMS often).
Thus, the rectification of evaluation mistakes is made as soon as they are detected and with little increased cost.
A consequence is that adjustments are more frequent in AMS than in mass pro- duction, but they are of smaller range.
Figure 6.7 illustrates the relation between capacity and cost. Dotted lines repre- sent actual events, while continuous lines represent foreseen situations. SP is the selling price; thus, as long as the production cost remains less than the selling price, the system remains profitable. In the figure, “*” indicates the points in time at which AMS is adjusted to face the demand, the goal being to force the AMS to remain profitable.
qf0 qr0 v qr1 qf1
* * * * * * *
Cost
Capacity Massproduction
AMS
SP
Figure 6.7 Actual and expected production costs for mass production and AMS
Note that, in this illustration, only the volume of the demand changes: a mass- production system would be unable to adjust to a change in a type of product.
As we can see:
• Let v be the expected production volume. When v is manufactured by a mass- production system, the production cost is greater in the actual event than it would be if the foreseen situation holds. Furthermore, the range of volume for which production remains profitable, actually decreases compared with the foreseen situation ([qr0,q1r]<[q0f,q1f]).
• When the production is done by an AMS, the increase of the production cost is less than the increase observed when a mass-production system is used; the ex- planation lies in the high frequency of adjustments in AMSs, which allow a better control of the profitability of the system.
In Figure 6.7, we can see that an AMS can always remain profitable due to fre- quent adjustments at low cost.