To conclude this chapter, we are going to connect themanufacturing engineering plandiscussed in Sect. 3.1and the implementation of the machine loading criteria just discussed in the previous section.
Let us remember that productive capacity is first planned for each industrial site in relation to market targets (specific product annual sales plans): During the product’s industrial life cycle, it is typical for there to be a peak of sales demand, related to the year of greatest success in the market.
Let us define QYmas the yearly demand forecast during the life cycle and QYp as the yearly demand in the peak year. If project productive capacity is set in relation to QYp, the medium utilization degree of productive capacity will be:
U=QYm/QYp.
Beneath the threshold value of U=80 %, for ‘‘capital intensive’’ productions, the incidence of structural fixed costs can cause a critical situation for the enter- prise’s earned income. So, in planning productive capacities, Top Management must research a balance between requests from Marketing and investments required by Production Management, calibrating industrial initiatives in relation to real market possibilities and profitability targets.
It is clear that a manufacturing system with a bigger operative flexibility and convertibility for new product insertions has a low risk of being less used due to a specific product’s life cycle. Additionally, a Component Maker is more likely to have the right degree of utilization of its productive capacity, when manufacturing systems are multi-functional and suitable for supplying more industrial customers, reducing market risk.
Considering that, it is possible to use the following two alternative criteria for setting ‘‘manufacturing systems’’.
Applying the1st criteriafor machine loading calculation, Available Productive Capacity (APC) relative to each similar group of machines or autonomous tech- nological modules (machining centre, multi-station or single press, machining cell…) is set, assuming that solutions implemented will correspond to the technical–
economic criteria mentioned inSect. 1.4. Consequently, machine tools and tech- nologically similar modules operating on parallel requirements are calculated by:
MR = machine requirements(number of modules required)= QY/(APC• AWT), where:
(QY) is the quantity of product required yearly, based on the marketing plan (including spare parts required for after sales);
(APC) is the available productive capacity (medium data related to each module);
(AWT) is the maximum available working time for production in a year, expressed in hours.
MR should theoretically be counted to the next full number, if it is not possible to use overtime to balance eventual marginal lacks, or partialout-sourcing.
For ‘‘one piece flow integrated productive systems’’, discussed inSect. 3.6, the 2nd criteria to calculatemachine load is applied. Productive flow speed neces- sary to satisfy market demand is determined by:
HVP¼OEEAWTQY = Hourly Virtual Productivityrequired by project, where:
(QY) is the quantity of product required yearly, based on the marketing plan (including spare parts required for after sales);
(OEE) is the overall equipment efficiency foreseen by the project for the manufacturing system;
(AWT) is the maximum available working time for production in a year, expressed in hours.
It is to be considered that, for each technological process, productive flow speed is characterized by a maximum sustainable threshold level. In fact, beneath a certain level of Working Cycle Time (WCT), inactive phases hardly influence the time sequence diagram. When this occurs, it is good to share productive flow between two or more ‘‘parallel systems’’, searching for the best conditions, as much from an investment point of view as a transformation cost point of view.
Both criteria for productive capacity dimensioning are based on annual product sales plans, during their industrial cycle life, without considering the effects of market season trends. It is assumed that eventual monthly requirement peaks can be sustained by longer working shifts and extra working time during the year. It is also possible to produce in advance, but only if there are guarantees of market absorption during the period of peak demand. If all this should not be enough, longer lead time on delivering is to be considered, by managing order reservations.
Value MR and HVP determine productive capacity by project and are the input data necessary for the manufacturing engineering plan and for the executive project for ‘‘manufacturing systems’’, following the methodology discussed in Sect. 3.1.
Starting from the definition of Hourly Virtual Productivity (HVP) above, it is possible to transpose the concept of Takt Time, meaning the ideal pace of a production system for satisfying the customer demand:
TT ¼ 1 HVP
The Takt Time is not the rhythm at which the customer is asking for products but is representative of the ideal pace the production system must have in relation to the average customer demand in the period considered.
Setting the production system to the Takt Time requires some preliminary con- ditions, such as:
• stability of production system (high technical availability and efficiency)
• levelling of customer demand in the period considered.
Once the Takt Time has been set, it is more effective to maintain it in as stable a condition as possible to consolidate production system standards and obtain the best level of performance.