Estimating the manpower requirement for production means considering local legal constraints for working times (different from region to region and depending also on agreements with local unions), as well as statistical records on labour present on the job. The substantial input data are:
• working days available for each worker during the considered period of time, minus collective holidays;
• duration of daily working shifts, minus free time for lunch;
• shift organization and rotation;
• sick leave, accidents and incidents of permission for individual leave.
Direct Labour Requirement (DLR)can be obtained considering the planned activity volume (PAV), compared to the individual amount of activity achievable, both being measured in ‘‘standard working time’’, referring to a specific period of working time (day or week).
DLR ¼PAV=IAA;where:
PAV corresponds to the calculation inSect. 4.1.
IAA¼g IWH ð1aÞ= Individual Activity Achievable, equal to the productive hours worked on average by each worker, being:
IWH individual working hours, corresponding to the hours of presence on the job determined by the collective agreement during the working period considered (average data that also considers shift organization);
g direct labour efficiency (measured as indicated inSect. 4.1);
a absenteeism index, estimated on statistical data;
DLR direct labour requirement, in other words, the number of workers necessary to carry out the assigned production plan, complying with the working hours, with the average labour efficiency and also considering predictable absenteeism on the job.
Normally PAV and IAA refer to a single working day of planned shifts (according to the PWT calculation reported inSect. 3.8). Conversely, when there are rest shifts on rotation during the week to be considered, it is necessary for PAV and IAA to refer to the complete working week.
These criteria can be simplified, assuming the direct labour productivity as a standard value, measured by the ratio QP/DLR, where QP is the produced quantity.
This criteria does not consider the variation due to product mix and the evolution of other productivity factors mentioned above (ST,g;a).
4.2.1 Indirect Labour Requirement
In addition to direct labour, there are other workers necessary to production management that must be considered in the manpower requirement; these workers are connected to auxiliary activities that are not specifically included in the standard operative procedures (indirect labour).
The principle auxiliary activities that contribute to the indirect labour requirement are:
(1) Quality Checks‘‘off line’’ (metrology rooms, quality labs, statistical control), the requirement of which is established by considering the quality control plans and checking methodologies; this requirement depends both on the PAV and on the number of planned working shifts, because a minimum fixed number of workers is required for each shift;
(2) Ordinary Maintenance of Equipment and Tools, the requirement of which is estimated considering a statistical work load and the required service level;
it depends both on PAV and on the number of planned working shifts;
(3) Material Handlingon the shop floor (in addition to what is included in the standard operative procedures), the requirement of which depends on the means and methodologies of handling, both on PAV and on the number of planned working shifts;
(4) Warehouses and Dispatch Management, the requirement of which is prin- cipally related to the number of planned working shifts, the workers being employed for fixed garrisons;
(5) General Plant Services, not directly connected to productive processes and the requirement of which are determined by fixed garrisons during the week, for industrial supervision and general equipment conduction.
In general, functions (2), (3), (4) and (5) are partially ‘‘out-sourced’’ to specialized providers; nevertheless, the manpower requirements should always consider the above-mentioned criteria.
In the same productive unit or in an entire plant, considering the same arrangement of services outsourced,the incidence of indirect labourrepresents a necessary statistical data for evaluating labour efficiency:
i¼HIL=DAV, where:
HIL is the total amount of indirect labour working hours;
DAV is the developed activity volume, in the considered period of time and in the same productive unit, measured in standard working hours and quantified according to evaluation of the progress of production.
It is important to consider that a part of the auxiliary activities mentioned above (not included in the standard manufacturing activities) can be assigned to direct labour; in this case, these hours should be included in HIL.
For the same manufacturing system and for the same volume of activity PAV, with some organizational improvements, it is possible to minimize the incidence (i).
Other activities, such as die construction, prototyping, laboratory testing and product experiments, are considered R&D activities and, for this reason, not related directly to the management of manufacturing.
4.2.2 Operative Plan and Staff Balancing: Requirements
Comparing the available manpower staff (MS) with the labour requirement (LR), including both direct and indirect labour, it is possible to evaluate excesses or deficiencies in the staff for each productive unit or plant, carefully distinguishing any specialization that could be a constraint. To assess the likely evolution of the staff during production, without anticipating new hires, it is necessary to consider the normal ratio of outgoing personnel minus any necessary substitution.
The dynamic difference between the available staff and labour requirement is measured by % variation:
D%¼ ðLSLRÞ=LS where:
• LR is the Labour Requiremt, made of direct labour and indirect labour.
• LS is the Labour Staff at disposal, counting direct labour and indirect labour.
If the indicator is positive, it means that there is an excess in the staff; if it is negative, it means that there is a deficiency in the staff. The initial balance between staff and requirement should be worked out at the plant level, moving the workers among the shop floors to minimize inefficiencies in the working hours and in the production flow.
If D % shows low staff deficiency, it is possible to make up for it through overtime, as per local standards and agreements (different country by country) or the use of temporary workers.
If D % shows astructural staff deficiency, at a stable or growing trend, the first countermeasure is to cover the turn-over and then immediately hire new workers, even if it is not possible to transfer part of the production plan to other plants.
If D % showstemporary excess in the staff—according to the medium term operative plan—it is possible to reduce the monthly working hours proportionally, managing compensations during the whole year. This countermeasure is recom- mended to compensate for the seasonal oscillations in the sales or‘‘phase-out/
phase-in’’situation related to new product industrialization.
If D % shows structural excess in the staff, at a stable or growing trend—
according to the long-medium term operative plan—it is necessary to take extraordinary action such as:
• assignment of new additional productive programs to the plant, complying with the general enterprise productive plans and after a feasibility check (making sure productive capacity is available and looking into the eventual necessity of additional investments);
• reduction of working days in a month/year, or temporary staff reduction through flexibility tools (temporary suspension from the job, example: CIG in Italy;
reduction of working shift…);
• definitive reduction of staff through the use of mobility plans toward the external, although only when the above-mentioned countermeasures are insufficient.
Considering the above, it is clear that achieving a balance of productive and sales capacity is the real key, especially because of the uncertain nature of the automotive industry, with demand from the market being very variable and individual economic and political scenarios not easily predictable.
An operative planning process, as described in detail inChap. 6, is an attempt to equilibrate the monthly production plan with sales demand, considering the pro- ductive capacity installed and the working staff available. Safety buffers are the final and intermediate product stocks; however, these stocks should be limited to the most requested models and versions, not determined by specific optional contents; in addition, their dimension should be limited as much as possible to physiological levels, to allow short lead time in delivering to the customers and avoid overstocks that increase the WIP level and influence the sales policies.
Bringing to mind what was discussed inSect. 3.8, we would also like to remind the reader that the manpower requirement setting should be calibrated according to the ‘‘technical system’’ productive capacities, searching for the more convenient working shift rotation over the course of a week.