## 2 Materials and Methods
### Aggregate Planning of the Production Staff  
The basic goal in the majority of manufacturing enterprises is to satisfy the demand for products through effective utilisation of their resources, e.g., the production equipment and workforce. The aggregate planning serves for supporting the development of the optimal production planning, for fulfilling the forecast demand in the future in a medium-term horizon. This planning procedure aggregates the demand for the capacity in the given time and states solutions for the required capacity. The objective is to find a possible solution through the internal possibilities of the company that have to correspond with the requirements on the production volume or to find the optimum by defining the solution that minimises the costs and fulfils the capacity requirements. The steps for creating an aggregate plan begin by determining the demand and defining the current production capacity. The capacity is expressed as a volume of production units that can be produced per a certain time period (this requires determining the approximate number as the manufacturing process can consist of several products that require different production times and costs). The demand is expressed as the total number of units that are to be delivered. If these two aspects are not in balance (they do not equal), the company has to decide if to increase or reduce the production capacity to fulfil the demand or to increase or decrease the demand to fulfil the production capacity. There are several situations when the company needs to increase or reduce the production requirements (reducing the price or making it more advantageous, the possibility to pre-order the products, etc.). However, this solution deals with the area of the capacity planning of the manufacturing staff and thus with the possibilities of increasing or reducing their production capacity to achieve the level of the current demand. Here we can mention [30]:  
* Overtime--the company can temporarily increase the production capacity without increasing the costs or hiring employees through ordering or asking them to work a certain amount of hours daily or days weekly. * Training for several working positions--the employees trained for several working positions are able to carry out several operations at the same time and this fact brings a certain flexibility of the production capacity planning. * Part-time employees--the utilisation of the part-time employees or casual workers (the employees who are considered permanent employees, however, they are used only when they are necessary and usually without the benefits of the workers with permanent jobs) can change the production capacity and solve the fluctuation of the demand [31]. * Hiring employees/unpaid leave--the balance between the production capacity and demand can be maintained through hiring additional workers when it is necessary and unpaid leave when the employees are not currently utilised for fulfilling the company's demand. 1. The current manufacturing enterprises utilise two basic strategies for their aggregate plans--the synchronisation and emancipation strategies. They can be used individually or in a combination. 2. The synchronisation strategy--utilises covering the production capacity and demand from period to period. This causes frequent hiring processes, making redundant or unpaid leaves, dissatisfied and uncertain employees, increased costs for storing residual inventories, problems with the Trade Unions and unstable utilisation of the manufacturing equipment. On the other hand, it means high flexibility of the company. The main advantage of the synchronisation strategy is that it allows keeping minimal inventories and it means big savings for some companies. The majority of the enterprises working on the \"just-in-time\" basis use the synchronisation strategy also for the aggregate planning. The emancipation strategy--creates an aggregate plan bringing a stable level of production and employment.