MASS PRODUCTION TYPE

The organization of this type of production occurs only when the permanent loading of each job with the execution of the same part is ensured, that is when the volume of production and the labour costs necessary to execute it satisfy for each operation of the technological process or all the operations performed by an executing, successively on each product unit, the relation:

Q . t ≥ Ft (3.98) where: Q represents the production

volume of the respective part during the period considered;

t - the time required to execute the respective operation or the total operation on a product unit;

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F^t - the time fund of the work place at which the respective operation is performed for the period considered.

From the analysis of this formula it results that the volume of work on each technological operation or on total operations must ensure full employment during the period considered, that is:

F_t = C (the cadence), that is, the period of time between obtaining on the flow line of two consecutive products of the same kind, it results:

t ≥ C or 1 C

t (3.100)

Therefore, the main condition of mass production organization is that the ratio between the time spent on the part of reference for a particular operation and the cadence of the line is over unitary. The ratio between t and C serves as an indicator for determining the degree to which a particular production has a mass character or not. With the help of this indicator, the number of jobs is calculated, which must be organized for the continuous execution of a certain operation, i.e., a rhythmic production is ensured under certain conditions.

The characteristics of this type of production are:

➢ The specialization of each performer or workplace in the execution of a certain technological operation during the considered period, which leads to the creation of the necessary premises for the increase of labour productivity;

➢ As a result of the full specialization of the jobs, it is possible to distribute a complex of machines to execute products of the same type size and thus to create specialized sectors or technological lines on landmarks or parts. This is possible by placing the machines, installations, and equipment in the sequence of the operations provided for in the technological flow of manufacture of the respective product or part. The parts and subassemblies move rectilinearly, which creates the necessary premises for the proper ordering in time of the production. The tasks of the operative management of the respective production are greatly simplified;

➢ The movement of the parts and subassemblies ensures the rapid development of the technological process, the transformation of the production material into finished product, in the shortest possible time.

Continuous execution of the same part or product avoids the formation of products batches, because each product, after completing a particular operation, immediately goes to the workplace where the next operation is performed;

➢ The production cycle has a minimum duration as a consequence of

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the rectilinear and individual displacement of each product:

Dcip = tl + t2 + … + tn =



= n

i ti 1

(3.101)

where: Dcip is the duration of the production cycle on the part or product i;

ti - the unit time of the operation of the technological process on the part or product i;

➢ For the production of the same product or part in large quantities, appropriate expenses for machinery, equipment, and work installations are properly admitted. That is, the specific weight of the specialized equipment with a high degree of technical endowment is high, and the S.D.V.'s can be specialized to the maximum, which allows the optimal execution of each operation;

➢ The norms regarding the duration of the operations, due to the continuous repetitions on the same workplaces, can be studied and established with special attention, as they are much closer to the actual duration of their execution, so the calculations for their foundation are more precise;

➢ Daily, each job consumes the same type and size of raw materials, materials and semi-manufactured goods, which makes the organization of the auxiliary activity not dependent on the production needs as is the case with the mass production and the individual production.

The basic condition for mass production can be satisfied with different products to a different extent. At a certain volume of labour costs of the operations, the production volume of the respective product can be so large, so that at each operation the mass character of the output (Im) is equal to one.

Depending on the extent to which the volume of production and the volume of labor costs of the operations as a whole satisfy the relation Im = 1, we distinguish the following variants:

➢ Automated flow mass production (automatic flow lines) characterized by complex automation of the production process in the sense that all technological operations are performed with machines and equipment, all in an automatic line, with minimal human effort;

➢ Mass production in non-automated flow, which is characterized by the continuous movement of natural production factors in the production process, that is, each part after being processed at one

operation is transmitted to the next operation, the transport is continuous.

This variant assumes that the Im indicator for all operations must be expressed in whole numbers, i.e. the duration of the operations must be multiple or equal to

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the cadence of the line, according to the relation:

t × Q = Nlm ×Ft sau Im = C

t = N1m (3.102)

where: Nlm represents the number of workplaces or machines from a given operation, expressed in whole numbers;

➢ Mass production in intermittent flow, characterized in that a part of the operations or all the operations have a duration that is neither equal nor multiple to the cadence of the line. It is frequently encountered in the mechanical processing units, and the inequality of the report is caused either by the reduced quantities of products that are executed from each kind, or by the impossibility of dividing and regrouping the related operations, or by the constructive and technological instability of the products to be executed, which limits the use of specialized technological equipment. To minimize the possibility of wasting time under the conditions of this variant, it is necessary to use a special form of work organization.