Network planning and management of technical preparation of production. Open Library - open library of educational information

Network planning systems are a set of graphical and calculation methods, organizational and management techniques that allow modeling of complex processes for creating new equipment and operational management of the progress of work on its creation. The main planning document in the network planning system is the network schedule (network model).

In the network model, events are indicated by circles, jobs – by arrows. The constructed graph must have one initial and one final event. An event is an intermediate or final result of one or more activities. It does not have a duration in time, but indicates the beginning of some work and can simultaneously be the completion of others.

Work in a network diagram refers to any process that requires labor; waiting, requiring a certain amount of time; a dependency indicating that the start of a given job depends on the completion of the previous one. Graphically, the work is indicated by a solid arrow. An arrow that expresses only the dependence of one job on another is called a fictitious job and is indicated by a dotted line. It has a zero time rating. Work requires a lot of time. The duration of work in days (weeks) is indicated above the arrow.

During the calculation of the network schedule, the following parameters are determined: duration of work and critical path; the earliest and latest dates for the occurrence of events and completion of work; all types of time reserves for work and events that are not on the critical path.

Any sequence of activities connecting the initial event with the final event is called a path. The path with the longest duration of work is called critical and is depicted with bold arrows.

Activities on the critical path have no slack. Therefore, failure to meet deadlines for any work on the critical path leads to a delay in the overall deadline for completing the entire complex. Activities that are not on the critical path have a slack time.

Before determining the critical path, it is necessary to calculate the early and late dates for the completion of events, as well as the slack for each event. Events with zero float will indicate the passage of the critical path. The earliest date of occurrence of an event () characterizes the earliest possible date of occurrence of an event. The duration of its completion is determined by the length of the longest segment of the path from the initial event to the one under consideration. The early date of events is determined as follows:

(3.1)

where is the early date of the subsequent event; - the early date of the previous event; - duration of work ij connecting event i with event j.

The late date for the completion of an event characterizes the date of the latest permissible period for the completion of an event. The late dates for the occurrence of events are determined by the following formula:

(3.2)

where - the late time of the previous event; - the late time of the subsequent event.

If the calculation of the early dates for the completion of an event is carried out from left to right, from the initial event to the final one, then when determining the later dates for the completion of events, the calculation must be carried out from right to left, from the final event to the initial one.

The slack time of an event is the difference between the late and early dates of the event:

(3.3)

The time reserve for events shows by what maximum permissible period of time the completion of an event can be delayed without causing the danger of missing the deadline for the completion of the final event. If the reserve is fully used, the event will fall on the critical path. If the deadlines for completing all work do not meet the guidelines, it is necessary to optimize the network. For these purposes, it is possible, firstly, to increase the number of performers, and secondly, to redistribute labor resources by switching some workers from jobs that have large reserves of time to performing jobs that are on the critical path. The network diagram is shown in Fig. 3.1.

Rice. 3.1. Network diagram for a complex of design and construction works

Calculations of the main parameters of the network diagram can be performed using electronic computing technology.

Based on arrays of data on the composition of products, calculation of material consumption rates, routes for manufacturing parts and assembling assemblies, the complexity of obtaining finished parts and assembled assemblies, they make up network schedule for completing the work of this project.

Drawing up a network diagram is designed to ensure:

• identification and analysis of all relationships that exist between project activities;
• preliminary analysis of the results of plan options and justification for the adopted plan;
• timely receipt of information about the actual state of affairs and concentration of the project managers’ attention on leading work;
• timely adjustment of operational work plans, thereby implementing the principle of continuity of planning;
• more efficient use of labor resources.

List of network schedule events:

• 1. The technical specifications and feasibility study for the project have been approved.
• 2. The electrical circuit diagrams of the device have been developed.
• 3. Design documentation for the device has been developed.
• 4. Technological processing of design documentation was carried out.
• 5. Materials and components were purchased at the request of the development departments.
• 6. Design and technological preparation of production was carried out.
• 7. A prototype of the device was manufactured.
• 8. The device has been debugged.
• 9. The mechanical part of the device was debugged.
• 10. Preliminary tests of a prototype device were carried out.
• 11. Acceptance tests of the device have been carried out.

The implementation of this task in the conditions of computer use is carried out on the basis of a network planning and management system (SPU). A specific expression of the SPU is a network diagram reflecting the logical sequence and interconnection of the project’s work.

To build a network diagram (Fig. 1), two logical elements are used: work and event.

Job- This is a process that requires labor and time. On a network diagram, work is represented by an arrow.

Event- this is the result of completing one or more works necessary to begin the next work.

An event on network graphite is depicted as a circle or rectangle (if the event corresponds to the end of the stage). All events are assigned a digital code from a natural series of numbers.

The numbering of events is carried out after constructing the network diagram and at the same time the logical and technological sequence of the project work is observed.

Rice. 1.

A chain of work in a network diagram, for example: 1-2-3-4 (see Fig. 1), in which the end of one job serves as the beginning of another, is called a “path”. Knowing the duration of each work of the network schedule, it is possible to calculate the duration of each path, and based on a comparison of all paths by duration, determine the path that characterizes the maximum duration of the entire technical preparation of production. This path is called critical.

In the network schedule, early and late deadlines for completing work and the occurrence of events are calculated, and time reserves for each work are calculated. An essential point in the network schedule is that all activities belonging to the critical path do not have time reserves, and therefore their untimely completion may cause the entire technical preparation of production to fail to meet the planned deadline. The management of technical preparation of production is built on this, i.e. at every moment the critical path is identified, and the work belonging to it becomes the object of attention of project managers.

The initial data for planning technical preparation for the production of new products is information about the following:

• project work indicating their interdependence;
• labor intensity and performers for each job;
• planned duration of the project.

Based on these data, a computer is used to create a network model, determine the timing and time reserves for completing each project work and the planned workload of the performers, and offer several options for the project execution plan. The resulting plan options are submitted for analysis to the project manager, who, together with the interested services, evaluates them.

The project plan that is finally accepted for implementation is approved by the manager and communicated to all performers, indicating the deadlines and time reserves for completing the work. In addition to the project plan, the workload of performers can be calculated based on the complexity of the work they perform.

At the stage of operational project management, periodic adjustments to project plans are made based on the actual state of work. For this purpose, factual information is identified about the work on the critical path, about the final completion of certain works during the reporting period. Based on the data received, the plan and workload of performers are adjusted.

Output documents from the computer are communicated to project managers, divisions of planning and project management, processing, storing and issuing information, and to responsible executors.

Network planning is a management method based on the use of the mathematical apparatus of graph theory and a systems approach to display and algorithmize complexes of interrelated work, actions or activities to achieve a clearly defined goal. The most famous are the almost simultaneously and independently developed critical path method - MCP and the method of assessing and revising plans - PERT. They are used to optimize the planning and management of complex, branched sets of work that require the participation of a large number of performers and the expenditure of limited resources. The main goal of network planning is to reduce project duration to a minimum. The task of network planning is to graphically, visually and systematically display and optimize the sequence and interdependence of works, actions or activities that ensure the timely and systematic achievement of final goals. To display and algorithmize certain actions or situations, economic and mathematical models are used, which are usually called network models, the simplest of which are network graphs. With the help of a network model, the manager of a work or operation has the opportunity to systematically and on a large scale represent the entire progress of work or operational activities, manage the process of their implementation, and also maneuver resources. The most common applications of network planning are:

• · targeted research and development of complex objects, machines and installations, in the creation of which many enterprises and organizations take part;
• · planning and management of the main activities of development organizations;
• · planning a set of works to prepare and master the production of new types of industrial products;
• · construction and installation of industrial, cultural and residential facilities;
• · reconstruction and repair of existing industrial and other facilities;
• · planning the training and retraining of personnel, checking the implementation of decisions made, organizing a comprehensive audit of the activities of enterprises, associations, construction and installation organizations and institutions.

The use of network planning methods helps reduce the time required to create new facilities by 15-20%, ensuring the rational use of labor resources and equipment.

In network modeling of construction production, two main concepts are used: network models and network graphs. Network models vary depending on the nature of the construction project, goals and a number of other indicators. Network models are classified according to the following main characteristics:

• 1. by type of purpose - single-purpose and multi-purpose models (for example, during the construction of various objects erected by one construction organization; 2. by the number of objects covered: private model and complex (for example, for one object and for the entire industrial complex of the plant);
• 3. by the nature of estimates of model parameters: deterministic (with pre- and fully conditioned data) and probabilistic (taking into account the influence of random factors);
• 4. models taking into account the target orientation (time, resource, cost).

The elements of the network diagram are (with the “vertices - events” type):

• 1. work - a process that requires time and resources (for example, digging pits, concreting foundations, installing columns, etc.;
• 2. event - the fact of the completion of one or more works, necessary and sufficient for the start of one or more subsequent works, which does not require the expenditure of either time or resources (for example, the completion of digging pits, concreting foundations, installing a roof, etc.);
• 3. waiting - a technological and organizational break between work, requiring only time (for example, hardening concrete, drying plaster, etc.);
• 4. dependency (or fictitious work) - an element of the network schedule that is introduced to reflect the correct technological relationship between the works, which does not require the expenditure of either time or labor of performers (such as the completion of digging a trench on the 1st section and the possibility of starting laying the foundation blocks on the same capture);

The following designations are accepted for the elements of the network diagram: Works and expectations are depicted by solid lines with arrows directed along the technological process (from left to right); events are represented by circles, and dependencies are represented by dotted lines with arrows. Events are numbered with one number, and jobs are numbered with two (the number of the preceding and subsequent events).

The length of the lines with arrows can be taken arbitrary, but sometimes the network diagram is built on a time scale, i.e. tied to calendar days of work. The name of the work is indicated above the arrow, and the duration of the work (n) is indicated below the arrow.

Elements of the network diagram are shown in Table 3.

Table 3 - main elements of a network diagram.

Network planning systems are a set of graphical and calculation methods, organizational and management techniques that allow modeling of complex processes for creating new equipment and operational management of the progress of work on its creation. The main planning document in the network planning system is the network schedule.

Building a network diagram. In the network model, events are indicated by circles, jobs - by arrows. The constructed graph must have one initial and one final event. An event is an intermediate or final result of one or more activities. It does not have a duration in time, but indicates the beginning of some work and can simultaneously be the completion of others.

Work in a network diagram refers to any process that requires labor; waiting, requiring a certain amount of time; a dependency indicating that the start of a given job depends on the completion of the previous one. Graphically, the work is indicated by a solid arrow. An arrow that expresses only the dependence of one job on another is called a fictitious job and is indicated by a dotted line. It has a zero time rating. Work requires a lot of time. The duration of work in days (weeks) is indicated above the arrow.

During the calculation of the network diagram, the following parameters are determined; duration of work and critical path; the earliest and latest dates for the occurrence of events and completion of work; all types of time reserves for work and events that are not on the critical path.

Any sequence of activities connecting the initial event with the final event is called a path. The path with the longest duration of work is called critical and is depicted with bold arrows.

Activities on the critical path have no slack. Therefore, failure to meet deadlines for any work on the critical path leads to a delay in the overall deadline for completing the entire complex. Activities that are not on the critical path have a slack time.

Before determining the critical path, it is necessary to calculate the early and late dates for the completion of events, as well as the reserve time for each event. Events with zero time reserve will indicate the passage of the critical path. The early date of the event (t p j) characterizes the earliest possible date for the occurrence of an event. The duration of its completion is determined by the longest segment of the path from the initial event to the one under consideration. The early period of events is defined as follows:

where is the early date of completion of the subsequent one; - early date of completion of the preceding event; t ij is the duration of work ij connecting event i with event j.

The late date for the completion of an event t i PP characterizes the date of the latest permissible period for the completion of an event. The late dates for the occurrence of events are determined by the following formula:

where is the late time of the previous event; -late time of the subsequent event.

If the calculation of the early dates for the completion of an event is carried out from left to right, from the initial event to the final one, then when determining the later dates for the completion of events, the calculation must be carried out from right to left, from the final event to the initial one.

The slack time of an event is the difference between the late and early dates of the event:

The time reserve for events shows by what maximum permissible period of time the completion of an event can be delayed without causing the danger of missing the deadline for the completion of the final event. If the reserve is fully used, the event will fall on the critical path. Algorithms for calculating other parameters of the network diagram are summarized in Table. 8.4. If the deadlines for completing all work do not meet the guidelines, it is necessary to optimize the network. For these purposes, it is possible, firstly, to increase the number of performers, and secondly, to redistribute labor resources by switching some workers from jobs that have large reserves of time to performing jobs that are on the critical path. The network diagram is shown in Fig. 8.1.

Table 8.4

Formulas for calculating network model parameters

An important task is to determine the amount of time required to complete all the work on the network schedule. If the labor intensity standards for design and engineering work are known and the number of workers employed in them is calculated, the duration of each work is established according to formula 8.2. If there are no standards, the minimum tmin, maximum tmax and the most probable tnv time estimates are obtained from the manager or responsible performer of the work. These values ​​are the initial values ​​for calculating the expected time t cool, which is the mathematical expectation of a random variable, in this case the duration of work.

Rice. 8.1. Network diagram for a complex of design and construction works

To more fully characterize the distribution of a random variable, the concept of dispersion is used. If the variance is small, then there is greater confidence about when the work will be completed.

With the law of distribution adopted in the network planning system

Table 8.5

Calculation of network diagram parameters

"St. Petersburg State Technological Institute

(Technical University)"

UGS (code, name)_____________________________________________

Specialty (specialization)_________________________________

Faculty_____________________________________________________

Department ______________________________________________________________

COURSE PROJECT

Topic: “Network planning and management of technical training

production of new products using the example

Student _________________ __________________

Supervisor,

job title ________________ ___________________

(signature, date) (initials, surname)

3) Subprogram for the design and manufacture of non-standard equipment and accessories;

4) Subprogram for technological development of production of new products to the specified design level.

For each subprogram, local network graphs are built, which are then stitched into a general network graph of the target scientific and technological program.

Decisions made under subprogram 1. Decisions under the subprogram provide for the use of high-tech technological processes; its implementation should begin after receiving fully revised technological documentation based on the results of testing prototypes of new products. Depending on the novelty of technological processes, decisions are made on the reconstruction of workshops and the layout of production areas.

The most important solutions for updating production technology should be considered the widespread use of CNC equipment in combination with robotic devices. Accordingly, the management system is also subject to change, as production becomes more flexible, focused on individual orders of product consumers. The primary organizational element in the management of flexible automated production (FAP) is a flexible production module (FPM), operating in autonomous mode. Several technologically connected GPMs and an automated transport and warehouse system (ATSS) form a flexible automated section (GAS). In turn, GAUs of different technological purposes, united by common production tasks, are included in the organizational structure of a flexible automated workshop (GAS).

In conditions of frequent changes in manufactured products, production flexibility is complemented by functional computer-aided design (CAD) systems and an automated system for technological preparation of production (ASTPP). At the same time, the possibilities for the effective use of automated control systems depend on the information content of design and technological classifiers, determined by the level of continuity of design solutions in CAD.