Bill of MaterialsBill of Materials (BOM for short) describes the composition of enterprise productsTechnical documents。In the processing capital industry, it indicates the general assembly, sub assembly, componentsparts、spare parts, the structural relationship up to the raw materials, and the required quantity.
In the chemical, pharmaceutical and food industries, the product composition describes the main raw materials, intermediates, auxiliary materials and their formulas and required quantities.BOM is to change the product composition represented by the figuredataIn the form of a table, it isMRPIICalculation in the systemMRPImportant control documents in the process.
List of all sub assemblies, intermediate pieces, parts and raw materials constituting the parent assembly, including the quantity of each sub item required for assembly.The bill of materials and the master production plan work together to arrange the issue of the warehouse, the production of the workshop, and the type and quantity of the parts to be purchased.Bill of materials can be described in many ways, such as single-layer method, indentation method, module method, pause method, matrix method and cost method.In some industrial fields, it may be called "formula", "element table" or other names.
BOM is amanufacturing enterpriseThe bill of materials is the core document of the.Depending on the purpose or characteristics of use, the bill of materials has many forms, such as single level BOM, multi-level BOM, percentage planning BOM, modular BOM, manufacturing BOM, and virtual BOM.
definition
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BOM in narrow sense(Bill of Materials) is usually called "bill of materials", which is the product structure.It only describes the simple decomposition of the physical structure of materials according to certain division rules, and describes the physical composition of materials.Generally, it is divided and described hierarchically according to functions.
BOM in a broad senseIt is the combination of product structure and process flow, and they are inseparable.It is of no practical significance to talk about product structure without technological process.To describe a manufacturing product objectively and scientifically through BOM, we must start with the manufacturing process to accurately describe and reflect the product structure.
formula
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BOM （Bill of Manufacturing）=technological process(Routing) (=set of operations)=Work CenterCollection of materials)+equipment and personnel of work center+Prod. Structure (=collection of materials)+cost information of materials
structure
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Figure 2 BOM Type
Bill of materials (BOM for short) is used to describe the final productspare partsWhat is the relationship between the time and quantity of these parts and components composed of raw materials.For example, as shown in Figure 1 and Figure 2 on the right, as shown in Figure 1 on the right, the final product A consists of three parts B, C and D, while B consists of a and b, and D consists of b and c.This kind of product structure is reflected in the time structure. Then, take the due completion date of the product as the starting point to reverse the plan, and the latest processing time or purchase order issuing time of each part can be calculated accordingly, as shown in Figure 2.It can be seen from this figure that due to the processing of various parts
Procurement cycleDifferent, i.e. calculated from the reverse schedule of the completion dateLead timeDifferent, when the production task of a final product is determined, the order release date of each part still exists first.That is, under the principle of guaranteeing the matching date,production cycle Order the longer materials first, and order the shorter materials later, so that all materials can be prepared when needed;Do not feed materials too early before they are needed, so as to reduceInventoryAnd the purpose of reducing the occupation of funds.
type
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BOM type (standard, model, plan, option)
1. Standard BOM: the BOM of standard materials.Standard materials refer to materials included in the bill of materials other than planned materials, options or models, such as purchased partsSelf made parts、Outsourced partsEtc.The standard bill of materials is the most commonly used list type, which lists legal sub items, the required quantity of each sub itemWIPControl information, material planning and other functions.
2. Planned BOM: the BOM of planned materials.Planned material
Planned bill of materials (bicycle)
It represents the material type of a product family. Its bill of materials contains sub item materials and sub item plan percentages.The plan list can be used to help execute the master plan and/ormaterial requirement planning。
3. Model BOM: the BOM of model materials.Model material means that when ordering the material, its bill of materials lists the options and types of materials that can be selected.The model BOM lists the option classes, options, and standard materials of the model. Different product configurations can be ordered in the sales system according to customer requirements.Model list can be assembled to order（ATO: Assemble to order) or select by order（PTO: Pick to order) type, the difference between ATO and PTO models is that ATO needs to be matched and then release a production order to complete assembly before shipment, while PTO will be shipped directly according to the selected components.
4. Option BOM: the BOM of option materials containing a series of related options.Option class is a classification of optional sub components in the bill of materials.As a material, the option class becomes a level in the model BOM.
(It can be model+option class or model)
Virtual part: a virtual part is an assembly without inventory. It can combine the materials required by its parent part to generate a sub assembly.The MPS/MRP system can be directly expanded to the sub parts of the virtual part through the virtual part, as if these sub parts are directly connected to the parent part of the virtual part.Application: As a common part, the bill of materials is easy to maintain, the product structure is clear, and the workload is reduced.
Public BOM: Any two materials with the same list type can share a common BOM.If two different materials share the same list, only one material list needs to be defined, which can be shared by another material
BOM Structure Diagram (Bicycle)
The two materials should have the same BOM type.When defining a bill of materials for a new parent part, another parent part can be referenced as a public bill of materials without entering any information in the bill of materials, which saves input time and facilitates maintenance.
Several main BOMs in the product development stage
The product development process is divided into engineering design, process design, prototype trial production and other important stages according to the realization function.In the application of PDM system, according to the requirements of product structure management at different stages, multiple types of BOMs will be generated to represent the product composition form and the values of related attribute items from different aspects, so as to realize the management and use of product data.
In the process of product formation, BOM types generally refer to entities in object form as material items. BOM is a formal representation of the structural relationships between material items (including assembly relationships, processing relationships, benchmark dependency relationships, and exchange relationships).At different stages of product development, each department designs, uses and maintains its own BOM for different purposes, and obtains specific data from it.Design BOM, process BOM and manufacturing BOM are the three main BOMs used in product development.
(1) Design BOM, also known as engineering BOM (EBOM), is generally generated by the product design department according to the product assembly system diagram and the product parts list to describe the product design structure.The product assembly system diagram illustrates the design and assembly relationship between the parts that make up the product, and the product parts list specifies the types of parts, such as general parts, standard parts, self-made parts, purchased parts and outsourced parts.EBOM is the basis of product data required by process, manufacturing and other application systems. Common text forms include product list, drawing catalog and material quota list.
(2) Process Planning BOM (PPBOM)
On the basis of EBOM, the process design department decomposes the process of the product structure, establishes the assembly process of the assembly parts and the manufacturing process of each part, and determines the tooling and molds that should be used in the processing and manufacturing process.PPBOM is generated after the redesign of EBOM according to the processing level and capability of the factory. Using PPBOM can clearly understand the manufacturing relationship between parts, track where the parts are manufactured, by whom, with what and other information. Its common text representation is the product process sub unit directory, etc.
(3) Manufacturing BOM (M BOM) The manufacturing engineering department has added the process flow (manufacturing and assembly process), tooling resources, raw materials, semi-finished products and other information formation of material items on the basis of PPBOM, reflecting the manufacturing method and assembly sequence of parts, assembly parts and final products, such as manufacturing, assembly process content and corresponding processing equipmentFixture, tool accessories, etc.It describes the manufacturing process of products in detail, and is the input information of enterprise resource planning (ERP) operation.The common text forms of this BOM are routing table, key process summary table, important parts and key parts list, self-made parts list, general parts list, general special tooling list and equipment list.
View structure conversion
Different types of BOM views are not constructed from scratch, but converted from existing BOM views.In PDM system, the key point of BOM view structure conversion is the conversion from design BOM to process BOM and then to manufacturing BOM.In the conversion process, different BOM views have different processing methods for various types of special components. Therefore, BOM view structure conversion mainly focuses on the processing of special components.By comparing various BOM view structures, it is found that the special components that cause the design BOM and process BOM to be heterogeneous are mainly related to key parts and outsourced parts, and the special components that cause the process BOM and manufacturing BOM to be heterogeneous are mainly virtual parts and process parts.The above special components are defined as follows:
(1) Key parts
In view of the process separation surface and other reasons, the assembly is generated by refining the parts that are too coarsely divided in the design BOM in the process of process decomposition.
(2) Outsourced parts
It is a part that needs outsourcing processing for itself and all its parts.The component to which it belongs will not appear in the process BOM.
(3) Dummy parts
A component that appears in the design BOM, is defined in the process BOM, but is not manufactured or stored in actual production.Dummy parts will be deleted in the manufacturing BOM.By dealing with virtual parts, manufacturing can be parallelized, so that resources can be effectively used when resources are sufficient.
(4) Process parts
Components that do not appear in the design BOM but need to be manufactured and stored due to process requirements in actual production will be added in the manufacturing BOM.At the same time, some components in the process BOM will be downgraded to the child components of the process part. These components are called process sub components in the process BOM.By processing process components, the manufacturing work can be serialized, thus saving resources in the case of limited resources.In the PDM system, the BOM view structure transformation mainly dealing with special parts is shown in Figure 1.The implementation process of the corresponding BOM view structure conversion is shown in Figure 2.In the conversion process, the design BOM, process BOM, and manufacturing BOM are three versions of the product structure at different stages of product development. BOM structure conversion is the process of generating a new version based on the existing BOM view version.Accordingly, in the conversion process shown in Figure 2,
Bill of Materials
Node N in the product structure tree also has three versions: NE, NP, and NM. Subscripts E, P, and M represent the design, process, and manufacturing versions of the node.In the whole process, various special parts need to be defined by design, process and manufacturing department personnel. When processing key parts, interaction with process personnel is required to obtain the subdivision information of key parts.
basic function
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The bill of materials is a technical description document of the product structure. It not only lists all the constituent items of the final product, but also shows the structural relationship between these items, that is, the hierarchical subordination relationship from raw materials to parts, components, to the final product, as well as the quantitative relationship between them.BOM is the core file of manufacturing enterprises. Different departments and systems use BOM to obtain specific data from BOM.
Design DepartmentAs the designer and user of BOM, you need to obtain the information of all parts and the mutual structure information from BOM;
Process departmentEstablish the manufacturing process of each part and the assembly process of the assembly parts according to the BOM, as well as the tooling and molds that should be used in the processing and manufacturing process;
Finance DepartmentDetermine the cost of the final product according to the cost of each self-made or purchased part in the BOM;
Quality Control DepartmentEnsure the correct production of products according to BOM;
Single level BOM expansion of front axle items
Maintenance DepartmentUnderstand the specific structure of the final product through BOM, and understand what is requiredspare partwait.It can be seen that BOM plays a very important role in the management of various departments of an enterprise;
The in-depth study of BOM functions is of great significance for the optimization and integration of various functions in business management.
Information management
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When computer aided production management is adopted, the first thing to do is to enable the computer to read theProduct compositionAnd all involvedmaterielAt this time, the BOM must be transformed from the traditional graphical representation into a data structure.For the convenience of computer processing and management, BOM must have some reasonable organization form;In addition, BOM is also an important interface between CIMS/MIS and subsystems such as CAD, CAPP, PDM, and is the key to system integration;Therefore, when using computer to manage BOM, it is necessary to fully considerinformation switchingQuestion.
In general, the following aspects should be paid attention to when building BOM:
1. In BOM, each item (part) must have a unique code.
2. For the convenience of management, sometimes different states of the same part can be regarded as several different project constructionsWIPIn the BOM.
3. According to the actual production situation, in order to strengthen the preparation of certain tooling and molds, these tools can also be built in the BOM.
4. In order to satisfy different departments to obtain different information of parts, it can be flexible
ERP2 management content
Design the attributes of each item in the BOM, such as plan, coststock, orders, etc.After the BOM data is input into the computer, it can be queried and displayed in different formats according to different requirements of users.The common output formats of BOMs are as follows: (1) Traditional BOMs include single level expansion, shrunk line expansion, summary expansion, single level tracking, shrunk line tracking, summary tracking, etc.
(2) Matrix BOM is used for a large number ofCommon partsIt is a BOM obtained after data consolidation of the product series of, which can be used to identify and combine universal parts in a product series.
(3) Comparative BOM is based on standard products and specifies which parts can be added or removed, which can effectively describe the differences between different products.
(4) Modular BOM can be used for complex products made of many common parts and with multiple combinations. Modules can be formed according to the requirements of assembling final products. Different final products can be combined through different module selections.
effect
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BOM is the core document of a manufacturing enterprise.The activities of each department need a bill of materials, and the production department needs to produce products according to the bill of materials,Storage RoomThe material shall be issued according to the bill of materials. The financial department shall calculate the cost according to the bill of materials. The sales and order entry departments shall determine the configuration of customized products through the bill of materials. The maintenance service department shall know what spare parts are needed through the bill of materials. The quality control department shall ensure the correct production of products according to the bill of materials,The planning department should plan the material and capacity requirements according to the bill of materials.
According to the requirements of the production plan, the enterprise inputs the inventory records and product structure, calculates the material demand by the computer, and outputs the production plan of parts, raw materials and purchased partsProcurement planAnd auxiliary reports, which are produced by enterprises
Tail BOM expansion of front axle main item
A basic mode of management.On this basis, on the basis of information sharing, conduct comprehensive management of business resources throughout the enterprisecustomer demandIntegrate with the manufacturing activities within the enterprise and the manufacturing resources of suppliers to form a completeValue chain, this isEnterprise Resource PlanningERP is an important symbol of enterprise management modernization.As a product structure data file that can be recognized by the computer, BOM is the leading document of ERP.As the most important basic data in the ERP system, whether the BOM is perfect and correct, whether the format design is reasonable, and how the functions are played directly affect the operation quality of the system.There are five types of BOM in the ERP system: indented BOM, summarized BOM, BOM for reverse query, cost BOM, and plan BOM.With the improvement of enterprise management level, people put forward higher requirements for BOM management and use, such as hierarchical BOM, customized BOM management, automatic BOM generation with PDM and other functions, and integration with process information and calculationDirect laborwait;The development and improvement of ERP system is also closely linked with solving the above problems.Therefore, BOM is the basis and key to implement ERP.The role of BOM can be summarized as follows:
（1）ERP systemTools for identifying individual materials.
(2) BOM is one of the most important basic data for MRP operation, and it is the key link for converting MPS to MRP.
(3) The routing of each material can generate the routing of the final product item through the BOM.
(6) It is the basis for the warehouse to match raw materials, parts and components.[1]
(7) It is the basis for processing and picking.
(8) BOM can contain cost information of each item. YesCostingImportant basis for.
(9) It is the basis for formulating product sales prices.
(10) It is a tool for quality management to trace parts, components and raw materials from the final product.
matters needing attention
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In order to make the ERP system run normally, the bill of materials must be complete and accurate.Otherwise, it is impossible to produce or purchase the right materials at the right time in the right quantity.This will cause a series of serious consequences:
1、date of deliveryThere is no guarantee and the level of customer service is low.
2. Increasestock, backlog of funds.Because the bill of materials is not accurate, in order to ensure the correctness of production
Multi stage material usage list of front axle tube
Frequently, the only measure that can be taken is to store more materials.
3、productivityLower.The production workshop cannot get the right materials at the right time and in the right quantity, and the production is always blocked.
4. Increased costs.The extra money was spent on unnecessary inventory. Expediting personnel ran around looking for materials to solve the shortage problem, and the cost of maintaining the bill of materials increased.
5. It is difficult for all departments in an enterprise to coordinate because the bill of materials is the basis for internal contact and coordination.
6. Affects employee morale.
7. Waste resources.Key resources include people, materials, capabilities, funds and time.Resources in any enterprise are limited, and correct bill of materials is the basis for effective use of resources.The benefits of establishing a list of main materials are very great.It is not only convenient for maintenance, but also lays a foundation for communication and coordination of various departments.
Many departments of an enterprise work according to a unified bill of materials.Therefore, among all the data, the bill of materials has the greatest impact on the enterprise, and the system has the highest requirements for its accuracy.In an enterprise that successfully uses ERP system, the accuracy of bill of materials should be more than 98%.If the bill of materials is not accurate, the result of running ERP will be completely meaningless.
test method
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(1) On site review: let the product engineer go to the assembly site to compare the actual assembly situation with the bill of materials.These engineers should work closely with the foreman and the assembler to correct errors immediately.
(2) Office review: form a team ofCheng Shi, foremanMaterial PlannerAnd a team of cost accounting personnel to jointly review the bill of materials.Correct any errors found immediately.
(3) Product disassembly: Disassemble a final product, compare the parts and their number with those listed in the bill of materials, and correct the errors found.This may be a good way.However, if the product is too large and complex, such as jet aircraft, this method may not be applicable.Another disadvantage is that it is difficult to identify sub assemblies.
(4) Unplanned issue/receipt: when the production personnel returnsStorage RoomWhen they go to get more parts, it may be because they have some waste products, or it may be because they didn't get enough at the beginning.In the latter case, there may be an error in the bill of materials, which may cause an error in the picking list.If some parts are sent back to the warehouse after a product is assembled, it is likely that these parts should not be taken away at the beginning.Similarly, the picking list error is caused by the BOM error.In both cases, once errors are found, they should be corrected immediately.This method is also a good method for continuous maintenance of material accuracy.
