What Is a Maintenance Checklist?

Bill of Material (BOM), which uses computer-assisted production management. First of all, the computer must be able to read out the composition of the products manufactured by the enterprise and all the materials to be involved. In order to facilitate the identification of the computer, the products expressed in diagrams must be displayed. The structure is transformed into a certain data format. The file that describes the product structure in the data format is the bill of materials, which is the BOM. It is a technical file that defines a product structure, so it is also called a product structure table or a product structure tree. In some industrial areas, it may be called "recipe", "element list" or other names.

BOM

(Bill of Materials)

What are the forms of BOM?

Divided by purpose

The product has to go through three stages of engineering design, process manufacturing design, and manufacturing. Correspondingly, in these three processes, a bill of materials EBOM, PBOM, and MBOM with very similar names but very different contents are generated. These are the three main BOM concepts.

Engineering BOM-EBOM (Engineering BOM):

A data structure used in product engineering design management, which usually accurately describes the design indicators of a product and the design relationship between parts. The corresponding file forms mainly include product detail lists, pattern catalogs, material quota details lists, various product classification details lists, and so on.

Plan BOM-PBOM (Plan BOM):

The process engineer redesigned EBOM based on the factory's processing level and capabilities. It is used for process design and manufacturing management. Using it can clearly understand the manufacturing relationship between parts, track how parts are manufactured, where they are manufactured, who manufactures them, and what they use. At the same time, PBOM is also one of the key management data structures for MRP / ERP production management.

In fact, BOM is a broad concept. According to different uses, there are many types of BOMs; BOMs on design drawings, planned BOMs, calculated manufacturing BOMs for final product assembly, calculated cost BOMs, maintenance and repair BOMs, etc. Depending on the application focus at different stages, we often see different BOM references. The common ones are:

Design BOM-DBOM (Design BOM):

The DBOM of the design department is the overall information of the product, and the corresponding common text format expression forms include product details tables, drawing catalogs, material quota details tables, and so on.

The design BOM information source is generally the title bar and detailed bar information in the package design drawings provided by the design department. Sometimes it also involves some information on the process card prepared by the process department.

The design BOM is generally generated at the end of the design. If there is a large number of borrowing relationships in the design situation, the design BOM can be basically summarized at the beginning of the design phase, and then the design tasks are arranged according to the newly generated parts.

The corresponding electronic view is often in the form of a product structure tree, and each node on the tree is associated with various attributes or graphical information. It appears mainly in PDM software as the basic data for product management and drawing management.

Manufacturing BOM-MBOM (Manufacturing BOM):

The MBOM of the production department is based on the EBOM and is perfected according to manufacturing and assembly requirements, including processing parts JBOM and PBOMs such as blanks, molds, and fixtures according to process requirements. It can also be called process BOM. Corresponding to common text format expressions include process table, key process summary table, important parts and key parts list, self-made parts list, general parts list, general purpose tooling list, equipment list and so on.

The source of manufacturing BOM information is generally prepared by the process department, but the design BOM should be used as the basic data content.

Corresponding electronic views are often the assembly process BOM form for product parts, and the specific process BOM form for parts. Most of them are machining process BOM or production process flow route process BOM, etc. Each node on the tree is associated with tooling, equipment, Process information such as man-hours, processing diagrams, etc. The larger value to the enterprise is the assembly process BOM, which appears mainly as the basic data of production planning in ERP software.

Customer BOMCBOM (Customer BOM):

The customer BOM actually has two meanings, one is to select the product catalogue ordered by the customer from all product organizations. A detailed list of products with specific specifications ordered by the user. This is mainly a practical expression for some companies that manage and organize product drawings according to customers. This situation is more common in the PDM system. In the ERP system, because the impact of different customers' ordering products on the production plan is also considered, the situation is more complicated, and it may be extended to the scope of planning BOM.

Sales BOM-SBOM (SALE BOM):

The sales BOM is a part of the product structure that is configured according to user requirements. Corresponding common text format expressions include basic parts list, general parts list, special parts list, optional parts list, replacement parts list, special request change notice, etc. In some manufacturing industries, higher requirements are placed on the sales BOM, requiring each BOM to track the material information of each batch in the entire life cycle, and each customer order has a unique or based on the product type of the order How much is determined by several sales BOMs. At this time, the sales BOM is often referred to as the customer BOM.

The sales BOM information source is generally a summary of detailed information of different types of components of different specifications for a series of products.

The corresponding electronic view is often in the form of a product configuration tree, and each node on the tree is associated with various attributes or graphical information. It appears mainly in PDM software as the basic data for product configuration management.

Repair BOM-WBOM:

The maintenance service department is generated according to the maintenance requirements, and the corresponding text format includes a list of consumable parts, a list of spare parts, a list of vulnerable and consumable parts, and so on.

The maintenance BOM information source is generally obtained by filtering the design BOM corresponding record attributes to obtain details of consumables, spare parts, and consumables.

Generally, the summary is completed in the PDM software, and it can also be used as the basic data in the ERP software.

Purchase BOMCBOM:

It is produced according to production requirements of purchased raw materials, standard parts, and complete sets of parts. The corresponding text format mainly includes the purchased parts list, the contracted parts list, the self-made parts list, and the material list summary table.

The source of purchasing BOM information generally comes from the information summary on the design drawings and process cards. The purchasing department or production preparation department arranges the purchasing plan and production plan according to it.

The PDM system can generally summarize the corresponding procurement BOM information according to the drawings and process information, but if you want to obtain dynamic procurement BOM information for product batches, you must complete it in the ERP system. For example, a batch of 100 purchased BOMs and a batch of 10,000 purchased BOMs may have significant changes in outsourcing and outsourcing. Some parts may have a relatively low outsourcing cost when the batch is small, but they can be completed by themselves when the batch is large.

Cost BOMCBOM (Costing Bill Of Material):

It is produced by MRP system. After the enterprise defines the standard cost, recommended cost, and current cost management standards for the part, the system automatically generates the CBOM by accumulating the PBOM and the machining center. It is used for manufacturing cost control and cost variance analysis.

Among them, sales SBOM = processing JBOM + purchasing CBOM,

Production MBOM = processing JBOM + PBOM + purchasing CBOM,

Among them, the most closely integrated is EBOM controlled by PDM and MBOM in MRP

According to the design software, the BOM design department in CAD is both the designer and the user of the BOM. Single piece of information such as drawing number, material name (material type such as 45 steel), weight, volume, design modification review number, material effective date and other information; components or parts also include outsourced parts, outsourced parts, general parts, Standard parts, borrowed parts, assembly quantity of each single part, part drawing number and other information; general drawings (assembled from parts, component parts, etc.) also include packaging, assembly list, technical documents, product manuals, warranty sheets, etc. These are all part of the BOM information. In the design department (CAD), the BOM generally referred to is actually a parts list, which is a kind of technical file, focusing on product information summary. The design department organizes BOM information according to the drawing number of a certain type of product. After receiving the order, the design department has three design ideas in generaltop-down design, bottom-up design, and middle-to-two-end design. Regardless of which design method, the organization of the drawing number is consistent, and the product information is combined according to the drawing number to form the product's general list, standard parts summary form, purchased parts summary form, and outsourcing parts. Summary tables, etc. can also generate product drawing catalogs when needed (to meet customers or subcontracting factories that do not run ERP systems). Sometimes the same part has different drawing numbers because it belongs to different products, so it is not necessary to consider the uniqueness of the company's material code. It should be noted that after forming the bill of materials, each material has a unique code, which is the material number. Do not confuse the parts list (CAD is commonly referred to as the BOM) with the BOM information in the ERP. The parts detail information table in the design department is converted into the BOM information in the ERP system. It requires the collaboration of the design department, the process department and the production department, and the management of PDM (product data management) design product relationship characteristics to solve the parts detail list and BOM. Similarity and difference information between tables, especially the inconsistency between drawing numbers and coding numbers (PDM product structure module completes its functions such as rule base, variables and parts list). In terms of use, whenever the product structure changes, or the customer changes technical documents, involves quality issues, or redesigns a part, to ensure the accuracy of the bill of materials, the design change notice must be in accordance with. Under the guidance of the design change notification document, the design department obtains the information of all parts and their mutual structural information through the BOM information table. Only with this information can you define, describe or modify it so that production can continue to run normally (especially for customers' urgent change notifications). According to the design change notification number, with the support of PDM, the change information can be easily retrieved to guide production activities such as production, shipment and after-sales service. In the actual production and operation process, design changes are important factors that lead to inaccurate data. Therefore, there must be a set of effective design change notification management methods to manage design change notifications. Since sales, procurement, production, engineering technology, and finance departments are involved, the design change notification is generally directly managed by the senior executive of the enterprise. This process must go through five steps of design change notification confirmation, analysis, approval, documentation and supervision. Part of the data generated by the design department (CAD) is transmitted to the ERP system after PDM processing. There are several concepts that need to be added in designing the BOM: The components of the components on the product structure tree can be divided into three types: standard components, structural components, and design components. The design component generation method can be generated from different 3D CAD or 2D CAD schedules, and is produced by our factory or cooperative factory design. Structural components can be photos or a simple sketch. The names of the nodes on the corresponding product structure tree are often product outline drawings, product size chain diagrams, product assembly relationship diagrams, packaging components, and so on. This information must be reflected in the product structure tree of many enterprises, but it cannot be obtained from the final assembly drawing. For example, product outline drawings and product assembly drawings are acceptable if they are hung on product nodes, but users are often used to thinking that product outline drawings It is at the same level as the product assembly diagram; in addition, the packaging sub-tree needs to be manually created and expanded after packaging, and cannot be directly linked from the detailed list through BOM expansion. Common parts include standard parts libraries and industry and enterprise common parts. And can be modified, deleted and merged, join the common parts library to be carefully tested. Universal parts can evolve from borrowed parts. There are many different options for structural parts, sometimes even design parts or standard parts of the same product. Therefore, the same product in manufacturing and sales quotation can also have different product information structure combinations (such as price, volume, delivery time) for different customers. But these situations are generally maintained in the ERP system, as long as the PDM system guarantees the integrity and consistency of the underlying data. After the BOM product in the CAPP is designed by the design department, part of the electronic data is transferred to the process department to formulate the process route (CAPP), and it becomes a document that explains the part processing or assembly process. It is not a technical document, but a planning document or a guidance production document. CAPP generally consists of process information cards, processing procedure cards, forging heat treatment cards, test cards, tooling materials, and man-hours. In a processing procedure card, it consists of procedures (processing steps) and man-hour quotas (occupying work center load time). ), Processing equipment, testing equipment, processing tools, fixtures, materials, etc. When preparing the process plan, in addition to every nuance of the design, it also involves the main work center materials, material materials, processing fixture materials, tooling materials, and auxiliary materials in the BOM. Maintaining the accuracy of these static data is a prerequisite for ensuring that production runs as planned. The main work center's equipment maintenance, spare parts management, maintenance records, material procurement and inventory changes, processing fixtures, tooling equipment, auxiliary materials and other changes must be reflected in the process planning. During the process planning process, it is necessary to be able to browse the BOM information at any time (object-oriented), enter the BOM information, alarm the BOM information (the process compiler finds an error alarm), and reflect the updated BOM information in real time. Without the support of a computer system, high demands are placed on the craftsmen: they must not only be familiar with the current status of the part processing process and processing equipment, but also know the technical parameters, inventory, processing fixtures, tooling equipment, etc. Happening. Generally, it takes 20 years for a company to train a similar person. Now, with the support of the computer system, the craftsmen can easily query the typical process database designed according to the BOM structure, obtain design information, and query technical parameters such as machine tools and equipment. They can also easily compile CAPP to ensure the integrity of process documents. , Consistency, correctness and implementation feasibility. The data generated by the process department (CAPP) is transmitted to the ERP system after PDM processing. BOM in PDM PDM is actually the core module that connects CAD / CAPP and ERP. It manages product-related "Information (ERP)" and "Process (CAD / CAPP)" technologies. It plays the role of "Process (CAD / CAPP) ) "Technology to" Information (ERP) ", the important intermediate process of" Information (ERP) "to" Process (CAD / CAPP) "technology, forming a two-way seamless transmission of data to avoid the generation of a large amount of coincident data . The following figure is a diagram showing their structure. Because different departments have different forms of BOM information, companies often need to spend a lot of manpower and time to complete these reports, and they must constantly maintain BOM consistency to avoid serious MRP calculation errors. A manual entry method originally adopted by a Sichuan Electric Appliance Co., Ltd. entered the BOM information counted from the CAD department. It takes about one week for a skilled entry person to enter the BOM data of a product, excluding the rework time and This has caused a bad impact; it now takes just a few minutes to automatically transfer BOM data for the ERP system via PDM. Structure relationship diagram Throughout the product's entire life cycle, PDM takes the data warehouse (all systems can share a database) as the underlying support, and uses the bill of materials (BOM) as its core to connect all engineering data and documents that define the final product to achieve Organization and management of product data, such as product configuration management, diagram document management, workflow management, design change management, authority (role) management, version management, project management, maintenance records, log management, and so on. PDM systems are divided into three categories according to their respective functional characteristics and the different engineering problems they can solve, namely: focusing on documents and data management; focusing on design process and product structure management; CAD-oriented; hardware- and software-oriented Architecture system integration platform. The second type is the most closely related to BOM information. After transformation, BOM information required by ERP is achieved. Today, most popular PDM systems can be integrated with ERP systems, and some ERPs also have their own PDM products, which effectively promotes communication and exchange among various departments in the ERP system such as production, design, procurement, and sales. BOM in ERP In addition to the system described above related to BOM, the production department, product costing department, material requirements planning (MRP) system, and sales department also have a great relationship. The production department uses the BOM to determine the manufacturing of parts or final products Method to determine the bill of materials to receive; the product costing department uses the current cost of each self-made or purchased part in the BOM to determine the cost of the final product and maintain the product cost, which is beneficial to the company's business quotation and cost analysis; material requirements The BOM in the planning (MRP) system is one of the main input information of the MRP. When using the BOM to determine the main production planning project, it dynamically determines the net demand for materials, knows which homemade and purchased parts are needed, how much, when, Analysis of the differences between standard materials and actual materials; sales departments can access data sources through the Internet, can easily quote, provide accurate self-service information such as part design information and track manufacturing processes, customers can also place orders to purchase product spare parts. With BOM information, you can also easily evaluate the performance of various departments, and you can easily extract information for statistics and analysis. If you have new BOM data requirements, you can also use the original BOM data to construct new BOM data, simplifying approximate BOM data. If you research the BOM information in depth, you can also study the error checking of the BOM information of other products through different product BOM information, so as to avoid errors caused by computer input or modification, and minimize the error rate. BOM is the foundation in any management system. It has relations with almost all functional departments in an enterprise. Without BOM, the same product cannot be manufactured, which directly affects the processing performance and use effect of the system. Therefore, to improve the efficiency of the production management system, it is very important that the BOM is correct. Although the data is already very accurate, do not ignore the importance of people. For special changes, you can manually add, delete, and modify the content of the BOM information in the system to complete the task smoothly. Through the establishment of two main lines of enterprise "information (ERP)" management and "process (CAD / CAPP)" technology, BOM is the information link, PDM is the core, and CAD / CAPP and ERP systems are combined, supplemented by the Internet and EDI systems , You can really achieve the goal of enterprise information construction

What are the forms of the product structure tree?

In order to facilitate the convenience of computer management and processing, various BOM lists must have some reasonable organizational form. The graphical display of this BOM is often designed in the form of a product structure tree, and in order to facilitate the use of the product structure tree in different situations The product structure tree should also have multiple organizational forms and formats.

After the product structure data is entered into the computer, it can be queried and displayed according to the different formats of each user. The goal of various information systems is to enable the input data to generate product structure trees in various formats to meet the needs of various users in the enterprise. The product structure tree generally has the following common output formats.

Figure 1 shows the product structure of A. Layer 0 is product A; A is composed of B, 10. C is composed of B, 10, and C forms the first layer; B is composed of 20 and D, C is composed of 30, 40, 50, and 20, D, 30, 40, and 50 constitutes the second layer D is composed of 10 and 30, and 10 and 30 form the third layer. In the figure, the letters indicate the assembly, the numbers indicate the parts, and the numbers in parentheses are the required quantities for assembly.

Figure 1 Structure of Product A

For products such as A, the following BOM output formats are available.

Common BOM forms

Single-stage expansion BOM

The single-level expanded format displays subordinate components used by an assembly. Using multiple single-level expansions can fully represent the multi-level structure of the product. The grouping list corresponding to many enterprises (especially those with a large number of product parts) is the specific form of single-level BOM. The following table gives a list of four single-level expansions given the four-level product structure.

Multi-level expansion BOM

Multi-level expanded BOM displays all sub-components used by an assembly. A multi-level expansion can fully represent the multi-level structure of the product. The product list corresponding to many enterprises (especially those with relatively few parts) is the specific form of multi-level BOM. The following table is a multi-level expanded BOM for the given four-level product structure.

Indent

The indented expansion format is to list their subordinate items in indented form under each upper level item. All part numbers on the same level are displayed on the same column. The indented format is used to represent products in the way they are manufactured.

Roll up

The summary expanded format lists the total quantity of all materials that make up the final product. It reflects the total number of various parts required for a final product. Rather than the number of parts required for each upper level. If a part is used in more than one assembly, a consolidated list can help determine the appropriate purchase quantity. This format does not indicate the way the product is produced, but it is good for product costing, purchasing and other related activities.

Single layer tracking

The single-layer tracking format shows the upper-level materials that directly use an item. This is a list of where the material is used, and it indicates the upper-level materials that directly use a material.

Summary tracking

The format of the summary track shows all high-level items with parts and the number of parts used for each item. This is an expanded "where used" list, which lists all high-level materials containing parts. "Required Quantity" indicates the total number of parts required to assemble the material for that level.

Indented tracking

The abbreviated tracking format indicates the use of a part in all high-level materials. It finds all high-level materials that use a part directly or indirectly, and this format is valuable. The following table shows:

Matrix BOM

A matrix BOM is a type of BOM obtained by combining data for a product series with a large number of common parts. This form of BOM can be used to identify and combine common parts in a product line. In the following output format, various common parts are listed on the left, and each final product is listed on the upper right. The numbers below indicate the number of parts required to assemble a final product. "#" Indicates that this product does not use this part. This form of BOM is useful for products with many common parts. However, the matrix BOM does not specify the manufacturing method of the product, it does not indicate the assembly level between the parts, so it cannot be used to guide the manufacturing process of multi-layer structure products.

BOM

Such BOMs are sometimes referred to as "comparative" or "different and similar" BOMs. It is based on standard products and specifies which parts can be added or removed. A specific product is described as a standard product plus or minus certain parts. The following table shows that the special product A / 1 is made by adding parts F and G to the standard product A, increasing the number of parts C to two, and removing parts 1-1-1. This method can effectively describe the differences between different products, but it cannot be used for market forecasting and is not very suitable for MRP.

Modular BOM

In practical applications, because product specifications are changeable, the parts list can be divided into the following types according to the product structure characteristics:

The product is single and the specifications are basically unchanged.

Various product specifications, you can choose to assemble

Products are serialized, but performance changes in the same series.

Different product series, multiple options for assembly.

Modular BOM is used for complex products made from many common parts and in many combinations. For example, in the automotive industry, different engines, transmissions, bodies, components, decoration and other things can be selected to assemble a car. Different options can be combined into different end products. The modular approach not only provides customers with a wide range of choices, but also reduces parts inventory. This method has been widely used in the automotive and agricultural equipment industries. When there are many optional features on a production line, many combinations can be obtained, and it is impossible to predict them separately in the main production plan. If according to the needs of MRP, a separate BOM is stored in the computer for each final product. The cost of storing and maintaining file records is significant. The solution to this problem is to use a modular BOM. The modular BOM builds modules according to the requirements for assembling the final product. The process of modularization is the decomposition of products into low-level modules. Forecasting according to these modules is more accurate than forecasting the final product directly. Modularization can serve two different purposes:

Can get rid of the trouble of combining optional product features;

Distinguish common parts from special parts.

BOM integration

In many companies, rebuilding traditional BOMs can greatly simplify master production planning. If the lead time of the order is shorter than the production lead time of the product, the demand is forecasted in the master production plan. Most enterprises use two methods to organize production, one is to prepare for production, and they plan according to the forecast; the other one organizes production according to user orders in the short term, and the rest is planned according to the forecast. The product must therefore be defined in a form that can be predicted in the production plan. Obviously, the final product is not the best predictor in the order-to-production environment. Some special BOMs are needed to link the master production plan with some related parts, which must be obtained before receiving the customer order. The BOM for planning performs this function, which reduces the number of items in forecasts and master production plans.

The planned BOM is based on the needs of the MRP, separating the products at level 0 from the BOM, and raising the components at level 1 or lower to the status of the final project. In this way, a new modular BOM for planning is established, which can meet the needs of forecasting, master production planning and material requirements planning.

The manufactured BOM enumerates the optional features necessary to manufacture the final product. It is only a BOM that aggregates independent modules in order to meet customer-selected products or warehouse orders. This BOM is generally not directly attached to the MRP system, but defines the required materials through the overall assembly schedule, and is related to The MRP system is integrated as long as these materials are planned and supplied using the MRP system.

In any manufacturing environment, different departments and systems use BOMs for different purposes (the BOMs below are different types in meaning and are collectively expressed as BOMs), and each department and system gets specific data from the BOM. The main BOM users are:

Design department

The design department is both the designer and the user of the BOM. As far as use is concerned, whenever the product structure changes or a certain part is redesigned, the department must obtain the information of all parts and their mutual structural information from the BOM. Define, describe or modify it.

craft department

The process department establishes the manufacturing process and assembly process for each part based on the BOM information. And determine the tooling, molds, etc. that should be used in the manufacturing process.

Production department

The production department uses the BOM to determine the manufacturing method of the part or final product, and to determine the bill of materials to be collected.

Product Costing Department

The department uses the current cost of each homemade or purchased part in the BOM to determine the cost of the final product.

Material requirements planning (MRP) system

BOM is one of the main input information of MRP. It uses BOM to decide which self-made and purchased parts are needed, how much and when.