Bill of Material (BOM)
Definition: To adopt computer-aided enterprise production management, the computer must first be able to read out the product composition and all the materials that the enterprise manufactures. In order to facilitate computer recognition, the product structure expressed in pictorial form must be converted into a certain data format. This kind of file that describes the product structure in a data format is the bill of materials, or BOM. It is a technical document that defines the product structure. Therefore, it is also called a product structure table or a product structure tree. In some industrial fields, it may be called "recipe", "element table" or other names.
1. Product structure-the importance of BOM
BOM (Bill of Material) is called the bill of materials, also called product structure table, material table, etc.
Disassemble the raw materials, parts, and assemblies of the product, and record each individual material in the order of the manufacturing process according to the material code, product name, specification, unit consumption, loss, etc., and arrange them into a list. This is the bill of materials. That is BOM.
BOM is:
(1) The basis of MRP.
(2) The calculation basis of the manufacturing order issued.
(3) It is essentially an engineering document, not only the specification of the product, but also the basis of the manufacturing process.
(4) The basis used to calculate product cost.
From the above, we know the importance of BOM and its wide range of influence, so its content must be kept correct and timely at all times.
2. Key points of establishing product structure
(1) BOM must be able to display the manufacturing level.
(2) BOM must avoid ambiguity.
The BOM must be able to show the manufacturing level. The
ideal BOM should not only show the specific structure of the product, but also indicate the stage of the product in the manufacturing process. That is, the BOM must define the product from the manufacturing level, each level represents the completion of a certain step in the manufacturing process, and each inventory item has the actions of inbound and outbound in the upper and lower levels of the BOM.
BOM must avoid ambiguity
. Unit nature of the job is the key. A batch of components, after assembly, becomes an independent unit and is a complete unit, and is sent to the inventory or the next workstation, so it is necessary to define a part number for this assembly. If the item number is not defined, MRP will not be able to generate the necessary orders for this component.
3. System file design of product structure
Although the product structure will have many levels, we record in a single-level manner in the system, and only need to maintain the two-level relationship between the parent item and the child item, and then connect them to obtain a multi-level relationship product structure.
The above is a four-level BOM. In the ERP system BOM data table, you only need to establish the relevant parent-child relationship to get the complete material table of the X product. As can be seen from the figure above, the child item of the upper structure becomes the parent item in the lower structure
BOM can be divided into many types.
(1) BOM for production
(2) BOM for sales
(3) BOM for packaging materials;
(4) BOM for customs.
1. BOM for production
In addition to explaining the relationship between parent and child, there are the following necessary fields, which are explained as follows:
(1) Serial number
Due to different processes or different effective periods or different plug-in positions, there may be multiple child items under each parent item. This situation cannot be explained by unit usage. Parent and child items may not be unique, so the same parent item is uniquely described by serial number. Due to the nature of the material or the priority of the issue, the sub-items are required to be arranged in a certain order, which is also achieved by serial numbers. When the BOM is expanded, it is also arranged by serial number.
(2) Unit consumption
Indicates how many children of the inventory unit are needed for each inventory unit parent item. The inventory unit of the material is defined in the material code data table.
(3) Base
Indicates the quantity of the parent item. For example, each carton (A material code) can store 100 watches (X), then the BOM indicates as follows:
Parent item: X serial number 1 Child item: A Unit usage: 1 Base: 100
(4) Loss rate
For some materials, due to machinery and equipment, or due to assembly, etc., the normal unit consumption cannot meet the needs of production, and the percentage of loss should be defined.
(5) Fixed loss
According to the wastage rate, different orders have different wastage and consumption. A small order has a small consumption and a large order. A large order also requires a certain loss. But sometimes even a small order requires a certain amount of consumption. Defined by fixed loss. That is: no matter how many orders, at least so much loss.
(6) Effective date and expiration date
Due to engineering changes or different product structures in different periods, the effective date and expiration date need to be specified. If it is always valid, do not specify the expiration date, or specify a large date, or let the expiration date = "1900/1/1"
(7) Sending process number
Each parent item defines a process route in the material code company data table, and each process route needs to define at least one process or multiple processes in the process route data table. Different sub-items of the BOM may be sent to the same process. , It may also be sent to different processes. Here is an explanation of which process should be issued when the child item is issued. When creating a manufacturing order to generate material details, if the process number is not specified in the BOM, the first process in the routing data table is regarded as the issuing process.
(8) Status
BOM has three states: To be confirmed, OK. When canceling the newly added BOM sub-item, it is the state to be confirmed. Only the sub-item that is confirmed OK can be used. Subitems that are to be confirmed or confirmed ok can be cancelled.
(9) Guest offering mark
Indicates the material provided by the sub-item for the customer, and the cost of this material is not considered in the cost calculation.
(10) Manufacturer
Certain materials under some parent items must use a certain brand. Specify the brand manufacturer here. You can refer to it when placing orders and producing materials. Even if the manufacturer is different, it is not necessary to define a new material code to simplify material management and reduce material substitution relations.
(11) Plug-in location
Specify where the child item is placed on the parent item. For example, place a capacitor on the P11 position on a circuit board, and specify the plug-in position as P11.
(12) Start lot number
Sometimes, a certain sub-item in the BOM is only used for the specified batch number, and is invalid in other batch numbers, which can be explained by the start batch number and the end batch number.
Note that batch number control is only required in the following situations:
(1) When the product or material has a storage validity period limit;
(2). When the product has special requirements or the printing and packaging are different without adding new models, try not to use batch number control.
(3) End batch number
Refer to the starting lot number above.
(4) Remarks
Only used for annotation description.
2. Sales BOM
It is also called the sample BOM, which is the parts list. It only describes the parts list and standard unit usage of a finished product (model). It has only one layer structure and does not contain manufacturing information. Most of its sub-items are the lowest-level parts. It is standard assembly parts or processed semi-finished products.
However, the assembly parts or semi-finished products are no longer expanded in the R&D BOM and are treated as parts.
When quoting products, refer to the standard cost of sales BOM materials.
3. Packaging BOM
Some companies require packaging of finished products according to customer requirements when they are shipped. Therefore, even for the same model, different customers, different orders, and different batch numbers require different packaging materials and different packaging processes.
If this part is placed in the production BOM, a lot of finished product material codes need to be generated. Therefore, separating this part, using the same finished material code and using different customers, orders, and batch numbers can reduce a lot of finished material codes.
This is not very necessary. If the packaging changes little, or the model itself is not many, you can put the packaging material into the production BOM. The packaging material BOM structure is roughly the same as the production BOM structure, plus the following fields:
(1) Customer code
If specified, the sub-item can only be used for the specified customers. If not specified, all customers can use this sub-item.
(2)
If the order code is specified, the sub-item can only be used in the specified order code. If it is not specified, all orders can be used in this sub-item.
(3)
If the batch number is specified, the sub-item can only be used on the specified batch number. If the batch number is not specified, this sub-item can be used.
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