What Is Master Scheduling?

Master Production Schedule (MPS). MPS is part of a closed-loop planning system. The essence of MPS is to ensure that the specified requirements (what is required, how much and when are required) of sales planning and production planning are consistent with the resources used. MPS considers business planning and sales planning to coordinate production planning with them. It looks at what is sold and what can be made, which can make a suitable "master production schedule" for the shop floor, and adjust this plan with crude capacity data until the load is balanced.

Master production plan

Master Production Schedule (MPS)

In the information industry, MPS stands for Master Production Plan.

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The main object of the main production plan is the ex-factory product after the product series in the production plan is specified. It is commonly referred to as the final project. The so-called "final project" is usually an independent demand piece, and its demand does not depend on the demand for other materials. Exist independently. However, due to different planning scope and sales environment, the meaning of the final project as a planning object is not exactly the same.

Starting from the principle of meeting the minimum number of items, the following three types of manufacturing environments consider the planning objects that MPS should choose.

* In the company that manufactures for inventory (MTS): a small number of standard products are manufactured using a variety of raw materials and components, and independent demand items such as products and spare parts become the final items of the MPS plan. For the case where there are many specific products under the product series, sometimes it is necessary to estimate the proportion of products to the total output of the series products based on market analysis. At this time, the planning object of production planning is a series of products, and the planning object of MPS is calculated according to the predicted proportion. A product series is in the form of a proportional structure of a specific product, similar to a product structure diagram, and is usually called a planned material or a planned BOM.

* For companies that produce to order (MTO): The final project is generally a standard shaped product or a product designed according to the order requirements. MPS planning objects can be placed at the lower level of the T-shaped or V-shaped product structure to reduce the planned materials. Quantity. If the product is a standard design or special project, the final project is usually the final product in layer 0 of the product structure.

* In order-to-order (ATO) companies: The products are a series with the same structure and a modular product structure, which are composed of several basic components and some common parts. Each basic component has multiple options and a variety of matching options (such as cars), which can form a series of variant products, and the main production plan can be set at the basic component level. In this case, the final project refers to the basic components and common parts. At this time, the main production plan is the production plan of the basic components (such as engine, body, etc.).

In general, for some products (such as personal computers) with a combination of standard modules and various models, such as personal computers, MPS is set up at the level of basic components. It is not necessary to predict the exact and final project configuration. , Assisted by FAS to simplify the processing of MPS. FAS is also an actual manufacturing plan, which can express the user's specific multiple configuration requirements for finished products, including the production and assembly of parts from the manufacture of components and parts to the delivery of products, such as the final product assembly. Testing and packaging. For projects with multiple options, MPS can be simplified when using FAS. The final assembly schedule (FAS) can be used to schedule the ex-factory product, and the multi-layer MPS and the planning BOM can be used to plan the common parts, basic components and optional parts. At this time, the planning object of MPS is equivalent to the "waist" material in the X-shaped product structure, and the top material is the planning object of FAS. Use FAS to combine the final projects, and make short-term production plans for finished product assembly based on user orders only. The coordinated operation of MPS and FAS realizes the entire planning process from the procurement of raw materials, the manufacture of parts to the delivery of final products.

For example, computer manufacturing companies can use spare parts to streamline MPS production. The computer model required by the market can be composed of several different parts. The optional spare parts include: 6 CPUs, 4 motherboards, 3 hard disks, 1 floppy drive, 2 optical drives, 3 memory, 4 One monitor, three graphics cards, two sound cards, two modems, and five chassis power supplies. Based on these different choices, there are 6 * 4 * 3 * ...... = 103680 types of computers that can be assembled, but the main parts are only 6 + 4 + 3 + ...... = 35 The total number of parts and components is much less than the total number of final products. Obviously, it is reasonable to set MPS at a certain level (parts) lower than the level of the final product (computer). After analysis of the assembly process, it was determined that only MPS was compiled for these parts, and the final assembly of 103,680 optional products will be formulated according to customer orders. This production planning environment is

Then, the main production schedule is used as the input of the material requirements planning MRP. MRP is used to formulate the production operation plan or material procurement plan for the required parts and components. When the production or procurement cannot meet the requirements of the MPS, the procurement system and workshop operation system To return information to MPS, form a closed loop

Rough-cut capacity planning (RCCP) is a tool to determine whether MPS is feasible. The role of RCCP is to transform the production plan of the planned object in the MPS into a pair

The compilation process of MPS is a process of continuous repetition and dynamic adjustment. First, MPS can only be used as a viable MPS after passing RCCP. If an MPS scheme cannot pass the balance of RCCP, the MPS must be modified. Second, when new customer orders are received that are not predicted, the MPS needs to be rescheduled. Only when the prepared MPS is reasonable, the frequency of the adjustment plan will not be too fast, otherwise adjustments need to be made frequently. in

In the process of MPS calculations, the concepts of 9 basic quantities are often used. These quantity concepts are: forecast quantity, order quantity, gross demand quantity, planned receipt quantity, estimated available inventory quantity,

The detailed calculation process of MPS is shown in the figure on the right. In this calculation process, the content of the system settings needs to be determined first. The system settings include the data environment required for the entire MPS calculation. For example, it is necessary to clearly compile the date of MPS, divide the time period and time zone, determine the demand time boundary, the planned time boundary, the production batch, the batch increment, the safety stock amount, and the lead time.

After the system is set up, the gross demand can be calculated. The basic data for calculating gross demand is the forecast and order quantities. How to get the gross demand based on the forecast amount and order amount depends on the type of enterprise, time zone and production policy. For example, a policy can be formulated: in time zone 1, gross demand is equal to the order amount; in time zone 2, gross demand is equal to the greater of the order amount and the forecast amount; in time zone 3, the gross demand amount is equal to the forecast amount.

Calculating planned receipts requires confirmation of the number of orders that have been placed before the planning date. In the ERP system, it can be confirmed automatically by the system.

Calculating the current PAB is often a confirmation of current data. Current PAB refers to the amount of inventory available at the time of the planning date.

Calculations are then performed on a time-by-time basis. Calculating the initial value of PAB in this period indicates that in a period, PAB has two values, one is the initial value of PAB, and the other is the value of PAB. This is because when calculating the PAB value, if the calculation result is negative, it needs to be adjusted with the aid of the planned output.

Calculate the net demand for the period. If the initial value of PAB is greater than or equal to the safety stock, it means that there is no need to replenish, so the net demand is 0; if the initial value of PAB is less than the safety stock, you need to replenish the inventory. At this time, the net demand is the safety stock minus the initial amount of PAB value.

If the net demand is 0, it means that no additional materials are needed, so PAB is equal to the initial value of PAB. If the net demand is not zero, you need to calculate the planned output.

Calculating the planned output needs to be based on the company's batch policy. The formula for calculating the planned output is as follows:

Planned output = N production lot

N production batch net demand (N-1) production batch

N is an integer greater than or equal to 1

After calculating the planned output, you need to calculate the PAB value. At this time, the calculation of PAB value must consider the impact of planned output. After calculating the PAB value, you need to determine whether all the periods in the planning period have been calculated. If all calculations are not completed, the data for the next period need to be calculated.

After the planning period has been cycled, the planned inputs and available sales can be calculated.