Equipment production types in APS system

In the field of discrete manufacturing, production equipment varies widely in various industries. In summary, it is mainly divided into two methods: flow production and batch production. The scheduling of batch production equipment requires calculation of the batch size and the need for closed furnace production. The traditional manual scheduling method will be more difficult.

This article discusses the scheduling needs of flow production and batch production equipment and the solution of PlanMateAPS.

With flow production equipment, products are manufactured one by one. Although the processing equipment for single-piece production is not arranged in an assembly line, because the product is manufactured in a single piece, we also attribute it to the assembly line equipment. The production time of a work order in the process is calculated as follows:

Production time = Takt time * Quantity

Some equipment may produce small batches. For example, in the molding industry, there is a mold with multiple cavities, and each mold produces multiple products. In actual scheduling, because the batches are small and different products cannot be combined, they are usually also used as Flow equipment processing.

Our common mechanical processing equipment, molding machines, SMT production lines, assembly production lines, etc. are all flow production equipment.

Flow production process control:

If adjacent processes are all flow production equipment, there is often overlap in time between the processes. as follows:

The time between the two orange lines is called the process buffer. Process buffers can be defined in the PlanMate APS model, and actual needs such as transportation batches and safety buffers need to be considered.

If the time difference between the front and back processes is large, and if the auxiliary resources of fixtures and molds allow, processes with longer production times will be separated and produced in parallel, which can shorten the WIP time between processes. For example:

Manual scheduling challenges:

?As shown in the figure above, if you want to make the time between processes close, you need to calculate when the subsequent process should start. When there are many work orders and production lines, if manual scheduling is used, this calculation will be difficult to perform because the calculation amount is too large.

Planners usually increase the buffer time between processes to simplify calculations. Many factories use 12 or 24 hours as the basic buffer time, and the front and rear processes are separated into two shifts or two days. In this way, there is no need to accurately calculate the start time of the subsequent processes. Consider production capacity. The disadvantage of this method is that there are too many in-process products and many semi-finished products are piled up next to the production line. However, it is difficult to avoid this with manual scheduling.

Import APS to shorten process delays:

After the introduction of the APS system, one of the important benefits is the reduction of inter-process delays. The system uses strict buffer time scheduling, the number of work-in-progress is greatly reduced, and the entire production cycle of the product is shortened.

A batch refers to a batch of products that are put into a large container at the same time and finally packaged. It is most common in chemical, food, pharmaceutical, beverage and other industries.

There are also batch production equipment in discrete manufacturing industries, which often mix and alternate flow production and batch production. For example, in the mechanical processing industry, CNC processing belongs to single-piece production, while pickling, quenching, etc. belong to batch production. Magnetron sputtering, vacuum evaporation, etc. are all typical batch production, and there are multiple single-piece operations before and after evaporation.

Features of batch production scheduling:

The capacity of each batch is certain. Where the process permits, furnace production should be combined as much as possible to improve equipment utilization.

1. The production process cannot be interrupted. For flow production equipment, tasks will be stretched during rest periods. Batch production cannot be interrupted, and breaks must be completed continuously and cannot be extended.

2.In the equipment scheduling of batch production mode, the furnace volume is determined, but the batch size of work orders varies greatly. In order to improve efficiency, large work orders are split into multiple furnaces, and small orders are produced in one furnace.

Different equipment has different calculation methods for heat size. The projects we have encountered are mainly divided into three categories:

• Fixed quantity: For example, in vacuum evaporation equipment, the number of holes on the workpiece plate is fixed. If the product sizes are the same, only the quantity needs to be considered.
• Calculated by equipment capacity: Each product does not need to use a specific jig during production, only the total capacity needs to be considered, such as large ovens, heating furnaces and other equipment. However, since the product size varies, it must be calculated based on the size of the product.

This type of equipment can define the total capacity of the equipment and define dimensional parameters for the product. Combine production according to parameters such as equipment capacity, product size, and number of work orders.

Example:

Suppose a heating furnace has a capacity of 500 based on standard size products, that is, the product size is 1 and 500 can be placed. If the product size is defined as 2, 250 pieces can be placed. Assuming that 200 products of size 1 have been placed in a furnace, the remaining capacity can be placed for another 150 products of size 2.

The definition of product size is not necessarily an integer, it can also be defined as a decimal. The number of products that can be placed = total capacity/product size.

• Calculated based on the jigs that can be installed on the equipment, the following figure shows four workpiece trays assembled into one furnace. Each workpiece tray has multiple holes. Each hole can be installed with one jig, and each jig can be installed with 1. or multiple products.

The calculation of this mode is more complicated. The simpler way is to combine 4 similar workpiece trays into one furnace.

Conditions for combining furnaces: If you want to combine them into one furnace for production, the production parameters must be the same and the required production time must be the same. In addition, the completion time of previous processes and delivery time are also constraints.

The figure below shows the relationship between quantity and time in batch production.

Example of splitting and merging batches in PlanMateAPS

• If the quantity of a work order does not match the size of the heat, combine several work order tasks into one heat for production.

As shown in the picture above, the capacity of the industrial oven is 100, and several work orders are combined into one furnace for production.

As shown in the picture above, both heat treatment and electropolishing are batch processing equipment, flow production and batch production are mixed, and there are splits and mergers between processes.

In the scheduling of heat treatment equipment, in addition to the capacity of each heat, the temperature of each heat must also be considered. The temperature should increase or decrease, and cannot jump too much.