Key points and difficulties in APS import

APS is the abbreviation of Advanced Planning and Scheduling System. Generally speaking, APS includes the following aspects:

1. Scheduling is based on process models, which can be defined by the user.
2. Contains automatic optimization features. Including automatic production scheduling, material collection analysis and material requirements planning of production plans.
3. Interactive, visual user interface that allows users to operate plans
4. Obtain planning goals and conditions from the outside: orders, work orders, inventory, material lists, etc. APS often needs to exchange data with ERP
5. Various adjustments to the plan based on the actual progress on site require interface with the MES system.

Production planning is a link in the entire supply chain system, and every enterprise is a link in the supply chain. As a supplier of downstream enterprises, failure to deliver goods as planned will affect the planning of downstream enterprises and lead to interlocking uncertainty. For upstream suppliers, the uncertainty of production plans also brings troubles to suppliers’ delivery plans. Excessive inventory or shortage of materials are all consequences of uncertain plans.

1. Relationship with ERP: It is usually necessary to import the ERP system first and then consider APS, although APS does not necessarily need to read data from ERP to run.
2. Interface between APS and ERP: There are several ways to implement the interface:
   1. Some ERPs do not allow direct access to tables or views, so the necessary data needs to be read in through development interface functions, such as SAP
   2. If ERP can open views, by defining tables and data structures, the required data can be read in. This implementation method is relatively quick and simple.
   3. Export reports from ERP to text and read them into APS. All ERP can implement this method.
   4. After APS completes the scheduling, it needs to return the production plan to ERP, such as the start time of the work order. ERP can read the report into the report to implement the required functions.
   5. Note: APS cannot replace ERP. Although APS has MRP functions, it cannot be used to generate purchase plans. Usually, the production plans generated by APS must be imported back to ERP, and ERP will generate purchase orders. APS can output the material requirements plan as a reference.
3. Is it necessary to import MES before considering APS? This is not required. Although APS requires on-site production progress to track completion of the plan, there are multiple ways to achieve this. For example, a production report entered every day at shift change is a fundamental source of data. In addition, some APS manufacturers provide simple reporting modules for reporting work through PC or mobile phone. These methods can achieve similar functions (for example, PlanMate provides reporting work through PC or mobile phone).
4. Optimization method: The APS system is based on constraint scheduling. There are two main ways to optimize:
   1. Scheduling by rules: Tell the system which tasks to schedule first under various conditions by defining complex sorting rules, weights, priorities, etc. The advantage of rule scheduling is that it is faster.
   2. Goal-based optimization: Set goals for the entire plan, such as lowest cost and maximum profit. Set costs for each job, such as equipment man-hour finished goods, idle finished goods, order delay penalty costs, etc., and find the lowest-cost solution that satisfies the constraints.
   3. No matter which algorithm is used, it must satisfy the model constraints
5. Regarding the bottleneck process: If there is a very clear bottleneck process, the bottleneck process can be arranged first, the process before the bottleneck is arranged in reverse, and the process after the bottleneck is arranged in the forward direction. But the reality is that bottleneck and non-bottleneck processes are often intertwined, so it is possible to back-schedule to a point in time in the past. This requires a more reasonable optimization method.
6. Regarding forward and backward placement: reverse placement is limited to insufficient orders, otherwise it will inevitably be queued to the past. Even when there are insufficient orders, reverse scheduling will produce many unreasonable work arrangements, such as work being intermittent and not starting on time, etc. In the system we implemented, the inversion method has never been actually used. When there are insufficient orders, it is more reasonable to plan by modifying the work calendar, adding holiday time, and closing several lines.
7. Tracking and modification of plans: The situation on the workshop site changes at any time, including order changes, production delays, and equipment abnormalities, all of which require modification of the plan. After the plan is modified, it is easy to cause conflicts, such as process conflicts, auxiliary resource conflicts, etc., which require system alarms and corrections.
8. Changes in orders: Order changes, emergency orders, equipment abnormalities, etc. all require rapid modification of the work plan. When multiple processes are intertwined, manually inserting orders will cause a lot of conflicts. The method PlanMateAPS usually uses is to rearrange the system (lock the parts you don’t want to change).
9. Multiple pipe scheduling: Although automatic scheduling is very fast, tracking the progress and modifying the plan takes time. If there are many devices, multiple pipe production operations are required. Division of labor by workshop or by process is a relatively common way of division of labor. The APS system needs a feasible solution to support multiple pipe scheduling.
10. Multi-factory scheduling: In finished product manufacturing companies, there are often mismatches between product assembly and branch factory plans. Half-product inventory is too high, and orders that need to be shipped often lack materials during assembly. Since the models of each branch are different and the order volume is large, it is impossible for one person to arrange all the branches. Therefore, how to coordinate the plans of various branches and assembly plants is a difficult problem that the APS system needs to solve.
11. Material status: In industries with serious material shortages, such as PCBA, scheduling according to material status is an important function that APS must implement. Material status should include in-stock and in-transit inventory. If you need to import APS and schedule according to inventory, you need to first sort out and standardize inventory management, especially the management of in-transit inventory (in-transit inventory refers to the incoming material plan given by the supplier)
12. Permission control: In large enterprises, model maintenance and scheduling are divided into different departments. It is a basic requirement that one person schedules and multiple people can view it. Therefore, data sharing and permission control are necessary.