The ERP system can generate plans, but it can't schedule additional orders.

Many Southeast Asian manufacturers have implemented ERP and MES systems. However, a recurring problem arises: customers suddenly place orders, raw materials are delayed, or a production line is temporarily shut down for maintenance. In these situations, the production plans provided by the ERP system become ineffective.

The warehouse manager went to ask the factory manager what to do, the factory manager called the sales department, and the sales department went to ask the customer if an extension could be made. In the end, the answer relied on the experience of the senior workers and the decision-making of the supervisor, not on data. This is not a problem of personnel ability, but a gap in tools: ERP is responsible for scheduling "what should be done", MES is responsible for recording "what was actually done", but "how to schedule in this situation" is not managed by the system.

This gap is what APS (Advanced Planning and Scheduling) aims to fill.

Three major pain points in scheduling for Southeast Asian factories

In medium-sized manufacturing plants in Thailand and Vietnam, scheduling problems typically manifest in three forms:

1. Frequent order insertions and difficulty in maintaining a stable schedule: Customers in industries such as electronics, consumer goods, and auto parts often have temporary order insertion needs. After the original plan is disrupted, rescheduling often takes more than half a day, during which the production line waits or runs idle.

Second, the high variety and low batch production lead to uncontrollable line changeover costs: When the same production line needs to switch production items five times a day, the time for cleaning, debugging and first piece confirmation for each line changeover may be longer than the actual production time. However, under manual scheduling, the line changeover sequence can hardly be optimized.

Third, delivery date commitments lack a basis: When sales staff provide delivery dates to customers, they usually estimate a figure based on experience or allow too much buffer. Once on-site production capacity changes, they cannot reflect this in a timely manner, resulting in either over-commitment or lost orders due to excessively long delivery periods.

The core logic of APS is to incorporate constraints into the scheduling.

ERP's scheduling module (MRP) calculates "material requirements," which assumes unlimited capacity. This is the fundamental reason why it cannot schedule in reality. The difference with APS is that it incorporates constraints such as limited capacity, work order priority, changeover time, equipment availability, and material arrival time into the calculation, providing a schedule that is "realistically executable."

The core operational logic of APS typically includes the following elements:

I. Limited Capacity Scheduling (CPS): This is based on the actual available man-hours for each piece of equipment and each production line, and over-scheduling is not allowed.

II. Changeover Matrix Optimization: Based on the characteristics of the product items (color, material, mold specifications), a changeover time matrix is established to automatically select the production sequence with the least changeover loss.

III. Priority Rule Setting: Priority logic can be set based on customer level, order urgency, penalty risk, etc., so that the system has a clear basis for choosing when multiple orders conflict.

IV. Dynamic Rescheduling (What-if): When order insertion, material shortage, or equipment malfunction occurs, the system can simulate multiple adjustment schemes within minutes for scheduling personnel to choose from, instead of spending hours manually recalculating.

Division of labor among APS, ERP, and MES

Implementing APS does not replace ERP or MES, but rather adds a "scheduling brain" between them. The division of labor among the three systems is as follows:

ERP manages master data such as orders, materials, and finances, and generates the Master Production Schedule (MPS) as input for APS. After receiving the MPS, APS outputs detailed process scheduling based on limited capacity and various constraints. MES receives the work order sequence generated by APS, executes it on-site, and reports the actual progress back as the basis for the next rescheduling.

These three systems form a closed loop: ERP provides direction, APS makes decisions, and MES manages execution. Currently, many factories in Southeast Asia are lacking this middle layer.

A pragmatic approach to phased implementation

APS is not a system that can be deployed across the entire plant at once. For factories implementing it for the first time, it is recommended to proceed in the following three stages:

In the first phase, a pilot test was conducted on a single production line. The production line with the most frequent line changes and the most prominent scheduling problems was selected. The line change matrix and available equipment information were manually compiled first, and the APS was run locally to verify whether the system logic conformed to the actual situation on site.

The second phase involves integrating with ERP data to establish an automatic import mechanism for ERP order data into APS, eliminating the need for scheduling personnel to manually enter work orders, and automatically updating the basic scheduling data daily.

The third stage involves integration with MES feedback, allowing the actual work progress reported by MES to be automatically transmitted back to APS, forming a scheduling closed loop. Only at this point is "dynamic scheduling" truly realized, enabling real-time adjustments to address any anomalies.

Each stage requires clear performance metrics. It is recommended to track: on-time completion rate of schedules, waiting time for line changes, and on-time delivery rate (OTD) as the basis for expansion or optimization, rather than just how many grandstands have been added.

Further Reading

If you are planning the overall manufacturing execution architecture for a Southeast Asian factory, the following articles can provide complementary background:

• Three preparations that must be made before implementing MES in Southeast Asian factories

• OEE Metrics in Practice: The Primary Measuring Tool for Automation Effectiveness in Southeast Asian Factories

• AGV Implementation in Practice: Three Starting Points for Material Handling Automation in Thai and Vietnamese Factories