Automatic scheduling solution for the electronics industry-APS system application

China is a major electronics manufacturing country. More than half of the world’s electronic products are manufactured in China. There are many PCBA factories, and costs are rising. Corporate profits have been repeatedly squeezed. Improving efficiency and reducing costs are the common needs of all PCBA companies. Efficient production scheduling is an important means for enterprises to reduce costs.
SMT production schedules have some common characteristics and difficulties. This article uses PlanMateAPS as an example to show how the APS system handles these problems:

一、Model maintenance issues:
difficulty:
1. The production process of each product may be different. Some have single-sided SMT, and some have double-sided. Some PCBs require AI or manual insertion, and some PCBs require ICT or ATE. Therefore, model maintenance is relatively difficult.
2. Special requirements for the machine. SMT production often specifies production lines, sometimes because of technical needs, such as long-term production of models with many parts, short-term production of models with few parts, high-precision new machines that produce high-precision models, sometimes because customers specify the line body . Therefore, each model needs to specify a few fixed lines for production, and the selection priority needs to be defined. This part needs to be defined in the model.
3. The PlanMate scheduling system supports the model structure required by SMT. The difficulty lies in how to ensure the accuracy of the model. Model inaccuracy directly affects the results of scheduling.

solution:
Model maintenance Although PlanMate can check the model before scheduling, it cannot detect problems such as incorrect PPH. It is actually a management problem of the enterprise. It does not rely solely on technology. It requires improving the management process and clarifying permissions. PlanMate adopts Independent permission control, the PMC department is responsible for production scheduling, and independent model maintenance permissions are opened to the engineering department. The product model can be checked and modified in both the modeler and the scheduling system interface.

//The engineering department needs to designate personnel to be responsible for model maintenance, with dedicated personnel responsible for it;
//For each machine model included in the work plan, the system automatically checks the model, and reports are given for all incomplete models, and the engineering department can supplement them based on the report;
//Export the model report regularly every week, and check it by the engineering department personnel. If the model is found to be inaccurate, modify it immediately.

Note: The system can quickly rearrange plans after model changes.

二、Material issues:

difficulty:
The SMT industry is an industry with a serious shortage of materials. In large enterprises, production is delayed every day due to lack of materials. Many SMT companies use the method of starting work orders to control production. The ERP system will query the material status, and work orders that have all the materials are released, but usually only work orders that can be produced in the last 2 days are released, and production management is only scheduled for 1-2 days. plan (only Released work orders are scheduled), the date when subsequent work orders will start production is not considered for the time being. The disadvantages of this are:

1. The company is unable to obtain the production and delivery plan for 2 days later, and cannot promptly reply to the customer’s delivery date, arrange shipment and transportation, etc.;
2. For work orders that are short of materials, as soon as the materials are put into the warehouse, the work orders are immediately released and the orders are inserted into production, causing the production plan to be changed immediately and causing chaos.

solution:
Using in-transit inventory constraints is a solution to the shortage problem. In the ERP system, materials cannot be put into the warehouse before they arrive, so there is no item in the inventory and the work order is short of materials. However, the purchasing department will generally get the incoming material plan within a certain period of time, and usually the incoming material plan within a week will be relatively certain. If the future material plan is used as in-transit inventory and participates in scheduling constraints together with the in-stock inventory, work orders will be scheduled after the material collection time point, instead of not being scheduled or arranged at will.

Using in-transit inventory constraints, you can get accurate production and delivery plans in advance, facilitate communication with customers and arrange delivery, prepare online accessories and SMT procedures, etc. At the same time, too frequent plan changes due to material conditions are avoided.

For the deduction rules of inventory in transit, see another article on this blog: Inventory deduction rules and constraints in production scheduling

Note: In the SMT industry, material condition is the key factor restricting SMT production. A production scheduling system that does not consider material condition is not feasible. Ignoring material condition during scheduling will result in frequent changes to the plan.

三、BOM version and alternative materials:

difficulty:
1. BOM version change: In PCBA production, BOM is often changed, and the version changes quickly. If the version of the same coded model changes, the BOM will change accordingly. If a fixed BOM is used in the model and the latest version of the BOM cannot be updated in a timely manner, the BOM in the scheduling system and ERP will be inconsistent. 2. Substitute material issues: Many machine models prepare a variety of substitute materials for some of the materials. Some work orders in the schedule will use alternative materials.

solution:
Usually, whether to use substitute materials is decided by ERP. ERP will decide which substitute materials to use for each work order individually. The scheduling system cannot decide the substitute materials by itself. BOM versions often change, and it is difficult for the APS system to obtain the latest version in real time.

A feasible and accurate method is to use the work order bill of materials instead of the static BOM. The requirement for using this method is that the ERP outputs the work order material list for each to-be-scheduled work order. When the APS system reads the scheduled work order from the ERP, it simultaneously imports the inventory and work order material list, and queries the inventory based on the material list. Ingredients time.

Most ERPs have a work order material list, and MES systems require a work order material list. Some factories use barcode material matching systems and also need to use a work order material list.

The main problem with using work order material tables is that the amount of data imported into APS each time is relatively large, so it is mainly used in the detailed scheduling stage. In the long-term planning stage, inventory constraints are generally turned off, and there is no need to use work order material tables.