How to manage work orders in the machining process

Production planning control is the core part of production operation management. Identifying the status of work orders is the core machining part of controlling the release of work orders. So how to distinguish work orders and identify the status of work orders is the primary task.

1. Form of work order

The work order link of a factory can generally be divided into four links: order, workshop work order, process work order, and operation.

1. Sales order (referred to as order)

Factory orders are generally composed of multiple finished products, which are explicitly expressed as a list of products required by customers, the number of requirements for each product, the required time and key technical requirements. Its implicit requirements are expressed as quality standards, quality control levels, BOM and process routes.

Enterprises with a poor management foundation or simpler business use the finished product of the sales order as the control unit.

2. Workshop work order

How much an order can be decomposed into workshop work orders from product dimensions and workshop (work center) dimensions. In the scenario where ERP is successfully implemented and MRP is calculated, workshop work orders are generated through MRP (net demand or gross demand) calculations based on sales orders and BOM. Often, a sales order can be broken down into a large number of workshop work orders.

In most factories with good management foundation (smooth ERP), the workshop work order is the control unit.

3. Process work order (dispatch work order)

Workshop work orders are decomposed into process work orders (also called dispatch work orders) according to the corresponding process routes. Process work orders are generally resource-related (equipment, molds,  die machining, operators). Process work orders generally have operation sequence and logic. Common process work orders generally have multiple methods: start/start, start end, end/start, and end/end. It also expresses the state of bifurcation, parallelism, and merging of material flow.

Enterprises with good management foundation and high control precision can optimize resources by using process work orders as the control unit.

2. Work order status and priority

The production and operation process is a real-time dynamic process: sales orders continue to flow in, and after MRP, they are converted into workshop work orders, subcontract orders and purchase orders, and the inventory dynamics are continuously realized based on material picking and storage.

If a workshop (work center) is regarded as the CPU (central processing unit) of a computer, the principle of calculation task management of the CPU (central processing unit) can be used for reference, and the workshop work orders can be divided into the following states:

  • 1. Work orders that are not ready, materials and resources do not match
  • 2. Ready, materials and resources are ready and can be released. But because the load is higher and the priority is lower, it is in the waiting state before release.
  • 3. Release, the work order has been released to the machine (or workshop), but because the machine does not have an immediate spare load, it is equal to the waiting state before processing.
  • 4. Start work, the work order is not only released but also in the start state
  • 5. Suspended, or because of abnormal material quality or abnormal resources, the work order is in a suspended state of shelving, and the load on the machine is released.
  • 6. Closed, the work order is either successfully completed, or closed abnormally, and is in closed state.

3. Work order load distribution and locking

In order to maintain the stability of the production order, the work order has the highest priority and its load is also locked. The load occupied by the released work order is in a semi-locked state: in general, the order is not disturbed. The load in the unlocked state can be adjusted at will.

4.insert single realization

In the entire production operation process, the insertion of sales orders is a common scenario, which is very difficult for production operation management, especially production planning and scheduling. Inserting an order is an inevitable scenario, and how to maintain the stability of the production machining process is a core issue in the realization of the insertion state.

Since the work order that has already started has locked resources and occupied materials, its status is locked and anchored and cannot be changed, otherwise the cost of changing it will be very high. So the only thing that can be changed is to make adjustments to the two states of release and ready (not ready can be changed in the first place). Therefore, according to the urgency of the sales order and the requirements of the optimization rules, the two intervals allowed to insert orders are:

  • First, or insert into the work order that has already been placed, where the earliest time to insert the order is after the current work order.
  • Second, or insert into the work order in the ready state, where the earliest time to insert the order is the first one in the current ready work order after the order is placed.

Inserting into that interval depends on the urgency of the sales order and the requirements determined by the optimization rules.

Copyright notice: This article comes from

Please keep the source and address of this article for reprinting: