Original Date: 02/09/1998
Revision Date: 04/22/2003
Best Practice : One-Piece Flow Manufacturing Overview
One-piece flow manufacturing describes a reliable method for production flow that is well suited for the low volume production of a wide variety of products. UE’s One-Piece Flow Manufacturing system is a masterful blend of many reliable methods that applies the concepts of Lean Manufacturing, just-in-time (JIT), Takt time, levelized scheduling, finite loading, KanBan card system, Heijunka box, one-piece flow, and Kaizen methodology.
UE manufactures over 2,000 different varieties of temperature sensing probes and thousands more varieties of pressure sensors, mostly per unique customer specifications from around the world. Previously, UE had a typical leadtime of four to five weeks for customized orders. Since implementing one-piece flow manufacturing, UE reduced its leadtime to two weeks, on average, and can provide same-day response for partial orders from customers.
UE achieved tremendous results by understanding and applying the basic philosophy of Lean Manufacturing and associated reliable methods for continuous improvement. Key factors include:
Reducing lot sizes to one piece, which leads to production flexibility and shorter leadtimes. Pulling production through the process at a rate equal to the rate of sales.
Producing only what is needed when it is needed (equal to the rate of sales).
Using pull systems that connect all islands of production from end to end.
Arranging production equipment in the order that employees work instead of grouping them by equipment function.
By applying Lean Manufacturing, UE can also identify and eliminate waste associated with storage, unnecessary production, inventory movement, and cost related to correcting a defect. Associated reliable methods that support Lean Manufacturing include JIT, autonomation, and Kaizen methodology. In JIT production, processes are arranged as orderly and close together as possible. Downstream processes pull small amounts of work from upstream processes at a pace that reflects the customers’ demands for finished products rather than pushing work downstream in batches. Autonomation refers to automating a process where possible to include mistake proofing (Poka-yoke) and inspection. The operator is alerted only when necessary, such as when a defect occurs. Kaizen methodology encourages employees to be an effective contributor to the ongoing processes by constantly identifying and eliminating waste.
The primary technique that runs the operation on the production floor is the KanBan card system. In one area, UE uses a very simple card form of KanBan based on color-coded paper in a vinyl envelope. Each card, representing one unit, acts as a signal to initiate the production of a test, assembly, or kit. UE also uses barcoding to assist with the paperwork and inventory tracking. KanBan cards and associated work instructions are loaded into the slots of the Heijunka box (Figure 2-2), which functions as a levelized scheduling tool. Each slot represents three minutes of production time (Takt time) for electromechanical switches and one minute for temperature sensors. The process flow coordinator removes a KanBan card/work instruction from the Heijunka box as a signal to build. The work coordinator sets the pace for the entire operation by depositing work at the stations and simultaneously delivering products to their next destination. The KanBan system is used for both stock items and made-to-order parts.
The KanBan system enables UE to be more responsive to its customers’ needs. UE significantly improved quality and now produces sensors at a rate of one per minute. In addition, the KanBan system offers minute-by-minute flexibility on the production floor, allowing UE to respond to any volume and variety of product with ease.
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