Flow Production (Pull Manufacturing)
With flow production manufacturing, the work to produce a product is chained together. By design, work at an operation is determined based upon a Takt time calculation. Takt time is the targeted work for flow process to achieve its designed capacity.
Simply put, if a manufacturer wanted to produce 24 products per day and they worked 8 hours per day, they would need to produce a product every 20 minutes. Takt time defines work in a flow process. The flow manufacturer designs the flow and pull process one time. Quality is designed into each operation for PPM quality. To adjust volume, they would adjust staffing to allow employees to flex from one operation to another. Typically, a flow line can run anywhere from 50% of capacity up to design capacity, without any changes in the operational work content or machine time.
Once the operations are defined, a Kaban pull technique is used to pull material to each operation. Kaban is sized based upon value, size, fragile, quality, etc. It focuses per part. No KITTING.
Schedule-Based (Push ) Manufacturing
In this methodology, production is controlled by a computer schedule. Quantities of fabricated parts or sub-assemblies are scheduled and completed based on their consuming (higher-level) products start date. Production is tracked and controlled by the MRP/ERP systems and design tools developed for the 1960’s. Production thru-put is based upon the scheduling lead time and measured in term of days, and days into weeks. Scheduling is common in America and Europe and it is batch quantity production. Single digit inventory turn-over is common in ERP scheduling.
The traditional, yet flawed “push” or “batch and wait” manufacturing philosophy is to pre-manufacture a batch of finished products, hold them in inventory, wait for customers to order them, and hope you eventually sell them all. This method is universally implemented via sales forecasts that seek to predict future customer demand in order to choose the size, schedule, and other facets of the production batch to hopefully meet the anticipated demand and ultimately create profit for the company. Unfortunately, the only sure thing about sales forecasts is that they’re usually wrong.
TPS (Pull Production & Material)
The TPS was created in the late 50's to get the Japanese manufacturing economy moving after WWII. With a focus on Flow Production productivity and in progress quality without unnecessary inventory; just-in-time pull materials. One of the original creators, Taiichi Ohno, a Vice President for Toyota Morot Corporation, is credited as for the pull (Flow) production and pull (Kanban) material system.
In discussion with Ohno, he stated "he studied American manufacturing and he preferred the supermarket replenishment method to the manufacturing scheduling method." Management is continuously trained on their Flow and Pull TPS and they continue to perfect it with their Kaizan(never ending improvement) systems.
Flow (Pull) Manufacturing
The Toyota Production System and Demand Flow Manufacturing are based on this methodology. Production is designed using flow technology, DFT (Demand Flow Technology). It takes production and material pull systems to a mathematical foundation which can be applied to any industry or volume. Production operations are balanced together into a mixed-model pull process. Quality is designed into each step and external inspection is greatly reduced or eliminated. Fabricated parts or assemblies are pulled into production as their consuming part or assembly requires them. Products go through the Flow process in minutes and hours of work content time, instead of the days and weeks it takes using the scheduling (push) methodology. Material is pulled internally to the plant and expanded to the supply chain. The ERP system is used to forecast long term supplier requirement with flexibility pull triggers in a short time period. The outdated ERP system is unnecessary in the production execution and there is no direct tie between the Demand-Driven Flow production and the supply chain forecasts. Double digit inventory turns are common and expected.
Flow Manufacturing is common in Japan and initially popularized by Toyota. Demand Flow manufacturing and DFT are often referred to as Any-Model, Any-Volume, Any-Day and single piece Flow because of the capability to build to Demand without a schedule or massive inventories.