Visit Pull System is the production and logistics organization model diametrically opposed to the Flux Poussé. It is one of the cornerstones of the Lean Management and the Toyota production system (TPS), aimed at producing Just-in-time (JIT).
In-depth definition : In a Pull Flow system, the production of a product or component is only triggered by a single event. actual consumption signal issued by the downstream workstation or by a firm customer order. In other words, nothing is manufactured until and unless it is needed. This system emphasizes responsiveness, the flexibility and, above all drastic reduction in waste and overproduction. It is the customer (internal or external) who «pulls» the flow of value.
The Operating Mechanisms of Pulled Flow
Implementing a Pull Flow system requires operational discipline and the use of specific tools, which a digital transformation consultant integrates into his or her approach to lean manufacturing :
A. Kanban: the heart of the draw signal
Visit Kanban (Japanese for “label” or “visual signal”) is the most emblematic tool of Pull Flow. It serves as an inter-station communication system:
- The downstream station consumes parts from the buffer stock.
- The label (or electronic signal in the Industrial Digitization) is removed and sent to the upstream station.
- This signal authorizes the upstream station to produce only the quantity consumed. Kanban therefore maintains the stock level between two stations at a pre-established minimum, avoiding the accumulation of unnecessary parts.
B. Level Production (Heijunka)
To ensure that Pull Flow does not create load peaks for the upstream station, the Lean system requires the following level production (Heijunka). This involves smoothing out production by mixing models (or references) on the line, in small batches, rather than producing large batches of a single reference. This levelling ensures a stable workload, which is essential for achieving the production target. Takt Time.
C. Takt Time: The Customer Rhythm
Visit Takt Time is the rate at which a product must be manufactured to satisfy customer demand. It is calculated by dividing available working time by customer demand. In a Pull Flow system, all processes are dimensioned and timed to respect this Takt Time, ensuring that production is perfectly synchronized with sales.
Strategic Advantages of Pull Flow for Industrial Performance
Adopting Pull Flow radically transforms a company's competitive advantage:
- Inventory reduction (Muda) : The main objective. By producing only what is consumed, you minimize your current stocks (WIP) and finished goods inventories. This frees up capital (reduced WCR) and space.
- Quality improvement : The reduction of Buffer stocks immediately exposes quality problems or machine malfunctions (the Choke bolts). When stock is low, any defect or breakdown quickly brings the line to a halt. This positive pressure forces the team to solve problems at source (Root Cause Analysis - RCA) via the’Continuous Improvement (KAIZEN). Flux Tiré makes problems visible.
- Lead time reduction : The product spends less time waiting in buffer stocks. The time between order and delivery is shortened, increasing customer satisfaction and responsiveness to the market.
- Increased flexibility : Working in small batches (reducing tool changeover times), SMED) enables the production line to be adapted more quickly to the variety of products required, unlike the Flux Poussé.
Challenges and the Role of Industrial Engineering
The transition to Pull Flow is complex and requires careful preparation:
- Process reliability : Pulled Flow does not tolerate unscheduled machine stoppages. It requires excellent Preventive Maintenance or Predictive (often aided by the digital transformation) and high quality right from the start (First Time Right).
- Demand management : Highly volatile customer demand can make total pull flow difficult. The Industrial Engineering is to help find the decoupling point ideal (the Supply Chain where the flow changes from push to pull) and to size the safety stocks needed to absorb upstream variability.
- Standardization : Processes must be perfectly standardized (via the Manufacturing file) to keep the system running without human error.
Ultimately, Flux Tiré is the expression of the Operational Performance. It enables the company to produce exactly what the customer wants, when he wants it, with the highest possible quality, and with minimal capital costs.