Mapping the Production Steps: How to Read Process Sequence and Flow Direction

Learning Objectives

• Identify and interpret process boxes and their sequence in a Current State Map
• Explain the direction and logic of material flow across production steps
• Read the data boxes associated with each process step and understand what each metric means
• Distinguish between push flow and pull flow signals within a VSM
• Trace the production path from raw material to finished goods using standard VSM icons

Imagine you are walking the floor of a stamping and assembly plant for the first time. Coils of steel arrive at the dock, get processed through a stamping press, move to welding, then to assembly, and finally into a finished goods area before shipping to the customer. The sequence seems logical enough when you are physically walking it. But when you sit down with the Current State Map, what you see is not just a physical layout — it is a structured visual language that tells you how work actually moves, where it stalls, and how long material spends waiting versus being transformed. Learning to read that language, step by step, is the essential skill this lesson builds.

The Process Box: Your Building Block for Reading Flow

In Value Stream Mapping, every manufacturing or assembly operation is represented by a process box — a rectangle that identifies a distinct step where material is transformed or worked on. The process box is not meant to represent a single machine or a single operator in isolation. It represents a flow step: a point in the value stream where material enters, something happens to it, and it exits. According to the Kaizen Institute VSM methodology, these boxes form the backbone of the Current State Map and are always drawn in sequence from left to right across the middle of the map.

Each process box carries a data box directly beneath it. This is where the real analytical power lives. A typical data box includes:

• C/T (Cycle Time) — the time it takes to complete one unit at that step, measured in seconds
• C/O (Changeover Time) — the time required to switch from one product type to another
• Number of shifts — how many shifts operate at that step per day
• Available time — the net working seconds available per shift or per day
• Scrap rate — the percentage of output that does not meet quality requirements

For example, a process box labeled “Assembly” might show: C/T = 45 sec, C/O = 800 sec, 3 Shifts, Scrap = 2%. These numbers are not just descriptive — they are the inputs you will later use to calculate takt time compliance, capacity constraints, and improvement priorities. Reading the data box carefully is not optional; it is how you move from observation to diagnosis.

Reading Flow Direction: From Customer Back to Supplier

One of the most important conventions in VSM is where you start drawing — and therefore where you start reading. As the Kaizen Institute training material states: always start with the customer. This means the customer demand box sits in the upper right of the map, and the supplier sits in the upper left. Material flows from left to right through the process sequence, eventually reaching the customer. Information flows, typically shown above the process boxes, run from right to left — from the customer back through production planning and out to the supplier.

Between each process box, you will find one of two key flow indicators:

• Push Arrow — a striped arrow indicating that material is being pushed from one step to the next, regardless of what the downstream process actually needs. This is the most common flow type in traditional batch-and-queue manufacturing.
• FIFO Lane (First In, First Out) — a narrow lane icon indicating that material moves in strict sequence to the next step, with a defined maximum quantity. This is a more controlled form of push, capping inventory between steps.
• Supermarket with Withdrawal Kanban — indicating pull-based replenishment between steps, where the downstream process signals when to produce or replenish.

When you see a series of push arrows running across the entire map, that is a clear diagnostic signal: the plant is operating in batch-and-push mode, with no mechanism to match production pace to actual customer demand. This single observation often explains why inventory accumulates in front of certain steps and why lead times are far longer than value-added time would suggest.

Inventory triangles — shown between process boxes — mark where stock accumulates. Each triangle is accompanied by a quantity and a time value (how many days of inventory that represents). These are critical for calculating the production lead time, which is the total elapsed time from raw material arrival to finished goods shipment.

Practical Example: Reading the Current State Map at MetalForm S.p.A.

MetalForm S.p.A. is a fictional automotive components manufacturer producing left-hand and right-hand brackets for a Tier 1 customer. Their Current State Map shows five process steps in sequence: Stamping → Spot Welding → Grinding → Assembly → Shipping. Each step has its own process box and data box. Reading left to right:

1. Stamping: C/T = 1 sec, C/O = 3,600 sec, 1 shift. A very fast cycle time but an extremely long changeover. Inventory downstream: 4,600 Left and 2,400 Right brackets — equivalent to 5 days of stock.
2. Spot Welding: C/T = 39 sec, 7.6 days of inventory ahead of it. The long inventory wait before this step signals a bottleneck or batching behavior upstream.
3. Grinding: C/T = 46 sec, 1.8 days of inventory.
4. Assembly: C/T = 62 sec, 2.7 days of inventory. This is the slowest cycle time — a strong candidate for the constraint step.
5. Shipping / Staging: 2 days of finished goods inventory before shipment.

All steps are connected by push arrows. Production Planning uses an MRP system and issues weekly schedules based on 90/60/30-day forecasts. The total production lead time calculates to 23.6 days, while the value-added time — the sum of all cycle times — is only 188 seconds. This dramatic gap is not unusual in batch manufacturing environments, and the VSM makes it impossible to ignore.

By reading the process sequence and flow direction carefully, the MetalForm team could immediately see that the problem was not the speed of individual machines, but the structure of flow between them. The push system, combined with long changeovers at Stamping, was generating enormous inventory buffers and a lead time that was nearly 23 days longer than it needed to be.

Key Takeaways

• Process boxes represent flow steps, not individual machines. Always read them as transformation points in the value stream, supported by the data in the box below.
• Material flows left to right; always start reading from the customer. The customer’s demand is the reference point that gives meaning to every number on the map.
• Push arrows are the most common and most revealing flow icon. A map dominated by push arrows signals a batch-and-queue system with uncontrolled inventory between steps.
• Inventory triangles between steps are not neutral. Each one represents time — days of material waiting — and contributes directly to the gap between production lead time and value-added time.
• The data box is where diagnosis begins. Cycle time, changeover time, and available time together tell you whether a step can meet demand and where the leverage points for improvement are likely to be found.