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Just in Time (JIT): Definition, JIS and MES in Production

By Christian Fieg · Last updated: March 2026

What Is Just in Time (JIT)?

Just in Time (JIT) is a production strategy in which materials, components, and sub-assemblies are delivered and produced only when they are needed in the manufacturing process, in the exact quantity required, and at the exact time required. The goal is to eliminate inventory buffers, reduce lead times, and expose waste in the production system.

JIT was developed as part of the Toyota Production System (TPS) in the 1950s and became the foundation for what is now known as lean manufacturing. For automotive suppliers, food and beverage manufacturers, and FMCG producers, JIT is not an optional philosophy. It is the operating model demanded by their customers.

In practice, JIT requires real-time visibility into production status, machine availability, and order progress. Without this visibility, any disruption (a machine stoppage, a quality defect, a missing component) can break the delivery chain within hours.

JIT vs. JIS: Two Levels of Delivery Precision

Dimension	JIT (Just in Time)	JIS (Just in Sequence)
Definition	Deliver the right part, in the right quantity, at the right time.	Deliver the right part, in the right quantity, at the right time, in the exact sequence the customer will install them.
Inventory at customer	Small buffer stock. Parts are called off in batches, consumed in production order.	Zero buffer. Parts arrive in the exact installation sequence. No sorting at the customer's line.
Order trigger	Kanban signal, blanket order call-off, or MRP-based release.	EDI call-off with exact sequence number. OEM sends the production sequence (pearl chain) electronically.
Typical industries	All manufacturing with lean principles: automotive, electronics, FMCG, metal processing.	Automotive Tier 1 suppliers delivering directly to OEM assembly lines: instrument panels, door panels, cockpits, seats.
Lead time window	Hours to days. Delivery within a defined time window.	Minutes to hours. Delivery must match the OEM's assembly sequence exactly.
Consequence of failure	Production delay at customer. Expedited shipping. Penalty costs.	Line stop at OEM assembly plant. Penalty costs of EUR 10,000 to 50,000+ per hour. Potential loss of future contracts.

The Core Principles of JIT Production

Principle	What it means	Why it matters
Pull production	Production is triggered by actual customer demand (pull), not by forecast-based production plans (push). Nothing is produced unless there is a confirmed order or Kanban signal.	Eliminates overproduction, the most fundamental waste in lean manufacturing. Reduces work-in-progress inventory and shortens lead times.
Takt Time alignment	Production rate is synchronized to customer demand rate (Takt Time). Every station on the line produces at the same pace, matching the rate at which the customer consumes products.	Prevents bottlenecks and buffers between stations. Makes deviations immediately visible. Requires real-time cycle time monitoring.
Continuous flow	Parts move through the production process without waiting, batching, or intermediate storage. Ideally one-piece flow: one part enters, one part exits.	Reduces lead time from days to hours. Exposes quality problems immediately (defective part is detected at the next station, not in a warehouse weeks later).
Kanban	Signal-based replenishment system. When a container of parts is consumed, the empty container (or electronic signal) triggers production or delivery of the next batch.	Simple, visual, self-regulating. Prevents both overproduction and stockouts. Works at the machine level, the line level, and the supply chain level.
Zero defects	With no buffer inventory, every defective part directly impacts delivery. JIT requires built-in quality (Jidoka): detect defects at the source, stop and fix the problem immediately.	A 2% scrap rate that is invisible with buffer stock becomes a 2% delivery shortfall in JIT. Quality is not a department. Quality is a prerequisite for JIT.

What JIT Requires from the Production System

JIT is not a software feature or a purchasing policy. It is an operating model that places extreme demands on every aspect of the production system. When these demands are not met, JIT fails, and the consequences are immediate and expensive.

Requirement	Why JIT demands it	What happens without it
High machine availability	No buffer stock means no production reserve. If a machine stops, the delivery chain breaks within hours.	Unplanned downtime causes delivery shortfalls. Expedited freight. OEM penalties. Lost trust.
Fast changeovers	JIT requires small lot sizes to match customer demand. Small lots require frequent changeovers. If changeovers are slow, JIT is economically unviable.	Manufacturers revert to large batches to avoid changeover time. This creates inventory, the opposite of JIT.
Reliable quality	With no buffer, every defective part is a missing part. Quality problems immediately become delivery problems.	Scrap and rework create shortfalls. Emergency production runs. Overtime. Expedited shipping. Quality escapes to the customer.
Real-time production visibility	JIT decision-making requires knowing the current status of every order, every machine, and every quality metric in real time, not at shift end.	Problems are discovered too late to correct. Shift-end reports reveal yesterday's failures, not today's risks.
Reliable suppliers	Inbound JIT requires suppliers to deliver on time, in the right quantity, at the right quality. One late delivery can stop the entire line.	Safety stock creeps back in. The JIT system degrades into a traditional push system with JIT labels.

How an MES Enables JIT Production

JIT without real-time data is JIT without a safety net. An MES provides the real-time visibility and control that JIT demands: machine status, order progress, quality status, and downtime detection, all in real time, all accessible from a single system.

MES function	Contribution to JIT	How SYMESTIC implements it
Real-time OEE monitoring	Availability, performance, and quality tracked per machine in real time. Deviations from Takt Time detected immediately.	Automatic OEE calculation from machine signals. Shopfloor dashboards, management dashboards, and mobile app. Alerts on threshold breaches.
Automated downtime detection	In JIT, every minute of unplanned downtime is critical. Automatic detection and classification of stops reduces reaction time.	Machine stop detected via digital signal or OPC UA. Duration, timestamp, and machine ID logged without operator intervention. Downtime Monitor and Downtime Analyzer.
Order monitoring	Real-time status of every production order: planned, in production, completed, on hold. Deviation from schedule immediately visible.	Order Monitor: order preview, real-time order status. Batch Production Control: order control from start of line to packaging. Mapping of machine cycles to production orders.
Bidirectional ERP integration	JIT requires seamless flow between ERP (orders, materials, schedules) and shopfloor (actual production status, quantities, times). No manual reporting at shift end.	SAP R3 (ABAP IDoc), InforCOM (file interface), Navision. Automatic backflush of quantities, times, and statuses. Production data flows back to ERP in real time.
Quality control	Quality status per part/batch. Dependency checks prevent defective parts from progressing to the next station. Scrap and rework tracked in real time.	Quality Status (OK/NOK/REWORK) per station. Dependency Check: "Part status OK? Previous process OK?" Scrap Analyzer, Rework Analyzer.
Alarm management	PLC alarms correlated with downtimes and quality defects. Root cause identification for systematic failures that threaten JIT delivery.	Event & Alarm Monitor, Alarm Ranking, Alarm Analyzer. SPS-based alarm capture. Correlation of alarms with stops and quality data.

At Meleghy Automotive (6 plants, bidirectional SAP R3 integration), SYMESTIC provides real-time OEE monitoring on press shops and joining lines. The result: 10% reduction in downtime, 7% improvement in output, 5% improvement in availability. In JIT automotive production, these improvements directly translate to fewer delivery risks.

At Carcoustics (500+ machines across 7 countries), company-wide performance analysis across all plants provides the transparency needed to identify bottlenecks before they become delivery failures. The 4% downtime reduction and 8% availability improvement across the group reduce JIT risk at scale.

JIT by Industry

Industry	JIT application	Critical success factor	Biggest risk
Automotive (Tier 1-x)	JIT and JIS delivery to OEM assembly lines. EDI call-offs (DELJIT, SYNCRO, VDA4916). Pearl chain production. Zero-buffer shipping.	Real-time order tracking, machine availability above 90%, fast changeovers, EDI integration.	OEM line stop. EUR 10,000 to 50,000+ per hour penalty. Loss of future contracts.
Food and beverage	Short shelf life products require JIT-like production close to demand. Overproduction means waste (expired products). Underproduction means lost sales.	Accurate demand forecasting, fast line changeovers, real-time production monitoring, batch traceability.	Product expiration before sale. Retailer penalties for incomplete deliveries. Food waste.
FMCG / consumer goods	Retailer-driven replenishment with tight delivery windows. High product variety requires frequent changeovers. Production must match daily demand.	Line efficiency (OEE), changeover time reduction (SMED), real-time quality monitoring.	Out-of-stock at retailer. Expedited freight costs. Retailer fines for missed delivery windows.
Metal processing	Make-to-order production for industrial customers. Reduce WIP inventory and lead times. Respond to customer demand changes quickly.	Setup time reduction, real-time machine monitoring, order tracking, capacity planning.	Excess WIP inventory. Long lead times. Inability to respond to urgent orders.

JIT Failure Modes and How Real-Time Data Prevents Them

Failure mode	What goes wrong	How real-time MES data prevents it
Undetected machine degradation	A machine gradually loses cycle time performance. Output drops by 5% over weeks. Nobody notices until delivery commitments cannot be met.	Continuous OEE monitoring detects performance decline in real time. Alerts trigger investigation before the problem becomes a delivery risk.
Hidden micro-stops	Dozens of 10- to 30-second stops per shift. Individually invisible, collectively they reduce output by 10 to 15%. Reported as "the machine was running."	Automatic stop detection captures every stop, including micro-stops below operator perception. Downtime Analyzer shows patterns and root causes.
Quality drift	Scrap rate increases gradually. With buffer stock, the effect is absorbed. Without buffer (JIT), the scrap directly reduces deliverable output.	Real-time quality tracking (OK/NOK/REWORK per station). Scrap Analyzer and Rework Analyzer identify trends before they become delivery shortfalls.
Order status blindness	Production manager does not know the real-time status of the current order. Promises delivery based on the plan, not on actual production progress.	Order Monitor shows real-time status of every order: pieces produced, pieces remaining, estimated completion time. Deviation from schedule immediately visible.

Frequently Asked Questions About JIT

What is the difference between JIT and JIS?

JIT (Just in Time) requires delivering the right part, in the right quantity, at the right time. JIS (Just in Sequence) adds one more dimension: the parts must arrive in the exact sequence in which the customer will install them. JIS is more demanding than JIT and is typically required by automotive OEMs for line-side delivery of variant-specific parts like instrument panels, door panels, and seats.

Can JIT work without an MES?

In theory, JIT can work with manual systems (paper Kanban cards, visual boards, walk-the-floor management). In practice, as soon as the production environment exceeds a certain complexity (multiple machines, multiple products, multiple shifts), the lack of real-time data makes JIT fragile. An MES provides the automatic downtime detection, order tracking, and quality monitoring that JIT requires to function reliably.

What is the biggest risk of JIT production?

The biggest risk is that JIT removes buffers, and buffers hide problems. Without buffers, every problem (machine stoppage, quality defect, supplier delay, changeover overrun) immediately impacts delivery. This is both the strength and the vulnerability of JIT: it forces you to solve problems, but it punishes you if you do not solve them fast enough.

How does JIT relate to OEE?

OEE (Overall Equipment Effectiveness) measures the three factors that determine whether a machine can support JIT: availability (is it running?), performance (is it running at the right speed?), and quality (is it producing good parts?). A machine with 60% OEE cannot reliably support JIT because 40% of its theoretical capacity is lost to stops, speed losses, and defects. JIT requires OEE above 85% as a minimum baseline.

What EDI standards are used for JIT/JIS call-offs in automotive?

The major OEMs use different EDI formats for JIT/JIS call-offs: Audi uses DELJIT/SYNCRO, Mercedes-Benz uses VDA4916, BMW uses SPAB (Status 5000 + 5300), Ford uses EDIFACT-DELJIT, VW uses EDIFACT-DELJIT/SYNCRO/SONATA, and Volvo uses EDIFACT-DELJIT/VCCBOM. A production control system for automotive JIT/JIS must support these formats natively.