You’re inside a transformer factory, witnessing firsthand how precision, quality control, and raw materials worth millions come together in a meticulously orchestrated process. On one side, engineers scrutinize every micron of wound wire; on the other, optimization specialists work tirelessly to make the process faster, better, and more cost-effective. And somewhere in between? Six Sigma and LEAN, two powerful tools promising perfection.

If you've ever searched for a job in the industry and come across mysterious requirements like "experience with LEAN Manufacturing" or "knowledge of Six Sigma at the Green Belt level," you might have wondered, "What does that even mean?" It sounds like a secret code, but in reality, these are well-defined methodologies that shape modern manufacturing—and it’s worth understanding how they work.

We know this topic inside and out—every day, we design, manufacture, and optimize to deliver transformers built to last for decades. We’ve implemented processes that refine every element down to the fraction of a millimeter, but we also know that blindly following a methodology can sometimes complicate life more than it simplifies it.

In this article, we’ll take you behind the scenes:

🔹 Six Sigma – why it’s not just about decimal points but about eliminating defects before they appear.
🔹 LEAN – is it really possible to “trim the fat” in transformer production without sacrificing quality?
🔹 Pros and cons – where these methods shine and where they can become a headache.
🔹 What works best in our industry – how to extract the most value from these approaches without getting lost in management textbooks.

In just 10 minutes, you’ll find out whether Six Sigma and LEAN are truly the blueprint for engineering perfection—or just another set of rules that work “in theory, but not in practice.” Let’s dive in!

Where did Six Sigma come from? – A history of precision in manufacturing

Six Sigma was born in the 1980s within the American technology giant Motorola. At the time, the company was struggling with a serious issue—too many defective products, leading to financial losses and dissatisfied customers. Bill Smith, an engineer at Motorola, noticed that most defects stemmed from minor deviations in the production process, which accumulated over subsequent stages.

Smith and his team began measuring, analyzing, and optimizing production processes, creating a system based on rigorous quality control. The key goal? Reducing defects to just 3.4 per million operations—a near-perfect level of reliability.

Motorola’s success caught the attention of industrial giants, and in the 1990s, General Electric (GE) under Jack Welch implemented Six Sigma on a massive scale. The company achieved billions in savings and significantly improved product quality. From that moment, Six Sigma became a gold standard across industries, including automotive, aerospace, medical, and power equipment manufacturing.

What does “Six Sigma” mean?

The term “Sigma” (σ) is a statistical measure of standard deviation, which reflects variability in a process. The smaller the variation, the more stable the process—and the fewer defects.

A Six Sigma level (6σ) means that process variation remains within extremely tight tolerance limits, minimizing the chance of producing defective products. In other words, every component is nearly identical, and the probability of error is close to zero.

Six Sigma operates through two primary approaches:

📌 DMAIC (Define, Measure, Analyze, Improve, Control) – A cycle used to enhance existing production processes.
📌 DMADV (Define, Measure, Analyze, Design, Verify) – Focused on optimizing and designing new processes from scratch.

This methodology is not just about detecting problems—it’s about eliminating them before they even arise. That’s why electrical engineers widely adopt Six Sigma to ensure transformers deliver unparalleled reliability for years to come.

Six Sigma – It’s not about numbers, it’s about controlling reality

Six Sigma is often associated with an obsession over statistics—graphs, standard deviations, variance analysis… But in reality, it’s far more than mathematical gymnastics. It’s a mindset that enables engineers to anticipate and eliminate defects before they become a problem.

Manufacturing transformers isn’t like assembling LEGO bricks—even the slightest inconsistency can lead to overheating, failures, or, in the worst case, power outages on a massive scale. Six Sigma provides precise tools to detect and eliminate such risks at the process stage—before they ever reach final testing.

🔹 How does it work? Imagine we’re producing transformer cores. Traditionally, if a lamination defect is found, we start looking for blame—was the machine improperly calibrated? Did the operator make a mistake? Was the raw material flawed? Six Sigma forces us to trace the problem to its root cause, break the process down into its key variables, and implement changes that prevent the defect from happening again.

🔹 The goal? 3.4 defects per million operations. Sounds extreme? Maybe. But in the power industry, this level of precision translates directly into reliability. If a trnasformer’s winding is manufactured with a 99.9997% accuracy, it means lower risk of electrical faults, overheating, and failures, which in large-scale power grids could cost millions.

🔹 More than just numbers—it’s strategy. Six Sigma is not just about data—it’s about making decisions based on evidence rather than intuition. That means better supply chain planning, optimized production time, and greater foresight into potential issues before they arise.

Does Six Sigma require investment? Yes. Does it require a shift in mindset? Absolutely. But if you’re creating something designed to last for decades without failure, you’d better make sure statistics work in your favor—before randomness does.

Six Sigma Belts – What’s the deal with the ranking system?

If you've ever seen a job posting requiring a "Green Belt" or "Black Belt" in Six Sigma and thought you were applying for a martial arts dojo, you’re not alone. Yes, Six Sigma has a belt system, but instead of punches and kicks, it ranks expertise in process optimization.

Why belts?
The Six Sigma methodology emphasizes a structured progression of knowledge and skills—the higher the "belt," the greater the responsibility and proficiency in data analysis, process optimization, and project management.

🔹 White Belt – A basic understanding of Six Sigma. Perfect for those new to the methodology who want to grasp the fundamentals of defect reduction and process analysis.
🔹 Yellow Belt – A supporting role in larger Six Sigma projects, assisting in data collection and waste identification but not yet leading independent initiatives.
🔹 Green Belt – Mid-level leaders who oversee smaller Six Sigma projects. They analyze processes, apply statistical tools, and drive improvements. In transformer production, a Green Belt might optimize material usage or enhance winding quality.
🔹 Black Belt – Six Sigma experts managing large-scale projects and training Green Belts. They tackle the most complex manufacturing challenges, using advanced analytics and statistics to eliminate process variability.
🔹 Master Black Belt – The true Six Sigma masters. They don’t just manage projects—they define strategic quality standards for entire organizations. In major electrical engineering firms, they establish quality benchmarks and oversee methodology implementation.

Where do Champions and Executive Leaders fit in? These are senior-level professionals who may not need in-depth statistical knowledge but must understand Six Sigma’s philosophy and support its execution at the corporate level.

Is certification worth it?

If you work in engineering or process optimization, earning a Six Sigma certification—even at the Green Belt level—can be a huge career advantage. Six Sigma may not solve every issue, but it provides powerful tools to make data-driven decisions rather than relying on intuition.

LEAN – The Manufacturing Philosophy that’s changing the industry

LEAN Manufacturing isn’t just another optimization method—it’s an entire philosophy of production, focused on minimizing waste while maximizing value for the customer. Unlike Six Sigma, which primarily targets defect reduction, LEAN eliminates everything that doesn’t directly contribute to the final product’s value.

Where did LEAN come from?

The roots of LEAN trace back to 1950s Japan, where Toyota developed the Toyota Production System (TPS),

model that revolutionized modern manufacturing. In the aftermath of World War II, Japan had to rebuild its industry without access to abundant raw materials, infrastructure, or capital. Toyota faced a challenge: how to produce more while using less?

In response, Taiichi Ohno and Shigeo Shingo devised a system that, unlike the mass production methods used in the U.S., eliminated waste and optimized every step of the process. This led to the development of the Just-In-Time (JIT) model—a production system ensuring that components were manufactured exactly when needed, avoiding excessive stockpiling, material waste, and unnecessary operations. TPS became the blueprint for what we now know as LEAN Manufacturing.

What is LEAN?

LEAN identifies seven major types of waste (Muda):

1️⃣ Overproduction – Producing more than is needed (e.g., excessive stockpiling of transformer cores).
2️⃣ Waiting – Delays in production, such as waiting for components or approvals.
3️⃣ Unnecessary transport – Inefficient movement of materials across the production floor.
4️⃣ Overprocessing – Adding extra steps that don’t enhance the final product’s value.
5️⃣ Unnecessary motion – Poorly designed workspaces and inefficient procedures.
6️⃣ Defects and errors – Every mistake requires rework, leading to wasted time and materials.
7️⃣ Excess inventory – Storing unnecessary parts and semi-finished products.

How does LEAN impact transformer manufacturing?

In the power engineering sector, LEAN helps:

✅ Reduce production time – By eliminating bottlenecks and improving workflow efficiency.
✅ Lower material costs – By avoiding unnecessary stockpiling and optimizing supply chains.
✅ Increase flexibility – By making it easier to adapt to shifting customer demands.
✅ Enhance workplace ergonomics – By streamlining workstations and automating repetitive tasks.

But can Six Sigma and LEAN truly optimize transformer production, or do they sometimes lead to excessive reductions? Let’s explore the challenges and pitfalls of these methods, which can sometimes make a "lean" production system dangerously thin.

Case Study: How Six Sigma revolutionized the Vapour Phase Drying (VPD) Process in transformer manufacturing

In one transformer manufacturing plant, engineers had been grappling for years with inefficiencies in the Vapour Phase Drying (VPD) process—a critical production stage designed to ensure proper insulation drying. Instead of delivering the expected results, the process led to frequent defects, inaccurate measurements, and financial losses.

Every day, up to 50 defects were detected, accumulating to 297 defects annually, translating into additional costs of approximately €400 per year. The core issues?

• Incorrect calibration of temperature sensors, leading to inaccurate readings.

• Uncalibrated moisture sensors, causing inconsistencies in water extraction measurements.

• Incorrect insulation weight entries in the ERP system, resulting in improper drying parameters.

Each of these seemingly minor discrepancies contributed to inconsistent insulation drying, requiring rework, increasing production time, and lowering the final product’s quality.

Applying Six Sigma DMAIC – Tackling problem at its root

Determined to eliminate defects at their source, the project team implemented the Six Sigma DMAIC methodology, treating the issue like a mathematical equation with a single goal: process optimization.

First, they conducted an in-depth analysis of the entire VPD process, identifying the root causes of defects.

📌 Key findings included:

• Poor placement of temperature sensors, leading to false readings.

• Irregular calibration of moisture measurement sensors, causing variations in water extraction tracking.

• Errors in insulation weight input, resulting in incorrect drying cycle settings.

After conducting a thorough statistical analysis, the team implemented checklists and automatic sensor calibration procedures, reducing defects by a staggering 90%. The cost of errors dropped by approximately €380 per year, while the entire process became more predictable and energy-efficient.

Beyond problem-solving – Setting new standards

The most significant benefit of implementing Six Sigma wasn’t just fixing existing issues—it was establishing new industry standards for drying ultra-high-capacity transformers. Previously, these transformers were dried using more expensive methods, such as hot-air drying, which consumed more energy and took longer to complete.

By enhancing quality and process stability, Six Sigma not only saved time and money but also led to the introduction of microprocessor-controlled monitoring, ensuring better insulation drying, shorter drying cycles, and increased long-term reliability of each transformer.

This case study serves as yet another proof that optimization is not a luxury, it’s a necessity in modern manufacturing.

LEAN Pitfalls – When “Lean Production” Becomes Too Thin

Not every optimization effort ends in success. This became painfully clear for a German manufacturer of medium-voltage transformers, which, in the name of LEAN, decided to cut warehouse inventory to the absolute minimum. The company adopted a Just-In-Time (JIT) model, assuming that components would arrive precisely when needed, eliminating the cost of storing transformer cores, windings, and insulating oil.

On paper, the idea looked brilliant—less waste, faster inventory turnover, and increased efficiency. But then, something happened that no one had anticipated.

The first crack in the perfect system appeared when one of the key suppliers delayed the delivery of laminated core sheets by 72 hours. Production had to halt. The following week, a sudden change in order specifications resulted in a shortage of critical insulation spacers, forcing the company to urgently source them from another facility at a 35% higher cost.

The biggest blow came in winter. In January, logistical delays stranded a shipment of insulating oil at the border, bringing production to a complete standstill. Customres started calling anxiously, demanding updates on their orders. The production team, which had previously praised the flexibility of LEAN, suddenly realized that eliminating inventory buffers meant total dependence on suppliers with zero margin for error.

Instead of lowering costs, the company saw a 15% increase in operational expenses, caused by production stoppages and emergency material purchases. Additionally, several key customers expressed dissatisfaction, forcing the company to rethink its LEAN strategy and reintroduce minimal material buffers instead of relying entirely on JIT.

Reducing inventory is beneficial—but only to a point. LEAN must align with real-world industry challenges rather than become a blind cost-cutting measure that sacrifices system resilience.

At Energeks, we understand that the key to stable transformer production is balancing efficiency with operational security.

Perfection isn’t an accident —it’s a strategy

Are Six Sigma and LEAN just buzzwords? If you look at them through the lens of corporate training manuals, they might seem like it. But when you see them through the eyes of an engineer responsible for delivering a multimillion-dollar transformer without a single defect, they take on an entirely different meaning.

At Energeks, we don’t play with theories—we design, manufacture, and implement real solutions that work in practice. In our industry, there is no room for “almost perfect” transformers.Precision, reliability, and proactively identifying potential issues before they arise are what truly matter. That’s why we apply these methods where they make a real difference, eliminating waste, improving efficiency, and delivering transformers built to last for decades.

See what solutions are ready at hand!

Every percentage point of cost savings, every hour removed from the production process, and every defect eliminated translates into real financial gains and a tangible competitive advantage.

How do you optimize your processes? Have you experienced Six Sigma or LEAN in action, making a real difference? Share your insights—let’s talk about engineering that works not just in theory but in real-world practice.

Sources:

1. ASQ - American Society for Quality

2. Lean Enterprise Institute

3. IEEE Xplore – Six Sigma in Power Transformer Manufacturing

4. Journal of Emerging Technologies and Innovative Research