Lean manufacturing basics: Who are your internal customers and suppliers?

Meet Bill. He works at the burn table, cutting pieces that will be formed, milled, machined, and welded into the assemblies his company sends to its customers. Bill is a nice guy, a dedicated employee who works hard and does what he’s told. But Bill doesn’t have a clue who his internal customers and suppliers are.

Meet Sally. She operates a press brake. She knows that after she bends parts, they go to a series of operations. Sally is a pleasant person, works hard, and gets the job done. But unlike Bill, Sally seems to be much more effective. Why? It’s because she knows who her internal suppliers and customers are. Ultimately, that knowledge can be a major source of a company’s competitive advantage.

What Are Internal Customers and Suppliers?

You receive work from your internal supplier and send completed work to your internal customer. This logic is straightforward, yet many manufacturers pay little to no attention to the idea. Whether you have 30, 300, or 3,000 employees in your company, consider the value of everyone understanding who his or her internal customers and suppliers are.

Note that everyone, from the CEO to the front line, works with internal suppliers and customers. Even salespeople and purchasers, who obviously work extensively with external customers and suppliers, need to work with internal ones as well. After all, salespeople will have a tough time serving external customers if they don’t work well with the estimators, engineers, and purchasers within your company.

In Bill’s case at the burn table, the internal customer is most likely someone in grinding or forming. In Sally’s case at the press brake, the internal customer is someone in welding. The welder is expecting formed parts to arrive at a certain time and in a certain quantity. He also expects the parts to fit in the weld fixture and be presented in a specific way.

The Customer and Supplier Relationship

One key internal supplier to the burn table is the nesting programmer (assuming it is someone other than the burn table operator). The nesting programmer’s quality and timeliness affect Bill’s performance significantly. Does the nest provide for reasonable clearances, or does it optimize the material usage, which in turn affects how Bill will unload the parts and skeleton from the table?

In Sally’s case, the internal supplier might be the burn table operator or the grinder. How could they affect Sally’s performance? If burned flat parts are delivered to the forming operation in a tote carrying blanks of different thicknesses, where work order quantities are mixed, or where the burned edges have excessive burrs or slag because the equipment was out of alignment, then Sally will have plenty of non-value-added work to do before she can actually do her job and bend parts.

What If You Don’t Know?

If people don’t know who their internal suppliers and customers are, they become compartmentalized. They see only the job in front of them and miss the big picture. This in turn affects the shop culture. People think, “I just do my job and pass it along; if something’s wrong, that’s somebody else’s problem.” This runs counter to quality-at-the-source methods, whereby people are expected to check the quality of their work.

They also don’t appreciate how their work affects overall quality and throughput. Your company is in business to serve customers and to be profitable. Quality and throughput have a direct impact on both.

Not only that, employees who don’t think about internal customers and suppliers have a narrow, limited job experience. Is this just a job for your employee, or are they part of a bigger purpose? Knowing the internal customer and supplier is an important element of enriching the work experience.

Learning these concepts is one of the least expensive, high-return lean ideas a company can pursue. Note, though, that I didn’t say these concepts are easy, especially if you’re new to lean manufacturing.

If your company is just starting the lean journey, try introducing the ideas behind the internal and external customer and how they relate to the classic wastes, 5S, and other concepts that help build the foundation of any lean manufacturing program. Train small groups comprising people from different areas of the company. Walk the floor, give people a chance to see how work flows, and let them talk and explore. Make the experience personal, and make sure everyone can identify the internal customers and suppliers and their respective needs.

If you already have a lean training program, evaluate the approach to see if you are currently addressing the internal customer and supplier. If not, build it into the curriculum. See firsthand how employees relate to internal customers and suppliers, and look for examples to include in the training. Reinforce the ideas in the daily standup meetings, and have participants share their experiences.

What If Everyone Understood Like Sally?

Sally really understands how her work fits into the overall process. She knows how the flat stock she receives was processed, where it came from, and even which person or group performed the previous operation.

In fact, Sally talks with internal suppliers during process analysis projects. She describes how she’d like her part presented at the press brake, the lot quantities that work best, the edge requirements, and the level of precision she needs. She shows her internal supplier (cutting operator) what happens to the bend when, say, the flat part is nested on the burn table in a different way and the grain direction changes.

Sally’s internal customers also convey what they need. She can fulfill some of those needs herself, while other needs may be met by engineers, material handlers, supervisors, or others. This gets everyone talking and allows change to occur smoothly.

The way Sally stacks and orients parts in the tote or on the skid helps her internal customer, the welder. He retrieves parts in one smooth motion that does not require flipping or turning. Sally also stacks the parts in the order they will be used; the welder need not unstack what is on top to retrieve what he needs on the bottom.

The welder sends a pull signal for more parts at Sally’s operation. Once Sally receives that signal, she knows that the welder has only so many parts left to weld, so she must replenish his operation with more parts within a certain time period. It’s not about how many workpieces Sally can produce in an hour. The fastest bending speed in the world doesn’t matter if she doesn’t give her internal customers what they need, when they need it.

Taken to its natural conclusion, Sally can look at the welder’s operation as an extension of her own process. Doing so helps her understand the larger process and how the job flows through the plant. A positive byproduct: All this helps Sally genuinely feel part of a larger team.

Bill comes in and gets his job done, but he really doesn’t know what happens upstream or downstream. Bending operators have issues because nesting programmers don’t take grain direction into account as they should. But that’s not Bill’s job, so that’s not Bill’s problem. Again, Bill’s a nice guy, and he’s a very good machine operator. But because he doesn’t communicate with his internal customers and suppliers, he also creates a lot of inefficiency and waste.

In contrast, Sally is a dynamo in making sure she understands what the welder needs from her, and she talks with the burn table operator about how work can flow smoothly through the forming operation. The internal customer and supplier relationships create opportunities for lots of small improvements. You could call them everyday kaizens.

The Power of Knowledge

Conduct training so that a consistent message is sent throughout the company. Set expectations that everybody, regardless of what they do, should know who their internal suppliers and customers are, and be empowered to act on that knowledge.

I am not suggesting that managers abdicate their right to manage. On the contrary, engaged employees will free up managers to work on problems and issues they are uniquely qualified for.

Do your employees know about internal customers and suppliers? Can they seek ways to make the work easier, more effective, and better for your external customers? If you make the investment and train your employees about how they can serve their internal customers and suppliers, your external customers will reap the benefits.

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