What is Lean manufacturing? Without the jargon

As someone with basically no formal Lean training, nor, obviously, certification, I feel eminently qualified to give you the REAL scoop about Lean. So let's get to it.

What is Lean? You might have heard that it's a way to reduce waste, but that's not really it. Or maybe you've heard it's a "pull," (demand-based) system vs a "push," (make-to-inventory) system, and that it's better in every way. I assume you're rightfully skeptical. Especially when that's generally followed immediately by the admission that, of course, pull isn't necessarily better than push in all ways, all the time, so it's more some kind of magic hybrid.

So, let me present a different angle. What lean really is, at the core, is an idea that an entire manufacturing operation can be run like an assembly line. It asks a basic question, with a seemingly obvious answer, "If I want to deliver a good to my customer, is it faster and more efficient to pull it off the shelf, or to make it new?" Obviously, it's better to pull it off the shelf, right? Lean will tell you, "WRONG!"

See, arguably, even more important than efficiency in an assembly line is balance. Sure, it's great to not have a wasted motion, but if you have one operation on your line that takes way longer than everything else, even if every step is 100% efficient, it's going to hold up the whole line. A perfect line is perfectly in sync, with each station taking exactly the same amount of time. As soon as any operator finishes their task, what they need to start again is waiting for them, delivered from the previous station. A perfectly synced, somewhat inefficient, line, is probably way better than a poorly synced, perfectly efficient one.

So back to that item on your shelf. If it takes you 5 minutes to pack it, but every step prior (including any travel/material handling) ALSO takes 5 minutes, you can make it new and (given some volume to get every step in the operation running) by the time you're done packing, another shiny item is waiting to be packed. Even better than a shelf fully pre-stocked with parts, as it's exactly where you need it, instead of a big shelf of parts getting progressively farther as you work through them.

Lean suggests you should try to run, as much as practical, your entire operation like an assembly line. So the key is balance. Your operation will go at the speed of the slowest step, so job 1 is to get all steps to take approximately the same amount of time. If that means breaking a step into multiple steps, even if, combined, they take longer, do that. Once you've got balance, you can work on efficiency.

Does that mean you hold no inventory? No, because that's not necessarily how a well balanced line runs. Sometimes, purchasing or making parts ahead of time, and supplying them to the line in quantity is the way to go. Or sometimes, the line itself lends itself to building up internal inventory.

At Crystal Fountains, we created a line for LED lights that included a potting step with long cure time that could not be broken up into multiple steps, smack in middle of the process. The process was fairly quick for the operator, but it had to sit for over an hour, when our per-station time was about 4 minutes. No problem! We ran one piece at a time until the station prior, and let them accumulate upon completion in a cart. When the cart was full, we did a shuffle. The full cart went to potting, the now-cured cart at potting went to the next step, and the now-empty cart at the next step went to the step prior to potting. The following step used the parts from the supplied cart, one at a time, at the line speed of approximately 4 minutes per light, so emptied a cart exactly as one was filled for potting, and the cart was sized so that this synced with the necessary curing time.

Applying this analogously to a larger manufacturing operation, you want to balance your operation to your longest step. If that step is best run as a batch, for whatever reason, do so, building up inventory to send to batch and consuming batched inventory after to maintain a balanced pace.

If your desired process speed demands that a particularly long or costly step be done offline, when there isn't necessarily specific demand, do so. It's all about maintaining the balance of your operation.

So that's lean in a nutshell. First, balance. Then, efficiency.

I'd be happy to hear your thoughts on this approach.