Lean and the eight wastes, on a glass line
Lean has a jargon problem. Strip it away and it is one stubborn question asked over and over: is this step actually adding value the customer would pay for, or is it just something we have always done? Here is what the eight wastes look like when the product is glass.
What lean actually means
Forget the belts and the Japanese vocabulary for a minute. Lean started on a car line, but the core idea is embarrassingly simple: every step you do to a product is either adding value the customer would happily pay for, or it is waste. Cutting the glass to size adds value. Walking to the far end of the shop to find a suction cup does not. The customer never asked you to do that, and they will not pay a cent more because you did.
The catch is that most waste does not look like waste. It looks like work. People are busy, glass is moving, the shop is loud, and almost none of it is idle. That is exactly why waste survives: it hides inside motion. Lean is really just a set of labels that make it visible, so you can see the difference between being busy and getting product out the door.
One honest warning before the list. Lean is not a project you finish. There is no morning where the shop is officially lean and you stop. It is a habit of noticing, and the shops that get real value from it are the ones that made the noticing routine, not the ones that ran a two-day workshop and put a poster up.
The eight wastes, in glass
The classic list has eight entries. A common way to remember them is the word DOWNTIME, which is fitting, because that is what they cost you. Here is each one at a glass plant, with the version you have probably seen:
| Waste | What it looks like on a glass line |
|---|---|
| D Defects | The expensive one. Scratches, edge chips, a tempering scuff, a wrong size, a failed fragmentation test. Every scrapped lite is money you already spent on glass, cutting, and oven time, thrown in the cullet bin. Rework is defects wearing a disguise. |
| O Overproduction | Cutting a batch ahead of the frames being ready, tempering before the IGU line can take it, making units nobody ordered yet to keep a machine busy. It feels productive and it quietly builds every other waste on this list. |
| W Waiting | Cut lites stacked at the oven waiting for a load. An operator standing at an idle table because the previous station is behind. Glass waiting for a QC sign-off. Whenever product sits still, you are paying rent on it and adding nothing. |
| N Non-utilized talent | The glazier who knows exactly why the corner keeps chipping, but nobody ever asks. The setter with a better rack layout in their head. Skill you already pay for and never tap is the quietest waste of all. |
| T Transport | Moving glass across the shop and back, handling the same lite five times, long hauls between cutting and tempering. Glass does not improve by being carried, and every extra move is another chance to chip an edge or break a sheet. |
| I Inventory | Stock sheets you may not use for months, racks of work-in-progress between every station, finished IGUs waiting weeks to ship. Inventory is cash frozen as glass, and in a shop it is also breakage risk and floor space you cannot use. |
| M Motion | People reaching, bending, and walking for things that should be within arm's reach: the tape, the pen, the offcut bin, the setting blocks. Different from transport, which moves the product; motion is the wasted movement of the worker. It is also where a lot of injuries start. |
| E Extra processing | Doing more than the job needs. Polishing an edge that ends up hidden in a frame, inspecting the same lite three times because nobody trusts the last check, printing paperwork no one reads. Quality is value; gold-plating is waste. |
Flow first, then pull
Once you can see the waste, two ideas do most of the heavy lifting.
Flow means arranging work so a lite moves smoothly from one step to the next without piling up in between. The enemy of flow is the big batch. Cut a huge stack, and it sits waiting for the oven; temper a huge load, and it sits waiting for the IGU line. Smaller batches moving steadily almost always beat big batches moving in lurches, even though the big batch feels more efficient at each individual machine.
Pull means letting real demand trigger the work, rather than making things to keep machines busy and hoping they sell. In practice it is the difference between "temper these because the oven is free" and "temper these because the IGU line needs them next." Pull is what stops overproduction at the source, because nothing gets made until the next step actually calls for it.
Where to actually start
Do not try to go lean everywhere at once. That is how these efforts die. Instead:
- Walk the glass, not the paperwork. Follow one order from raw sheet to shipped unit and physically watch what happens to it. Note every time it stops, waits, or gets carried somewhere. You will find waste in the first ten minutes.
- Pick one waste, at one station. Maybe it is the scrap rate at the cutting table, or the wait time at the oven. One measurable thing, not a grand transformation.
- Ask the people who do the job. The non-utilized-talent waste is free to fix and usually points straight at the others. The operators already know where it hurts.
- Measure before and after. If you cannot show the scrap rate or the wait time actually moved, you cannot tell improvement from a good week. This is where a running dashboard earns its keep.
Lean and housekeeping go hand in hand. The fastest way to kill the motion and waiting wastes at a single station is usually the discipline in the next guide: 5S.