I’m going to jump right into an issue that I’m dealing with today: Baby bottles need to be washed.
Typically, we collect bottles (or actually, sippy cups) throughout the day and then load them into the dishwasher for the overnight load. That made a lot of sense when we were using twenty-four bottles a day.
But now we are just using six bottles a day, and those bottles are easier to clean than the earlier ones were because they have many fewer parts. Does it still make sense to keep collecting bottles for the night dishwashing load and do them in one big batch?
Our current baby bottles are also very easy for the kids to make a mess with; squeezing their soft openings against a table or floor or windowsill is apparently the height of fun. So we’re going to be switching over to a new, more grownup sippy cup soon. How many should we buy?
If you think about it, the buying question relates directly to the washing question. If we wash bottles in overnight batches, we’ll need at least six new cups to get us through a day without washing. Those six cups will need to be loaded into the washer, washed, and put back into a cabinet for storage until they are needed (almost twenty four hours later for two of them).
One principle of lean production is that small batches are almost always better than big batches. When you do things in big batches, you get economies of scale (like being able to use the dishwasher rather than doing it by hand), but you lose a lot in terms of flexibility. You also give yourself extra inventory, which has to be stored and maintained somewhere.
Worst of all, you lose some quality control, since if something goes wrong during a big batch run, you won’t know about it until the batch is complete, and all of the units in the batch will be affected. I’ve certainly had the disappointing experience of opening the dishwasher in the morning only to discover that I didn’t put in the soap or something, and none of the bottles are clean.
Using small batches has some disadvantages as well, including the loss of some economies of scale and increased changeover times as you switch between batches more frequently. However, these disadvantages can be dealt with through the process of ongoing improvement, which is the core of lean production. (More on that later.)
So the answer to my question about baby bottles is clear from a lean perspective: We should buy just two bottles and quickly hand wash them as needed. With that approach, we won’t need to set aside an entire cabinet for clean bottle storage, we won’t have to spend money on a bunch of extra bottles that spend most of their time not being used, and we’ll have a much better sense of whether the bottles are being cleaned properly as we are washing them.
It’s hard to resist the temptation to buy upwards of a dozen bottles just to save ourselves the momentary task of washing the same two bottles over and over again. Inventory can definitely become a crutch. However, it seems likely that the time we’ll spend washing two bottles by hand three times a day won’t total as much time as it takes to disassemble six bottles, load them into the dishwasher each night, reassemble them in the morning and then move them to the storage cabinet.
This is a simple example of a lean solution to a everyday problem, but it has all of the earmarks of larger lean initiatives: Reduced inventory, reduced batch sizes, reduced costs, and better quality control. I will discuss all of these things at more length in future posts.