Go One Piece Flow!

In a previous article I explained how SMED was born, in Brazil in the late 50's. In this article you will understand why SMED is so important!

If I have to sintetize what Lean really is about, I would just sketch it in this way:

Lean looks to the overall system, end to end, with the continuous obsession to reduce the time between order to cash. Cash is king, cash is the life-blood for every company to survive and grow. For a strange reason, it looks like only the CEO and CFO are interested to cash balance, then when you get off from the President's office, people talk about other things: productivity, efficiency, cost reduction, waste reduction etc..

What the Japanese call "Muda" (the 7 Muda, that are the 7 categories for waste defined by the Lean phylosophy) are actually the responsible for the increased time (and effort) between order to cash. In this article I would like to explain how Muda are only an effect, while one of the main cause is actually the batching approach. Batching unfortunatelly is a mindset that humans have and unfortunatelly it's present everywhere. This is an example of a "batch" of people, waiting to be "processed" at the Hospital

The modern market competition forces us to get rid of this mindset and go to One Piece Flow, if you want to survive.

Let's make an example: You are a company that is producing sandwiches and your customer one day asks for 100 sandwiches with ham and butter. Let’s say that for simplicity there are 4 steps to produce a sandwich :

-??????????Cut the bread – 1 minute/sandwich

-??????????Spread the butter – 1 minute/sandwich

-??????????Put the ham?– 1 minute/sandwich

-??????????Wrap the sandwich – 1 minute/sandwich

You can out the numbers you like for the single operations, the result will not change.

You start by cutting the first piece of bread in two halves, then you think "I have the knife in my hand already, so it is maybe better if I cut the other 99 sandwiches to save time". You immediately notice that the table you were working on is filled with many, many pieces of bread: on one side the whole bread, half-cut pieces on the other. Maybe you need a bigger table, and you need to start putting cut sandwiches on a shelf somewhere or in a box.

At this point you might think that a good idea is not to cut the bread completely, otherwise half pieces will mix together. Anybody likes a sandwich that has 2 bottom sides, or 2 top sides, or half slice from a piece of bread and the other form another piece of bread because the 2 halves do not match properly. So at the end the typical characteristic of the "industrial" sandwich is that they have the incomplete cut, exactly to avoid halves mixing.

I personally prefer something like this, with an uniform layer of ham all over!

Anyway, now you have cut 100 sandwiches, it took 100 minutes. You have a mountain of pieces of bread cut in half, ready to be buttered. The cut bread is in a box that it is quite heavy, so when you have to move it you need a cart.

Cut bread ages, perhaps it would be better to work in a room with controlled humidity?

Anyway, the time has come to butter the bread: since I have the butter out of the fridge and the knife in my hand - you will think - it will be better to butter all the sandwiches, right? So you start from the first, that - if you have put the sandwiches in a box after the cutting phase - it will probably be one of the last pieces you cut. Something like a "First In Last Out" - sounds good?

Anyway, you take out a big piece of butter from the fridge, prepare your station and the tools, wear the proper gloves, then you start to process the 100 sandwiches. Other 100 minutes. When you spread the first sandwich the butter is cold, it does not spread well... when you spread the last sandwich after 100 minutes out from the fridge the butter is soft, so the 100 sandwiches have different butter layers.

The same thing will happen for the insertion phase of the ham: if you are a "batcher", you have probably cut the ham in advance (today? yesterday? last week?) and put in a fridge. The ham slices now are sticking each other, so it is difficult to take a slice without breaking it. Let's say other 100 minutes. You left over some ham - I'm sure.

Finally additional 100 minutes for the packaging phase.?

After – in the best case, efficiency 100% – 400 minutes, you have 100 sandwiches ready. You call your customer and ask him to try a sandwhich. In the modern industry, this phase is called “FAI” – First article inspection. It is there to check that the customer likes what you have produced. It doesn’t say anything of your process – i.e. if it is capable or not – it is only an assessment to understand if the product has the fit, the form and the function that your customer needs.

Let’s say that I am the customer: as I told you, I don’t like sandwiches with non symmetric cut. You have 100 sandwiches made in that way. I also like sandwitches with just a small amount of butter and a lot of ham: you’ve put a lot of butter in your 100 sandwiches, and just little ham. Now you have 2 options:?

1.?start an infinite discussion on contract terms, saying that the requirement of the simmetric cut was not stated anywere and there wasn’t any specification of the maximum amount of butter or minimum amount of ham. In this case at the end I will accept your position, but I will not enjoy the sandwiches: you sell your sandwiches, but I (the customer) will be unhappy.?

2. The second alternative you have is to rework all the parts: your production?department will get crazy because in the meantime there are other sandwich batches being processed, and this rework was not planned. Moreover, if you cut the sandwich completely in 2 halves (as I asked) maybe it is better to serialise the pieces of bread so that if they mix they can be reassembled correctly. So at the end, if you choose this option, I (the customer) will be happy (relatively happy, because - you know- I will start to get quite starved while you rework my sandwiches..) but your cost will increase a lot, your production plan will be be blown away and the excess of butter that you have put in the sandwiches will be thrown in the bin. The other customers of your company will be unhappy because the sandwiches will arrive later compared to what you promised. If you choose this option, after – let’s say – other 200 minutes (you have to be very, very good) I receive my sandwiches.

In this sim story, you have an example of how he main source of waste is actually Batching. Let's review and identify the famous 7 wastes:

Inventory: you have - at every step, at every minute - 99 pieces of inventory idle, and only one piece being processed. Incresing the batch size, your inventory will increase.

Waiting: The first 2 half pieces cut, have to wait until the remaining 99 are cut. This delay is technically called “batch delay”: in this example, at every step you have 99 minutes of batch delay. 396 minutes out of 400 total lead time is batch delay, 99%. Increasng the batch size, your waiting will increase.

Overproduction: you have cut 100 pieces of bread at the first step, that you don’t need. You have left over some cut ham, that you have put in the fridge again, ready for the next time you have to make a ham sandwich (tomorrow?next month?)

Over-processing: if you decide to put a humidity controlled room to avoid your bread gets old while it waits, or if you serialise the pieces, it is over-processing. The customer doesn’t care, it is your problem if you want to keep the sandwich exposed to the enviroment for 400 minutes.

Transportation: you need to move a big box from a station to the other: the box is heavy, and delicate…you don’t want my sandwiches to fall in the ground, isn’t it? If you need a chart, it is your problem, the customer is not happy to pay for it.

Movement: you have a big station (it has to contain 100 pieces) so your operator will move a lot.

Defects: let’s say that you didn’t have any defect, for the moment you have already enough troubles! :)

Let's imagine that you are the general manager of the company: after this disaster, you decide to engage the expert: a consultant with 50 years of experence in Lean Manufacturing. You are paying a lot of money to have this guy, so your expectation are high. Very high. He will arrive, and will simply say:go from batch to one piece flow.

It will be difficult to accept because-afterall- it looks very reasonable to cut 100 pieces once I have my station and my operator ready to cut.

Also here you have 2 options:

1. Send the expert to hell

2. Try one piece flow

If you try one piece flow, you will start building the cell: it will be significantly smaller: just a little table, with the knife ready to use, the butter in a controlled temperature location, the ham readility available (maybe positioned in a slicing machine, so you can cut for every sandwhich the exact amount of ham you need, and it will be fresh and tasty!) the packaging material.

You start the first sandwich: after 4 minutes it is in your customer hand. He can taste it and maybe give suggestions… does he want more ham?ok, pay 1 Euro more and I put double ham. After other 4 minutes you have the second, maybe the customer want another little change. Ok, now the article has exactly the fit, form and function that my customer want. He is extremely happy, and he is not starved. While he is testing his FAI, I can do the FAI sandwich for the customer number 2.?

And so on.?

You don’t need to serialise the bread, you don’t need the room to be with controlled humidity- the piece is exposed to the enviroment 4 minutes instead of 400.

Somebody would notice that at the end in both cases (in the best case) it will take 400 minutes to satisfy the order. Yes, but there are substantial differences:

1. The customer is very happy in the one piece flow scenario. In the batch scenario is not, and if you decide to do the sandwiches as he want to satisfy him, it will cost you more money. Unhappy customers always look for alteratives - as you do, when you are unhappy.

2. You don’t need a cart, or a umidity controlled room, and you will need less space. This means less indirect cost.

3. Finally: Do you remember the sketch at the beginning?let’s say that you sell a sandwich for 3€: when you batch, you receive 1200€ cash after 400 minutes (best case for the cash - considering that you will "stay to the contract"; worst case for the customer, that will be unhapy). When you work one piece flow after 4 minutes you get 3€ and (without considering the opportunity to raise the price if the customer likes more ham) you get a constant cash flow of 3€ every 4 minutes. Your CFO will be happy.

There is much more waste hidden in the batching scenario, but this example shows that also in the ideal condition batching generates waste, by definition.

Conclusion: save the money for the expert, stop listing why one piece flow is not possible in your plant/office/shop wherever you are, and go one piece flow.

Now I know which your objection will be: “wait a second, it takes a lot of time to put every time the bread knife in his place! And what about the safety gloves that I have to use when I cut the bread? I have to take out them at every sandwich and wear the gloves for butter spreading…and so on.

Ok, now you have understood why the starting point for Lean operations is SMED.