Tag: Heijunka

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Accurate Forecasting

Why can’t we get a more accurate forecast from sales?
Manufacturing managers the world over have the same complaint.

Maybe the word “forecast” is tripping everyone up.

A forecast is a prediction. Maybe it is based on some kind of market analysis, maybe even asking the dealers what they think they will sell. It could be based on a lot of things.

Once a forecast is complete, it is regarded as the best guess for how things will pan out, but those things are (felt to be) largely beyond our influence.

We forecast weather. How many hurricanes will we have this season? Will it rain on the outdoor wedding? Tides are forecast (accurately, but we can’t change them).

A competitor’s sales might be forecast, because we really don’t know their plan.

A sales forecast gets put together, approved, agreed, and entered into the data system.

Then two things happen.

Manufacturing bets the farm on it. They order long-lead parts, establish production plans, set factory capacity. They decide, based on that forecast, how much money is going to be spent, whether anything is actually sold or not. Those decisions often have to be made months in advance.

Meanwhile, all too often, sales has forgotten about the forecast, except perhaps, the top line sales figures. They work hard to sell whatever they can. They push for the big order. They offer the world to prospective customers. They will offer discounts, then push for higher unit volumes to close the dollar targets. Many times they operate on a quarterly (or worse) cycle.. as long as they have a great June, then April and May don’t matter so much.

Meanwhile, back in the factory, when April and May have been dry, they get slammed on June 4th, and end up expediting in parts (at great expense), and working overtime (at great cost), to make product that was sold at a discount.

This is no way to make money.

Let’s get back to what I think is the original issue – the word “forecast” meaning “prediction” (or “educated guess”).

Let’s change one word.
Sales Forecast Plan

That changes the entire meaning.

A “forecast” is a prediction of some event we have little or no control over.

A “plan,” on the other hand, is a set of actions which, if carried out as intended, are predicted to give a specific result. This is a different kind of prediction. This is the kind of prediction that an engineer makes. She analyzes her design, applies her considerable understanding of materials, structure, load transfers, then she predicts at what point that design will fail. If it is a brand new design, it is often tested to destruction (like a new airplane wing). This isn’t to test the design so much as to validate the models used for the prediction.

Sales isn’t engineering, I know that. It involves the most complex thing we know about – human psychology.

The sale planning process goes roughly like this:

  • Financial, margin, volume targets to hit the higher level strategy for profit and growth.
  • What must be sold, when, where to hit those targets. There may be more than one set of options.
  • What must be done to achieve those numbers. This includes consideration for:
    • Unit volumes and mix. (Which are really the only thing the factory cares about.)
    • Total profit targets.
    • The margins that have to be held to hit those profits, at those volume and mixes. (Yes, sales is responsible for margins and profit.. how much money the company can actually keep, not just top line results. “We’ll sell it at a loss and make it up in volume” is not a long-term strategy to stay in business.)
  • Then a process of looking realistically at what must be done, what can be done, deciding on a course of action, and producing a detailed plan to carry it out.

That sales plan then plugs into a production plan. Where there are planned fluctuations, we can apply planned levels of buffer inventory – FIFO inventory, not just make-to-stock inventory, to allow a small time disconnect between when it is made and when it is shipped. This is part of heijunka. (This works in both make-to-order and make-to-stock models, only the mechanics differ.)

Now the entire organization can carry out PDCA.
Are the activities in the sales plan being carried out, as planned, when planned?
If not, why not?
Are they producing the results that were intended predicted? (One-by-one confirmation.) No? OK, what have we learned that we can apply to making a better prediction next time? AND, most critically, What else are we doing to do, because we still have to hit the numbers!

And hit the numbers we must. Not by the end of the quarter. By the end of the month to start. Then in two week increments. Then in one week increments. (And all of this assumes you are making and selling something that doesn’t spoil if it is sitting on the lot for a week.)

The sales plan is the production plan for sales. It is not a guess at how well they will do Just like the manufacturing production plan, it is a firm commitment on how they will support the organization’s overall goals. Yes, reality intrudes and plans rarely get carried off exactly as written. But the thinking that went into making the plan, and the commitment to deliver the results, means the organization, as a whole, is prepared to deal with the unexpected and still stay on track.

Is this idealistic? Absolutely. It is pursuit of perfection. But until the thinking is in place, we will be stuck where we are… waiting for something outside of our control and hoping.

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The Importance of Heijunka

My friend Tom poses an interesting question to production managers:

“If I ask you to produce different quantities and types of products every day, what quantity of people, materials, machines, and space do you need?”

Of course the answer is usually, at best, inarticulate and, at worst, a blank stare. There isn’t any way to know. Add to this the well-established research of the “bullwhip effect” which amplifies the magnitude of these fluctuations as you move up the supply chain, and it is easy to see the suppliers are really set up to fail.

Then he asks another question:

“If I ask you to produce the same quantities and types of products every day, or every hour, could you then answer the question?”

And, of course, the answer is that this is a “no brainer.” It would be very easy.

So the rhetorical question to ask is: Why does Toyota place such emphasis on heijunka?”
But my question is “Why don’t we all do it?”

Heijunka is a process of dampening variation from the production schedule. In English it is called “production leveling.” It comes in two steps:

  • Leveling the daily workload – smoothing out variations in the overall takt time.
  • Leveling the product mix within the daily work load – smoothing out variations in the demand from upstream processes.

Production leveling, however, is difficult, and the management has to have the fortitude to do it. Honestly, most don’t. They don’t like to deliberately set the necessary inventory and backlog buffers into place. So I’d like to explore some of the consequences of not doing it and then ask if these costs are worth it.

Consider this analogy.

Take a look at what modifications are necessary for a vehicle to traverse a rough, irregular road. The suspension must be beefed up, more power is required, the drive train is far more complex for 4×4. The road itself is unmarked, so the driver does not know where he is or where he is going without sophisticated navigation equipment.

Most of this additional hardware is actually unnecessary most of the time. But it might be needed, so it has to be there… just in case.

The driver of this vehicle is primarily concerned with what is right in front of the vehicle, and far less concerned about what is a mile (or even a few dozen meters) up the road. He will deal with that problem when he comes to it. Driving in this environment requires skill, training, experience, and continuous vigilance. People do this for recreation just for these reasons.

Now smooth out the road. Straighten out the hard curves. Give it some pavement. Put in signs so it is possible to navigate as you go. The same speed can be maintained by a vehicle which is lighter, has less power, a simpler drive system, a simpler suspension. Even though the engine is smaller, it is more efficient because it can run at a constant power output, the sudden accelerations are not necessary. Everything is easier.

The vehicle is much less expensive and much more efficient. The driver’s task is far simpler.

When you allow outside-induced variation to work its way through your system, you are putting potholes in the road. You are introducing sudden turns, sudden changes. Sometimes you are washing out entire bridges. People must be more and more vigilant and they simply miss more things. Their mental planning horizon shrinks to what they are working on right now, and maybe the next job. They certainly aren’t checking what they need tomorrow. They will worry about that in the morning.

The Effect on Materials

Even in the worst managed operations, people generally want to be able to provide what they are supposed to. They are motivated to be “good suppliers.” They also intrinsically understand that if they are idle (not producing) this is not good. Even if they are not provided with the tools and resources to do so, they will do the best they can to succeed – even if those things hurt the overall organization.

(I should note that most “management by measurement” systems actually encourage people to do things that hurt the overall organization, but that is another article.)

When these well meaning people encounter problems, they try to mitigate the effects of those problems with the resources they have available.

  • If their upstream suppliers do not deliver reliably they will add inventory so they have what they need.
  • Likewise, if their upstream suppliers do not deliver good quality, they will add some more inventory to make sure they have enough good material.
  • If there is quality fallout within their own process, they will add inventory and up production to cover that. By the way, that increase of production also increases the demand on the upstream suppliers, sometimes in unpredictable ways.
  • If their customers have irregular demand patterns, they will add inventory so the customers can have what they need, when they need it.
  • If there is batch transportation either upstream or downstream from them, they have to accumulate inventory for shipping.
  • If there are on a different shift schedule from either their customer or supplier, inventory accumulates to accommodate the mismatch.

Do you notice a theme here? The key point is: Without the system level view from their leadership, and without the problem solving support, all they can do is add inventory to cope.

Without leveling, any variation in demand will propagate upstream. At each step, two things happen:

  1. Processes that accumulate and batch orders progressively add to the amplitude of the variation.
  2. Irregularities within each process are added to the variation that comes from the customer.

By the time this hits your supply base, it is a tsunami. First the beach goes dry as it looks like the order base has dried up. (This is why you need to constantly reassure your suppliers with a forecast – because they can’t see regularity in your orders.) Then all of that water comes rushing in at once – and your suppliers can’t cope. Worse, they may have allocated the capacity elsewhere because they were tired of waiting on you. Lead times go up, things get ugly.

But even internally, all of this self-protection just adds more and more noise to the system.
So they add more and more inventory.

For a management team that is reluctant to deliberately add some inventory or backlog buffer to contain sources of variation and protect the rest of the system here is some news: Your people are already doing it, and in aggregate, they are adding FAR more inventory than would be needed with a systematic approach. They can only see the local problems, and each is just trying to be reliable – even if their efforts work in the opposite direction and actually introduce more variation into the system.

The Effect on People

I live in the Pacific Northwest of the USA. A fact of life living here is that, occasionally, the earth literally moves under our feet. I can tell you from experience that this is psychologically unsettling.

In our factories we do the same thing to people when the schedule changes every day. In the name of flexibility we shift requirements up and down. Add to that chasing shortages and hot list jobs around, and the daily work place is chaos. People are not sure if they are succeeding. Or, at best, they declare victory because they were not buried today.

Daily kaizen? That is just not going to happen in this environment. When you start talking about introducing flow, you threaten the self-protecting inventory buffers, and I can assure you that you will have a fight on your hands. Why? Because your people believe they need these buffers to get the job done – the job you want them to do. Now you are taking that away? Are you insane?

This is why it is critical to establish a basic takt as early as possible, then immediately start aligning the expectation to just meeting that takt.

Anything that keeps people from meeting takt becomes a problem and must be addressed. This is jidoka. Heijunka is a block in the foundation of the TPS “house” for a reason. Unless people are standing on solid ground, they can’t even consider anything like “just in time” or “stop and respond to problems” because they are spending all of their mental bandwidth just trying to figure out what is going on hour by hour.

Conclusion

When I was a military officer, we were trained in tactics designed to present our opponent with a constantly changing picture of what was happening. We wanted to inject as much confusion and uncertainty as possible. The mechanics of defeat on the battlefield are simple: The force subjected to this first shifts from action to reaction. They lose initiative, and therefore lose psychological control. Next the horizontal control linkages start breaking down. Each sub-unit starts to feel isolated from the others. They feel less a team and more on their own. Then, as more and more of their attention is shifted to self-preservation, the vertical chain of command breaks down. Each sub-unit is now mentally isolated and can be defeated in detail.

Ironically many factories are managed such that the workers on the shop floor are subjected to exactly these same conditions – and we wonder why they have a cynical view. We are defeating ourselves.

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A Systematic Approach to Part Shortages – Part 2

For kanban to work well, there has to be a solid foundation under it. That foundation is production leveling or heijunka.

Before I get to far into this, though, I would like to point something out: At the mention of leveling, people who are only just learning about kanban will point out all of the good reasons why leveling is difficult. Here is a key point: The problems caused by running kanban without good leveling pale in comparison to the total chaos that ensues if you try to run MRP without leveling. I’ll stay out of that little rabbit hole until another day though.

Production leveling has two parts.

  1. Leveling the production volume.
  2. Leveling the production mix.

The operation I described in Part 1 was relatively small, so it was a simple matter to set up a totally manual system to do this. By small I mean they had two major assembly lines running at a rates on the order of 10 units / day. The product was about the size and complexity of a medium to large-sized photocopier (though not a photocopier). The assembly lines had about half a dozen positions each. There were several hundred parts from about as many suppliers. (Different story.)

The objective in leveling volume is for the production line to see demand as an image of the takt time, and to protect that signal from variation in actual orders and shipping. At the same time, the shipping dock was to see deliveries to the finished goods buffer at takt time, regardless of minor and medium problems in production.

To accomplish this they separated the “big lump” of inventory that typically existed in shipping into two physically separate buffers.

The Withdrawal Loop

Customers, unfortunately, rarely order at takt time. The purpose of the buffer in shipping was to absorb this variation and make the actual demand appear as if it arrived exactly at takt. The organization also tried to take out some of the bigger spikes in customer orders by working with dealers to get more transparency into actual customer order patterns; as well as trying to level actual promise-to-ship dates at least weekly if they couldn’t get it to daily. That helped a lot. A more sophisticated order entry system would have worked better, but that luxury wasn’t in place yet.

Back to the buffers. Each unit in shipping had a withdrawal kanban card attached to it. As orders were released, a unit would be pulled from this buffer and shipped. The withdrawal card went back to the production control department. Those cards were placed in the inventory management box. This box had series of slots that indicated authorized inventory levels. A card in one of the slots indicated inventory we didn’t have, an empty slot indicated inventory on-hand.

There were limit markers at near each end of the row of slots. As long a the end of the row of cards stayed between those limit markers, everything was regarded as OK. They did not try to chase a particular level of inventory with production.

The scheduled production rate was 10 units / day.

Each morning Production Control would take 10 cards from their box and put them into the leveling box in shipping. That box had slots that corresponded to times of day. The cards were evenly distributed at the takt-time interval. As that time came up, shipping would take the withdrawal card from the box, go to the end of the production line, attach their card to a unit, and move it to the shipping buffer.

This seemed like a lot of trouble, but it served a purpose. It was to hide the irregularities of shipping schedules and actual order dates from assembly. They saw a clean, paced signal exactly at takt time. The process was designed so that assembly saw a perfect customer, even if the customers were far from perfect.

If management didn’t like the size of the shipping buffer, they knew exactly what problem(s) must be solved to reduce it – they needed to improve the dealer ordering and management processes so dealers would stop using deep reorder points and ordering weeks worth of product at once.

The Production Loop

When units were withdrawn from the end of the line, they were actual pulled from a FIFO buffer. In this case, the buffer held about 4 hours of production. Why? Most problems in production were cleared within that time. Only a bigger problem would starve the buffer and affect the withdrawal loop. Thus the purpose of this buffer was to make assembly appear as a perfect supplier to their perfect customer. They could supply exactly at the agreed-upon takt time.

Each of these units had a production kanban card attached to it. When shipping came to pull a unit, they would pull the production card and leave it in a kanban post. They would attach their withdrawal card and take the unit. Thus switching the cards transfers ownership of the product from one loop to the next. Since a kanban card authorizes a specific quantity to be in a specific location, if someone wants to take something somewhere else they need to attach a card authorizing them to do so. That was the case here.

The production cards went to the front of the assembly line. There were three slots there. One green, one yellow, one red. If everything was running smoothly, the card would go into the green slot, and when the next unit was started, the card would be pulled from the box and attached to the unit.

If the line were a little bit behind, there might still be a card in the green slot. Then the next card would go into the yellow slot. This would automatically signal the assembly manager that there was something that needed some attention.

The next card would end up in the red slot. This was the point when, if they weren’t already there for a known problem, they were in “line stop” mode. Anyone who could be helping to clear the problem should be helping to clear the problem. Why? The money machine has stopped running. Everyone is now being paid only because the shareholders are lending them money. The idea is to get the money machine running as quickly as possible, and it is the most important thing. This was a simple phased escalation process, and was part of their overall andon / escalation system.

Did it work?

All I can say is that it worked a hell of a lot better than what they were doing before. It took two or three serious tries to get this into place and keep it working, and they probably fell off the wagon a couple of times after that. There were always immense pressures to “reduce inventory” at the end of the quarter, for example, which would have management directing to starve out the shipping buffer, or push it out early. But, in general, when it was working, overtime was lower, things were more predictable, problems were identified very quickly.

But…

Yes, it looks like a lot of manual work involved. But I want to be really clear – the total time spent moving all of these cards around was a fraction of the time that had previously been spent investigating status, working action messages, making calls to find out what was happening, etc, etc. For some reason people seem to think that deliberate activities raise the total amount of labor involved, and that somehow, the time spent running after information and chasing problems is free.

Setting a standard and following it injects an element of stability and calm into an otherwise chaotic workplace. Once this basic foundation is in place it is far easier to improve overall efficiency because now there is an actual process to improve.