Takt time

Takt time = Customer demand / working hours, it means the maximum of time per piece in output which can achieve the customer demand.

Cycle time = the total process time in sum of all work station.

In process design, we are following the thinking of takt time to work on, but it is hard to achieve perfectly. When we received customer demand, usually, it is an annual usage, we would calculate the takt time accordingly. Then, we will select a manufacturing mode to fit with the takt time. Nowaday, most of the process engineers always jump to the select the mode according to their experiance without the supporting from takt time. Actually, the engineers can intuit to know what kind of manufacturing mode is suitable according to the annual usage quantity. Whatever, I suggest we should calculate the takt first, and I called this with "customer takt time".

For selecting manufacturing mode, I have some explanation here. No matter what kind of manufacturing mode you selected, the consumption of process time is located in a specified range. In other words, you can not adjust the process time in a big gap. We was challenged if the takt time is 100% ramp up or 50% drop. If we face the cases stated in unstable of customer demand, what should we do? Can we adjust the process time as the takt time changed? Negative, but we can choose another manufacturing mode.

Afterward, according to the selected mode, we can calculate the cycle time according to the mode. According to what kind of manufacturing mode, you can adjust the configuration of the process flow to have a cycle time and process time for every stations. With that numbers, we can fine tune the process flow to meet with the takt time. I called this with "process takt time". Compare these two takt time, "customer takt time" and "process takt time", to see the process can achieve with customer requirement or not.

Finally, all the production schedule must be arranged according to the balanced takt time. It is talking about the execution force to sustian the process flow.

Another question we always have, how about if there were many different products produced in one production cell? For this case, we should do the same in most of the stages above, but we have to balance all the takt time together. Let's say if we have three products are producing in a cell, we need to adjust the sum of takt time of three products together. make sure that there is no exceed working time left for the scheduling. It looks difficult, but just try for that. We always found that it is not difficult as we though.

Production smoothing

Many months ago, we held a Kaizen program with external consultant for production smoothing. Below is the study from me to summarize the concept of production smoothing for your reference.

It came from Japanese term "Heijunka" (平準化), sometime, some people called it as "production balancing" or "production leveling". It is a system designed to achieve a more even and consistent flow of work. Heijunka as a concept is closely related to lean production and just in time manufacturing. It also means two different, but related, things. One is the leveling of production by volume. The other is leveling production by product type or mix. Use for level the resource of production in machine capacity, working space, operation capital and manpower arrangement including supporting departments.

According to the figure shown above, the red line represents the customer demand and the green line represents the production capacity. If we plan for production schedule as red line, because of its high variance of demanding, due to the resource issue, it will cause much of waste in manpower or machine capacity. Production smoothing is using to plan and try to lower down the variance of scheduling but achieve the target for customer demand. Offcause, it is no way to retain the capacity in a straight line profile, but versus the red line, it becomes more consistent and easiler for planning.

The slower but consistent tortoise causes less waste and is much more desirable than the speedy hare that races ahead and then stops occasionally to doze. The Toyota Production System can be realized only when all the workers become ortoises. ~~~ From Ohno, 1988

Leveling by volume: Toyota's view is that production systems that vary the required throughput suffer from mura and muri with capacity being 'forced' in some periods. So their approach is to manufacture at the long-term average demand and carry an inventory proportional to the variability of demand, stability of the production process and the frequency of shipments. The advantage of carrying this inventory is that it can smooth production throughout the plant and therefore reduce process inventories and simplify operations which reduces costs.

Leveling by product: Most value streams produce a mix of products and therefore face a choice of production mix and sequence. It is here that the discussions on economic order quantities take place and have been dominated by changeover times and the inventory this requires. Toyota's approach resulted in a different discussion where it reduced the time and cost of changeovers so that smaller and smaller batches were not prohibitive and lost production time and quality costs were not significant. This meant that the demand for components could be leveled for the upstream sub-processes and therefore lead time and total inventories reduced along the entire value stream.

At last, we adjusted the customer demand forecast and production schedule in the program. But, one thing so important we must remember that, "the world is changing everyday". The requirement from customer is also changing as well. Production smoothing is not a improvment program, at some point of view, it should be said as a scheduling concept. We can not fix all the resource planning problem in one program, actually, it imply the concept needed to be combined with daily planning job.

Benefits of leveling the schedule,
1. Flexibility to make what the customer wants when they want it.

2. Reduced risk of unsold goods.

3. Balanced use of labor and machines.

4. Smoothed demand on the upstream processes. (people, machine, suppliers)

Belief 2 - Flamingo 火烈鸟

On last week, I read a magazine and learned some knowledge of Flamingo. It was found that the migration of flamingo is interesting and shown us some ideas when we are facing the challenge of leading, or we can say the challenge of culture change in organization.

Flamingo is a gregarious wading birds in the genus. They are found in both the western hemisphere and in the eastern hemisphere, but are more numerous in the latter. Flamingo has white color originally and its red feather came from the mineral from its feeding. The migration of flamingo is not its habit periodically, it only migrates to other area when the food was shortage or mutation of its living area. Its migration is always started in the night to prevent the attacks from other accipiters.

The most interesting thing is its way how it starts the migration. The migration is usually started by one flamingo and it is always identified as the leader of the group. When the leader started to fly to other area in the first trial, there are only a few members to follow the action. There were only 5 to 10 flamingoes to follow and the leader will fly back to the base and take a rest. Afterward, the first tier of 10 flamingo starts the migration again. This time, they will fly many turns on its living base to attract more followers to join the tier, it may be 100 flamingoes to follow the action but 100 flamingoes were still the less portion of the group. Therefore, the second tier of 100 would back to the base. It is hard to say how many tiers can start the migration successfully, it started from 1 to 10, to 100, to 500, 2000, ... to all finally. We can find that if the number of bird in that tier exceed a certain portion or percentage of the group, all the group will start the migration.

In my point of view personally, the migration of flamingo is similar the way we implement the lean transformation. The leader starts to train the team and it will has some members found that it is meaningful and follow the way to do. After many improvement actions, some other members will find that worth to follow according to the result of improvement project and the number of follower will increase accordingly. When we are pushing the culture change, it needs a certain number of members to change and follow first. When it exceed the certain percentage, the culture will form in the organization. The problem is the leader has the passion enough to lead so many tiers until the culture is formed. It is the same way of how to start migration of flamingo. Why we give up the lean transformation when we faced the resistance of culture change? If you face the problem on the way in lean, let's tell your members for this story.

Belief 1 - Kong Zi 孔子

"Lun Yu" is a ancient book of China which wrote by "Kong Zi". He was the great teacher of all Chinese and his thinking influence all of us till now.
Here is a story in Lun Yu recorded a conversation between Kong Zi and his student,

Student asked, "Master, what are the core factors to establish a country?"

Kong Zi replied, "Army, food and belief!"
Student asked, "If we needed to ignore one factor, which is your choose?"

Kong Zi replied, "Army!"

Student asked, "If we needed to ignore one more factor, which is you choose?"

Kong Zi replied, "Food!", he explained. "Everybody will die from of old, nothing can be done without belief."

Yes, if everybody believe and trust their country, even no food and they are starving, even no amry and they are attacked by other civilization, the country still can be stable. Without their belief, even they have food and weapon, the people in that country attack each other for more fortune and power. The country is mess and all the citizen are unhappy.

Belief, also is a core factor of culture. It is existing in every company, even in lean manufacturing transformation. During implementation of lean manufacturing, even the result of improvement is not significant enough to shown all the members, if the people still trust the methodology can help them to improve, the implementation is continuously going on. In some companies, the belief of lean is not enough, even they have a little bit improvement in any kind of field, once they faced the problem or block, they will step backward and are going to give up. Culture change is so important of success in lean transformation. On the way for improving efficency, we should do something to improve the culture and enhance their belief of lean as well. Otherwise, the lean can not be sustained and it is the most common of failure of lean transformation.