了解如何提升工作效率和提高质量标准，学会分析和改善服务业或制造业商务流程。主要概念包括流程分析、瓶颈、流程速率和库存量等。成功完成本课程后，您可以运用所学技能处理现实商务挑战，这也是沃顿商学院商务基础专项课程的组成部分。
多样性单元班次 4 视频课程
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En provenance du cours de University of Pennsylvania
运营管理概论（中文版）
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À partir de la leçon
第 4 单元 - 质量
质量并不是运营管理唯一的重点，但是质量对于企业长期发展和成功至关重要。本模块将介绍运营中与质量的几个主要方面，导致缺陷的常见原因、发现质量问题以及保障可靠性和标准的常用实践方法。本模块教学结束后，您将了解缺陷可能发生的原因，并且能针对质量和稳定性提出合理的方法。
Rencontrer les enseignants
Christian TerwieschAndrew M. Heller Professor at the Wharton School, Senior Fellow Leonard Davis Institute for Health Economics Co-Director, Mack Institute of Innovation Management
The Wharton School
The size of a batch is not written in stone.
The size of the batch is under the control of management.
Maybe by being smart about the batch size, we can try to improve the process.
We could potentially increase capacity or we can reduce the inventory level.
But how do you set a good batch size? What is a good batch size.
This is the topic of this session. In the previous session, we chose the
batch size B based on demand. We pretty much ignored the rest of what's
setup. Now, consider again the process of the apparel making.
Recall the four steps in the process including the cutting department, section
one, section two and finally, the finishing.
Recall that only the first step, the cutting department, actually had setups.
Now, let's first consider and arbitrary batch size of B equals to five.
With B equals to five, our capacity to cutting is, remember the formula, B
divided by the setup time plus B times the processing time which turns, in this case,
to five divided by twenty plus four times five, and that is five divided by 40 which
is 0.125. Then, the next step we have eight divided
by 40. Notice there's no set-up time here and so
we can just use our good old formula, number of workers divided by the
processing time. So, eight by 40 that is 0.2, five by 30
which is 0.1666. And then, one divided three which is
0.333. So, for batch size of B equals to five, we
see that the bottleneck is going to be at the cutting machine,
Right? You notice that the capacity here is at
its minimum. Now, that was just an auditory backslash
of B equals five. Let's consider another one.
Say, B equals to 50. Now, at B equals to 50, here's what's
going to change. At the cutting machine, we now have to
look at 50 divided by twenty plus four times 50, and that is simply 50 divided by
220, which is roughly 0.227. And the other capacities have not changed,
because there was really no setup involved.
Their capacity is independent of the batch size and remains at 0.1666 for section
two, 0.333 for the finishing department. Now, look what has happened.
By increasing the batch size on B equals five to be 50, we have been able to shift
the bottleneck. Now, the bottleneck is at section two.
Now, this is interesting in the sense that, by choosing the batch size, we
determine the bottleneck.. For B equals five, it looks like all batch size
currently is too small. Why is that?
Because everytime we, we shut down the machine, everytime we shut down the
cutting machine, we shut down the entire plant because cutting is the bottleneck..
However, for B equals to 50, The batch size seems to be too big.
Why is it too big? Well, we are optimizing the capacity or we
are increasing the capacity of the cutting machine that is really of no value.
We are ultimately constrained by section two.
And so, what's the point of operating in higher batches?
Hence, higher inventory at the cutting machine.
Only to notice that the constraint is then at section two.
To choose a good batch size, what you want to do is you want to balance the line, you
know that you can increase capacity here by increasing the bench size, but only to
a point, only to the point of the capacity of the next lower step.
So, at a good batch size, the line is balanced which means as you UNKNOWN
there's a capacity as a function of the batch size, which in our case, is B
devided by twenty plus four times B is exactly the same as the capacity at the
next, lower, step, which is five divided by 30.
Solve this and you get 30 b, B after you cross multiply, is equals to 100 plus
twenty B and then you see that b, B has to be, equals to ten.
At B equals ten, we balance those forces of the one hand, the desire to increase
capacity at the cutting machine but on the other hand, not to waste capacity because
there's a constrain downstream of the resource with the setup.
So, what is the bigger lesson here? The insight I want you to get is that, if
setups occur at the, the bottleneck machine, you have a strong incentive to
increase the batch size. After all, every time that you're setting
up, it's a bottleneck, it's like shutting down the entire plant.
If however, the setup, the setup requires a non-bottleneck resource, then we have
plentiful capacity at that resource, since the process capacity is going to be
constrained by some other resource further down the line.
Now, to see this in action, consider the following example.
A little while ago, I went to a place in Disneyland called The Haunted Mansion.
Here is how the Haunted Mansion works. Like the most Disney attraction, you the
long line of people standing outside, waiting to get in.
Inside the Haunted Mansion, there is an elevator that takes people down into the
basement. Here's how the elevator works.
The elevator has a certain number of people that are allowed in and then
independent of whether there is one or fifty people in the elevator, it takes
roughly two minutes to go down in the elevator.
Once you're in the basement, there is like a long line of moving chairs that take you
through the dungeons, through the basement of the haunted mansion.
There is basically a never ending line of moving chairs.
They make you see quite spooky stuff. Standing in line here and the operations
professor that I am, I was wondering how many people at once should these folks at
Disney let into the elevator? If they just take one person at a time,
Well. what's going to happen is the flow through the elevator would be rather
small. In which case, many of the seats down here would be empty.
If however, you're going to squeeze 50 people into the elevator at once, the
result will be, that the force of the elevators are going to be big, but at the
expense of the inventory of working people in the basement.
How do you set the number of people in the elevator? You want to find exactly the
balance so that the flow through the elevator is equal to the flow of the
size. It applies in my little spooky example here at Disneyland, that is
exactly the same insight I want you to take out of this session.
Setups wastes capacity. So what?
If the resource, the machine we're setting up is not the bottleneck, capacity at that
step is plentiful. So, wasting a little bit of capacity and
return of a lower inventory level, is actually a pretty good idea.
If however, the setup occurs at the bottleneck machine, setting up the machine
is like stopping the entire process. For this reason, when we choose a good
batch size in the process, We're looking for the sweet spot at which
the capacity of the resources was a setup is just at the point of the capacity of
the slowest step in the rest of the process.
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