Resultados

One day, a manager at FPL was describing his plans for a major power plant upgrade to Dr. Noriaki Kano (a conversion from oil-fired to both oil and gas-fired capability). After listening for a while, Dr. Kano asked the manager where his Quality Process Chart was. Our plant manager didn’t know what he was talking about, but all Dr. Kano was looking for was the PLAN (the “5W1H”) for the project. Many Process Control System examples that we’ve seen look confusing. They usually depict the details of specific industrial processes (and often just a portion of a complex process). Let’s take a very simple “production” process to illustrate the concept and application of the Process Management Chart - we’ll make instant coffee!

Process Control Chart Elements

Since we’re the customers, we’ll ask ourselves how we like our coffee (the customer needs):

Customer Needs: Hot, Sweet (but not too sweet), Smooth, not Bitter, Served in a Mug, Slight “Chocolaty” taste, and Enough to last through Breakfast. Also, the price per cup should be less than 25 cents/cup.

Product Quality Characteristics (some are CTQs!): We’ve developed a product called Swiss Chocolate Coffee that we think meets “our”

customer’s needs. The quality characteristics of the product include:

Customer Need Quality Characteristic Measure/Target/Specification Limits C. Sigma Target Sweet (but not too) Sweet 3 +/- 0.5 (on 1 - 5 Sweet Scale) 6

Smooth Smoothness 5 + 0, -0.5 (on 1 - 5 Smooth Scale) 5

Not Bitter Bitterness 1 + 0.5, - 0 (on 1 - 5 Bitter Scale) 5 Chocolaty Taste Chocolate-ness 2 +/- 0.5 (on 1 - 5 Chocolate Scale) 4.5

Hot Temperature 160 F, ± 10 F 3

Enough Volume 7 oz, ± 0.5 oz. 6

Served in a Mug Served in a Mug 8 oz Mug + 1, - 0.2 oz. 5

Price Sales Price 25 cents/cup N/A

Now that we know what we’re trying to produce, we move to the production process. We’ve identified a supplier (Major Foods) who makes an instant coffee powder mix that meets the first four quality characteristics.

The city water supply has too high a mineral content, we’ve done experiments to show that we can’t meet the Bitterness quality characteristic with city water, so we have decided to purchase distilled water in bottles to meet this need (OOPS, the cost just went up!). We’ve also purchased a nice 8 oz. ceramic mug that has a picture of our favorite commercial air conditioning system on the side.

Having obtained the raw materials, the production process can now be laid out:

This picture assumes the availability of the coffee mix and distilled water. We could add the steps of obtaining these supplies from our vendors, but let’s keep the example simple.

The next steps in constructing our Process Chart are iterative. Since we’ve established the How, we could address the Who. For this example, we’ll assemble the following work force: Filler/Heater and Mixer/Server.²¹

With this “organization,” we have assigned authority for the production operations and can then think about how to control production so that the quality characteristics (and their targets) are achieved.

Let’s take each step and determine what needs to be controlled there and how control will be accomplished.

Fill Ceramic Mug with Distilled Water - The quality characteristics that this step affects are Served in a Mug and Volume. Our Filler/Heater must then obtain the correct mug and fill the mug with 7 oz. of distilled water. These become his control points. One of his checkpoints may include “Mug with Commercial Air Conditioner Picture” to assure the correct mug is obtained. Production engineers have decided to mount the distilled water bottle on a stand with a spigot. Since the same mug is used every time, they’ve also scribed a fill line inside the mug - this is the Filler/Heater’s check point to assure that 7 oz. of water are added.

Heat Mug/Water in Microwave - Here, the Filler/Heater uses the microwave to heat the mug and water. Experiments have determined that the Filler/Heater must actually heat the water to 175F so that the actual served temperature is 160F (for temperature losses due to adding room temperature coffee mix and the ambient losses during the mixing/serving process steps). The 175F becomes his control point for this operation;

his checkpoint is to set the microwave at “2 minutes, High Power setting.”

Add Coffee Mix to Hot Water - Given that the vendor has provided us with the right coffee mix, our Mixer/Server is responsible for adding the correct quantity of mix to the heated water. We’ve determined that three teaspoons of coffee mix in the 7 oz. of hot water will satisfy the taste-related characteristics. The amount then becomes the Mixer/Server’s checkpoint.

Stir Coffee Mix/Water - This step’s main purpose is to assure that the coffee mix is dissolved in the hot water. Since the coffee mix has been found to float on the water surface, the mixing must continue until no “lumps” of coffee mix are on the surface. This is the control point for this process. The Mixer/Server achieves this by first pushing the mix into the water and then stirring the mix.

Serve Coffee - This is a transportation step. Control items include not spilling the coffee, not dropping the mug and delivery to the right customer.

Note that for these last three steps, the processing time is a control item. If this is too long, the water will have cooled too much, if too short, it may be too hot for the customer. Again, experiments have determined that processing time should be 1 minute (plus/minus 10 seconds) to meet the

21We know that you “downsizers” want to combine these jobs, but come on, it’s just an example!

Swiss Chocolate Coffee Production

quality characteristic of coffee temperature. Note that the “factory environment” plays a role here - the ambient temperature of the production area is a major factor influencing heat loss during this time - does it need to be “controlled” or could we make the production process “robust” by insulating the mug during production?). Measurements of the current process’ capability indicate that this can be achieved. If not, the previous process’ target level for temperature could have been increased.

All of this information can now be summarized on our Process Management Chart for Swiss Chocolate Coffee Production (next page).

Now, although this chart looks complicated, you can track how the word descriptions of each process step are summarized on the Process Chart.

The chart is a form of “shorthand” for the Who, What, When, Where, Why and How (5W1H) of the process. With a little practice, these charts can become an effective way of designing a production process or standardizing a current process. A few notes on the Process Management Chart:

1. Do Not get trapped into one format (or even try to copy the one shown below). The basic questions you want answered on the chart are the 5W1H, but think through how each application should be designed. Some process management charts also include a “response” column. How will special causes of variation be addressed? How will process capability improvements be prioritized and worked?

2. For manufacturing-type processes, the Process Chart may be developed in two stages - during design, the production process is “roughed out”

on a Process Chart; as the production planning moves closer to actual production, the details are fleshed out in the actual production Process Chart.

3. In the process chart shown above, the actual “how-to” do a certain process step was listed as a Work Standard (SCC-001, SCC-002, etc.). The development of both the process chart and the work standards needs to be coordinated.

4. The Process Chart should be followed during actual “production.” It should identify not only what should happen when the process is going along smoothly, but also who and what actions are to be taken when something “bad” happens. You’ve probably seen the Saturn™ TV commercial where the production worker talks about the first time he “pulled the cord” and shut the production process down. This is an example of authority delegated to the best place on-the-line. Response plans for assignable causes of variation may be different from those associated with common causes.

5. Notice that, although there are many factors that could affect the quality of our Swiss Chocolate Coffee, only the most important factors have been identified on the process chart. Here’s the Pareto Principle at work.

6. We’ve included the QCD (Quality, Cost, Delivery) column in our process chart. We put it there to help remind us that QUALITY is multi-dimensional and that we need to think about how we control all the important dimensions.