7
Create House of Quality 2, the Translation House
The second House of Quality will be built in this chapter by using the Quality Control (QC) metrics from Chapter 6. How does this new house relate to the previous one? House of Quality 2 (HOQ2) is built by interconnecting elements of the previous House, House of Quality 1 (HOQ1) the Customer house. We will use the Critical to Quality (CTQ) metrics from HOQ1 defined in Chapter 5 and combine it with the recently defined QC metrics. The combination will help us translate the CTQs into QC metrics and that is where HOQ2 gets its name as the Translation house. The following sections will show how these parts are organized and assembled together.
7.1 Organize the QC Metrics
In the previous chapter, we captured the QC metrics of our paint coating from our R&D team. Figure 7.1 shows the process of placing the QCs in HOQ2. These will be the first building blocks for creating the top room of HOQ2. This room has the QC metrics with their expected values and acceptable ranges. The QC details are highlighted in Table 7.1. In the table, the rightmost column indicates how the best results are attained either as reaching a target value or the direction for improvement.
TABLE 7.1
QC Metrics for HOQ2
QC Metric |
Specification |
Metric Improvement Direction or Target |
Gel time @ 250°F |
<60 seconds |
Lower is better |
Number of cracks |
0–5 |
Lower is better |
Viscosity |
Ford #4 cup (20–24 seconds) |
Target |
Orange peel appearance |
Pass = 1 no orange peel Fail = 0 orange peel present |
Target |
60° gloss |
40–70 units |
Target |
These variables will be placed on the top room of HOQ2, using all the information gathered in Table 7.1. Once that data has been placed in the house, it should resemble Figure 7.2.
FIGURE 7.2
QC targets and units of measure added to HOQ2.
7.2 Combine the CTQ and the QC Metrics
We cascade from HOQ1 the CTQ metrics into HOQ2. The structure is like the first house we built, HOQ1, by placing the descending CTQs on the left side of the main room of HOQ2, as shown in Figure 7.3. This step is important to note since it connects the two houses together and flows the concepts captured from the customer side with our internal quality of the product. In other words, it connects the customer’s expectations via the VOCs and CTQs with our R&D technical definitions given by the QC metrics.
FIGURE 7.3
Cascading the CTQs from HOQ1 to HOQ2.
We ranked the CTQs in HOQ1 for our example customer Tubing Experts back in Chapter 5. We then created a CTQ rankings Pareto chart that summarizes the effect that each CTQ had when combined with the impact of the VOC as shown in Figure 7.4. Later, we will construct the main room of HOQ2 once the top and side rooms are filled in as shown in Figure 7.5. Then, we will examine and evaluate each combination as we did for HOQ1 in Chapter 5.
FIGURE 7.4
CTQ rankings Pareto chart.
FIGURE 7.5
CTQs and weights added to HOQ2.
7.2.1 Build the Main Room of HOQ2
We are now ready to combine the QCs with the CTQs. The order on how to interpret the relationship between QCs and CTQs is shown with the direction of the arrows in Figure 7.6.
FIGURE 7.6
How to rate the relationship of a QC with a CTQ in HOQ2.
The interpretation of the relationship between QCs and CTQs with the arrows is similar on how we did it in Chapter 5. We will use the same rating scales of the 9, 6, 3, 2, and 1 with strong relationship being a 9 and weaker ones down to 1. If there is no relationship, it will be kept empty. We will start with the leftmost column and going down the rows one by one to assess each CTQ. The calculations are the same as it was done for the first house.
7.3 Rank the QC Metrics
7.3.1 House of Quality 2
The findings in HOQ2 are just as impactful as the first house. HOQ2 was combined with metrics that have been gathered from various sources and reveals interesting relationships (Figure 7.7). These interactions are expressed by looking at the ranking of the QC metrics either at the bottom of HOQ2 or at the Pareto chart in Figure 7.8. Gel time is the highest ranked QC metric with a value of 25.3% followed by two others that are ranked also near the 20% range: 60° gloss (22.6%) and number of cracks (19.4%).
FIGURE 7.7
Completed QCs and CTQs in HOQ2.
FIGURE 7.8
QC rankings Pareto chart.
The Translation house is now completed. This House of Quality combined the requirements from the customer side by using CTQs and adding the R&D defined QC metrics. The matrix of weighted information from the two sources cited helps us understand those requirements in a balanced manner.
As mentioned before, the information will be used later to assess proactively the Quality metrics that can be used in operations. Just like how we cascaded HOQ1 into HOQ2, we will be doing a similar approach to build HOQ3 the Manufacturing house. This linkage is vital to create a seamless connectivity between what the customer wants and how we can make it in manufacturing. We are now one step closer of hearing the customer voice all the way to the factory floor.