OSP: Development Tooling Update

If you are new to this series, you may want to read some of the earlier articles listed in the Series Index.

Personal Schedule

This has been a hectic week. I closed on a house on Friday, flew to Anaheim early Monday morning for SAMPE, returned late last night, spent all of today catching up on messages, and I'm leaving early tomorrow morning for my college reunion in Boston. I'm effectively taking a ten day vacation from OSP work. These are the kinds of things taht don't get accounted for in early scheduling efforts, and are a big reason for including slack in the schedule.

Because I'm so rushed, this week's article will be rather short. Next week's may be a couple days late (I don't get back from Boston until very late Sunday) and will be a review of the SAMPE exhibition.

Tooling Material

In my last article about the OSP fairing, I wrote about the problems we were having in machining the dough molding compound. This forced us to switch to an aluminum groove tool.

Chiachung of Swales Aerospace wrote to ask why we selected aluminum if thermal expansion was a concern.

We really don't know if expansion of the tooling will affect the grid pattern, but we suspect it might be an issue. Aluminum has the highest CTE of the materials we are considering. If it works, then we can safely use another material. If it doesn't, we will probably have to test a lower CTE material before beginning work on the production tooling.

Using aluminum now seemed to give us the most information. If we used steel or some other low CTE material for the test panel but were then forced for some reason to use aluminum on the production tool, we would definitely have to make another flat tool to check for expansion problems.

If you have any questions about the OSP fairing program, please send it to me at composite@aboutguide.com. I answer all questions by e-mail, and I only print names with permission.

Current Tooling Status

The local machine shop finished the aluminum groove tool on time. However, they offset the groove pattern to one side by about 0.015 inches. The pattern itself was correct, so Boeing was able to compensate for the shift in the CNC program.

Two of our technicians hand carried the tool to Seattle last Monday (yes, they worked on the holiday) so machine setup could begin on Tuesday. At this point, we discovered that several other tooling features, primarily the attach holes on the back of the groove tool and the locator bushings on the base plate, were mislocated.

The techs' immediate reaction was to call up the machine shop, yell at them a bit, then tell them we would never use them again. Having been in similar situations before, I was able to convince them of an alternate strategy.

First, I wanted to make sure that the drawings were correct and the machine shop really had made an error. I asked the techs to measure the features and mark up a drawing. When they return, we will compare it to the drawing we gave to the machine shop.

Next, I wanted to try to get something back from the machine shop (i.e. a discount). If we simply call and say we won't use them anymore, they are likely to say OK and let that be the end of it. This was the first time we had used the shop, so they don't see us as a loyal customer.

My plan instead is to explain the problem to the shop, try to find out what happened, and suggest that we would like to use them again if they can correct the problems. This gives them an incentive to make us happy on the current project.

This strategy has worked well for me in the past. While building an airplane wing at Aurora Flight Sciences, we received a batch of epoxy with the wrong hardener. This system was used to bond the ribs and spar to a wing skin, but the bond never cured. We were able to separate the parts without any damage, but we wasted close to 200 man-hours. Even worse, if the bond had cured, it may have been weaker than expected, and we would never have known about it.

When I first discovered the problem, I called the adhesive manufacturer. The engineer I spoke to told me that we did have the wrong hardener and that he would do some further checking.

When our business manager heard about the problem, his first reaction was to threaten the company with the loss of our business. Of course, I tried to convince him this wouldn't get us very far.

As he was getting ready to make the call, the president of the adhesive company called us. They had already isolated and fixed the problem in their QA system which had let the bad batch get to us. Furthermore, he was getting on a plane to our place to see how he could make up for the error.

In the end, we were able to negotiate a long-term discount on future purchases. It didn't immediately pay for our lost time, but we were able to maintain a good relationship with the company.

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