A process that requires the inspection of each individual unit or component received from a process or manufacturer is said to be “100 percent inspected.” When fabricators initially consider a quality program, this is what they imagine is necessary.
This 100% process, however, is time- and labor-intensive, so it should only be employed when the results or negative outcome become more important or valuable than the cost to perform. An example might be inspecting O rings on a space shuttle. Should all the rings be inspected? A device used for surgery? Some mission critical processes might have a very high failure cost, so the need for 100% inspection is apparent. But what about less obvious situations? How much inspection should we perform?
Fault tolerances or failure tolerances are generally evaluated as an industry. Examining the truss industry and its history, we find the most likely issues that cause failure actually involve the installation of the product. Installation-related failures are far more probable than manufacturing issues. Much lower in likelihood are failures that involve design errors, including wrong loading, misapplication of material values, and incorrect interpretation of design elements.
So, if manufacturing errors are rare, then what needs to be done? Do you need to address it? The answer is: YES. The truth is that each manufacturer must address their responsibility to produce a product free from manufacturing defects that can affect their performance.
Manufacturing quality may not be a major issue in a different context of potential product failures, but it is a critical issue for the success of your business. Let‘s discuss a few reasons to employ a TPI 1 compliant program.
ANSI/TPI 1-2014 Chapter 3 covers quality standards for the manufacture of metal plate connected wood trusses. It requires the use of a manufacturing quality assurance procedure, and periodic auditing by an approved inspection agency. This program has been in use by many manufacturers for decades and has proven to be an essential part of their organization.
- A fabricator who recently adopted the program after a year describes the experience as cathartic. Implementation has relieved the owner of worrying about his process and quality. He now understands where his product stands in the way of industry requirements and he knows his plant is functioning properly. For this reason alone implementation costs are justified.
- Another side of the equation is legal responsibility. In the event of a product liability situation, quality will almost always be brought into the case. Sometimes that lack of a quality assurance procedure on the part of the fabricator sinks his chances to prevail.
- Quality has a major impact on repeat sales. Purchasers migrate to suppliers that build products that are dependable. Once the reputation for inferior products is created, it is difficult to overcome.
- Implementation of a solid QAP will streamline manufacturing. It will focus on areas that need fine tuning and will reveal areas that are running well and need less attention.
Inspecting every truss, every member, and every plate is not a necessary or reasonable expense based on the failure tolerances—and a proper quality assurance program will not require that level of commitment. On the contrary, a program that uses sampling over time will provide an accurate measurement of quality.
- This program requires three inspections per building station, per shift, per week.
- This data is collected and analyzed on an individual basis and often is accumulated in a database to evaluate trends and areas that require attention.
- The accuracy of the data depends on randomness, consistency, honesty, and integrity.
- The reports should be an accurate “as-built” snapshot of the truss being inspected.
- The information gleaned from the report should be shared through the shop process so corrections can be made.
- The program should be tailored to the facility.
There is not a one-size fits all application. Each program should be adjusted to fit the needs of the manufacturer while meeting the minimum requirements of TPI 1. And once you have a proper QA program in place, you’ll see the benefits.