Production can only begin after the final engineering samples have passed all tests and have been fully approved by the Quality Support Center as well as all of the involved development groups. But that is by no means the end of quality management. Monitoring and testing continue throughout the manufacturing process to ensure that quality goals are maintained.

Quality Assurance for Incoming Parts

Parts received from external suppliers must pass testing at the Toyooka factory Quality Assurance Center before they can be accepted as stock or passed on to the assembly staff. If a sample from an incoming shipment does not meet specified standards, the entire lot will be returned to the supplier. Testing at this stage is rigorous, extending to details like finish durability and micron-tolerance dimensional precision. Here are some examples.

Cell Production & Inspection

Yamaha employs a cell-production system at the Toyooka factory for final assembly rather than the more traditional assembly line approach. Assembly and basic inspection for each product takes place entirely with a single "cell," which is manned by anywhere from one to about ten workers, depending on the complexity of the product. This approach offers a number of advantages. Once a traditional assembly line is set up it is very difficult to modify, and it will occupy the same amount of factory space regardless of the production volume. Production cells, on the other hand, can be dynamically adjusted and rearranged to meet production needs. Production can be interrupted at any time to allow improvements in the process, such as the implementation of different tools or jigs. In many cases the cell workers design and construct their own jigs to suit the task at hand. In fact, cell workers at Yamaha factories are true specialists in the sense that they have extensive knowledge of the product they are working on, and take responsibility and pride in a large portion of its production. When assembly is complete, each and every unit produced undergoes a thorough final inspection right in the cell, so if a problem is detected it can be rectified immediately and effectively.

Sampling Inspection

In addition to cell inspection and testing of every unit produced, samples are taken from every production run for even more in-depth testing. Approximately five samples will be taken per month, depending on the product, with at least one sample taken at the beginning of each production run. Sample production units are taken to a separate area of the factory where they are tested under actual-use conditions. In addition to computer-generated signal sources, standard music sources are used to aurally check sound quality and performance in ways that no test equipment can. All functions are carefully checked as well.