Sep 21 2020
As part of a discussion started by Lance Richardson on LinkedIn, I stated as a fact that SPC was not part of the Toyota Production System (TPS), which prompted several contradictors to tell me I didn’t know what I was talking about. The “evidence” they provided, however, does not refute my statement. It confirms it instead.
What is SPC?
By SPC, I meant the body of knowledge currently taught by the ASQ and as part of Six Sigma training, and centered on Control Charts, as developed by Walter Shewhart in the 1920s and refined until the 1940s. It includes none of the data science developed since the computer was invented.
SPC on the Toyota History Website
As evidence that SPC is part of TPS, Steven Bonacorsi directed me to a page on the Toyota history website describing the company’s actions regarding quality from 1949 to 1965. That it is the most recent reference to SPC by Toyota does not say anything about 2020.
You can find the most recent picture of a Toyota employee working with a Control Chart on Art Smalley’s website. It is from the 1950s. According to him, by the time he worked at Toyota, in the 1980s, “these charts were essentially gone.”
Quality in a Toyota Forklift Plant
Then Robert Testerman instructed me to watch “SPC applied all over a Toyota forklift plant” in a Youtube video from 2016:
Perhaps he should take his own advice and watch this video. About half of it is about quality but none of it about SPC. It’s all about all 900 employees inspecting their own work and checking every part. There is not a single control chart in sight.
Toyota achieves quality with methods that have nothing to do with SPC, and it is misleading to promote SPC by describing it as part of TPS in 2020. The keywords are the following:
- One-piece flow, for rapid problem detection
- Rapid response
- Successive inspection, with each operator checking the work of his or her predecessor
- 100% go/no-go checking
The approach is now called JKK, for Ji Kotei Kanketsu (自工程完結), which literally means “autonomous process completion.” It works in automotive; it may not in semiconductors or frozen foods.
For the Curious
Several reactions to this post on LinkedIn meant “curious.” This topic has been a concern of mine for some time, and I have written articles and blog posts about it over the years that may satisfy the readers’ curiosity:
- When to Use Statistics, One-piece Flow, Or Mistake-Proofing to Improve Quality (2001)
- Is SPC obsolete? (2011)
- Is SPC Obsolete? (Revisited) (2017)
- There Is More To Data Than Just Numbers (2017)
- Acceptance Sampling In The Age Of Low PPM Defectives (2017)
- Updating the 7 tools of QC (2019)
And Renaud Anjoran also chimed in: