A Dialogue on Precision: A Matter of Millimeters

Julie Chu (Plant Manager, CAF Hangzhou Plant) and Yao Lijian (STA Manager)

Recently, the Ford Nanjing REC hosted the latest session of its Problem Solving Series Forum. The event featured insights from senior leaders, including Jerry Lin, Mike Chang, Jade Song, Beryl Bai, Julie Chu, and Yao Lijian, bringing together colleagues from Manufacturing, Quality, and New Model Launch teams for deep discussion.

Julie Chu (Plant Manager, Changan Ford Hangzhou) and Yao Lijian (STA Manager) presented a compelling case study regarding Body-in-White (BIW) and Trim Fit & Finish (PCF) optimization.

The challenge involved a high volume of components located in areas highly visible to the customer (such as door panels and the instrument panel). In these zones, a gap difference of just 1 or 2 millimeters is enough to trigger customer complaints.

The Debate: ±2.5 mm or ±1.0 mm?

To solve this, the factory embarked on a two-year continuous improvement journey. The process involved extensive Gemba walks, identifying variable factors, redefining control standards for every point, tooling adjustments, joint "slow-builds" with suppliers, and rigorous daily monitoring.

This success story sparked a heated debate among the attendees:

Spec vs. Satisfaction: In our daily work, do we prioritize meeting the technical spec or ensuring customer satisfaction?
The Standard Paradox: If a part meets the spec but still causes complaints, is the standard itself flawed?
Over-Engineering: If customers aren't complaining, is tightening our internal standards considered "over-spec"?

The Philosophy of Precision

Jerry Lin, Ford China Manufacturing, Quality and New Model Launch Director, pointed out that every part has inherent tolerances. If we only rely on tightening design tolerances during development, costs will inevitably rise.

Director, Ford China Manufacturing, Quality and New Model Launch

He cited a lesson from his time on the front lines at Mazda 20 years ago: While the BIW welding spot accuracy spec was ±1.5mm, the welding line voluntarily pressured themselves to control process capability within 1/3 of that standard. Why? To prevent tolerance stack-up (the accumulation of minor variations) from causing quality issues downstream.

Jerry Lin: "We must elevate our process control capabilities and strive for perfection. That is the only way to achieve stability across the entire production process."

Key Takeaways: Root Cause Analysis

Through the analysis, the team reinforced several critical principles:

Genchi Genbutsu (Go and See): The critical importance of going to the scene and seeing the actual object immediately.
No Silver Bullets: There is no single magic solution for all problems; every issue requires specific analysis.
Data Integrity: Is the data reliable? Is the measurement process behind the data valid? Uncalibrated tools yield fake results.
Prevention: How do we stop the problem from recurring?

The Hangzhou Plant example also provided a blueprint for sustaining improvement. This includes frequent site visits, continuous identification of new variables, dual control (supplier & plant), unified measurement methods, and calibration of online auto-inspection tools.

Crucially, this two-year manufacturing struggle yielded a valuable lesson for the upstream teams: potential quality risks must be anticipated and mitigated during the Product Development phase.

Jade Song (Ford China Quality Director)

Jade Song, Ford China Quality Director: "Quality improvement brings value. We shouldn't focus too much on 'Trade-Offs.' Instead, our energy should be directed toward quality control, sustaining our improvements, and preventing recurrence."

Building a Culture of Problem Solving

This dialogue is part of a broader "Problem Solving" curriculum. Earlier this year, the team identified "Problem Solving" as a critical capability gap. In response, a series of customized courses was launched, including: 6-Sigma Green Belt Training, 3L5W (Five Whys) + 8D Review, Hypothesis Testing etc. Trainings on Correlation Analysis, Regression Analysis, and MSA (Measurement Systems Analysis) are coming soon.

Additionally, the team has translated and compiled 6-Sigma Black Belt textbooks to help colleagues in PD, Manufacturing, Launch, and Quality systematically master Lean Manufacturing and continuous quality improvement.