What to Do When Three Special Characteristics Lists Don't Match? —— A Five-Step Method for Compiling and Verifying the SC/CC Master List

The customer requests a special characteristics list. The quality department copies one from the drawings, the design engineer exports one from the DFMEA, and the process lists another according to the control plan. When the three lists are placed together: the drawings have 12, the DFMEA has only 9, and the control plan includes 2 that are not marked on the drawings. The auditor asks, "Which one is the standard?" and no one on-site can answer.

The root cause of such issues is that four documents are all referencing special characteristics, but none of them is suitable as a master ledger. Drawings are organized by part dimensions, FMEAs by failure modes, and control plans by processes. Each has a different organizational logic, making it impossible for any to serve as a consolidated ledger. The value of the list (SC/CC List) lies here: it provides a master ledger that is not constrained by the document structure, with each characteristic on a single line, clearly stating its source, level, who is responsible, and how it is controlled.

1. What Fields Should a List Include?

A usable list is not just a simple enumeration of characteristic names; it should at least include the following fields:

With this ledger, "not matching" transforms from a debate into a line-by-line verification.

2. Five-Step Method: From Three Non-Matching Lists to a Single Table

Step 1: Fix the Transmission Order and Identify the Source.

Special characteristics always follow this chain: "Customer/Regulatory → Design (Drawings) → DFMEA → PFMEA → Control Plan." Once the order is fixed, any inconsistency can be directly judged and the appropriate document can be updated: if a characteristic is not marked on the drawings but is listed, either add the marking to the drawings or delete the line from the list; if a characteristic is marked on the drawings but lacks a monitoring action in the control plan, the control plan is missing. Without a fixed order, each verification will turn into mutual blame between departments. It's also important to clarify: when the customer's drawings do not mark a characteristic but the company deems it necessary to control, it can only be listed as an internal strict item and cannot be upgraded to a customer safety characteristic on its own; conversely, if the customer marks it but the internal team deems it unnecessary, it cannot be unilaterally deleted without customer confirmation.

Step 2: Establish a Numbering Rule for the List to Ensure Traceability.

Two rules are crucial. First, the number must be unique and stable; once SC-001 is assigned, it is not recycled or reused, and when a characteristic is obsolete, it is marked as such rather than deleted. Second, each number must be directly referenced in the FMEA and control plan—write the list number in the corresponding sections of the documents. With the numbers, when the drawings are revised, the three places can be verified by number rather than by the text of the characteristic name, which can lead to ambiguous matches. The numbering rule need not be complex; a common practice is "Part number + level prefix + two-digit sequence," such as ZJ-102-CC-01, which clearly indicates the part and level.

Step 3: Conduct a Three-Place Consistency Check, Focusing on Four Types of Discrepancies.

• Missing Transmission: The list and drawings have it, but the FMEA does not, indicating a missing failure mode analysis; supplement the FMEA.
• Missing Monitoring: The list and drawings have it, but the control plan lacks a monitoring action; supplement with poka-yoke, inspection, or SPC.
• Inconsistent Symbols or Levels: The drawings mark it as CC, the FMEA as an important characteristic, and the control plan as a key characteristic; unify to the same level dictionary.
• Version Lag: The drawings have been revised, but the list has not been updated, and the FMEA and control plan are still using the old version; use the latest published version and trace the change records.

A practical and efficient method is to export the drawing annotations, FMEA items, and control plan into a single table, with the list number as the row and the document name as the column. Any empty or mismatched cells can be immediately identified. After verification, each discrepancy must be registered with a responsible person and a completion date to ensure that the verification does not become another instance of "finding issues but no one making changes."

Step 4: Integrate the List into the Change Process.

The list itself must be controlled: any changes to the drawings, customer requirements, design, or process must trigger a joint review of "List → FMEA → Control Plan → Inspection Work Instruction" and leave a change record in the list (what was changed, based on which document, and corresponding to which version). Listing the list as a mandatory item in the change review is the only way to prevent it from becoming a "dusty" document after compilation.

Step 5: Regular Verification and Clarification of the Authoritative Version.

It is recommended to verify the list whenever a new version of the drawings, FMEA, or control plan is released. During mass production, a full verification should be conducted at least once every six months, and the results should be archived in a "Consistency Verification Form." It should also be clearly stated that the list is the sole authoritative version, and other documents should reference the list number.

3. A Simplified Example

For a certain stamping bracket part, the list has 4 entries:

From the four rows of data, two issues are immediately apparent, and it is clear which documents need to be updated and who should do it—this is the role of the list. After verification, the three actions to be taken are also clear: supplement SC-003 into the DFMEA and confirm the failure consequences, first confirm in writing with the customer whether SC-004 needs to be marked as a regulatory characteristic, and then update the list version number and effective date after both are completed.

4. Three Common Pitfalls

1. The list is compiled by one person in one go and then never touched again. The list is a dynamic document and must be integrated into the change process; otherwise, it will be out of sync with the drawings after three months.
2. Using the text of characteristic names for association. The same characteristic may have different names in different documents; whether "tensile strength" and "welding strength" are the same must be judged by the number, not the text, to avoid errors.
3. Inconsistent level dictionaries. Mixing customer symbols (SC, CC, ▼, △) with internal levels requires first establishing a symbol and level correspondence table before discussing consistency.

5. One Sentence Summary

The challenge in managing special characteristics has never been about "identifying them," but about "whether the four documents are talking about the same thing"—a numbered master list is the nail that pins the drawings, FMEA, and control plan together.

The value of the special characteristics list: ensuring that the drawings, FMEA, and control plan are talking about the same thing

Knowledge code: 8.2.2

Version: v20261009

Author: QTank QTank is dedicated to providing systematic professional knowledge, methodologies, and practical tools for quality management practitioners, helping companies continuously improve their quality capabilities.