Implementation logic and common misconceptions of the confirmation of production and service provision processes
I. The core objective of process validation: From "formal inspection" to "capability verification"
The validation of production and service provision processes is a key requirement of ISO 9001. In essence, it is to verify whether processes (such as continuous extrusion, welding, and heat treatment) where the quality "cannot be fully verified through subsequent inspections" can stably produce products that meet the requirements. Its core is not "to conduct a single inspection" but "to establish a set of mechanisms to ensure that the personnel, machines, materials, methods, and environment in the process always match the quality requirements." However, many enterprises fall into the "formalization" trap when implementing it, and the problems are concentrated in four directions:
1. Equipment identification: "In good condition" ≠ "Meeting process capability"
Enterprises often equate the "physical integrity" of equipment (such as no oil leakage and the ability to start) with "meeting process requirements", but fail to correlate with the core requirements of process parameters. For example, the appraisal report of an extruder in a wire and cable enterprise states that "the equipment is in good condition", but does not check the temperature stability of the heating zone - the temperature fluctuation in the heating zone of this extruder reaches ±5°C (the process requirement is ≤±2°C), resulting in the deviation of the insulation layer thickness exceeding the standard. The essence of equipment appraisal is to "verify whether the equipment can stably provide the conditions required by the process", rather than "check whether the equipment can operate".
2. Process parameters: Fixed value ≠ Dynamic adjustment
The work instructions of most enterprises only list a set of "general process parameters" (such as "extrusion temperature: 180 - 200°C, traction speed: 5 m/min"), while ignoring the differences in materials, specifications, and environments. For example, when an enterprise produces 1.5 mm² cables with PVC materials, the process parameters are effective. However, when switching to cross - linked polyethylene materials (melting point: 190 - 210°C), using the original parameters still leads to poor plasticization. Or when the ambient temperature drops from 25°C to 10°C in winter and the temperature is not adjusted, it results in uneven shrinkage of the insulation layer. More commonly, after problems are found during audits, enterprises only expand the parameter range (e.g., 170 - 210°C), which makes the parameters lose their guiding significance - operators don't know "when to use 170°C and when to use 210°C".
3. Personnel capabilities: "On-the-job assessment" ≠ "Skill matching"
Enterprises often equate "safety training" and "sign - in records" of employees with "qualified capabilities", but fail to design requirements around the "special skills" of the positions. For example, the assessment for an extruder operator only tests "how to start and shut down the machine", but does not test "how to adjust process parameters" and "how to self - check product quality". When this worker changed the material, the insulation layer was burnt due to the failure to adjust the temperature, but he was not identified as unqualified because he "passed the assessment". The core of personnel capabilities is "whether they can meet the process requirements", rather than "whether they have participated in training".
4. Reconfirm: "Do regularly" ≠ "Do as needed"
Enterprises often set re - verification as an "annual fixed action", but ignore the "dynamic changes" of process factors. For example, a wire and cable enterprise conducts re - verification of the extrusion process once a year. However, in actual production, changing materials, specifications, environment (such as the temperature drop in winter), and molds (the change in extrusion volume due to wear) will all affect the process parameters. Once, because the enterprise did not conduct re - verification in winter, the temperature of the extruder could not rise, the thickness deviation of the insulation layer exceeded the standard, and a large number of products were scrapped. The essence of re - verification is to "verify whether the changed process can continue to meet the requirements", rather than "going through the process regularly".
II. Root cause of the problem: Deviation in understanding of "process validation"
The core of all problems is equating "process validation" with "result inspection" rather than "systematic verification of process capability". The goal of process validation is not to "prove that the process was once qualified" but to "prove that the process can always stably output qualified products" – it is necessary to systematically verify the compatibility of "personnel, machinery, materials, methods, and environment" around the "quality requirements".
III. Taking the wire and cable extrusion process as an example: The planning logic of process validation
1. Step 1: Define the quality inputs of the process – start with the result requirements
The first question in process validation is: What quality of products should this process output? The quality requirements of the extrusion process need to be specified as "verifiable indicators":
Appearance: No scorching, pockmarks, scratches, or bubbles.
Dimensions: Insulation layer thickness deviation ≤ ±0.1mm (complies with product standards);
Mechanical properties: Tensile strength ≥ 12 MPa, Elongation at break ≥ 150%.
Electrical performance: Breakdown voltage ≥ 20 kV/mm (the insulating layer shall not be broken down by high voltage).
These indicators are the "bullseyes" of process validation - all subsequent planning should revolve around "how to meet these indicators".
2. Step 2: Identify the key factors affecting process capability - the "dynamic adjustment" of process parameters
The core of extrusion is "the matching of process parameters with materials and products". Process parameters (temperature, speed, pressure) are not "fixed values" but "programs adjusted according to variables":
Material variables: Different materials (PVC vs cross-linked polyethylene) and different grades (PVC SG-3 vs SG-5) have different melting points and plasticizing temperatures.
Product variables: Different traction speeds and extrusion pressures for different specifications (1.5mm² vs 10mm² cables).
Environmental variables: In summer, when the temperature is high, the barrel temperature needs to be reduced by 5°C; in winter, when the temperature is low, it needs to be increased by 10°C.
Therefore, the work instruction should not state "a set of fixed parameters" but "adjustment procedures" - for example:
- Thin thickness: Reduce the traction speed (by 0.5 m/min) or increase the barrel temperature (by 2°C).
- Thick thickness: Increase the traction speed (by 0.5 m/min) or decrease the barrel temperature (by 2°C).
Only such a program can guide operators to "adjust parameters according to actual situations" rather than "copy fixed values".
3. Step 3: Equipment Confirmation – Design evaluation criteria based on process requirements
The core value of the equipment is to "stably provide the conditions required by the process". Therefore, equipment qualification should closely adhere to the requirements of process parameters rather than conducting a "general inspection". The qualification content of the extruder shall include at least:
Temperature stability: The temperature fluctuation in the heating zone ≤ ±2°C (continuously monitored by a temperature recorder for 2 hours) —— Large temperature fluctuations will lead to uneven plasticization.
Instrument calibration: Thermocouples and thermometers are sent to the metrology institute for calibration annually, with an error ≤ ±1°C —— Inaccurate instruments can lead to incorrect parameter settings.
Speed uniformity: The speed fluctuation of the tractor is ≤ 1% (measured with a tachometer for 10 minutes) —— Speed fluctuation will cause deviation in the insulation layer thickness.
Auxiliary equipment: The water temperature of the cooling water tank should be controlled at 20 - 30°C (detected with a thermometer) —— If the water temperature is too high, it will cause uneven shrinkage of the insulation layer; if it is too low, it will cause brittle fracture.
These contents should be included in the "Equipment Identification Procedure" to ensure that the equipment "can meet the process requirements" rather than "can operate".
4. Step 4: Personnel Competence – Design Assessments Centered around Skill Requirements
The capabilities of operators need to be directly related to the "execution process requirements" rather than the "theoretical knowledge". The capability requirements for extrusion workers shall include at least:
It should be known: the purpose of the extrusion process (to uniformly plasticize the insulating material and wrap the conductor), and the relationship between process parameters and quality (high temperature → scorching, high speed → thin thickness).
Skills to be mastered: Methods for adjusting the temperature of the extruder (how to set the temperature values of the heating zones), Steps for adjusting the traction speed (how to switch gears and fine-tune the speed), Self-inspection methods (measuring the thickness with a micrometer, visually inspecting the appearance, and checking the plasticization degree by hand).
Assessment method: Theoretical exam (exam topic: "Influence of temperature fluctuation on quality") + Practical operation assessment (exam topic: "Adjust the temperature to meet the process requirements and detect the thickness deviation").
Only by passing such an assessment can we ensure that the personnel know how to do it and can do it correctly.
5. Step Five: Specific methods and procedures – Matching the "production characteristics"
Wire and cable are produced continuously, and the process quality cannot be verified through "full post-production inspection". Therefore, the confirmation method needs to be "advanced":
Confirmation timing: before power-on, when changing materials, changing specifications, or changing molds.
Confirmation steps:
1. The operator adjusts the process parameters according to the work instruction.
2. Conduct a trial production of 10 meters, and conduct a self-inspection on the appearance (no scorching or scratches) and the thickness (deviation ≤ ±0.1mm).
3. Send it to the laboratory for testing the tensile strength (≥12 MPa) and breakdown voltage (≥20 kV/mm).
4. Formal production can only commence when all results meet the requirements.
For this purpose, the enterprise needs to be equipped with laboratory resources (tensile testing machine, withstand voltage tester, micrometer) - this is a necessary condition for confirmation. Otherwise, the process capability cannot be verified.
6. Step Six: Reconfirmation - The dynamic mechanism of "any change triggers an action"
There are many "variable factors" in the extrusion process. Therefore, re - confirmation needs to be "triggered as needed" rather than "done regularly". Scenarios for triggering re - confirmation include:
- Replace the material (e.g., replace PVC with cross-linked polyethylene);
- Change the specification (e.g., from 1.5 mm² to 10 mm²);
- Change the environment (e.g., the temperature drops from 25°C to 10°C in winter);
- Replace the mold (the extrusion volume changes due to wear).
- After equipment maintenance (e.g., replacement of the heating tube).
The method for reconfirmation is the same as that for initial confirmation: trial production → self-inspection → laboratory testing. If the results do not meet the requirements, the parameters need to be adjusted and the test repeated until they are qualified. The reconfirmation records should include "change factors, adjusted parameters, test results, and the person who conducted the confirmation" to ensure the traceability of the process.
IV. The essence of process validation is "system verification"
The core of the confirmation of production and service provision processes is not "filling out forms and following procedures", but rather centering around "quality requirements" and systematically verifying whether "personnel, machinery, materials, methods, and environment" can be continuously matched. The case of the wire and cable extrusion process essentially transforms "abstract standards" into "executable steps" by "deriving process requirements from the results" - each step is closely related to "how to ensure the stable output of qualified products in the process", rather than "how to meet audit requirements".
For enterprises, the value of process validation is to "prevent problems before they occur" - by verifying process capabilities, avoid "batch scrap" and "customer complaints". For ISO 9001, this is the key defense line for "ensuring product quality". Only by truly understanding "the essence of process validation" can we avoid being merely formal and achieve effective implementation.