In the factory, many people’s first reaction to inspection is incoming inspection or outgoing inspection. It seems that the work of the quality department is either to stop materials at the warehouse entrance or to check the finished products before they leave the factory.
But the middle stage of production is also prone to problems.
At this point, process inspection becomes particularly crucial.
To put it bluntly, process inspection is to monitor the quality status in advance when the product is still in the production line and hasn’t been finished yet, to check if there are any abnormalities emerging, if the process is deviating, and if any unqualified semi-finished products are about to flow to the next station.
Its core task is not to wait until products are damaged before sorting them out, but to address issues as soon as they emerge. Doing this well can significantly reduce the number of defective batches, rework, and repair, as well as minimize the disputes between the workshop and the quality department.
Therefore, process inspection is essentially not about “taking a few extra glances at the product”, but rather a pre-control step in the production process. It does not focus on the outcome, but rather on whether the process is stable, whether the technology is under control, and whether there are deviations in personnel, equipment, materials, and methods.
1. What exactly is inspected during process inspection? Many novices tend to interpret IPQC as “spot checking while production is in progress” at the beginning. This interpretation is not incorrect, but it is too superficial.
Process inspection not only focuses on the product itself, but also involves the following aspects.
First, check the product status.
Are there any abnormalities in appearance, are the dimensions within tolerance, are there any errors or omissions in assembly, and are there any deviations in function? These are the most basic aspects to consider.
Secondly, inspect the execution of the process.
Have the process parameters been set as required? Has the first article confirmation been conducted? Have re-verification been carried out after mold and line changes? Have the key processes been operated according to standards.
Third, check the device status.
Whether the equipment parameters are stable, whether the fixtures and clamps are abnormal, and whether the measuring tools are inaccurate, all these factors directly affect the process output.
Fourth, inspect the operation of personnel.
Whether employees are following the operation manual, whether there are any key actions omitted, and whether error prevention measures have been truly implemented in place.
Fifth, inspect the flow control.
Whether defective products are promptly identified and isolated, and whether there is any mixing of materials, batches, or states in semi-finished products, are all potential pitfalls that are most easily overlooked on-site.
So you will find that IPQC is not simply looking at “whether this product is qualified or not”, but rather “whether this process is stable or not”. This is the true value of process inspection.
II. How to Conduct Process Inspection Process inspection is not a one-size-fits-all approach; it often involves a combination of methods. The three most common methods are first article inspection, fixed-point inspection, and patrol inspection.
1. First article inspection is the first hurdle.
For any new batch production start-up, line and mold change, equipment adjustment, tooling replacement, personnel change, or even restarting after a production line shutdown, one cannot simply proceed without first conducting a first article confirmation.
What should be inspected for the first article? Generally, it’s a comprehensive inspection. Appearance, dimensions, assembly, performance, and key characteristics – none of these can be overlooked. After confirming that everything is in order, relevant personnel sign off on the release. If necessary, the team leader, process technician, and workshop manager also need to confirm together.
If the first piece is not qualified, mass production cannot proceed. This rule may seem slow, but in fact, it is the fastest approach. Because if you don’t stop it at the beginning, you may end up scrapping dozens, hundreds, or even an entire batch later on.
2. Fixed-point inspection: Fixed-point inspection primarily focuses on key processes and special processes.
Which processes should be set as control points? Typically, these are processes that are prone to major issues, have high repair costs, are of particular concern to customers, or are difficult to control stably relying solely on employees’ visual inspection and experience. Examples include welding, torque, press fitting, sealing, and critical dimensional machining.
The focus of targeted inspection is not to cover every aspect, but to fixate on key quality characteristics. Conduct full inspection where necessary, and perform inspections at regular intervals where required, ensuring that the points with the highest risks are guarded against.
Many factories encounter major problems not because the entire process is out of control, but because a certain key point is not monitored properly. The job of fixed-point inspection is precisely to do this.
3. Circuit inspection Circuit inspection is the most common action in process inspection.
The quality inspector conducts spot checks on-site at a fixed frequency, such as once per hour, once every two hours, or by sampling one product out of every ten, to inspect products from various production processes. At the same time, they check for issues with process parameters, equipment status, work discipline, and identification and isolation.
The value of inspection lies in dynamically detecting anomalies. Many on-site issues are not persistent; they may emerge during a certain period of time. For instance, the dimensions of equipment may drift after it heats up, the movements of a new employee may change after he/she starts work, or the surface of a batch of materials may become unstable after being replaced. If you don’t inspect, these issues will slip away quietly.
Nowadays, many enterprises combine “quality inspection tour + team leader spot check + employee self-inspection and mutual inspection” to ensure greater stability on site. It is definitely insufficient to rely solely on the quality department’s personnel to run around. Process inspection needs to form multiple layers of protection to be effective.
Thirdly, process inspection must be implemented, and basic management must keep up. Merely having people to inspect is not enough. Whether process inspection can truly be effective depends on basic management.
The inspection standards must specify what to inspect, how to inspect, what criteria to use for judgment, how many samples to take, and how often to inspect. All these details must be clearly written and included in the operation manual, inspection specifications, and control plans.
The most feared thing is relying on experience for on-site inspection. Today, this person says it’s okay, but tomorrow, that person says it’s not. In the end, the workshop disagrees, and the quality department can’t clarify. Without clear standards, the site will definitely be chaotic.
2. Inspection records should be complete. Many factories have an old problem: they conduct inspections but fail to record the results, or they record the results but do so haphazardly. This makes it impossible to trace issues when they arise.
The process inspection record must be complete, at least indicating who conducted the inspection, when it was conducted, what was inspected, the results, and how any abnormalities were handled. Whether it’s in paper or electronic form, the core principle remains the same: it must be traceable, analyzable, and revisable.
3. What is the biggest fear in timely process inspection for exception handling? The biggest fear is discovering problems but taking slow actions.
Once an anomaly is detected, the first step is to identify and isolate it, preventing the problematic product from continuing to flow down the line. The second step is to notify the production and quality supervisors, and if necessary, to halt the line, machine, or process. The third step is to issue an anomaly report, driving cause analysis and rectification. The fourth step is to conduct a re-inspection after rectification to confirm that the issue has indeed been resolved.
Note that identifying a problem is not the end; it is only considered complete when the problem is closed.
4. Data analysis should keep up with more mature enterprises, which will not rely solely on the inspector’s “feeling wrong”. It will look at the data.
For example, using SPC to monitor key dimensions and parameters to see if there are any deviations in trends, abnormal fluctuations, or exceedances of control limits. Many issues are signaled by the data before the product becomes completely non-conforming.
Therefore, if we delve deeply into process inspection, we will eventually reach the step of “data-based early warning”, rather than perpetually staying at the stage of “handling issues only after defective parts are identified”.
IV. The 5 most common pitfalls in process inspection 1. Inspecting too much can affect efficiency; or inspecting too little can lead to unmanageable risks. The correct approach is to stratify based on risk, being stricter for key processes and more flexible for ordinary processes.
2. Responsibilities are unclear. Production can participate in the initial inspection and self-inspection, but the quality department must take charge of the patrol inspection, rejection judgment, and independent judgment. It is not acceptable to produce, judge, and claim that there is no problem by oneself.
3. Only identifying problems without resolving them. Reporting anomalies today, and the situation remains unchanged tomorrow, such inspections are meaningless no matter how many are conducted. We must adhere to the “Three Not-Let-Go” principle: not letting go of unclear causes, not letting go of unclear responsibilities, and not letting go of unimplemented measures.
4. Measuring equipment is unreliable. If calipers, micrometers, inspection tools, and torque tools are inaccurate themselves, the inspection results will have no reference value. Therefore, metrological calibration cannot be a mere formality.
5. The management of defective products is chaotic. There is no clear identification, no timely isolation, and reworked products, products pending judgment, and qualified products are mixed together, which is most likely to lead to batch accidents in the end.
5. Ultimately, process inspection is not about the product, but about the level of on-site management. Many quality personnel will discover a fact after working for a long time: whether process inspection is done well or not, it appears to be an inspection issue on the surface, but in fact, it reflects the level of on-site management.
Whether the first product can be maintained indicates the rigor of the process.
Whether the inspection can detect any abnormalities indicates whether the personnel are in good condition.
Whether defective products can be clearly isolated indicates whether on-site discipline is enforced.
Whether anomalies can be closed-looped indicates the effectiveness of departmental collaboration.
Therefore, process inspection is by no means “the quality department picking out flaws on site”, but rather helping production maintain process control, assisting in process verification and control, and enabling management to identify risks in advance.
To put it bluntly, process inspection is not about catching up at the end, but about intercepting it halfway; it’s not about waiting for problems to occur, but about trying to prevent them from happening in the first place.
For quality personnel, whether the IPQC (Incoming Quality Control) is done solidly or not often determines whether the workshop relies on luck or control for production.