Process Interlock

Process interlock can be used in both automated and manual production. However, it first requires a certain basic level of technology. This means that you need the appropriate systems and solutions to ensure that processes are actually interlocked if certain conditions are not met.

For process interlock, it is not enough for your worker to recognize that a measured value is outside the tolerance range, for example. After all, without a control system, he still has the option of simply continuing.

However, the technological basis is only half the battle. It is crucial to define strict conditions for process interlock.

To do this, you first define a process plan with the associated quality routes for all assemblies, parts, etc. in advance.

Next, set clear process parameters within clearly defined process windows. In other words, determine the tolerance ranges within which you can achieve optimum quality.

You also define criteria for checking and evaluating the processes.

You need all of this as a basis for the system-side decision as to whether a process needs to be blocked or not. If parameters are not adhered to, the system blocks further work and thus prevents errors in production.

In very general terms, you could say that process interlock protects the process, the product and the employee. It enables the early detection and thus avoidance of errors - right from the start of the production process. Fewer errors mean fewer rejects and less rework. Process interlock intervenes where quality-threatening errors and defects could arise.

Process interlock not only benefits the product, but also your employees. Process interlock is part of clearly defined workflows and processes and helps to ensure that work steps are carried out in the correct sequence. It also brings clear guidelines and automatic checking mechanisms into everyday production, which your employees can rely on when carrying out their tasks. This leads to a noticeable mental relief.

And let's turn briefly to possible hazardous situations in the production process. Here too, process interlock can provide valuable services by specifying preventive measures and structured processes that serve to avoid hazardous situations.

In order to establish process stability, you first need to listen to your processes. What happens and how? What goals are your processes working towards? Within what limits do they operate and within what limits should they operate? Process stability is initially a definitional framework in which you determine when a process is stable.

Once the framework has been set and the necessary prerequisites have been created, the next step is to monitor process stability. Nothing works here without process data, which you must of course record over a defined period of time.

Prepare the data in the form of control charts (in the sense of statistical process control or SPC) in order to monitor processes analytically and identify trends, outliers and patterns.

You can also analyze scatter and position based on the recorded data. You can evaluate mean values and fluctuation ranges and derive an assessment of process stability from this.

If you determine that instabilities are occurring in your process, you can use the recorded data to analyze the causes. Use methods such as the Ishikawa diagram (fishbone diagram) or the 5 Why method to identify and eliminate sources of disruption. This in turn contributes to greater stability in your processes.

What could process interlock look like in specific production scenarios?

Let's disregard the numerous necessary parameters and assume that we are talking about material removal in the production process. A specific material must be provided for the next work step. If you do not use a process interlock and your worker picks the wrong material, this will result in bad parts or at least costly reworking.

Alternatively, your worker can enter the material number in their worker assistance system using a scanner, for example. The system then checks the number. If the material number is incorrect, further process steps are blocked. The worker cannot continue with their work. Only when the material number matches the specifications can the process continue.

In this scenario, the assembly of the component has already been completed and quality control is being carried out. You have defined the corresponding values as quality criteria for the process interlock - for example, as test steps in the digital work instruction provided by a worker assistance system.

The worker or quality controller now carries out the corresponding tests and enters the measured values. If they do not meet the predefined quality criteria, the component is returned for reworking. If everything fits, the next work step can follow.

Process interlock is a "tool" in your production that is designed to ensure that processes run safely and correctly. It can become an important milestone on your way to zero-defect production.