Fail-safe designed vision systems are not off-the-shelf solutions?

Having vision systems on production lines is an essential way for pharmaceutical companies to ensure that the integrity of their products are consistently maintained.

However, what makes fail-safe designed vision systems on production lines so necessary?

Packagers of pharmaceuticals must ensure that if packaging errors occur on their lines, there must be zero risk of them going undetected. And fail-safe systems are a vital tool in this risk management.

What constitutes fail-safe design?

A system based on a fail-safe design is one that is constructed on the assumption that component and/or function failures may occur, and if they do, system controls are in place to manage and tolerate such failures in the safest way possible (ie., alarms, safe state, etc.). Therefore, the goal of the fail-safe design is to have a system where failures or faults are dealt in such a way that the integrity of the line is always maintained.

Systems with fail-safe design require more than basic software protective measures; they require electrical and mechanical protective measures that are linked to the system’s overall functionality. Therefore, for a vision system to be truely constructed with a fail-safe design, it must include additional elements such as alarms, product tracking and accurate rejection of “bad” products. Furthermore, these elements must continually work efficiently together as a whole to ensure that once the vision system detects a “bad” product, it registers it, it supplies notification of this event, it tracks the product down the line and it ensures that the product is rejected at the eject station. However, the required fail-safe measures don’t end there; the system must also ensure that no “bad” products pass the eject station.

To ensure that all “good” products are permitted to pass the eject station and that all “bad” products do not pass this station, the fail-safe design functions of the system must include a “positive” feedback control. This is achieved through the installation and integration of sensors. These sensors send a “positive” (ie., “good” product) signal for good products and do not send a signal for “bad” products. No signal reaching the eject station for a product results in the rejection of that product from the line.

What if the system fails due to power loss or other error?

A fail-safe vision inspection system must also ensure that the integrity of the products is maintained under conditions such as power loss. For example, if the system encounters a undefined state, no signal will be sent to the eject station so as a safety measure, all products moving down the line will be rejected.

Furthermore, a fail-safe system also protects the integrity of the production line when events occur such as missing bottles or when a bottle has been added to a line after the inspection station. Once again, this is achieved through complete tracking of the products down the line from the inspection station to the eject station through the use of sensors and encoders.

But what if the ejection mechanism fails?

A verification sensor at the eject station must be present to verify that a “bad” product has been in fact rejected. If there is no verification, an alarm signals and the line subsequently stops.

Therefore, a fail-safe system involves multiple components and features. This entails far more than off-the-shelf vision solutions can provide. For example, there is the vision system, sensors, tracking, alarms and most importantly, all the customization, installation and integration of all of these elements at the same time so that they can be validated. Therefore, off-the-shelf systems hardly meet these standards since they do not deal with the integration and merging of additional settings, sensors and alarms, which all play an essential role in the functioning of a fail-safe system.

Optel Vision has measured the risk of undetected errors occuring so as to ensure that its systems are designed in such a way that either the mistakes cannot occur or there is zero risk of them going undetected. Furthermore, as a complete solution supplier and integrator of fail-safe systems, Optel Vision also realizes the importance of having a highly trained project management team and installation team behind each of its systems.