Visio Nerf teams up with Inficon for leak testing of refrigerators

Earlier this year, Visio Nerf and Inficon gathered up to offer a solution for a leak testing application using our Cirrus 3D sensors. Volker Trieb, Market Manager at Inficon, wrote an article about this. Please find a translation of this article below :

To automatically check the exact positions of solder joints on the back of a refrigerator for leaks, Inficon and Visio Nerf have jointly developed a robot-based inspection system. With a special LED strip light and four high-resolution cameras, it generates a 3D point cloud of the work area and localizes the relevant solder joints in it.

 In the EU, every refrigerator must pass a leak test at the end of the manufacturing process - manufacturers are required to do so by law.

In order to efficiently integrate the leak tests into their production, more and more refrigerator manufacturers are therefore looking for an automated solution. However, the requirements for leak testing refrigerators are very high, because the refrigerant, which is harmful to the climate, must be prevented from escaping into the environment. In addition, the loss of refrigerant leads to poorer cooling performance as well as increased energy requirements. The weak points on the refrigerant lines are the soldered joints on the back of the refrigerator, where the freely accessible lines of the refrigerant circuit run. Due to the structural conditions, these are difficult for a robot arm to access. Due to manufacturing tolerances of +/-1cm in all directions when mounting the coolant lines, the location of the solder joints varies from unit to unit, making localization with a conventional CAD data-based 3D image processing system impossible.

Precisely approaching the solder joint

To detect the very small leaks on the lines, some of which are only two millimeters thick, a sniffer leak detector is used. This sucks in escaping refrigerant with a sniffer tip specially developed for automation in order to reliably detect any leaks. It is therefore necessary for the robot arm to hit the solder joint as accurately as possible in order to enclose it with the sniffer tip. This is where the 3D image processing system comes in: it determines the exact position of the solder joint by visually detecting the individual points on the surface of the coolant lines within the generated 3D point cloud in real time. The 3D system stores the individual coordinates and guides the robot arm with the sniffer tip to the individual inspection points one after the other.

Dynamic robot guidance in real time

The software developed specifically for this application also uses collision-monitored robot guidance, which prevents collisions with the sniffer tip. The biggest challenge - besides the required precision - is that the individual components of the coolant line that need to be localized are bent manually for soldering and are never identically shaped. Localization therefore works dynamically in real time and not on the basis of CAD data. As a rule, six to twelve solder joints have to be located and checked on the back of the refrigerator. The system also takes care of optimized path planning, including collision monitoring of the robot, so that the leak test can be performed within the required cycle time.

Quick changeover to other models

For the easiest possible integration in production, the IPC is already built into the 3D system as standard. An additional external PC is therefore not required. The image processing system is also compatible with all common robot brands and, thanks to IP65 protection, is very well protected for long-term industrial use. Moreover, it is possible to adapt the image recognition system to the individual requirements of the plant manufacturer. The robotic cell including the 3D system is very compact and requires as much space as a human inspector. In addition, the image recognition system works independently of ambient light, i.e., it can cope with darkness and daylight as well as artificial lighting. The smart assistant can be changed over to new refrigerator models by a trained employee within a very short time. External technicians are not required for this. The manufacturers have it in their own hands to ensure that no more leaky refrigerators reach the market.


Don't hesitate to check the original article (in German).