Every tenth baby is born prematurely, many of them weighing less than 4 lb. The chances of survival and the health of these newborns largely depends on flawless breathing support and, if necessary, an increased level of oxygen. This is where the continuous positive airway pressure (CPAP) generators, produced in northern Bavaria, Germany, by whr Hossinger Kunststofftechnik GmbH, come into play.
“Our generators can save lives starting at the 24th week of pregnancy or at a birth weight of 14oz,” explains Armin Hossinger, managing director. “This is something we’re very proud of.”
CPAP generators deliver oxygen- enriched air via tube, administered with a slight positive pressure, helping the baby breathe on its own – stimulating lung development. The positive pressure is created within the CPAP generator’s plastic housing, and the oxygen is transferred without leakage to the patient’s nasopharyngeal zone via a silicone prong or mask. To burden the baby as little as possible, whr Hossinger Kunststofftechnik connects the product’s individual plastic components using a connector system instead of an adhesive to keep the CPAP generator airtight.
Measuring lab challenges
Christian Bindl, quality management supervisor at whr Hossinger, lists the challenges he faces when measuring components for the CPAP generators: “Wall thickness of just 0.3mm, tolerances of just a few hundredths of a millimeter, freeform components with a complex shape, different product colors.”
Capturing the complex geometry of the freeform components can be time consuming because this step must be performed from different angles. Thin wall thicknesses also make contact measuring difficult, and certain product colors require illumination, which must be appropriately adjusted for optical measurement.
Previously, these requirements made quality inspection difficult, protracted, and sometimes costly with the company’s existing optical measuring machine. Measurements sometimes had to be outsourced, creating added costs and reduced throughput. Additionally, there was no space on the company’s optical measuring machine for inspecting other products.
Three in one
In 2014 Hossinger and Bindl began looking for a new measurement strategy as well as an expansion to their existing optical measuring machine. They wanted to measure more products in-house, faster and more accurately. Their search revealed the Zeiss O-Inspect multisensor measuring machine that combines three measurement principles in one machine – a contact sensor, a camera sensor, and a chromatic white light sensor. The machine promised greater precision and increased efficiency, but its measuring range (400mm x 400mm x 200mm) was too small for the large workpieces they manufacture, so Hossinger and Bindl got in touch with Zeiss to get a machine with the larger measuring range they needed – 500mm x 400mm x 300mm.
Freedom to choose
“Contact, optical, white light sensors: the way these three measuring methods interact is unbeatable because these make us highly efficient,” Bindl says, as he demonstrates the capabilities using one of the half casings for the CPAP generator. These half casings, which will later form the hollow space where the CPAP pressure is generated, are measured at the start and end of production, as well as for random sampling. The goal is zero defects during the final function test of all CPAP generators in the cleanroom.
Random sampling of the half casings on the measuring lab’s multisensor measuring machine consists of three phases. In the first step, the Zeiss O-Inspect performs a contact scan of the workpiece, taking about one minute. During this time, the contact sensor captures the location of the positioning holes for the pins which will connect the two halves after assembly. The position and diameter of the sealant shell, to which the tube adapter for administering oxygen is attached, are also defined using contact measuring. This requires achieving tolerances between 0.01mm and 0.02mm to prevent the component from leaking or fracturing.
In the second step, the machine automatically switches from contact to optical measuring. Within about 1.5 minutes, the camera sensor measures the receiving contour for the tube adapter. The translucent half housing – yellow in this version – is illuminated in blue, accentuating the structure. The measuring machine offers blue or red illumination, depending on the workpiece color, to create various contrast levels. The sensor can image wall structures elevated by 0.02mm or 0.03mm. These are used later to modify the CPAP generator to fit the shape of the particular patient’s nose. Optical measuring with the camera is best-suited for this task because it images geometric elements quickly and flexibly.
The process then moves to the third step where the chromatic white light sensor captures the workpiece topography in 15 sec., a point cloud consisting of 3,000 characteristics that identify the sealing contour of the half casing for the matching part.
Precise, fast measuring
“The multisensor measuring machine affords the metrologist a lot of freedom to decide which sensor to use and for what. If the program is already set up, it is even possible to switch from one method to the other without any fuss,” Bindl says.
Bindl and his colleague use Calypso software to program measuring routines, no matter which of the three sensors they’re using.
Calypso is used with different sensors and different machines, so the two colleagues only needed to use one software, although they also added a Zeiss Contura coordinate measuring machine (CMM). Contact measuring programs for one machine can be used on the other. Data captured by the service provider on the computer tomograph can be exchanged with data from other measuring machines.
“This makes us very flexible when choosing our measuring methods,” Bindl says.
The acquisition of the multisensor measuring machine has paid off for whr Hossinger because of its flexibility, accuracy, and speed. Today, the company outsources fewer measurements and, with the Zeiss O-Inspect, Bindl and his colleague conduct measuring tasks with a high degree of accuracy and repeatability.
According to Bindl, adding a Zeiss O-Inspect has given metrologists room to breathe.
whr Hossinger Kunststofftechnik
Zeiss Industrial Metrology LLC