Measuring multi-material components

You turn to quiet the children who are arguing in the back seat, sternly telling them they’re too loud while you need to pay attention to driving. That’s when a bell chimes from the dashboard. You’re approaching the truck in front of you too quickly, and if you don’t brake now, there could be a collision.

Those life-saving sensors use radar to determine the distance to the nearest vehicle and inform drivers with a loud beep that the safe following distance has been undershot. These sensors are subject to inclement weather, so to remain functional, they must be watertight, and the metal and plastic components on the sensor must flow seamlessly into each other.

Germany’s Kramski Group annually produces more than 2.5 billion such parts and other complex punched and hybrid parts for the automotive, electronics, telecommunications, medical technology, solar, and consumer sectors. For Kramski, hybrid technology refers to components and assemblies, such as high-quality distance sensors, that are punched and then coated with plastic. The manufacturer designs and builds the tools needed to manufacture the punched and hybrid parts, using comprehensive measurements and sampling tests.

Anyone that manufactures complex hybrid metal-and-plastic parts has to master more than just working with these different materials. It is also vital for the multi-million-dollar production system to enter service quickly. Manufacturers often measure more than 100 initial samples to adjust tooling before conditions are right for volume production. For each measurement, the objective is to ensure the quality of up to 500 characteristics. Kramski uses multisensor measuring machines from Zeiss Industrial Metrology for this.

Fast, reliable

Mathias Schlegel, measuring technology team supervisor, has become familiar with many different departments at Kramski the past 28 years and has been responsible for measuring technology for the past seven years.

“We are constantly faced with new challenges. After all, we have to ensure the quality of increasingly complex parts,” Schlegel says.

Schlegel and his team must ensure compliance with form and location tolerances using random samples. This procedure allows the automotive supplier to guarantee that the plug connections sit properly or that seals work. The position tolerances of such parts are 0.1mm to 0.2mm. Line form tolerances vary between 0.05mm and 0.30mm depending on feature size.

But, it is more than just precision, the measurements must also go quickly. This also applies to initial sample inspections – the clock is ticking on the measuring technicians from the time the first parts are punched with a new tool or coated.

“Reliable results then have to be delivered very quickly,” Schlegel says.

The sooner they are available, the sooner the toolmakers learn what they have to change (if anything) for the new parts to meet the requirements. In some cases, faster inspection results can put a multi-million-dollar production system into service earlier.

Fast initial sample inspections are made more difficult by the large number of parts being measured. For numerous products distance sensors, the company produces the plastic components with a 4x form. If five workpieces are subjected to an initial sample inspection for each form, 20 units must be measured for a 4x form. This number is multiplied by up to three corrective loops for each tool. Furthermore, machine capability checks are required before a item can finally go into production – the first 100 to 200 parts are measured to ensure that the machine precisely manufactures parts in volume. The result is 500 characteristics must be checked on each workpiece.

Key time benefit

To complete these measurements in such a short time, Schlegel and his team rely on two Zeiss O-Inspect 442 multisensor measuring machines.

“We save an enormous amount of time today because we can create the measuring programs offline. This was not possible with our previous measuring machines,” Schlegel explains.

Off-line programming allows technicians to program measuring runs on a computer away from the machine. With Zeiss Calypso measuring software, it is possible to program directly on the CAD model, allowing employees to begin generating measuring programs while the tools are being made. According to Schlegel, this provides his team with an invaluable time bonus because programming can take up to two weeks.

Once the first samples have been manufactured, the measuring technicians need a run-in phase because the real parts deviate from the ideal dimensions of the CAD model used for the measuring program. The results are available in about one day and provide information on the extent to which a tool meets the requirements.

Sensors, software, support

Off-line programming on the CAD model was one of the key reasons to first purchase the multisensor measuring machine in 2010, as well as another four units through 2014. Furthermore, the manufacturer and measuring machine met the automotive supplier’s demands on the sensors, measuring software, and international support.

Because numerous workpieces at Kramski contain characteristics that can be captured with the camera sensor in just a few seconds, as well as characteristics that can only be measured with a contact sensor, the company was interested in the multisensor measuring machine from the beginning. With the Zeiss O-Inspect 442, contact and optical measurements can be made on the same machine very quickly. The combination of both sensors helps to meet the complexity of hybrid parts and save time.

Calypso measuring software impressed Schlegel and his colleagues beyond just the off-line programming feature. On the basis of a prototype program with 200 or 300 characteristics, for example, measuring technicians can generate a serial measuring program with 100 or 150 characteristics for random sampling measurements relatively easily. They simply select the required characteristics in the existing program. The machine then automatically calculates the travel paths for the selected characteristics.

“None of the other machines we looked at could do this,” Schlegel says.

Another selling point was the ability to bundle measurement data with the Zeiss PiWeb quality data management system. Using a graphic provided by the program, the user immediately sees which values deviate from the specifications in which direction for a workpiece type – and that over multiple measurements.

“This makes it much easier for us to identify trends,” Schlegel says.

The availability of professional support impressed the decision-makers. Because Kamski has subsidiaries in the U.S., India, and Sri Lanka in addition to its headquarters in Pforzheim, Germany, it is beneficial that Zeiss provides service from sites in North America and India.

Zeiss support has already passed its test. A measuring machine in Germany had been scheduled for use during a weekend, but it malfunctioned with motor damage, so a bottleneck was looming. Schlegel contacted service, but did not have much hope in finding a solution before the new week started. He was that much more surprised when Zeiss sent an employee that same day to replace the motor.

“We were able to work that weekend without a problem,” states Schlegel.

Comparable and stable

Kramski engineers now use Zeiss O Inspect 442 multisensor measuring machines at three sites – two each in Germany and Sri Lanka and one more in India.

“We create a measuring program and share it with the labs in Sri Lanka, India, and Germany,” Schlegel says.

The manufacture of certain products is often transferred from one site to another as the company manufactures for different brands at multiple factories, or development and initial inspection can occur at one site, but production at another. To ensure the comparability of the measurement results, Schlegel and his staff use the same styli and fixtures in all three countries, and also precisely describe each measuring process with the help of images from Calypso software.

The company also introduced a multisensor check to guarantee that employees use the same approach for measurements and measuring machines run reliably. Kramski uses this monitoring method to check the precision of its measuring machines on a weekly basis.

Zeiss Industrial Metrology

www.zeiss.com

Kramski Group

www.kramski.de/en.html