Manufacturing Processes Metrology Challenges Solutions – Plastic Injection

Production Control of Large Plastic Parts
Automated 3D metrology at Coko-Werk GmbH & Co. KG

LOCATION: Bad Salzuflen, Germany

ZEISS SYSTEMS: ScanBox Series 6

SOFTWARE: ZEISS INSPECT

Flexibility and mindset by tradition

Coko-Werk GmbH & Co. KG has a long tradition in plastic injection molding. Established in 1926, Coko started off with a unique product – the unbreakable celluloid comb. In the mid-1980s, Coko produced computer housings for the legendary Commodore Amiga. Today, the injection molding company sees itself as a system supplier for technical plastic articles and specializes in large parts. The company uses the ZEISS ScanBox optical 3D measuring machine at its development and innovation site in Bad Salzuflen, Germany, to ensure efficient quality control in the production process.

Coko is a one-stop shop offering various manufacturing methods

Coko has set up large plants and equipment at its four locations in Germany, Poland and Turkey and manufactures small, medium and large injection-molded parts weighing up to 10 kg. It also installs complex assemblies. “We manufacture products for the automotive, white goods, heating & climate control, medical technology and industrial sectors,” explains Andreas Spilker, Head of QA/QM at Coko. Such a wide range of parts can be produced only with different manufacturing methods: The parts are injection-molded, assembled and painted. In some cases, the workpieces are electroplated or stamped with the pad printing process.

Assembly processes are fully automated and use robots. “Coko consistently increases the degree of automation to have a competitive edge, especially when it comes to large parts,” underscores Andreas Spilker.

Large and dark parts such as mudguards are digitized in the ScanBoxusing an ATOS 5X sensor.

Optical 3D metrology meduces start-up times and ensures quality

Automotive engineering is part of the core business in Bad Salzuflen. Parts such as mudguards (fenders) for utility vehicles are produced on a machine with a closing force of 2400 tons. Coko also manufactures a large number of headlight housings for several OEMs

The company draws on its wealth of experience to ensure that ramp-ups and automated processes for manufacturing these injection-molded parts are mastered and implemented within a short time span. Its experts benefit from the ZEISS optical 3D measurement technology systems while managing these challenges. The full-field measuring results guarantee a faster first article inspection and targeted tool correction, thereby reducing production lead times.

“We have been using a ScanBox for efficient quality control in our production and manufacturing processes since 2020,” says Andre Gromann, Head of Metrology at Coko. The optical 3D measuring machine is equipped with industrial high-precision 3D scanners which inspect the entire surface geometry of the parts by executing non contact scans in two working areas. “During shape and dimension analyses, the actual coordinates based on the 3D scan are matched against the drawing in the inspection software or directly against the CAD data set.”

Multi-part fixture increases throughput and provides flexibility

Coko’s metrology engineers have to be able to thoroughly inspect as many parts as possible in a short time window to ensure that they can initiate corrective action where needed. Given this large number of parts, self-developed fixtures are of critical importance.

The mudguards are digitized using a standard fixture based on the 3-2-1 principle. “During this measuring job, we used a multi-part fixture as a measuring fixture in order to increase throughput,” explains Andre Gromann. Thanks to the multi-part fixture, two mudguards can be scanned simultaneously. However, not only does the device increase throughput – it also provides the metrology engineers with more flexibility. Andre Gromann is content: “We no longer need a storage space for a second large and heavy fixture, handling is easier and we reduced our costs.”

The fixture concept developed by Andre Gromann in the ScanBox enables the simultaneous measurement of several parts.

In series inspections, the measuring job is initiated via the simple and self explanatory Kiosk Interface of the ScanBox. Measurement and inspection programs are stored as templates in the virtual measuring room. Users can access them in the Kiosk mode. The operator enters his name into a matrix, selects the template for the item, enters an inspection job number and initiates the scan. The inspection takes only a short while. The inspection results are then automatically migrated into Coko’s CRQ system.

Universal fixture reduces set-up times and optimizes measuring speed

Dimensions ranging from a few centimeters up to several meters and a variety of parts – in the field of injection molding, metrology systems have to be able to inspect all kinds of different tools and components within a short period of time. The two working areas of the ScanBox can be operated separately from each other. The metrology engineers, for instance, can scan two mudguards in the right-hand working area while digitizing several small components in the left-hand working area on their self-developed universal fixture. “The towerlike universal fixture was developed as a cage to ensure that many parts can be adapted as quickly as possible and to reduce set-up times,” says Andre Gromann. “The cage can be equipped with eight gauges. In order to avoid confusion with locating devices that have already been calibrated, the spacing of the locating pins varies,” he adds. The universal fixture can be set up from the front or rear end when dealing with small parts. Larger and heavier parts or locating devices do not have to be carried around the rotation table, however. The table can be rotated in any direction for front loading.

ZEISS INSPECT is crucial during the product development process

No matter whether you are conducting first article or series inspections: each measuring project is planned and prepared at an offline workstation in the metrology area. Coko uses the ZEISS INSPECT software for detailed 3D data evaluations. “When inspecting headlight housings, we typically measure diameters, cylindricities and position deviations,” explains Björn Sonters, metrology engineer at Coko, and adds: “We concentrate especially on the RPS alignment and point-to-point evaluations.”

GD&T evaluation is also very important in the field of plastic injection molding. Thanks to ZEISS INSPECT, it is easy to verify whether form errors are within permissible limits. “You can see the error at first glance. If the headlight socket has slight deviations, it cannot be installed in some cases,” explains Björn Sonters.

Coko uses ZEISS INSPECT throughout the entire product development process (PDP) while communicating with its customers – working with 3D data has proven to be very convincing. The data quickly shows whether the product is feasible or not. In subsequent PDP phases, users can set up trend projects in the software to execute inspections loops. The full-field 3D data is easy to understand and illustrates what has been achieved during theimprovement. Inspection jobs for the headlight housing are more complex during digital assembly. Users can simulate various orientations, change requests or ideas for assembling the parts. Visualization helps the engineer to adjust dimensions in the drawing to ensure that the headlight he creates functions.

ZEISS INSPECT visualizes hidden defects with a surface comparison.

 

With the digital assembly feature, Coko‘s  metrology engineers can bring together individual parts centrally and digitally. This ensures that parts produced at other locations can also be assembled.

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Heading into the future with virtual clamping, volume inspection and automatic loading

Coko’s experts are currently investigating three topics to speed up their own measuring processes: a batch processing system to load the ScanBox automatically, volume inspections via computed tomography to analyze defects and assembly situations for the entire component, and Virtual Clamping.

The Virtual Clamping option in ZEISS INSPECT simulates clamped parts and computes the clamped state based on the data of the real part in free state. The metrology engineers hope that they can save even more time by using the new clamping frame they developed in-house.

Coko has started to deeply integrate technology into its production processes. “This integration needs fast, reliable and efficient metrology systems,” as Andreas Spilker, Head of QA/QM at Coko, points out. And he adds: “Of course, we want to oversee the production process. We want to have qualified results, and most of all: We want to be fast.”