Measure Without Losing Time: High-Precision System Enables 3D Inspection in Real Time

July 7, 2020
The high-speed metrology and inspection system from DWFritz Automation processes complex geometries faster than traditional inspection methods.

Conventional measurement systems such as coordinate measuring machines (CMMs) are typically used for quality control in various industries. Most traditional contact-based inspection systems are characterized by long measurement cycle times. Changeovers to measure other parts and the attendant programming also add to the delay. Further, contact-based measurement technologies are not suitable for generating large amounts of data points required for complex surfaces. Because of these limitations, systems like CMMs are not an ideal solution for 3D inspection on the production line. To solve these problems, the ZeroTouch measuring platform uses multiple non-contact sensor technologies to rapidly measure in three dimensions and in real-time. ZeroTouch's proprietary software then creates a highly accurate dense 3D point cloud. In addition, by simplifying complicated programming procedures, ZeroTouch reduces the system configuration time to just a few hours saving substantial production time and costs.


“Quality control is critical in production operations,” explains David Mendez, vice president of the ZeroTouch business unit at DWFritz Automation. “Preparations, such as programming, as well as the measuring process itself, often take a great amount of time and result in high costs. In addition, inspection tasks requested for manufacturing often collide with other measurement requests such as those from other manufacturing lines, pre-production tests or even R&D." The measurement platform features a 5-axis architecture that captures millions of data points per second in a single scan to create a dense 3D point cloud. The system enables the rapid measurement of complex part geometries and precise inspection of the most complicated parts with high repeatability.


The system uses a unique planar air bearing design that minimizes tolerance stack error. The near-zero friction design provides an extremely smooth, high-speed motion of precision stages and improves gage repeatability and reproducibility (GRR). In contrast, tactile probes typically operate at slower speeds as they require physical contact with the part surface. Contact measurements are primarily limited to 2D scans–typically generating sections or contours whereas ZeroTouch can generate complete 3D surfaces with an accurate and dense grid of data points. Acquisition of the data points is extremely rapid, at a rate of up to 4 million points/s. In addition, the system combines various technologies such as laser and chromatic confocal sensors with high-resolution cameras with multi-spectral illumination. Further, the user has flexibility in choosing the right sensing technologies to get the most optimal measurement results. For example, shiny or specular surfaces will require specific sensors such as white light confocal or interferometric sensors. On the other hand, laser profile sensors may be needed for surfaces with “matte” like finishes.


During the development of ZeroTouch, special attention was given to problems that conventional CMMs face: obtaining quick, accurate, and reproducible results to keep pace with manufacturing cycle times. Most traditional inspection systems have issues specifically with speed, ease-of-use, and machine availability. As a result, traditional measurement technology does not lend itself to inline inspection or even fast sampling.


Providing the operator a tool that is easy to use to perform rapid quality checks of various types of parts produced by different lines is vital to ensure the qualification of manufacturing lines, in addition to speeding up the production ramp. CMMs are typically located in environmentally controlled inspection rooms, which often impact machine availability. If the parts are to be inspected in the metrology room during the production process, part "queues" are to be expected, due to limited machine availability coupled with long CMM setup times.


The sensor bridge is configurable, allowing the most optimal and appropriate sensor selections to suit the part and surfaces, in addition to the complex dimensions being measured. Such innovations in the system result in higher throughput of parts and increased capacity, enabling 100% in-line inspection rather than just sampling.


ZeroTouch has been designed precisely to mitigate these issues by being fast, flexible, easy to use, and compatible with the manufacturing environment.


ZeroTouch enables 100% part inspection. In addition, the ZeroTouch is characterized by its ease of use. By giving the operator an easy-to-use tool, different types of parts produced on different lines can be quickly inspected. Such capability will enable the rapid qualification of manufacturing lines and speed up production ramp.


ZeroTouch’s unique architecture features 5 independent axes; a rotating bridge–Gonio like–equipped with multiple, non-contact sensors, including lasers and chromatic confocal sensors, which dramatically increase inspection speeds in measuring the entire part surface, as there is no sensor change time. The sensor bridge is configurable allowing for the most optimal and appropriate sensor selections to suit part geometries and surfaces, in addition to the complex dimensions being measured. Such innovations associated with a horizontal rotary table and 3 translation axes result in higher throughput of parts and increased capacity, enabling 100% in-line inspection rather than just sampling.


The innovative design of ZeroTouch presents a remarkable improvement in surmounting the challenge of repeatability in a hostile manufacturing environment. Since it can perform multiple measurements in parallel using different sensors, parts and assemblies can be analyzed significantly faster than a conventional CMM.


“The sensors can be configured to the specific GD&T measurements and the part, and in one scan the system can capture data points to create a high-density 3D model,” says Mendez. “This makes it possible to measure objects made of a wide variety of materials with complex geometries, including holes, undercuts, bevels, and surfaces, quickly and with micrometer precision. At the same time, the system provides very high reproducibility and repeatability of results.”


The various non-contact sensors on the metrology bridge can be easily calibrated by software directly via the metrology platform. Further time is saved by the simplicity with which parts and assemblies can be placed on the measuring table, instead of requiring complex positioning fixtures. This, not only decreases the metrology preparation time but also enables direct cost savings in fixture design, development, and management.


“It was also important that ZeroTouch shows no signs of wear, and delivers the same performance year after year,” says Mendez. “So we gave it a planar air bearing system”. The moving parts, such as the measurement platform and sensors, generate virtually no friction during the measuring process. Part inspection plans can be created within a few hours and stored in the manufacturing execution system (MES) for management and retrieval. “The user is assisted by menu-guided intuitive tools, making deep programming knowledge superfluous now,” says Mendez. “Instead, inspection plans can be prepared using drag-and-drop functions.”


Measurement data for each component is retained to ensure data integrity. Thereafter, component-specific plans can be accessed in the MES for fast measurement. Optionally, components or assemblies can be given barcodes to be read by an onboard barcode reader. The respective inspection plan is then automatically loaded from the MES. The control software provides high personal safety by ensuring that the system does not move as long as the doors of the switchgear cabinet are open or if the system light curtain has interference.


The three-dimensional point cloud can be analyzed immediately after the measurement process. Integrations to proven analysis tools enable the accurate comparison of the scan results with part CAD models or a reference part previously scanned and measured to not only check for geometric and dimensional tolerances but for other previously undetected issues such as surface aspect defects. Using statistical process control (SPC), faults or outside-tolerance deviations can be quickly detected and appropriate reporting can be sent back to the MES. This could enable the adjustments of process parameters in upstream manufacturing processes to minimize rejects downstream.


The current system measures 240 x 150 x 190 cm (L x W x H) and weighs 3,550 kg. It can measure parts measuring up to 300 x 300 x 300 mm and weighing up to 10 kg. It uses a high-performance GPU PC with Intel Core i7-7700T Processor and two capacitive industrial monitors with touchscreens.