Coordinate measuring machines with integrated multiple sensors
Flexibility for dimensional measurement in production control and laboratory
Flexibility connected with high accuracy has led to wide ranging use of coordinate measuring machines for dimensional measurement in production control, as well as for 1st piece, tool, and developmental inspection in the laboratory. The special advantage of coordinate measuring machines with multi-sensor systems is that the operator can choose the sensor best suited to a given measuring task. He is not limited, given a choice of sensor types, to a specific measuring strategy, and therefore is able to generate an optimized testing plan in one measuring run. This guarantees economic advantages and higher reliability.
The design of the basic instrument is appropriate to the measuring task
The modular design principle can accommodate different methods of application, and therefore different measuring ranges. Requirements concerning accuracy as well as environmental conditions can be considered. The Werth ScopeCheck® series was designed for cost effective quality control in the shopfloor environment.
The solid steel mechanical design and construction of the basic machine is unmatched in this class of equipment. Completely covered guideways allow use under rough conditions in production control. The main measuring axes are separate from each other. In contrast to a stage with one axis stacked on the other, this design improves precision especially in the case of relatively flat workpieces. Due to the solid design of the Z-axis, the ScopeCheck® has full 3-D capability and accuracy. The measuring range of this series of instruments extends up to 400 mm.
The machines in the Werth VideoCheck® series readily meet higher demands for accuracy. Among benchtop instruments, the stress free, full bearing stage design is unique in the world, and provides unbeatable accuracy. Temperature sensitivity is also minimized. The high performance control system in this series of machines allows the use of continuous path scanning systems. Therefore these machines are capable of fast 3D scanning. The maximum measuring travel is also 400mm for this series of machines
Where demands for accuracy and flexibility are the highest, the Werth VideoCheck® granite fixed-bridge series provides the optimum solution. Modern air bearing technology, combined with mature and intelligent solutions in mechanical design, maintain the outstanding characteristics of this machine. The performance is superior to any machine in this class worldwide. Solutions to the most complex measuring tasks are provided with the incorporation of rotary or rotary/tilting axes. With the combination of super high resolution linear scales and 3D error compensation, measuring uncertainties down to 0.5 µm are provided.
The Werth Inspector FQ® series of machines was designed for fast production control. The modern drive system, based on linear motors, makes it possible to drive to up to 5 positions per second and to measure several geometric elements at each position. Given such high measuring speed, economic production control with coordinate measuring machines is now available for most industries for the first time. Industries as wide ranging as machined and fabricated parts, electronic and automotive components, semiconductors, telecommunications and fiber optics, and medical products, can all benefit from these advances.
A common advantage of all the systems mentioned above is that they can integrate multiple probing systems, as well as laser sensors, with the primary optical sensor system.
Fast and flexible image processing
The basic configuration of each instrument includes an image processing sensor system that is tailor made for metrology. It is perfectly suited for fully automatic measurement of complicated workpieces, even with poor contrast conditions, in transmitted and in incident light.
Special gray scale image processing filter methods reduce the influence of dirt particles, for example, upon the measuring result.
The illumination of the workpieces is CNC controlled for all models. For highly accurate measurements, the transmitted light and the incident light that is integrated in the image beam path, are primarily used. For example, for the measurement of plastic and stamped metal parts, a flexible darkfield illumination is of great importance. A multi-segmented ringlight is ideal for these applications. The ringlight provides uniform illumination. However, when required, individual segments can be illuminated separately to enhance the image of specific features.
An ideal solution for many standard measuring tasks is the newly developed Werth-Zoom. The design principle (patent pending) is based upon linear guideways and provides highly reproducible and stable measurements. The optics are calibrated during the final inspection at the factory. Additional calibration before measuring or after zooming is not necessary. Another unique feature of this zoom is the fact that both the working distance and the magnification can be adjusted automatically. Measurement into the depth of workpieces up to 200mm is possible. It is also possible to search workpieces with a large field of view and a large working distance without the risk of a collision. Further advantages are to measure round parts with large diameters. Due to the availability of a long working distance, a combination of vertical and horizontal lenses can be used for measurements in different views.
Telecentric lenses are recommended as the preferred choice of optics for high precision measurements. An automatic change of magnification may nevertheless be provided with electronic digital zoom or multiple beampaths.
Measurements in the Z-axis are done with the image processing sensor using the integrated fast autofocus. Precision in the submicron range is obtainable, depending on the object measured. When compared with a laser sensor, autofocus offers the fundamental advantage of being relatively unaffected by material surfaces.
Touch probe sensors extend the range of applications for the machines
The integrated marriage of optical and mechanical sensors makes an ideal economic alternative to measuring projectors, measuring microscopes, and pure touch probe coordinate measuring machines. For example, for the measurement of the cylindrical form of bores or undercuts, each optical measuring method has its limits. The touch trigger probe therefore belongs in the basic configuration of a modern multi-sensor coordinate measuring machine.
Rotating/indexing axes and probe heads and probe changing devices provide nearly unlimited flexibility. In Werth coordinate measuring machines fully automatic 3D scanning is already provided with this sensor. Mapping of freeform surfaces is therefore possible for subsequent evaluation.
In contrast with touch trigger probes, continuous contact analog type probes have integrated path measuring systems. Therefore a continuous evaluation is provided in 3D scanning. Higher point densities and positioning speeds allow economic operation during the measurement of freeform surfaces. Additionally, these probes may be mounted on rotary/tilt heads and probe stylus changers to further increase flexibility.
Laser and Fiber Probe round out the possibilities of the machines
Laser distance sensors are well suited for the rapid measurement of the flatness of workpieces as well for the measurement of low slope freeform surfaces. Challenges arise, however, where high speed is desired on the one hand, but the characteristics of the part cause changes, on the other hand (i.e., changes in slope, surface texture, reflectivity or color). Where the sensor may fail at some portion of a task, the multi-sensor machine provides the answer. In combination with rotary/indexing heads or rotary axes, a solution for fully digitizing 3D freeform surfaces is provided.
Modern glass fiber technology has made it possible to develop the Werth Fiber Probe. Measuring the smallest 3D micro feature elements (i.e., sphere radius from 12 - 250 µm) opens completely new applications. Due to the extremely low probing force, measurement of rubber and plastic parts can be made by contact without part deflection. The gap between optical and traditional contact probing is therefore closed. With this probe (patented), the flexing of the probe styli, stick-slip effects, unacceptably large stylus forces, and intrinsic vibrations have little effect on measurement results.
If a high precision coordinate measuring machine is used, the sensing uncertainty may be smaller than 0.5 µm. Also, the measurement of gages and high precision tools is now in reach
In specific cases, it may be of interest to record and to log the temperature in the measuring volume. This is provided by integrating thermal sensors in the system. Also, roughness measurement with contact or non-contact sensors, and with the Fiber Probe, is provided within the same measuring run This is another advantage of the multisensor concept, and is of main interest in process inspection.
Ergonomic software for use on the shop floor and in the gage lab
The WinWerth measuring software allows efficient and easy operation of the machines. Here the graphically interactive user interface is of special importance. Measured geometry elements are graphically presented as a CAD drawing. With simple mouse clicks they can be connected for measurements and constructions. Therefore measurement is as easy as the reading of a drawing . In the CAD-Online mode, the operation is reduced to the absolute minimum. An operator has only to select the geometry elements to be measured on the presented CAD drawing via mouse clicks. These elements are then measured automatically.
With password protection, the user interface can be set so that operators have access only to the software that corresponds to their skills. Program initiation with a bar-code reader to launch complex test runs is therefore optimally supported. With the aid of the software modules Werth CAD-Offline and Werth CAD-Paramess, offline programming of multi-sensor coordinate measuring machines is provided on a high level.
Contour data obtained in the scanning mode with different sensors can be evaluated in two fundamentally different ways: The WinWerth Software includes special contour elements that allow a direct evaluation of the scanned freeform geometries in the automatic mode. For example, measures of smallest contour distance, extreme points, or the composition of different contour parts is provided.
The Werth BestFit Software has been using graphic comparison for the efficient evaluation of free-form contours for over 10 years. The latest version, Werth ToleranceFit (image 10), provides the option of adjusting to the actual tolerance zones rather than the nominal contour. Thus, for the first time, an evaluation that corresponds fully to a hard gage is possible. Again, measuring suited to the particular application is now a reality.