HIGH SPEED VISION BASED DIMENSIONAL INSPECTION

HIGH SPEED VISION BASED DIMENSIONAL INSPECTION
FOR SCREW MACHINE COMPONENTS

The high speed vision based inspection system for screw machine components is intended to provide manufacturers of high volume screw machine components a means for inspecting 100% critical geometry features. The systems are provided turnkey, including the parts feeding, inspection positioning, and output sorting.

The feeding system can be supplied for a specific component or may be fitted with tooling to allow setting to any component within a family. The output of the feed system will then feed the parts into the inspection fixture. Feed rates are basically governed by the component shape, size, and orientation requirements. Typical speeds range from one to ten parts per second.

The inspection positioning mechanism is driven by the inspection requirement. Components that require a large number of features to be inspected and need the inspections to be performed for multiple sections of the part, require that the component be precisely located for the inspection process. Mechanisms requiring a cycle time of at two to four components per second utilize cam driven mechanisms to provide smooth, reliable operation. These systems require component specific tooling and are intended for long run jobs. Reduced numbers of features to be inspected at a single section allow he ability to provide linearity settable tooling which can accommodate a family of components. These configurations are typically utilized for short run jobs and have typical cycle times of one to ten parts per second.

The sorting mechanism accepts parts from the inspection stage and provides a fail-safe method for sorting the components into accept/reject/unknown bins. Parts are constantly monitored via part passage sensors for verification of proper sorting for each cycle of the machine.

The inspection is performed by digitizing a high resolution CCD camera with 1300 x 1030 pixel format. High inspection accuracy is maintained via a digital camera interface which reduces jitter common to most RS-170 based systems to zero. The camera is operated with an asynchronous electronic shutter allowing for strobed operation when stop motion imaging is required. A collimated backlight operating in strobed or continuous mode is utilized to provide a high definition of the component edges. The component edges are imaged by a telecentric lens which provides a high definition minimally distorted image to the camera CCD array. This element is key for achieving full accuracy over the entire field of view.

The camera image is processed by a high performance, industrially hardened IBM PC compatible processor. The processor also provides the system timing and control functions for part movement as well as image capture. The user is provided a VGA monitor and full alpha numeric keyboard for user setup and operation of the system.

The processing software is extremely flexible and provides the user with the ability to quickly configure the inspection tools to the features that need to be inspected. All part inspection configurations are saved to a file for storage and later retrieval. Subpixeling techniques are utilized to provide inspection resolutions of .000040”. the various edge tools provide edge positions and can be combined in a number of ways to form any desired feature. Each feature is provided with tolerance limits to allow accept/reject determination.

The software also provides correction for lens distortions in order to work within the entire image field at the specified resolution. Additional software exists to allow parallel processing to be implemented in the case of high speed requirements and multiple cameras. This is typical when a part needs to be inspected in multiple sections such that roundness and concentricity’s may be computed. Each associated camera processor reports its preprocessed features to the master processor which performs the final dimensional computations as well as the system timing and control functions.

Networking is provided as well which allows the inspection data to be retrieved over a network for analysis by the computers statistical processing package of choice. This provides the ability to monitor the performance of multiple machines and allow for immediate corrective action to be taken if required.