Using NI LabVIEW and Vision Products to Create Parts Manufacturing Inspection Systems

Author(s):
Jochen Schütz - GEFRA

Industry:
Imaging Equipment

Products:
Vision, PXI/CompactPCI, LabVIEW

The Challenge:
Developing an inspection system for parts manufacturing that has high accuracy and flexibility, is readily available and user friendly, and has maximum output.

The Solution:
Developing an inspection system for parts manufacturing that has high accuracy and flexibility, is readily available and user friendly, and has maximum output.

The Need for a Flexible, Accurate System

With increasing productivity in manufacturing, the possible error rate rises, which makes the use of faster, more accurate and flexible inspection systems necessary. These inspection systems possess characteristics making the use of automatic, contact-free vision technology indispensable. The systems must be able to create a task in which it is necessary to take care of a wide spectrum of units under test (UUTs) and their production methods, as well as the possible problems that could result out of that. We developed Autocontrol for the inspection system Optisort to achieve a simple and overall optimized operation, where the operator does not need to have any knowledge in programming and the concept of the existing system does not have to be changed.

System Functionality

The system consists mainly of feeding, separation, and the inspection system. An operator feeds the UUT into the inspection system, where a transport unit takes the UUT to the measurement devices. Next, a laser sensor detects the UUT existence. Then, a real-time system generates a trigger that starts the image acquisition. From here, the software evaluates several images generated simultaneously corresponding to the reference values. After reaching a certain time limit, the system has to complete all UUT evaluations. The system determines whether the UUT passes or fails the test. Finally, the system separates the UUTs that pass the test from those that fail.

Our solution was to create the system with the following criteria:

• The system had to ensure the possibility to realize a real-time system based on Windows 2000.
• The software needed to adapt to the system by way of a programming method that was as easy as possible.
• The package had to be multifunctional and without any restriction in terms of EDP vision processing component use.

We combined NI LabVIEW and IMAQ Vision to provide the essential open programming method and corresponding complexity to handle all the facts mentioned. Our next step was the realization of the real-time capability using LabVIEW. Here, the LabVIEW-based system proved to be multifunctional, too, since the synchronization of LabVIEW and the external real-time trigger unit was easy. As a result, the system can determine the UUT timing and spatial position (by the real-time trigger unit) and can control the conformity with the reference data (evaluated by the host computer).

Next, we created a control program. As a result, we had to consider a wide component spectrum, such as five different laser sensors and three different camera types. It was also imperative to create a polyglot and operation-optimized HMI. Thanks to the ingenious LabVIEW graphical development environment, the realization of this step was very simple. Furthermore, using functions like the VI Server, we reduced helped programming costs.

Finally, we developed an inspection algorithm. Here, the major problems included the existence of the variety and possibly individuality of UUTs, the indispensable inspection processes, and the evaluation time that is substantial for the performance availability. However, the most important issue was that the system had to be able to be operated by people with no vision systems knowledge. The program had to work independently and had to recognize the edges on a part or detect the UUT twisting on its own. As a result, the tools had to provide all these functions and use them without any entries by the operator.

NI Products Provide Flexibility

We considered almost any possible problem during the LabVIEW development. On the one hand, we needed an algorithm that recognized UUTs independently of their rotation or position and the inspection of the UUTs without a predefined ROI. On the other hand, it was necessary to define a ROI to acquire a special section of the image. However, during the planning phase, we soon found out that we also needed a third method. Pattern-matching was required to be able to find a part by a determined sector of the UUT contour and determine the rotation by help of the sector recognized. For the realization of this assignment, we needed not only an exorbitant vision library but also equivalent and subtle functionalities for the operator guidance. Even this was no problem with the help of LabVIEW. We wrote the extremely complex and demanding inspection algorithm using the extensive IMAQ Vision library. Using LabVIEW and the IMAQ Vision software, we had an almost inexhaustible stock of functionalities.

For more information contact:

Jochen Schütz

GEFRA

Tel.: +49 2743 932024

Fax: +49 2743 932025

E-mail: J.Schuetz.GEFRA@t-online.de

Web: www.GEFRAgmbh.de

 

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