Optische Inspektion nach Maß

Customized optical inspection

Effective inspection solution for small series from batch size 1

For the visual inspection of small lots, ways beyond the AOI are required. As an effective method, augmented reality inspection has become established in combination with inspection of part numbers. In order to automate the handling costs incurred for the imaging, the company proServ electronic from Witten has implemented an intelligent inline solution.    

appeared in the Productronic 11/2017 

Small batches pose very similar challenges to EMS providers, such as medium and large batches. The works in the run-up to production are almost identical. A considerable amount of time is spent on data preparation, production preparation and the programming and set-up of the production machines. If the expenditure is based on a single board, the time invested per printed circuit board produced is significantly greater for small batches than for large series.

Economic consideration

Considering the optical inspection of small batches under this condition, the ratio is significantly worse. Although the purpose of the AOI is the automation of optical inspection, it can not fulfill this task for first time small series. For correct parameterization of the AOI program, all printed circuit boards of the small series are often required. Throughout this time, a well trained AOI operator is needed to fix the unavoidable pseudo errors and incorporate them as program enhancements. In this procedure, none of the boards really "automatically" tested. In addition to the high staff and time spent during the inspection, creating the program itself is time-consuming (see Figure 4). If the total effort is converted to a single printed circuit board, the cost of automatic check per board of a small series are very high. Often the clients are not willing to pay these costs.

As an alternative to AOI is often purely inspected manually. This procedure offers little security. The inspection process is incomprehensible. There is no documentation of the complete examination. The test personnel expect a high concentration capacity, which, however, also causes rapid fatigue. Necessary information for the evaluation of printed circuit boards must be selected from the documentation. Of course, this procedure offers too little security for the clients.

EMS provider proServ electronic

The company proServ electronic from Witten was in 2016 looking for a suitable system for the optical inspection of small batches. The existing AOI could not meet the requirements. The aim was to find a procedure for the optical inspection of small batches, which runs fast and easy and offers as an alternative to the AOI some automatic in the process and in the support of the operator.

ProServ electronic was founded in 1999 and has since grown significantly with the ever-increasing demands and needs of its customers. In 2015, the last move to larger premises took place, which now provides 1500 sqm of modern production space. The continuous investments in the machinery ensure a high degree of flexibility in the realization of all customer requirements. So all series sizes can be easily implemented. A line is available exclusively for the production of prototypes, zero and small series. The qualified employees work with a high quality awareness.

ProServ electronic found their requirements for the optical inspection of small batches in the EFA Inspection System of Lebert Software Engineering from Hanau.

Efficient inspection system for small batches

The programming process is quick and easy in EFA Inspection without wasting much time. On average, 5 minutes must be invested in programming. Here, all relevant data such as the pick-and-place list, the BoM data, the assembly plan, as well as manufacturing instructions or additional information per component can be integrated. All this information is targeted during the inspection. About the augmented reality functionality, the information about the image of the board can be displayed on the currently relevant component. 

In order to be able to cover different test tasks, a variety of inspection procedures and methods of representation are available. For example, all parts of the same part number can be displayed and evaluated together in the inspection according to part numbers (see Figure 3). The image sections of the components are rotated back to zero degrees according to the stored angle of rotation. For the examiner, this means that all components of a part number must be the same. "The flexibility with which we can adapt EFA Inspection to our process is an important factor for us," explains Managing Director Sabrina Frühinsfeld.

Also an inspection by means of golden board function is possible. Here, the images of a good board and a DUT are displayed alternately. The alignment of these two pictures takes place via fiducials and is thus extremely stable. The inspection cut-outs can be individually set up and thus adapted to the conditions of each board.

For the small series inspection, the inspection procedure can be fixed, so that the operator no longer has to make any device. The next created image is automatically loaded and displayed for inspection. The process is guided, repeatable and documented. In addition, the employee is supported in the inspection decision by displaying the augmented reality. All relevant information is available for assessment at a glance. The average inspection time is 3 minutes on average for a printed circuit board with approx. 500 components.

With a batch size of 20 boards, this means a total effort including programming of about 65 minutes. In comparison, the setup time of the AOI for the example board is already around 120 minutes - without consideration of the pseudo errors. (see also picture 4)

Inline functionality without handling effort

The basis of the system is a high-resolution image of the board. When creating the EFA desktop device, a certain amount of handling is required for inserting and picking up the boards. With permanent use of EFA Inspection this handling effort is quite significant.

As an alternative, an EFA inline device is available (see Figure 5). Supplied with a loader and unloader, the recordings can be created automatically. A magazine with boards to be inspected is inserted into the inline device and then the associated recording profile is selected. The track width adjusts automatically out of the profile and the automatic recording process for the magazine starts. After imaging, the boards are sorted back into the magazine. This inspection island with inline functionalities is available for many applications. Also recordings of THT-equipped boards are of course possible.

The complete images are transferred to inspection sites, where you can even inspect in parallel. The images are automatically loaded into an open EFA project, so that the operator has to concentrate exclusively on the assessment of the displayed image sections.

"The EFA inline solution convinced us with its automatic image creation," reports Marco Schönefeld, Managing Director of proServ electronic. "We can easily inspect lot sizes from 0 to 1000 with EFA Inspection."

Smart solution also for work preparation

The decision for EFA SmartSuite was also made by proServ electronic because of the flexibility and expandability of the system. In addition to the inspection, EFA is also interesting for work preparation. Data processing for the machines now also takes place with EFA SmartSuite. The different formats of the customer data are read in EFA and the data for the own production are always output in the same format. This significantly saves time, because uncertainties and renewed data preparation in production are a thing of the past. "The different formats of customer data can be converted into a standard format for production with EFA," reports Marco Schönefeld.

As a result, EFA Inspection, the EFA Inline device and the use of EFA SmartSuite saved a considerable amount of time. "This has a direct impact on the quality of our products," explains Managing Director Sabrina Frühinsfeld.

proServ electronic plans to further integrate EFA SmartSuite. The next step is to implement the connection to the ERP system. The fuzzy search algorithms can be used to find the right part numbers directly from the scanned customer parts list. EFA SmartSuite interprets the individual values so that the spelling, unit of size or sequence are irrelevant in the list of component descriptions.

EFA SmartSuite is designed as a complete solution for EMS providers (see Figure 6). The various EFA applications can be used from the quotation phase to the work preparation to production and use smart automatic functions to optimize previously purely manual production steps. "In the constant development of EFA SmartSuite, we rely on close cooperation with our users," explains Hans Jörg Lebert, Managing Director of Lebert Software Engineering. This ensures that every customer can find their individual solutions through personalized processes - the result is a practice-oriented application "from customer to customer".

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