Motion and Vision Combine to Detect Flaws

Plastic film is highly valued in the computer industry where plastic sheeting is used in the creation of printed circuit boards (PCBs). MicroCraft, a Japanese company, was challenged by a plastic sheeting manufacturer to come up with an inspection system that could find and categorize the micron-sized defects that can occur in plastic film production.


Plastic film is highly valued in the computer industry where plastic sheeting is used in the creation of printed circuit boards (PCBs). MicroCraft, a Japanese company, was challenged by a plastic sheeting manufacturer to come up with an inspection system that could find and categorize the micron-sized defects that can occur in plastic film production.

The manufacturer’s current method for detecting defects required an operator to evaluate an image projected onto a wall with an overhead projector. The operator would circle defects on the sheet and then carry the sheet to a microscope with a film camera attached (to photograph the defect). Next, the operator estimated the defect

National Instruments

National Instruments' PXI IMAQ 1422 board.

area, length, and width based on other calibrated pictures and made a handwritten log entry for all the information. The operator then placed the picture in a “picture book,” in a section for the defects category. This process was time-consuming and only done sporadically, because no more than 10 samples could be completed in an 8-hour work shift.

Defects appear as bright spots

MicroCraft re-conducted the manufacturer’s original test procedure using a cross-polarized light field, along with vision and motion systems. In this method, distortion of the aligned polymer chains in the material made defects appear as bright spots. A two-step analysis was then conducted using two cameras—ones with large and small fields of view (LFOV and SFOV, respectively) and different magnifications (LFOV: 0.3X, SFOV: 6.4X). The LFOV camera was used for initial film inspection to find defects. Operators used the SFOV camera for secondary defection evaluation, and to capture images and measurements for data storage.

Machine Vision, May '09, Control Engineering

Other articles in the May 2009 Control Engineering North American print edition supplement:
- 415 Parts Seen
- Intelligent Vision Stops Bypass of Quality Control
- The New Look of Facial Recognition

A backlight table was covered with a polarizing sheet and placed on a 2-axis linear rail system to control the lighting and motion of the manufacturer's 8-in. diameter samples. Motion, vision, and data collection were combined using a National Instruments PXI-7324 motion board and two PXI IMAQ boards.

After the operator orients a sample for correct polarization, the system automatically scans its 16 2-in square “quadrants.” Using the LFOV camera, the operator looks for defects. Using vision analysis virtual instruments (VIs) to determine the center of a suspected defect, the PXI system commands the table to move so that each potential defect is in the field of view for high magnification. Several image analysis VIs also are used to counter common lens problems, such as pin-cushioning. Motion analysis VIs create an algorithm that properly positions the defect area directly under the SFOV camera.

When the operator locates a suspect area using the SFOV camera, a live image appears. The operator can reject the image—if it is a dust speck, for example—or classify the defect and make calibrated measurements for area, length, and width. Resolution in the SFOV camera was achieved through calculations using NI Vision Builder and a USAF resolution target at 1.17 microns/pixel. With this resolution, the system can detect and quantify defects in the manufacturer’s required 10-100 micron range. At roughly 15 minutes per sample, operators can now test up to 30 samples per shift.

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
A cool solution: Collaboration, chemistry leads to foundry coat product development; See the 2015 Product of the Year Finalists
Raising the standard: What's new with NFPA 70E; A global view of manufacturing; Maintenance data; Fit bearings properly
Sister act: Building on their father's legacy, a new generation moves Bales Metal Surface Solutions forward; Meet the 2015 Engineering Leaders Under 40
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Pipeline vulnerabilities? Securing hydrocarbon transit; Predictive analytics hit the mainstream; Dirty pipelines decrease flow, production—pig your line; Ensuring pipeline physical and cyber security
Upgrading secondary control systems; Keeping enclosures conditioned; Diagnostics increase equipment uptime; Mechatronics simplifies machine design
Designing positive-energy buildings; Ensuring power quality; Complying with NFPA 110; Minimizing arc flash hazards
Building high availability into industrial computers; Of key metrics and myth busting; The truth about five common VFD myths

Annual Salary Survey

After almost a decade of uncertainty, the confidence of plant floor managers is soaring. Even with a number of challenges and while implementing new technologies, there is a renewed sense of optimism among plant managers about their business and their future.

The respondents to the 2014 Plant Engineering Salary Survey come from throughout the U.S. and serve a variety of industries, but they are uniform in their optimism about manufacturing. This year’s survey found 79% consider manufacturing a secure career. That’s up from 75% in 2013 and significantly higher than the 63% figure when Plant Engineering first started asking that question a decade ago.

Read more: 2014 Salary Survey: Confidence rises amid the challenges

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.