Precision Plastic Molder Uses Vision for 100% Inspection

"We must provide the highest quality product to our customers.  This has been our goal since day one." Pierre Dziubina, President of Spectrum Plastics, is a stickler on quality, and it shows in every aspect of the company's operations.   Founded in 1967, Spectrum specializes in close tolerance molding, insert molding, and continuous reel-to-reel moldings on metal or plastic carriers of precision thermoplastic parts for the electronics, medical, telecommunications and automotive markets.  They operate 64 presses and ship parts worldwide. As a part of the company's commitment to quality through progressive use of the latest technologies, Spectrum employs high-speed machine vision systems to ensure the shipment of only the highest quality product to their customers.  As an additional benefit, 100% inspection has also reduced mold damage and machine downtime.


The reel-to-reel precision molding process begins with a reel of stamped parts on a continuous strip being fed into the molding press. The mold closes, and a thermoplastic resin is injected into the mold around each of the stamped parts. After a few seconds to allow the plastic to harden, the mold is opened, and the completed parts are ejected and indexed out for the next cycle.  Problems can occur before, during or after the molding press. If the reel contains any stamped parts that are bent or crushed in any way they may damage the mold as the press closes resulting in expensive repairs and downtime. Parts may also be incorrectly molded or damaged as they exit the mold. "Part rates of up to 960 ppm can occur as the strip is indexed.  Some applications require two cameras to inspect the infeed and two cameras for the payout. High speed vision inspection systems are needed because we require 24 images per second for complete inspection and protection," explains Kieran Coleman, Spectrum's Process Engineer in charge of vision.



Spectrum currently has 26 vision systems supplied by PPT VISION, Inc. (Minneapolis, MN) performing 100% inspection of their critical reel-to-reel, insert molded products. Each of the PPT Passportä or Scoutä systems consists of multiple cameras and lights to capture the image of each part both prior to and after the molding process. High-speed strobe lighting is needed to "freeze" the motion of the strip as each individual part passes under the camera during the index cycle. The vision system then processes the image to inspect and measure each part for malformed inserts, misalignment, short shots, flash, and other part features. 


When a non-conforming part is found, the vision system sends a signal through discreet I/O to the line PLC which then stops the press and flashes a tower light to signal the operator that there is a problem. The image of the non-conforming part is locked on the vision system's operator control panel with a red border around it, and the system records and displays exactly what the problem was for future analysis and process improvement. The operator examines the defective part, cuts it out, reconnects the loose ends of the strip and continues running. "We are able to easily customize each inspection station while also providing consistency for the technicians by maintaining the same look and feel of each operator control panel. The icon-based programming makes it easy," says Coleman.


Pass/Fail, gauge results, failure analysis, SPC, MTBF and other data or images can be gathered and saved on a hard disk or sent over a serial or network connection to allow real-time or delayed process monitoring and control.  All the process and inspection information is collected and stored at each press, yet it is available for central processing and analysis via the network


In addition to quick turnaround reel-to-reel applications, Spectrum Plastics operates seven days a week handling multi-cavity molds to accommodate production requirements for its customers. Spectrum's need to be flexible is extremely important due to volume requirements. The vision systems easily accommodate more that one type of part being manufactured on a line by quickly loading a new inspection file during part changeover. "I like the flexibility of the new digital systems.  If we need additional cameras or strobes we just add them as plug-and-play items," says Coleman. "Things are always changing. Speed, flexibility and ease-of-use are key to the benefits we have received from vision inspection."


Dziubina concludes, "We are very pleased with the benefits we have achieved by using vision systems.  But, more importantly, our customers have seen the benefits and appreciate the quality of the product we provide."


This application note was provided by PPT Vision.  PPT VISION, Inc. is the world leader in the design and manufacture of completely digital 2D and 3D machine vision systems. Since our founding in 1982, we have specialized in industrial applications where accuracy, repeatability, high speed and flexibility are important requirements. For more information on PPT Vision, please visit their website at: