Martha K. Raymond
Packaging-equipment designers are developing products to run faster and smoother for lower costs. The packaging industry covers an array of equipment, including material handling systems that move products, controls that dictate timing, and valves that quiet a conveyor. There are also the machines that move packages from one station to the next and specialty devices for wrapping.
And then there’s the particular requirements of various industries that need their own custom machines and equipment. Plastics are sensitive to temperature, and food requires pristine cleanliness. Taking care of the basic requirements can seem a daunting task. But by simply taking a tour through the various twists and turns of the packaging industry and stopping to look at some of the trends, can help guide designers.
A machine-vision system that guarantees high-quality packaging in the pharmaceutical, food, beverage, and cosmetics industries is a system from Cognex, Natick, Mass. Because proper package sealing ensures consumer safety, while pristine labels and decoration enhance the consumer’s image of the product, manufacturers are turning to 100% inspection, and machine vision automates the inspection process.
In an application for inspecting caps and lids on cans, a manufacturer needed to verify that the inner seals were properly formed, decreasing the chances of contamination in the final product. The company also needed to ensure high-uality decoration in the closures. A line speed of 600 closures/min created two complications: delays in catching a production problem resulted in large volumes of defective closures and expensive waste, and also inspection was beyond the capability of the human eye.
As a solution, a vision system above the caps and lids inspects logos and decorations in full color, rejecting any caps with print quality defects. Underneath the closures, the vision system inspects the inner coating to ensure proper sealing. By combining vision tools, the system ignores the acceptable variations in coatings, while rejecting tiny variations that could compromise the seal. Other closure inspection applications include inspecting beverage can ends for correct placement of pull tabs and detecting defects such as dents and rivets in beverage cans.
Other machine-vision applications in packaging include defect detection that locates defects in labels, decorations, containers, closures, and seals. Also, code verification ensures correct date and lot code printing, while code reading tracks parts by reading 2D Data Matrix or OCR codes. Sorting differentiates between various products or containers by size, shape, or color to ensure the correct products are placed in the correct containers. Robot guidance finds the part for the robot to pick up and the position where the robot should place it.
Another machine vision system also takes on the duty of on-line gauging, inspection, assembling verification, and machine guidance. Prophecy 600 from Imaging Technology, Bedford, Mass., is a Windows-based, high-resolution, gray-scale system that uses Sherlock 32 software for applications at speeds up to 1,800 parts/min with accuracy to 0.0001 in. Tasks include detecting flaws, measuring dimensions, and verifying size and location.
To start the analysis, an external signal triggers the system to take a picture. After running a preconfigured investigation, the software extracts measurements and compares them to preset tolerances. Results are automatically interfaced to other factory equipment.
For a flexible transport link between workstations, a modular assembly conveyor easily expands or reconfigures and can be converted from manual to automatic stations with practically no effort. The Modular Assembly Conveyor from Rapistan Systems in Grand Rapids, Mich., consists of aluminum sections with connectors, drives, conveyors, turning units, lifts, curves, workpiece carriers, and power supply systems.
Another option for modular conveyors includes a line of nonsynchronous over/under pallet conveyors from Bleichert in Sterling Heights, Mich. These combine high-load capacity with energy efficiency. Individual pallets hold up to 220 lb and can be linked together to carry large or heavy workpieces. The link-hinge feature lets a group of subpallets traverse the conveyor ends for empty pallet return on the underside.
Each pallet runs on four ball-bearing cam followers which traverse a steel rail in an extruded aluminum side track. The cam followers support all pallet weight through their travel on top of the conveyor and during return travel under it. Up to eight pallets can be linked together and connected to a pair of drive chains via an adjustable polymer slip-clutch sprocket. The arrangement consumes little energy compared to conventional chain-pull conveyors. A single drive can power up to 90 ft of conveyor with fully-loaded pallets. Centerguided pallets simplify tracking, metering, and controlsystem design.
The cylinder’s novel design incorporates a piston rod supported with two composite bushings. One is in the nose of the cylinder and other is in the tail assembly. These support the rod throughout its stroke, and also support most couples induced by side loads and/or stress reversals. The separated bearings minimize stress raisers, a major source of early failure in cylinders. With this configuration, the piston and piston seals aren’t load-bearing members, typical in traditional cylinders. This innovation ensures smooth operation for millions of cycles, even at 50 cycles/min without external lubricant.