Product category:
Vision and scanning systems
News Release from: Festo | Subject: Checkbox
Edited by the Manufacturingtalk Editorial
Team on 10 June 2005
Vision inspection streamlines parts
production
Specialist parts handling company RNA Automation has developed a machine based on the Festo Checkbox vision inspection system to verify the quality of small component parts.
Specialist parts handling company RNA Automation has developed a machine based on the Festo Checkbox vision inspection system to verify the quality of small component parts A benefit of the new machine is that it enables the inspection process to be switched very quickly from one type of component to another, with minimal disruption to production, said Festo
This article was originally published on Manufacturingtalk on 7 Jul 2004 at 8.00am (UK)
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RNA Automation supplies parts handling machinery for manufacturing applications.
It specialises in the development of turnkey systems for orienting, feeding and conveying small components, to help parts manufacturers streamline their production processes.
According to Andy Perks, the sales manager for RNA Automation: "We already produce systems with integrated vision inspection facilities but for this particular application we wanted a camera system that combined fast throughput capabilities with a high degree of product changeover flexibility.
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After surveying the market we realised that the Festo Checkbox system had exactly the right performance attributes.
We were particularly impressed with its control software, which uses a learn mode to minimise programming and allows part changeovers to be accomplished very quickly and easily.
As a consequence, we intend using Checkbox as the core technology for our latest-generation intelligent parts inspection machines." The first user of the new machine is Tappex Thread Inserts, which designs and manufactures a range of brass and steel threaded inserts and fasteners for use in plastics, structural foam, composite materials, wood and metal.
The small components are manufactured to very tight dimensional tolerances and Tappex has built up a reputation for the quality and consistency of its products by applying rigorous process control and post-production inspection procedures, added Festo.
The quality control department at Tappex's main UK manufacturing facility in Stratford-upon-Avon uses a combination of visual and automated inspection systems to verify that manufactured parts are within specification, depending upon the type of insert.
The company wanted a new vision inspection system, primarily for inspecting inserts that will be fitted by robotic assembly systems, as they tend to be particularly sensitive to tolerances and can jam if the feed components are not perfect.
Until now, it has relied mainly on visual inspection and conventional measurement equipment for those parts, which is time-consuming and can never be 100 per cent accurate.
And although Tappex already uses automated vision inspection for some product lines, it can take up to eight hours to reconfigure the system to inspect a different part.
As the company wanted to inspect some inserts in batch sizes as low as 10,000, perhaps switching parts up to three times a day, its existing system did not provide the flexibility needed for that application.
The new component inspection machine includes a vibratory bowl feeder, a Festo Checkbox vision system - comprising an integrated camera and conveyor and control unit, as well as a number of air jets and solenoid valves, all mounted on a worktop height plinth.
The conveyor and inspection chamber, which contains the Checkbox line scanning camera and a laser target illuminator, are supplied to RNA Automation as a fully-assembled unit, with all control electronics housed in the separate enclosure.
The inserts to be inspected are loaded into the vibratory bowl feeder and progressively 'climb' to the top along a spiral track - a baffle plate encourages longitudinal settlement.
At the top of the bowl, an air jet blows any inserts that are still standing vertically onto their sides and a gating gauge on the rim then ensures that all inserts are queued up end-to-end, with any that are out of line falling back into the bowl.
At that stage, as it exits the bowl feeder, the front-most insert is pushed onto the Checkbox conveyor belt by the other inserts in the queue.
The belt is driven at a constant speed that is higher than the feed rate of the bowl feeder, using a brushless DC servomotor and an encoder to provide positional feedback data to the control unit.
As each insert lands on the belt, it accelerates away from the one immediately behind it, ensuring there is always a gap between components presented for inspection.
Throughput is normally about 120-180 inserts per minute, although the conveyor belt's speed potential of up to 800mm per second provides considerable scope for higher productivity applications, added Festo.
The imaging system can check up to 12 separate parameters - length, height, circumference and cross-sectional area are measured to within 0.1mm and by counting the number of pixels to the right, left, top and bottom of the insert's centre point, the system can also verify shape conformance and other critical factors, such as thread pitch and chamfer angles.
After inspection, each insert is categorised as 100 per cent good, or of unknown quality.
Ninety-nine per cent of Tappex's inserts that 'fail' inspection are not defective.
They were either incorrectly oriented or too close to the camera for thorough inspection, or the inspection result was ambiguous, which is typically caused by two small inserts being presented end-to-end without a gap between them.
The software that comes with the Checkbox includes a tool known as CheckKon, which enables users to download different programs, edit inspection parameters and display an analysis of the most recently scanned insert, as well as providing a 'learn' function that allows the system to be taught about new components through automated inspection rather than discrete programming.
If the standard teach-in process is unable to resolve very small component details, a tool known as CheckOpti can be used to optimise the component recognition process, said Festo.
Although the system has a facility for automatically returning any incorrectly oriented components to the bowl feeder, it is not currently used by Tappex, as the company prefers to return all 'failing' parts to the bowl for second pass inspection at the end of a batch.
The company also operates the system on a fail safe basis, so that all inserts exiting the inspection chamber are conveyed to the 'reject' chute - only those that have passed all quality checks are blown off the conveyor belt and directed to the packaging area, by a pulse of air from a nozzle located in the body of the conveyor.
The air jet is controlled by a solenoid valve driven by the control unit.
Festo said that it had to develop special valves for Checkbox imaging applications as most conventional valves have a response time of around 12ms, which would be inadequate for controlling an air jet intended to accurately hit a small component travelling at up to 800mm per second.
The high speed valves have a claimed response time of 1ms. Request a free brochure from Festo ...
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