Product category:
Vision and Colour Sensors
News Release from: Cognex UK | Subject: Machine vision
Edited by the Engineeringtalk Editorial
Team on 15 March 2001
Vision System Ensures Nasal Inhaler
Quality
BesPak, an American anufacturer of HFC and CFC pharmaceutical metering valve products, needed to measure various critical dimensions on injection-molded plastic inserts
BesPak, an Apex, North Carolina-based manufacturer of HFC and CFC pharmaceutical metering valve products, needed to measure various critical dimensions on injection-molded plastic inserts as they were assembled to inhaler shells While the company had already attempted to use a machine vision system in place of an older random-sample checking process, the system had trouble adhering to BesPak's strict Repeatability and Reliability testing requirements
This article was originally published on Engineeringtalk on 12 Mar 2001 at 8.00am (UK)
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"Our internal requirement was no more than 20% variability in performance, though our ultimate goal was to achieve less than 10%, with that particular system we were struggling to get below 30-40% variability, which was unacceptable and was leading to an excessive amount of falsely-rejected products." claims Jim Gallion, BesPak Manufacturing Engineering Manager.
This limitation combined with the system's inability to pass even basic validation tests, caused Gallion and his team to investigate other alternatives.
After evaluating several competing products, BesPak chose a Cognex Checkpoint 900 vision system to inspect both the diameter and "ovality" of the inserts.
"The purpose of the vision system is to reject inserts that do not meet the 0.63 - 0.77mm diameter tolerance, and verify that the insert's orifice is not more than 20% oval when comparing the longest axis against the shortest.
The Checkpoint system proved capable of measuring the inserts within these strict tolerances, and passed the original validation tests - as well as many additional validation tests - with flying colors" says Gallion.
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Cognex have introduced the In-Sight 2000, an entirely new type of industrial machine vision sensor at a cost usually associated with "smart cameras"
New machine vision system for SMD placement
Cognex has introduced SMD4, Cognex's next-generation machine vision system for guiding the placement of surface mount devices onto printed circuit boards and other assemblies
The vision system consists of the Checkpoint 900 PC plug-in card housed in a Pentium PC, two Sony CCD cameras, and a remote controlled Fostec fiber optic light source.
Inhalers are assembled on a custom, fully automated assembly machine built by BesPak.
First, inhaler inserts are automatically picked from feeder bowls and placed two at a time into fixtures on a rotary indexing table.
The two vision cameras are mounted horizontally in the machine and placed side-by-side so they are parallel to two parts as they are seated in the individual fixtures.
Once two parts are indexed into view, motion stops and both left and right cameras capture an image of the part is sees.
The images are then sent to the Checkpoint system, which first uses PatMax geometric pattern matching software to determine the exact position of the orifice in the insert.
"Locating the pattern accurately can be very challenging due to machine vibration," explains Gallion.
"Because the inserts are so small - typically 1/8" high by 1/8" in diameter - we need to use extremely high magnification to get a high quality image of the orifice.
Even slight machine vibration can shake the field of view and cause the pattern's position to vary.
The general robustness of the system took care of these issues." Once the location has been determined, the orifice diameter is checked using Checkpoint's (name of) tool which perform 72 individual radial measurements.
The vision system then measures the orifice to determine if its shape is within the Ovality tolerance set.
The entire inspection cycle takes place in two seconds, at which time a new set of parts is indexed in front of the camera.
If a defective part is detected, the defect is automatically logged into a database on the PC and the part is automatically picked off the turnstile and placed into a reject bin.
"Logging rejects is one of the key parts of the validation process we need to perform," says Gallion.
Parts that pass both inspections are picked and placed onto a offload conveyor, where they proceed to a final packaging and are then shipped to the customer for filling.
Key to the ability to capture good images, according to Gallion, is Checkpoint's ability to monitor the intensity of the lighting and adjust it accordingly.
"We use the Fostec light to backlight the part, and because the part is white plastic, light actually transfers through the part very diffusely with no shadowing," he explains.
"However, if the intensity weakens the vision system will not be able to get as clear of a view of the parts, which could effect the accuracy and reliability of the results.
Checkpoint can automatically analyse, control, and improve the operation of light, so if the light dims with age, the system will automatically increase the power to restore its original intensity." Linking Checkpoint's CPComm tool with Visual Basic, Gallion's team was able to develop a custom graphical user interface for the vision application, which appears on a 17" monitor built into the assembly machine.
The interface displays a live image of both parts as they are being inspected, as well as a running tally of the number of rejects.
According to Gallion, the interface makes Checkpoint easy for plant operators and maintenance personnel to operate, test, and calibrate Checkpoint without having access to the more complicated features of the full system.
Since the system was installed in (date needed), it has providing 100% inspection 20,000 inserts a day with an exceptionally high degree of reliability, resulting in fewer false rejects and less scrap.
Gallion reports that unlike the previous vision system, which struggled with getting below 30-40% reliability during R and R tests, they are now seeing numbers well below their previous ultimate goal of less than 10%.
"Even under tighter tolerances that we normally use, the system is measuring 3% variability on the right camera and 4% on the left, which was completely unheard of to us," claims Gallion. Request a free brochure from Cognex UK ...
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