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Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
Pharmaceutical tablet packing and inspection
Introduction
Pharma Packaging Systems (PPS) based in Pershore, UK, specialise in packaging systems for
the pharmaceutical industry. Primary business is design and manufacture of electronic
counting systems for tablets and capsules, either standalone, or as part of an integrated
packaging line. With over 50 years of experience in this sector and references worldwide
PPS are considered a leading supplier of this technology.
Multipix Imaging, a distributor specialising in machine vision, has been working with
Machine Vision Technology Ltd (MVT), Leamington Spa, since 2003. Multipix offering advice,
supply and support of machine vision components which include assisting with application
evaluation and loaning equipment to MVT when necessary. MVT are independent vision
systems integrators which means they are totally free to choose the right vision system for
each application. Their staff, individually, have up to 30 year’s experience in the Machine
Vision business.
Vision provides competitive advantage
MVT were approached by PPS after they identified an opportunity to offer their customers
the benefits of Machine Vision by creating an inspection solution for their existing range of
counting and packaging machines.
The purpose of the inspection is to check for broken, partially formed or cross
contamination (rogue tablets from another batch). In the pharmaceutical industry, cross
contamination, if left undetected before it leaves the manufacturer can cause the whole
factory to be shut down for a period in addition to crippling fines.
Key advantages of the PPS online inspection system
• Verify it is the correct tablet so avoiding cross-contamination
• Measure length, width, area, completeness
• Verify colour
• Ensure quality
• Avoid product returns and the possibility of substantial fines/losses
• 80 images per second across 24 lanes of continuous tablet flow
PPS ideally wanted to work with a local company that also had the experience and capability
of developing such a specialised system, MVT had previously developed a system for
Schwartz Pharmaceutical, USA to inspect tablets and so the cooperation was formed.
Challenges to overcome
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
In general terms the bulk product (tablets or capsules) feed from a hopper onto vibrating
trays that feed and separate the product and guide them along the stainless steel trays. As
the tablets leave the end of the feed trays they pass through high speed infrared optical
sensors that count the products in free fall. The products are counted with high accuracy, at
high speed, into bottles that are indexed on a conveyor by a scroll drive system.
This innovation has been to place cameras above the final feed tray to inspect the tablets
just before they are counted and bottled. As the tablets are vibrating they are often
touching and moving irregularly and therefore the trays can present the tablets to the
camera in any possible orientation.
Another challenge to overcome is the bright and reflective finish of the stainless steel tablet
feed trays which cause the tablets to reflect in the channels of the tray. Therefore the
challenge for the Vision system when measuring the tablet length, width, area and colour is
to differentiate between actual product and its reflection.
Innovative tablet tracking and multiple inspections ensure robust results
Each camera positioned above the tray images 6 lanes of tablets. Each tablet is typically
inspected ten or more times as it passes from top to bottom through the camera’s Field Of
View (FOV). The main problem to overcome was the product appearing to be either good or
bad at any one instant in time depending on which face it was presenting to the camera as it
feeds. MVT spent over one year developing some very sophisticated tablet tracking
software that tracks each individual tablet.
As the tablets leave the tray and get counted into a bottle the vision system outputs the
tablet inspection result. Once the inspection returns a ‘good’ result for a tablet it is ‘locked-
in’ as good, even if it then bounces onto an edge and so appears to be ‘bad’ in subsequent
inspections. The tablet must be deemed ‘good’ in at least one image, otherwise it is ‘bad’,
and when a bad tablet is detected the bottle will be rejected.
The vibratory feeders start and stop several times a minute and feed at varying rates to
maximise the throughput into each bottle as the bottles index past. This continuous tracking
of numerous tablets, with their associated inspection results, is therefore a real
accomplishment.
The Vision System has to find every tablet in each image, predict where it will be in the next
image and match its new position and orientation in the new image to be able to identify it
as the same tablet and so individually track it, building up its good / bad history.
Looking ahead
The machines described above are based on standard PPS machines with modifications that
allow integration of machine vision and are basically still tablet counting machines.
The latest MVT/PPS evolution is designed as a machine vision inspection system and has a
flat belt tablet feeder between the last vibrating tray and the output of the machine. This
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
means the tablets are lying flat and are evenly separated and this system is designed to
reject individual tablets as they leave the belt based on the good/bad status of the tablet.
This system will inspect the tablets for width, length, area and colour in addition to
thickness and will ensure only good product is discharged for further processing. This
system can inspect up to 10,000 tablets per minute but is scalable to suit any application.
Technologies used in this solution
For lighting MVT chose to use multiple LED arrays and selected GigeVision colour camera’s
for the image acquisition into one industrial PC. MVTec’s Halcon image processing software
forms the basis of Machine Vision Technolgy’s customised C# application code.
A typical feed rate is up to 2500 tablets per minute per 6 track feed tray.
Websites:
www.pharmaps.com
www.machine-vision-technology.co.uk
www.multipix.com
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
Fig 1. Typical PPS Pharmacount tablet counting system.
Fig 2. Bulk product in the machine just before it reaches the vibration trays.
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
Fig 3. Counting machine with integrated vision system and controls.
Fig 4. Counter vision controls are full integrated into one colour touch screen
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
Fig 5. Main vision inspection screen used by the operator during production.
Each camera view at the bottom of screen can be switched to the main display above. The
image shows white capsules traveling down from top to bottom of the camera field of view.
At the bottom of the image the capsules pass through the counting head and the vision
system’s good/ bad status output determines whether the bottle is passed or rejected.
Fig 6. Here we see an excellent image despite the bright finish of the feed trays.
Each tablet has good (G) and bad (b) scores associated with it.
Success Story
Contact Details: Lynne Potter +44 (0)1730 233332 [email protected]
Fig 6. MVT use techniques to help the operator visualise how the software works and
guide them through the process of training new tablets. Once an operator has been shown
how to train new product they typically take two minutes to fully train a new tablet prior to
testing in production.
