Seeing the way to a better product

The UKIVA highlights the benefits of industrial vision systems for inspection in quality control applications, which are being increasingly recognised in the pharmaceutical sector

Vision inspection systems offer specific key benefits over their human counterparts, namely speed, accuracy and repeatability to meet the industry's demands to make products at high speed and with minimal (or ideally zero) defects.However, vision systems bring additional benefits to the manufacturing process; an increase in compliance with manufacturing regulations, a reduction of returned products, the ability to produce electronic records of batch performance, increased traceability and the capability to integrate with higher management-level software.

While vision quality control systems are used to prevent 'out of tolerance' products reaching the consumer, they can also significantly reduce 'false rejects'. This is where a product which actually meets the specifications is incorrectly rejected. Reducing the incidence of this clearly cuts down on wastage, saving costs.

Vision has a host of applications throughout the industry. The combination of a camera(s), PC and image capture, processing and analysis capabilities form the basic elements of extraordinarily powerful and versatile inspection equipment. In this article the various components involved in intravenous (IV) drug delivery and the multi-faceted role that vision can play are discussed.

IV administration of drugs can be as diverse as self-administration of insulin by diabetics, to the supply of fluids by paramedics, blood transfusions, administration of chemotherapy treatments and delivery of anaesthesia for operations. Checking of labels and markings is another important consideration.

Monitoring of pharmaceutical containers can range from checking the integrity of bundled bottles in a high speed packaging line to the counting of individual vials on different sized trays. Components such as rubber stoppers can also be inspected (figure 1).

Manual counting of filled and capped glass vials containing drugs such as anaesthetics can be both slow and unreliable. Manufacturers operating to FDA guidelines are required to track all pharmaceutical containers.

Counting can be carried out automatically, accurately and cost-effectively by positioning a camera on a bracket above the trays containing the vials. The use of high frequency lighting and appropriate filters can ensure good contrast on the vial caps, which are often colour-coded according to the dosage in the vial. An example of such an image is shown in figure 2.

The camera captures an image of the entire array of vials using the individual caps as reference points. The captured image is transferred to a dedicated image processor where the image is analysed and provides counts of the vials.

performance keys

An object location tool can be used to handle variations in part positions caused by moving vials or trays being in slightly different positions. Key to the performance of systems such as this is the speed at which counts can be made and the reliability of the system.

In one such application the system is used to count vials of three different sizes, ranging from 2cm³ to 10 cm³. As many as 456 of the smaller vials and up to 196 of the larger ones can be located on individual trays.

A customised graphical user interface provides a real-time readout of the number of vials in a tray, the number of trays counted and a running total of the number of vials in the lot. Since such systems can operate 24 hours a day and count an entire tray in 500 milliseconds with no manual counting errors, they offer the manufacturer the potential to increase production quantities.

The inspection of labels is becoming an increasingly important contribution from machine vision to the pharmaceutical industry.

Clearly it is vitally important to ensure that a given product is correctly labelled to avoid the possibility of incorrect dosage, but also machine vision has a key role to play in the identification of pirate products: grey imports and copycat products.

One particular application involves the use of vision systems to reliably inspect syringe body closure gap sizes and to use optical character verification (OCV) techniques to check that the correct label is applied to the syringe. The system is integrated into the packaging line. First an image of the label is acquired and a reference point determined. The label pharmacode is then verified and two lines of overprint are checked against a match string entered by the operator at the start of the batch.

The OCV is extremely flexible and is capable of dealing with different font sizes and qualities. If all aspects of the inspection are correct, the label is passed and applied to the syringe. The second stage of the process involves measuring the size of the gap between the body and chamber (the part which contains the product) of the syringe.

If the gap is larger than 1/8 mm, the syringe is marked for rejection. This ensures integrity of the product. The results of both inspections are passed to the packaging line programmable logic controller (PLC) which tracks the product via fail-safe digital signals.

IV cannulae are assembled automatically. At the simplest level the cannula is inserted into a hub and an adhesive is applied to seal it in place. Other stages could involve placing a shield over the cannula, applying a seal over the shield and marking with a lot and date code. The requirements of the machine vision system are quite demanding as the product is assembled at speeds up to 750 per minute and multiple inspections have to be undertaken. Typically this would include checking:

for burrs on the insertion end of the cannula

for the correct angle and height of the cannula above the hub

that the adhesive is correctly applied to the hub

that the shield is in place

that the lot and date code are legible and correct

If the cannula assembly has 'wings' it is important that the bevel on the cannula tip is in the correct orientation with respect to the wings otherwise the cannula point will not be correctly aligned to the skin.

This requires that the bevel angle is checked and brought into line prior to attachment of the wings. Inspection is also likely to include checking for the presence of and damage to the wing assembly.

As the cannulae need to be viewed from different angle, a number of camera orientations are required. A simple user interface (figure 3) can allow the operator to select the camera as well as displaying the results.