Automated testing: A critical component of high-throughput tablet production
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CORRELATION BETWEEN TABLET PARAMETERS
Measuring the compression force for each tablet punchhas become a standard feature of modern tablet presses inorder to be able to take immediate corrective action in theevent of a fault. Although the compression force allowsconclusions to be drawn about product specifications –such as the weight, thickness and hardness of tablets –additional testing of each parameter is required to ensurethat the product characteristics are within the limitsspecified. It is important to understand that, even thoughall three parameters are directly related, only theircombined test results will provide a basis for reliable quality control.
Tablet hardness not only relates to the disintegration time of a tablet, it is also an indicator of whether the combination of weight and thickness is correct. In other words, if hardness is out of limits, then either weight or
thickness (or both) will also not meet product specifications. It does not, however, tell the operator which parameter needs to be adjusted in the production process (for example, compression force or filling quantity). Only testing of all three parameters will give a complete picture – and allow for appropriate corrective measures to be taken. -
Weight Thickness Hardness Out of limits Correct Out of limits Correct Out of limits Out of limits Correct Correct Correct
FULLY INTEGRATED IPC
In order to take full advantage of modern high-capacity presses, in-process tablet testing also needs to be automated. Modern tablet testers automatically measure the weight, thickness, diameter and hardness of tablets, and can be operated on a standalone basis or fully integrated with a great variety of tablet presses from different manufacturers. Measured test results are transferred to the tablet press in real-time to automatically adjust production parameters or alert the operator. Often referred to as ‘lightly attended operation’, the combined system of tablet press and tablet tester provides for maximum efficiency and reliability, as tests are conducted automatically at pre-set intervals without any operator interaction required. When making a purchasing decision for an automatic tester with fully integrated in process control (IPC), the following key factors need to be considered:
1. Can the tablet tester be used in-line with existing presses?
A high-quality popular tester would usually have in-line interface software written for it by a wide variety of leading international press manufacturers. Tests are started automatically during the production process, and production parameters are adjusted automatically based on measured test results. Recommended product: AutoTest 4
2. Can the tablet tester handle a wide variety of tablet sizes and shapes?
It is important to select a tester that is capable of testing an assortment of tablet sizes and shapes. Oblong, hexagon, diamond and custom-designed shapes should be correctly oriented automatically and fed to sequential
width, thickness, diameter and hardness test positions.
3. How reliable and precise are the test results?
Force measurement of hardness must be reliable and consistent, and posses unquestionable linear accuracy. The best precision is achieved by an S-Beam type load cell; this state-of-the-art transducer is internationally
accepted for its accuracy and reliability. To provide for reliable weight measurement, there are two key factors: precision of the integrated weighing system (balance) and vibration-resistant design of the tester itself. As test equipment is located directly in the compression room, the tester need to be able to absorb vibrations from the tablet press, as well as air draughts in the production environment.
MECHANICALLY INTEGRATED IPC
Even tableting operations that still employ traditional, lower-output presses can benefit immensely by converting their manually operated tablet testers to fully automated models. Besides the obvious significant labour-saving advantages, automated weight, thickness, diameter and hardness testers provide real-time, accurate test data that can be identified and evaluated immediately. Resultant corrective action, if any, is therefore timely and prevents costly continued production of a substandard product. Productivity and quality are enhanced, along with reduced waste and the need for costly remakes.
Additionally, test data generated by a quality automated tablet tester can be electronically captured, stored and secured on a PC with CFR 21 Part 11 compliant software. Data can be retrieved onsite or remotely at any time and displayed in either tabular (for example, Microsoft Excel®) or graphic format. Data required for client or regulatory audits is easily compiled and generated. Automatic tablet testers can be networked with multiple tablet presses, and operational control performed by one, centrally located, Windows-based PC.
