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Tabletting equipment: common problems and how to avoid them
To prevent or reduce the occurrence of these common problems, I have three key recommendations for manufacturers:
Seven steps to maintenance best practice
Tool maintenance is essential for problem-free production of tablets and to obtain the best service life of both the tooling and the tablet press. There are many systems and equipment choices available, but the ‘Seven Step’ approach can be adopted as a logical guide to best practice for tool maintenance.
Step 1. Clean: When the tooling is removed from the tablet press it should be thoroughly cleaned to remove all traces of product, lubricant and contamination. Whilst there are many systems available to clean the tooling, there are three key elements to consider: i) the cleaning should be thorough and remove all contamination from embossing, keyways, holes etc.; ii) once the tooling is clean it is vulnerable to oxidation and should be protected with corrosion inhibitors; iii) the tooling should be handled carefully during the cleaning process as accidental damage may occur if punch tips make contact with each other or the cleaning equipment.
Step 2. Assess: Once the tooling is clean we can then assess the condition. The condition can show if the process is running well or not; various types of damage and wear can give clues to problems with the press or tooling. The assessment is usually carried out by visual inspection of the tooling under magnification — for which there are systems available from a simple magnifying eyeglass to a sophisticated high magnification camera inspection system where images can be stored and transferred.
Step 3. Repair: The assessment will help to decide if any repair is necessary. Repair can be carried out on lightly damaged tips and minor head wear. Equipment is available in various forms, but the person performing the repair must be well trained and experienced in these techniques.
Step 4. Measure: Tooling should be measured to check for natural wear during the compaction process and also after any repair work. The essential measurement is the critical working lengths of the punches because this controls the thickness, weight and dosage of the tablets. Other measurements include the tip size and die bore size/condition. Again, it is important that the personnel are well trained in this procedure.
Step 5. Polish: Keeping the punch tip faces polished to a high degree of surface finish will maintain the tooling life and reduce problems, such as sticking and capping. Polishing can be carried out manually using polishing motors or automatically using special polishing machines.
Step 6. Lubricate: When the tooling is polished and ready for future use, it is essential to protect it from oxidation. Various types of rust inhibitors are available, including food safe options.
Step 7. Store: The safe storage and transportation of tooling is also essential to maintain the condition of the tooling and prevent damage to the delicate punch edges. There are various systems available, including custom-designed storage boxes and cabinets with special insert trays for keeping the tooling separated. These systems are also good for inventory control and tool management.
Selecting the right equipment
When selecting tablet equipment the following factors are key: