Lapping & Polishing Punch Dies with Diamond Paste

Tablet punches are essential tools used in the pharmaceutical industry to produce medication in a precise and uniform manner. The surface of the punch must be smooth and polished to prevent adhesion of the tablet material and ensure accurate dosages. Diamond paste is a highly effective tool used in lapping and polishing punches, providing a smooth and mirror-like finish.

Process of Lapping and Polishing Tablet Punches

Before lapping and polishing, the tablet punch must be cleaned and inspected for any damage. Any nicks or scratches should be removed with a fine abrasive paper. The punch is then placed in a lathe-type chuck, which rotates the punch during the polishing process.

The lapping process involves using a series of lapping sticks to gradually remove any scratches and imperfections from the surface of the punch. Hardwood lapping sticks are first used with Kemet Diamond paste 6-KD-C3 or 6-W-C3, along with a very small quantity of Kemet Lubricating Fluid Type OS. This process helps remove any scratches or imperfections on the punch's surface. Afterward, softwood lapping sticks are used with the same diamond paste to achieve a finer surface finish. The pressure applied during the lapping process should be consistent to ensure an even finish across the punch's surface.

After the lapping process, the final polishing stage is used to achieve a mirror-like finish on the punch's surface. Felt bobs or cones are used with Kemet Diamond paste 1-KD-C3 or 1-W-C3 and small quantities of Kemet Lubricating Fluid Type OS. If the punch has raised or sunken letters or patterns, brushes are used to polish these areas. The polishing process is carried out using light pressure, and the punch is frequently inspected to ensure that the desired finish is achieved.

After the polishing process, the punch must be cleaned thoroughly using an ultrasonic cleaner to remove any diamond paste residue. The punch is then coated with a protective lubricant before storage to prevent rust and corrosion.

In the manufacturing industry, producing high-quality components with a mirror finish is a crucial requirement. The test components are two punch dies that require a mirror finish. To achieve this finish, the lapping and polishing process was performed on a Kemet 15 lapping machine. The machine is designed to produce a high-quality, precise finish on various components, including punch dies.

Part A: To begin the process, a temporary fixture was made to hold the part during both the lapping and polishing stages. The first step was to lap the part for 10 minutes, after which it was inspected to ensure that all machine grinding marks had been removed, leaving a uniform lapped finish. Next, the part was thoroughly cleaned using CO42 cleaning fluid to avoid contamination during the polishing stage. Finally, the part was polished for 5 minutes to produce a mirror finish.

Part B: In the case of part B, the required surface face was small, and thus the lapping and polishing process was performed by hand. However, a fixture could have been made to allow multiple parts to be lapped and polished automatically. Similar to part A, part B was lapped for 5 minutes to remove all grinding marks, followed by thorough cleaning with CO42 cleaning fluid. Finally, the part was polished for 3 minutes to produce a mirror finish.

Additional Info: After the lapping and polishing process, the parts were cleaned using CO-42 cleaning fluid. If a large number of parts require lapping and polishing, ultrasonic cleaning is recommended, as it reduces cleaning times and produces repeatable excellent results.