What is Bakelite Relief in Tablet Tooling? [Purpose and Downside]

Anyone who has worked in the tablet production area or on a tablet compression machine is familiar with punch tightness or stickiness caused by sticky materials. Sticky materials can cause damage to the tablet tooling if a proper measure is not taken.

Here comes the term Bakelite Relief which is commonly used in tablet tooling, explicitly referring to a particular design feature on tablet compression punches.

Bakelite Relief is a sharp undercut in the lower punch tip. This relief area is located precisely at the back end of the punch tip, away from the tablet’s imprinted face. Bakelite Relief aims to prevent the tablet material from sticking to the die bore/inner wall during the compression process by scraping the adhering powder.

Image: Bakelite Relief Drawing

When tablets are formed, the powder or granules are compressed under high pressure. Without Backelite Relief, the tablet material could potentially adhere to the die’s inner surface, leading to problems such as sticking or picking. Sticking occurs when the tablet material remains attached to the punch, causing defects and impacting tablet quality. Picking refers to the tablet material being torn or pulled away during ejection from the die, resulting in tablet damage or inconsistency.

By incorporating Bakelite Relief, the design ensures that the tablet material can flow smoothly during compression and ejection, minimizing the risk of sticking and picking issues. The relief area allows sufficient clearance for the tablet material to separate cleanly from the die inner wall, ensuring proper tablet formation and reducing the potential for defects.

However, if the Bakelite Relief is not properly designed or maintained, it can lead to problems. For instance, if the relief area is too deep or poorly machined, it may cause excessive wear on the punch tip or compromise the structural integrity of the punch itself. This can result in punch breakage, increased tooling costs, and production downtime.

Recently I faced a lower punch tip breaking issue due to a sharp bakelite relief angle. This happened because the structural integrity was compromised. The area on this Bakelite relief area is a weak spot since the Bakelite relief is cut 1.5 mm deep in the tip body and being 6.5 mm, it is breaking under the pressure of compression force.

Image: Tip breakage due to Bakelite Relief

Furthermore, inadequate or inconsistent relief dimensions across different punches can cause tablet weight and thickness variations, affecting dosage accuracy and overall tablet quality.

It is crucial to ensure that the Bakelite Relief design is well-calibrated and regularly inspected to maintain optimal tablet production performance while avoiding associated problems.