Tablet tooling, including punches and die, is one of the main factors to affect the quality of tablets. Of all mechanical parts, tablet tooling is the most active one in the tablet manufacturing process. Punches will go up and down to complete compression job in the die hole. Consequently, tab tooling becomes the most easily worn and damaged part, and frequent replacement of the compression tooling develops an obligatory work. As shrewd as you are must have noticed that deferred wear and extended life of punch tooling must save a large sum of money and labor force as well. In this article, we will analyze factors to affect tool wear from 7 points.
- Tool Material
The wear of punches and dies depends largely on the properties of material, like hardness, toughness, ductility, and carbide insert, etc. Stainless steel has good mechanical strength, and a better toughness and hardness with carbon insert. Stainless steel punch tooling thus become popular punch mold. Aluminum is an abrasive material that is more aggressive on tools but with polished smooth surface.
- Tool Manufacturing
The procedure for tool’s construction must be carried out carefully to avoid deformations, let alone the key tablet compression part－punches and dies. Before a mature metal material, the tools must undergo a series steps of strict annealing, normalizing, quenching, tempering, precooking, hardening, and heat treatment.
As for tool construction, it would be started from machining, and then continue the rest technology of wire EDM cutting, grinding, milling, and polishing, in order to avoid internal stresses of working surfaces.
- Tool Configuration
A station of tab tooling contains two punches and one die. To complete the tabletting process, the punches will do up and down, and then run into the die hole to finish compacting course. Punches are the direct part to embrace the particles and are more easily to get abrasion. In common practices, punches will generally wear faster than the dies for which are less osculatory to the abrasive particulars and external factors. And the small punches are more prone to wear then the larger punches. In addition, sharp corners will show wear quickly than straight or curved edges, particularly on punches. Narrow sections will wear faster than heavier sections.
In shearing operations, punches and dies must be designed with a small geometric offset, called clearance, to allow the cutting of the sheet metal. Narrow clearance heightens the friction between punches and dies in the “up-and-down” course, thus accelerate wear on the punches. While broad clearance cause a big gap from where the particles may run away, which seriously bring about weight variation of tablets.
- Turret Alignment
It’s critical to regularly check turret alignment in order to prevent turret wear and unacceptable part quality. Narrow clearance on one side of a punch and die will accelerate wear at that point. Any wear on the punches or dies will definitely affect the turret alignment. In such case, more mechanical components subsequently get wore.
- Production Conditions
Punching speed: every tablet press machine is set with rated punching speed that is to make most use in practical applications. To some extent, high punching speed generates lots of friction and heat that may soften and damage a punch, because softer punches will wear much easier and faster.
Pressure stability: the tool’s life also depends on the pressure stability. Unstable pressure work on the punches and dies will absolutely form unpredictable damages. The operator should check and adjust the pressure to a certain and right range of compacting pressure.
- Clean and Maintenance
Sticky powders on the punches and dies are aggressive to corrode the tool material. Every time when we finish a batch of production, we should clean the punch tooling and make a maintaining work before storing.
Punch tooling with slight deformation or damage is acceptable and should be corrected with the help of some tools to remove the burrs, to polish the surface, to balance the length of punches. With a regular check and maintenance, the tooling is kept in good condition and has a generous longevity.Loading Likes...