What Is a Pellet Press?
A pellet press is a machine that presses and forms tablets, resins, and other materials.
Pellet presses are generally designed to press various materials into a mold and press a plunger into the mold to form the material. Manual, manual hydraulic, and automatic hydraulic types are available. Formed pellets are used as samples for various measuring instruments, test pieces, electrodes, recycled samples, etc.
Applications of Pellet Presses
Pellet presses are ideal for preparing sample pieces for X-ray fluorescence analysis, infrared spectroscopic analysis, and electron microscopic analysis. There are also applications for pellet presses in the preparation of cathodes and anodes for all solid-state batteries, sample pieces for research and development of dental materials, sample pieces for research and development of new products, and pellets for solid electrolytes.
Other examples of applications include tablet cleaner molding, metal powder molding, magnesium molding, ceramics molding, functional material molding, and food molding. It is also used for molding crystalline materials, zeolite, waste paper and plastic fuel RPF, resins, and silica/alumina.
Machines called press pelletizers or pellet molding equipment are used to solidify and reduce the volume of fuels, fertilizers, feedstuffs, and industrial wastes. Continuous production of pellets is possible. Conical rollers press the raw material with uniform pressure.
Principles of Pellet Press
The pellet press works as follows: First, the material is filled into the mold. Then, the plunger pushes the material into the mold, and pressurization begins. As the pressure increases, the air inside the material is pushed out, increasing the density and defining the shape of the pellets.
Once the maximum load is reached, the pressure is held for a certain amount of time so that the particles of the material adhere to each other, resulting in a stable pellet. Higher pressure ensures reliable molding and pellets with a smooth surface. With the automatic pressurization system, pressure can be controlled in steps, making it possible to create high-quality pellets even from materials that are difficult to mold.
The type that incorporates a heating device in the pellet press can press by increasing the temperature. High-temperature pressing is possible for compression molding tests and sample preparation of resins and powders.
Types of Pellet Presses
1. Classification by Driving Method
- Manual-type
This method uses the principle of leverage to move a plunger by a lever or screw to produce pellets hydraulically. Since hydraulic pressure is increased by hydraulic pressure, the press can be operated with light force. Since it is manual, it does not require electricity and is easy to use. Subtle adjustment of pressure increase and speed is possible. It is used for trial products in laboratories and for making a small number of pellets.
- Manual-automatic type
The built-in electric hydraulic pump allows easy adjustment of pressure. The speed of pressure increase, upper limit of pressure, holding time, etc. can be automatically controlled.
- Automatic type
Programmable, automatic, homogeneous pellets can be produced. For mass production.
2. Classification by Press Method
There are two types of powder press methods using dies: uniaxial and biaxial. Uniaxial pressing is a method in which the lower die is fixed and pressed by the pressurizing force of the upper punch. Friction between the walls of the powder-filled mold can cause a density difference between the upper and lower pellets, resulting in deformation and cracking.
Biaxial molding is a method in which the mold is not fixed, and the pellets are pressed in a floating state. The mold moves up and down in accordance with the movement of the powder during molding, thereby reducing the density difference between the top and bottom.
3. Classification by Added Functions
- Heating device
The specimen can be pressed at high temperatures. There are also high-temperature types capable of temperatures up to 400°C. Some are equipped with a water-cooling device. Some models are equipped with a water-cooling system, which enables fine adjustment of the mold temperature.
- Pressurization equipment
Combined with the pressure-resistant cleaning device CIP, this method applies pressure to the sample and presses it. Pellets are formed by applying uniform pressure from all directions using water pressure. Pressing is possible up to a surface pressure of about 2 tons.
Other Information on Pellet Press
KBr tablet method
The KBr tablet method is a basic method for infrared spectroscopic analysis of solids. It is suitable for measurements when the sample is rare. Potassium bromide KBr to which a small amount of sample is added is pressed into tablets to be used as a sample for the infrared spectrometer.