Ballpoint pen (also “biro” and “ball pen”) is a writing instrument that has a metal ball at its point which rolls and moves ink from an internal reservoir to the surface on which pen writes and, at the same time, works as a buffer between the ink in the reservoir and the air outside and protects this ink from drying.
Ballpoint pens are made of metals, plastic, and some other chemicals. When they were first made, for a ball it the point was used steel. Today is used textured tungsten carbide because it is resistant to deforming. The point that hold the ball is made of brass - alloy of copper and zinc. Brass is strongly resistant to corrosion, it has a beautiful color, and can be easily shaped into desired form. It is often used for other parts of the pen like ink cartridge, the body of the pen, or the spring. Some cases are made of aluminum and can be plated with gold, silver, or platinum with more expensive pens. Ink is made to be thick, clean of particles, not too dry too quickly in the reservoir and yet to dry sufficiently fast on the paper.
Ballpoint pens are made in mass-production, and the first step is making the ink. Workers (called compounders) control computers that in turn control how the raw materials for ink will be treated. Materials are poured into the batch tanks and mixed according to the formula for ink. To help them mix thoroughly, materials in the containers are heated or cooled, depending on which materials are used and how they interact with each other. Computers also control this as well as the speed of mixing. During the making of ink, quality controls are performed to assure that finished ink has desired properties at the end.
Metal parts for ballpoint pens are done while the ink is mixed. Tungsten carbide balls are rarely raised by a pen manufacturer and are usually bought from outside vendors. Metal point and body is made from brass which is first cut into small discs. These disks are heated which softens them. Softened disks are poured into a compression chamber where they will be shaped. This chamber has a steel ram and a spring-backed ejector plunger. When the steel ram presses the metal, it causes the plunger to retract. That forces the metal into a die cast mold where it takes the desired shape. Excess metal that doesn’t fit the mold is then scraped off and recycled while the die opens and releases the shaped pen part.
Because they use a different machine, plastic pen parts are done at the same time. They are made by extrusion or by injection molding. Plastic, as a raw material is in granules or powder and like that, it arrives in the factory. It is fed into a large hopper and from there into a large spiral screw which leads granules into a heater which liquefies it. Mass is then forced through a die, cooled, and cut. More complex pieces are shaped by injection molding. Liquefied plastic is forcibly injected into a mold. It is the left to cool off. After cooling mold is opened and plastic piece retain its shape.
When all pieces are formed, ballpoint pen is assembled. First, a tungsten ball is attached to the reservoir which is then injected with ink of the desired color. If the finished ballpoint pen will be retractable, spring is added in the next step. Assembled parts of point and reservoir are then placed in the casing with cap and ends. When the coating and decorations are added, the pen is cleaned and packed ready to be sold.