Coining is the general name for several types of operation that involve squeezing a piece of material between two parallel dies, usually forging and cutting operations. Its purpose is to cut, shape and form metal blanks into parts using precision tools. The size of a part produced by the coining process is determined by the size of the tool set.
The type of material used in the coining process has a large effect on the outcome. Depending on the characteristics of the material, the coining process can yield parts with very high precision and accuracy. The type of material also affects a key aspect of the process known as flash or parting line clearance.
Clearance is the gap between the top half of the die and the bottom half of the die. The size of this gap is determined by the type of material used in the process and the specific characteristics of the die. The size of the gap affects the quality of the part and the life of the die. If the gap is too large, it can affect the quality of the coining part and cause premature wear to the die. If the gap is too small, then the dies can become “locked”, meaning they are unable to move freely and the process stops.
As the gap is so important, it is necessary to ensure it is appropriate before beginning the process. To do this, a counterbalance is often used. A counterbalance is a tool, typically made of rubber or polymer, that is placed between the top and bottom halves of the die. The counterbalance compresses the rubber/polymer, thus creating a space that is just the right size for the material to be processed. This ensures the process runs smoothly and that the quality of the part is not compromised.
Another important aspect of the coining process is lubrication. While lubricants are not required for every type of material, they are highly recommended when using metals such as brass, aluminum and stainless steel. Lubricante adds a layer of protection between the dies, which increases the life of the tool and results in improved part quality.
Finally, it is important to mention the importance of temperature control in coining operations. While it may not seem important, precise temperature control is necessary for a successful operation. If the temperature is too low the material may not be malleable enough to be properly shaped. If the temperature is too high, then the material may become too soft and the coining process may become ineffective.
In conclusion, coining processes require precise control of several parameters to ensure successful outcomes. The size of the gap between the upper and lower halves of the die must be set properly, lubricants should be used whenever possible and temperature must be closely monitored. All of these measures will help ensure success.
