Precision Stamping

Freely deformable metal has excellent strength, so it is often used as a structural member that requires strength. At the same time, we also found that when the applied stress (that is, the force per unit area) exceeds its tensile strength, the metal will not break immediately like brittle materials such as ceramics or bricks, but will deform. That is to say, metal has plasticity, we call it plastic deformation. Every metal has different deformability, the most obvious example is gold. Utilizing the plastic deformation characteristics of metal, the metal is formed into various shapes.

How can we plastically deform the seemingly strong metal? Then you have to use die steel that is stronger than metal. The mold steel is made into upper and lower molds according to the shape to be formed, and then the upper and lower molds are opened and the raw materials are placed, and then the molds are fixed on a device called a punch. Let the punch provide the force required for forming, and drive the mold to close and open the mold up and down. The mold is closed to form the material, and the mold is opened to allow the raw materials to enter and exit. The punch, mold, and raw materials constitute a set of stamping forming systems. Under strong pressure, even very strong metals have to deform with the shape of the mold.

The most common stamping processes include punching, bending, and drawing. Take the key to be used every day as an example. If you design a lower female mold with the same shape as its inner hole, and an upper punch with the same shape as it but a smaller upper punch, place the sheet on the female mold and use a punch to fix it on the upper punch punches down through the sheet to get the key of the desired shape. Such as the use of automated punch production, two to three hundred pieces or more can be produced in one minute. This is the simplest example of punching. In order to enhance the required functions or quality of the product, some subsequent machining procedures are still needed.

Regarding the bending process, it can be imagined that the upper and lower molds first press the sheet metal with the spring force, and then use the punch to apply force to the part that needs to be bent. An example of the bending process can be illustrated by the strap of a watch. A general metal watchband is made of stainless steel and is divided into two parts, a chain strap, and a buckle. When you look at the fastener, you will find that it contains 3 plates, and the inside of the joint also contains a hosel and a spring. Each piece of the plate must be bent or curled in a certain part for the function of a buckle. A closer inspection will find that it also uses other forming techniques. The part of the chain strap is also a series of punching, bending, and pressing of the plate to make a strap with the function of the chain and beautiful. Of course, if you disassemble the watch, you will find more stamped parts distributed in it. Another common example is the stapler. It is obvious that its structural parts are made by bending metal plates.

Factors to Consider When Choosing a Material for Precision Stamping

 

Ductility & formability
Forming occurs somewhere between the yield strength and tensile strength of the material. If yield isn’ t exceeded, forming doesn’ t occur but exceeding the tensile strength results in a material fracture. In higher-strength materials, the window between yield and tensile is very small. The grain size of a material is commonly used to indicate its formability, and consistent grain size is highly desirable for forming operations. Grain size can be controlled by a rerolling mill within a very close range by monitoring the temperature of the annealing furnace and the speed at which the strip passes through the line.

Tensile strength
Tensile strength measures the amount of force a material can withstand without breaking. Some metals are stronger than others, and the strength varies depending on the component materials in a metal alloy. You should consider the tensile strength of the metal you choose to ensure that it can withstand the amount of force applied during use.

 

Machinability
Machinability measures how easily the material can be cut or shaped. Because properties that improve a material’ s performance often reduce its machinability, you should consider the machinability of the metal you choose after satisfying other requirements for your part. A machinable material can be cut quickly with a good finish, which reduces costs. However, it’ s more important to choose a material that meets the requirements of your part rather than choosing a machinable material.

Work hardening rate
As metal is worked or stamped, the temper changes, and the metal either becomes harder and more brittle. The rate that this occurs is work hardening. Depending on how much work is done to the metal and how much it needs to be deformed in a particular operation, the material may require annealing to reset its properties to prevent cracking, breaks, and other material imperfections.

Forming operations in precision stamping
In precision stampings, manufacturers use metal forming operations to make parts from metal and metal alloys. It is highly versatile and can be used to create complex, detailed components with an exceptional degree of accuracy and repeatability. What's more, deep-drawn parts are exceptionally strong due to the extreme amount of compression exerted on the metal during the forming process. The fundamental structure of deep-drawn metals is often highly compressed into a very hard crystalline structure.

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