This article reviews the production variables that influence the selection of various stamping die materials: ferrous, nonferrous, and plastic die materials.
It provides a discussion on the specific types of die materials for tool steels, cast irons, plastics, aluminum, bronze, zinc-aluminum, and steel-bonded carbides.
The article describes factors to be considered during the selection of materials for press-forming dies. Keep up to date with the latest aerospace materials and technologies. Register today for Aeromat !
Sign In or Create an Account. User Tools. The SK material is rarely used. When the machining tolerance of SKS3 is of concern, the material SKD11 may also be used which is a decision based on the wire cutting characteristics. While the main function of a stripper is to remove scrap, very frequently it is made to have important secondary functions of pressing the material or guiding the tip of the punch punch guide.
When removing scrap in small volume production is important, materials such as S50C or pre-hardened steel are used which do not require heat treatment. When materials without heat treatment are used, although they are made to have the functions of pressing the material and guiding the punch, the plate may get deformed when there is wrong punching. When a punch guide or a material pressing member is added, a material such as SKS3 or SKD11 is used after heat treatment.
SK materials or SKS3 is used in dies for small volume production. The standard material used is SKD This trend has become established because preparation of dies using electric discharge wire cutting machines has become widespread. The descriptions given above assume single type plates. Whenever you adopt this king of tooling for any tablet compression machine, some of the key benefits include:. It basically implies that, you will only operate the tablet compression machine within a short time to get thousands of tablets.
This will save the machine from possible wear and tear, besides saving on energy costs. Like other tablet press tooling, the multiple tip tablet press tooling come in a wide range of shapes and designs. This will depend on the specific objectives of the pharmaceutical company — whether you need standard or custom designs.
First, the best material for punch and die systems of any tablet compression machine should adhere to the Current Good Manufacturing Practice cGMP. This implies that they meet specific quality standards hence, performance and longevity are predictable. Second, the type of material you intend to compress into powder should dictate the type of punch and die material. For instance, compressing abrasive materials require a special tool unlike the soft and non-abrasive materials.
This should go hand in hand with your ability to understand the specific properties of various materials. In most cases, die are made from stainless steel that has superior wear resistance. Some of the most common materials include:. Generally, a good material should combine extremely high wear resistance and compressive strength.
The material is subjected to both compressive and tensile stresses. These stresses will be highest at the edges of the die and punch and material will stressing beyond its elastic limit and start cracking there.
The forces developed in the shearing operation is represented by a triangle as shown in the below-given figure. The vertical shearing force and horizontal lateral force are represented by V and H respectively. The resultant force is represented by R.
The value of Vertical Component V depends upon the area to be sheared and the shear strength of the material to be cut. Shear Area is a multiple of the length of cut and sheet thickness.
The value of horizontal or lateral force H depends upon the die clearance. The horizontal force can be stated in terms of vertical force percentage. This percentage is the same as the die clearance percentage. The amount of space between punch cutting edge and the die-cutting edge is known as clearance.
Clearance has a significant role in all cutting operations and forming operations. The die clearance depends upon the work material, it ranges from two to ten percent of the thickness of the worksheet. Ductile material should have lesser die clearance otherwise soft material would be drawn into the gap and harder material needs more die clearance for good shearing action.
Excessive clearance causes more burr on the sheared sheet while less clearance reduces the burr but it also damages the edges of the die and punch. This results in frequent resharpening of the die and the punch and decreases the press tool life. The range of die clearances for various materials for stamping work:. Note that the die clearances are specified in the percentage of Sheet thickness.
For a close cutting profile, there would be a die clearance between the die and punch all around in profile. Note: It is not possible to get tolerances than die clearance on components so it is necessary to perform an additional shaving operation for high precision work.
The hole pierced in the sheet is a tapered one, with minimum opening equal to punch size. The maximum size of the hole at the bottom of the sheet depends upon the width of the die opening. The Die clearance on the die cut out is bigger than the size stated on the component drawing.
The blanked profile sheet is also tapered one, with minimum size at the bottom and maximum at the top. The maximum size of the hole at the bottom of the sheet depends upon the die opening. The maximum dimensions of the blanks should not exceed the sizes stated in components drawing. So in blanking the die cutout is made equal to the die profile hole and the punch must be lesser on every side by the clearance size.
Note: What is the difference between punching and blanking tools? Ans: Blanking and Punching tools both are similar however the workpiece in the blanking tool called blank and used in further operation whereas in the punching tool the piece falling through the die is scrap.
The bending process changes the shape of a flat blank to make it angular, curved, or both without much change in its thickness. It is a very common process for changing sheets and plates into channels, drums tanks, etc. During the bending operation, the outer surface of the material is in tension and the inside surface is in compression.
The strain in the bent material increases with a decreasing radius of curvature. The minimum radius to which a blank can be bent without cracking depends upon the material and its hardness. The minimum inside radius also depends upon the direction of rolling.
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