What Is a Drawing Press?
A drawing press involves the process of shaping thin metal sheets using a press machine. This method is in contrast to the ‘shallow drawing’ process commonly used for items like cups.
The standard for deep drawing is the relationship between the diameter and height of the bottom surface using a cup, as an example. If (diameter) < (height), the cup is considered to be deep drawn.
A drawing press can only be made by combining a die and a press machine. The quality of the finished product is determined by the processing accuracy of the die, the material of the thin plate used, and the capability of the press machine.
Uses of Drawing Presses
Drawing presses are used to manufacture products and parts in a wide range of fields, including automotive parts, home appliance-related parts, housing equipment-related parts, air conditioning-related parts, stationery-related parts, electric material-related parts, and precision metalworking products.
Drawing presses are used to produce a wide variety of products, such as containers, covers, motor yokes, cases, and housings.
As drawing presses involve the use of press machines, safety regulations govern the manufacturer’s responsibilities during operation.
Characteristics of Drawing Presses
In normal drawing processes, the dies used, such as punches, dies, and blank holders, are one of the factors that greatly affect the quality of the finished product.
Since the material used also has a great influence on the quality of the finished product, the work hardening index (n-value) and plastic strain ratio (r-value) of the material are the criteria for material selection.
A higher work hardening index (n-value) indicates that the material is more suitable for drawing. Typically, values in the range of 0.15 to 0.45 are considered common, with materials ranked from largest to smallest n-value as follows: stainless steel sheet, 7-3 brass sheet, pure copper sheet, pure aluminum sheet, and cold-rolled steel sheet.
The higher the plastic strain ratio (r-value), the easier the material is to draw.
In the drawing process, lubricant is often used because of the slippage between the material and the die when the material is pressed.
Phenomena that occur when the proper lubricant is not selected include rupture, burning, and galling. Two types of hydraulic lubricants, oil-based and water-based, are used for different applications.