deep drawing metal water pump casing part

(1)  What is deep drawing?

Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch.[1] It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies. The flange region (sheet metal in the die shoulder area) experiences a radial drawing stress and a tangential compressive stress due to the material retention property. These compressive stresses (hoop stresses) result in flange wrinkles (wrinkles of the first order). Wrinkles can be prevented by using a blank holder, the function of which is to facilitate controlled material flow into the die radius.

(2)  What are workpiece materials and power requirements?

Softer materials are much easier to deform and therefore require less force to draw. The following is a table demonstrating the draw force to percent reduction of commonly used materials.

Drawing force required for various materials and reductions [kN][9]

(3) Which materials are suitable for making tools?

Punches and dies are typically made of tool steel, however carbon steel is cheaper, but not as hard and is therefore used in less severe applications, it is also common to see cemented carbides used where high wear and abrasive resistance is present. Alloy steels are normally used for the ejector system to kick the part out and in durable and heat resistant blankholders.

(4) Which factors will have effects on deep drawn parts’ quality?

a. Material suitability;

b. The design of the tools, including shape rationality, surface treatment, dimension varation;

c. Lubrication and cooling during deep drawing process;

d. Equipment reliability;

e. Others like process design, transfer, etc. sometimes are also important.