Forming Processes - EXTRUSION - Numerical Problems with Solutions (solved)

FORMING PROCESSES (Extrusion)

EXAMPLE 3.11 (EXTRUSION)

Estimate the maximum force required for extruding a cylindrical Aluminium billet of 50 mm diameter and 75 mm length to a final diameter of 10 mm. The average tensile yield stress for Aluminium is 170 N/mm². What percent of the total power input will be lost in friction at the start of the operation?

FORMULAE

SOLUTION

The ram force is obviously maximum just after the start of the extrusion process as l is maximum. For the given dimensions and assuming a 45°-dead zone, the value of l at the beginning is given as

Next, the value of µ is determined by solving equation (1) through a trial and error method. Thus, we get µ = 0.15. Now, σ_x|_BB is found out from equation (2) with this value of µ. Hence,

Finally, using equation (3), we have

If the velocity of the ram is V_B mm/sec, then the frictional power loss (using equations (4) and (5)) is given as

Now, the total input power is

Therefore, the power loss in friction is