A 200 kN universal testing machine (Make: Fuel Instruments & Engineers Pvt. Ltd., Model: UTE 20) was used as an extrusion press [Appendix A]. Figure 3.1 shows the photograph of the setup. The container, die, punch and base plate were made of die steel (H13). To study the effect of vibration on the flow process, extrusion load and the radius of curvature, the vibration was induced to the container wall from the external source.
Figure 3.1. Extrusion set up
In the present experimental set up, vibration is imposed to the container of the multi-hole extrusion process. The hand-held grinder is used as vibrator. An eccentric mass is attached to the wheel to increase the vibration. On the outer wall of container, the arrangement was made to place the tri-axial accelerometer for measurement of the frequency and the acceleration of vibration during the multi- hole extrusion process shown in Figure 3.1.
The maximum amplitudes of the acceleration generated by the vibrator are 49, 51 and 70 m/s2 along x, y and z directions respectively. A schematic of the multi- hole experimental set up is shown in Figure 3.2.
Figure 3.2. Schematic of extrusion set up
Schematic diagrams of 9-hole die with different die land lengths are shown in Figure 3.3. The die land lengths of 6.5 and 3 mm are produced on the holes designated by ‘A’. For the holes designated with ‘B’, the die land length is 10 mm.
Figure 3.3. Schematic of 9-hole die with different die land lengths (a) 10 mm (b) 6.5 mm and (c) 3 mm
(All dimensions are in mm; drawing not to scale) (c)
(a) (b)
The different die land lengths are produced on the alternate holes of the periphery at a pitch circle diameter of 12 mm. Counter bore of hole diameter of 3 mm are drilled with required depth from the bottom side of the alternate holes of 9- hole die. This reduces the die land lengths. The 9-hole die with die land length of 10 mm is designated as Die I. The die land length of 6.5 mm produced on alternate holes of the peripheral holes as well as on centre hole is designated as Die II.
Similarly, die land length of 3 mm produced on alternate holes of the peripheral holes as well as on centre hole is designated as Die III. Table 3.1 shows the different die land lengths used for 9-hole die extrusion.
Table 3.1. Different die land length used for 9-hole die extrusion Die land length (mm)
Centre hole Periphery holes
Die Type
A A B
Die I 10 10 10
Die II 6.5 6.5 10
Die III 3 3 10
The three types of multi-hole dies (Die I, Die II and Die III) are made separately and allowed to tight fit to the bottom of the container. The production of different die land length will give the information on the effect of die land length on bending of the extruded products along with the combined effect of other parameters. Study of radius of curvature and the effect of lubrication, die land length and vibration was carried out with the dies mentioned in Table 3.1. The 9-hole die, container and punch used for lead extrusion are shown in Figure 3.4 (a). The extruded products form the 9-hole die is shown in Figure 3.4 (b).
Figure 3.4. (a) 9-hole die, container and punch (b) extruded products from the 9- hole die
To study the effect of die land length and lubrication on the mechanical properties and surface roughness of the extruded products, the multi-hole extrusion was carried out with different set of dies. For the extrusion of lead three different types of dies were used as shown in Figure 3.5. In 5-hole die (extrusion ratio, 35.55), one hole is at centre and other four hole are at the pitch circle diameter of 12 mm (Figure 3.5 (a)). In 9-hole die (extrusion ratio, 19.75), one hole is at centre and other eight holes are at pitch circle diameter of 12 mm in periphery (Figure 3.5 (b)).
In 13-hole die (extrusion ratio, 13.67), one hole is at centre, four holes are at pitch circle diameter of 7 mm and other eight holes are at pitch circle diameter of 14 mm (Figure 3.5 (c)). Low extrusion ratio was used for cold extrusion of aluminum in order to get low extrusion load. For this study both lead and aluminum are used as billet material. The details of the dies, die land length and billet dimensions used for extrusion of lead and aluminum are given in Table 3.2.
(a) (b)
(a) (b)
(c)
(All dimensions are in mm, drawing not to scale)
Figure 3.5. Top view of (a) 5-hole die (b) 9-hole die (c) 13-hole die
Table 3.2. Geometrical parameters for extrusion of lead and aluminum Parameters Lead extrusion Aluminum extrusion
Billet diameter 20 mm 20 mm
Billet length 20 mm 20 mm
Extrusion ratio
35.55 (5-hole die), 19.75 (9-hole die) and
13.67 (13-hole die)
4.94 (9-hole die)
Die land length 10 and 3 mm 15 and 10 mm
Diameter of each hole 1.5 mm 3 mm
For each extrusion test, the container wall, die, punch and the specimens were first cleaned with ethanol to remove any oil or dust content on them. The lubricant was applied manually on the die, punch and container for lubricated tests. Extrusion test were conducted at ram speeds of 1.5, 1.2, 0.9 and 0.45 mm/min for 20 mm billet length. At these speeds the strain-rate effects are insignificant. The strain rates are of the order of 10-3 s-1. The ram displacement was kept as 5 mm. After each test, the entire set up was removed from the universal testing machine and the extruded products were cut carefully without disturbing their curved profile for measuring the radius of curvature and length. Three replicates were carried out at different conditions. Replicates are needed to assess the repeatability of the experiments.
Three replicates are sufficient, if there is good repeatability in the process. More number of replicates may be required in case of poor repeatability. After the measurement of radius of curvature, the surface roughness of the extruded products was measured. At each replicate, microhardness and surface roughness measurements were carried out at 4-5 places. The combined data of all measurements was used to make inference about average quality attribute along with the standard error in the estimate. The standard deviation was also estimated. The tensile test and micro hardness test are carried out after the measurement of surface roughness.
0 10 20 30 40 50 60 70 80 90
0 0.2 0.4 0.6 0.8
Engineering strain
Engineering stress (MPa)
Aluminum Lead