Fig。 7。 Velocity vector of the material flow during pin head embossing at different punch stroke at diameter = 3 mm, distance to edge = 0。7 mm and depth = 2 mm。

Distance to the Edge, DTE (mm)

Fig。 9。  The effect of DTE to width of the bulging。

shows that in increasing the 1 mm depth, i。e。, from 1。5 to 2。5 mm, the increment is only about 0。04%。 Therefore for this process, the optimized parameters were at embossing depth of 2。0 mm and punch diameter of 3。0 mm。 The pin head is intentionally designed to allow the part to be firmly fixed during assembly and based on the result, it is clear that the DTE has the most significant effect。 But due to design constraint, the value of DTE is limited to 1 mm to prevent from affecting the mating part i。e。, the hub。 As shown in Fig。 8(c), there is a larger increment in the area ratio as the distance increases。 There is approximately a 3% increment or about

0。7 mm2  of the total area; thus, increasing the distance by about

0。3 mm, i。e。, from 0。7 to 1。0 mm。 Purposely, the distance of 2。0 mm is carried out to observe the effect, and the filling region for this case is evidently almost perfect or has no defect at approximately 99。2% filled。 Based on the result, it is clear that the DTE is the most significant parameter to the fillingability of the embossed pin head。 But since the value of the DTE Š l, therefore 1 mm was choosen。

In other case, the size of the bulging was estimated。 Fig。 9 shows the effect of DTE to the width of the bulging generated from the sim- ulation。 The larger the DTE, the lower the defect observed。 Fig。 10 shows the material flow pattern of the investigated parameter i。e。, the DTE of the embossed part。 Here, three different DTEs were stud- ied (0。7, 0。8, and 1。0), and the FE simulation results showed that there is a significant effect on the material flow with respect to the punch stroke。 With the small punch stroke, the right end of the fea- ture, the material seems to flow outward to the right section。 Until

Fig。 8。 The effect of (a) punch diameter, (b) embossing depth and (c) distance to edge to the filling ratio。

It can be observed that as the punch stroke increases, the mate- rial follows the punch and the cavity can only be formed after the

1。0 mm stroke。 This is because, at the beginning i。e。, stroke less than

1。0 mm, the material tends to flow outward to form bulging instead of cavity。 Only after the 2。0 mm punch stroke, the material tends to flow into the workpiece to form cavity as shown in Fig。 7。

Since the pin head is located at the edge of the workpiece, the geometries that may affect its accuracy are embossing depth, punch diameter, and the distance to edge (DTE), which can be referred in Figs。 2 and 4。 To study the effect of these features on the embossed pin head, a parametric study and optimization were performed。 As a result, the increasing diameter is caused in less unfilled area as shown in Fig。 8(a) or the higher diameter, the higher the ratio of filled to unfillled area。 The effect of depth to the filling ratio is less compared with the punch diameter。 Fig。   8(b)

the end of the process, the material is continuously forced to flow toward the edge, and the height and width of the bulge increases。 With an increased DTE, the effect of bulging height and width can be clearly seen。 Similarly, by increasing the DTE, the distribution of the stress is more uniform (Fig。 11)。

Other alternative is to study the influence of the tapered punch on embossed part features。 To this purposes, the stress distribution and material flow analysis with respect to the punch stroke were investigated。 The results are shown in Figs。 12 and 13, respectively。文献综述

Here, the 2◦, 5◦, and 10◦ tapered angle punches were studied。 As