¼ —E1  þ G—3−    —T

clinging to the outside diameter of the runner 1 mm at   the

¼ −6:3445−7:1214 þ 10:233

lower outside diameter of the runner and 2 mm at the lower

¼ −3:233ðdBÞ

outside diameter of the runner as shown in Figs。 5a, 6a, and

7a。 The pressure profiles are as shown in Figs。 5b, 6b, and 7b。

In addition, the confidence interval (CI) of the S/N ratio prediction value, at a  95 %  level  of  confidence, can     be

According to the pressure profiles, regardless of the sensor mounting height, the runner pressures were similar to    the

Fig。 5 Sensor tip just clinging to the outside diameter of the runner。 a Sensor install position。 b Runner and cavity pressure profiles

(a) Sensor install position。 (b) Runner and cavity pressure profiles。

Fig。 6 Sensor tip aligned below the outside diameter of the runner of 1 mm。 a Sensor install position。 b Runner and cavity pressure profiles

(a) Sensor install position。 (b) Runner and cavity pressure profiles。

profile of the cavity pressure at the filling and melt compres- sion stages; however, the maximum pressure values differed。 The pressure of the secondary runner was higher than that of the tertiary runner。 At the cooling stage, when the top surface of a sensor was mounted clinging to the outside diameter of the runner and 1 mm at the lower outside, the pressure profile of the secondary and tertiary runner was apparently different from the cavity pressure profile。 This happens when the melt fills the cavity, a frozen layer forms on the surface of the runner, and the pressure profile gradually decreases to atmo- spheric pressure。 Therefore, a runner pressure profile similar

to that of a cavity cannot be effectively obtained。 When the top surface of a pressure sensor was mounted at 2 mm at the lower outside diameter of the runner, the two runner pressure pro- files were identical to the pressure profile of the cavity, i。e。, decreasing after 1。7 s packing。 Therefore, the sensor mounting position difference must exceed the maximum thickness of the specimen (1。492 mm), which is about 2 mm, in order to obtain a profile similar to the cavity pressure at the cooling stage。 As the melt entering a sensor mounted location with a large difference is like entering a chill well, melt freezing is delayed, and a pressure profile similar to that of a cavity can be

Fig。 7 Sensor tip aligned below the outside diameter of the runner of 2 mm

(a) Sensor install position。 (b) Runner and cavity pressure profiles。

Fig。 8 Cavity pressure profiles at optimal parameter combination。 a Cavity。 b Secondary runner。 c Tertiary runner

Table 5 Form accuracies for various parameters with levels

Factor Level PV (μm) σ

mounting location should approach the sprue as possible, and the runner pressure history profile is similar to that of

  the cavity。

Melt temperature (°C) 220 Short shot

230 1。091 0。051

240 1。480