The mold used in an injection molding process consists of a top half and a bottom half. Each half is 60 mm × 60 × mm × 20 mm and is constructed of metal ( ρ = 7800 kg/m 3 , c = 450 J/kg ⋅ K ). The cold mold ( l 00 ° C ) s to be heated w 2 00 ° C with pressurized water (available at 275 ° C and a total flow rate of 0.0 2 kg / s ) prior to injecting the thermoplastic material. The injection takes only a fraction of a second, and the hot mold ( 2 00 ° C ) is subsequently cooled with cold water (available at 25 ° C and a total flow rate of 0.0 2 kg / s ) prior to ejecting the molded part. After part ejection, which also takes a fraction of a second, the process is repeated. (a) In conventional mold design, straight cooling (healing) passages are bored through the mold in a location where the passages will not interfere with the molded part. Determine the initial heating rate and the initial cooling rate of the mold when five 5 − mm -diameter, 6 0 − mm -1ong passages are bored in each half of the mold (10 passages total). The velocity distribution of the water is fully developed at the entrance of each passage in the hot (or cold) mold (b) New additive manufacturing processes, known as selective freeform fabrication, or SFF, are used to construct molds that are configured with conformal cooling passages. Consider the same mold as before, but now a 5 − mm -diameter, coiled, conformal cooling passage is designed within each half of the SFF-manufactured mold. Each of the two coiled passages has N = 2 turns. The coiled passage does not interfere with the molded part. The conformal channels have a coil diameter C = 5 0 mm . The total water flow remains the same as in part (a) ( 0.0 1 kg / s per coil). Determine the initial heating rate and the initial cooling rate of the mold. (c) Compare the surface areas of the conventional and conformal cooling passages. Compare the rate at which the mold temperature changes for molds configured with the conventional and conformal healing and cooling passages. Which cooling passage, conventional or conformal, will enable production of more parts per day? Neglect the presence of the thermoplastic material.
The mold used in an injection molding process consists of a top half and a bottom half. Each half is 60 mm × 60 × mm × 20 mm and is constructed of metal ( ρ = 7800 kg/m 3 , c = 450 J/kg ⋅ K ). The cold mold ( l 00 ° C ) s to be heated w 2 00 ° C with pressurized water (available at 275 ° C and a total flow rate of 0.0 2 kg / s ) prior to injecting the thermoplastic material. The injection takes only a fraction of a second, and the hot mold ( 2 00 ° C ) is subsequently cooled with cold water (available at 25 ° C and a total flow rate of 0.0 2 kg / s ) prior to ejecting the molded part. After part ejection, which also takes a fraction of a second, the process is repeated. (a) In conventional mold design, straight cooling (healing) passages are bored through the mold in a location where the passages will not interfere with the molded part. Determine the initial heating rate and the initial cooling rate of the mold when five 5 − mm -diameter, 6 0 − mm -1ong passages are bored in each half of the mold (10 passages total). The velocity distribution of the water is fully developed at the entrance of each passage in the hot (or cold) mold (b) New additive manufacturing processes, known as selective freeform fabrication, or SFF, are used to construct molds that are configured with conformal cooling passages. Consider the same mold as before, but now a 5 − mm -diameter, coiled, conformal cooling passage is designed within each half of the SFF-manufactured mold. Each of the two coiled passages has N = 2 turns. The coiled passage does not interfere with the molded part. The conformal channels have a coil diameter C = 5 0 mm . The total water flow remains the same as in part (a) ( 0.0 1 kg / s per coil). Determine the initial heating rate and the initial cooling rate of the mold. (c) Compare the surface areas of the conventional and conformal cooling passages. Compare the rate at which the mold temperature changes for molds configured with the conventional and conformal healing and cooling passages. Which cooling passage, conventional or conformal, will enable production of more parts per day? Neglect the presence of the thermoplastic material.
Solution Summary: The author explains the initial heating rate and cooling rate of the mold. The specific heat of metal is c=450 J/kgK.
The mold used in an injection molding process consists of a top half and a bottom half. Each half is
60
mm
×
60
×
mm
×
20
mm
and is constructed of metal (
ρ
=
7800
kg/m
3
,
c
=
450
J/kg
⋅
K
). The cold mold (
l
00
°
C
) s to be heated w
2
00
°
C
with pressurized water (available at
275
°
C
and a total flow rate of
0.0
2 kg
/
s
) prior to injecting the thermoplastic material. The injection takes only a fraction of a second, and the hot mold (
2
00
°
C
) is subsequently cooled with cold water (available at
25
°
C
and a total flow rate of
0.0
2 kg
/
s
) prior to ejecting the molded part. After part ejection, which also takes a fraction of a second, the process is repeated.
(a) In conventional mold design, straight cooling (healing) passages are bored through the mold in a location where the passages will not interfere with the molded part. Determine the initial heating rate and the initial cooling rate of the mold when five
5
−
mm
-diameter,
6
0
−
mm
-1ong passages are bored in each half of the mold (10 passages total). The velocity distribution of the water is fully developed at the entrance of each passage in the hot (or cold) mold
(b) New additive manufacturing processes, known as selective freeform fabrication, or SFF, are used to construct molds that are configured with conformal cooling passages. Consider the same mold as before, but now a
5
−
mm
-diameter, coiled, conformal cooling passage is designed within each half of the SFF-manufactured mold. Each of the two coiled passages has N = 2 turns. The coiled passage does not interfere with the molded part. The conformal channels have a coil diameter
C
=
5
0
mm
. The total water flow remains the same as in part (a) (
0.0
1 kg
/
s
per coil). Determine the initial heating rate and the initial cooling rate of the mold.
(c) Compare the surface areas of the conventional and conformal cooling passages. Compare the rate at which the mold temperature changes for molds configured with the conventional and conformal healing and cooling passages. Which cooling passage, conventional or conformal, will enable production of more parts per day? Neglect the presence of the thermoplastic material.
Both portions of the rod ABC are made of an aluminum for which E = 70 GPa.
Based on the given information find:
1- deformation at A
2- stress in BC
3- Total strain
4- If v (Poisson ratio is 0.25, find the
lateral deformation of AB
Last 3 student ID+ 300 mm=L2
724
A
P=Last 2 student ID+ 300 KN
24
24
Diameter Last 2 student ID+ 15 mm
Last 3 student ID+ 500 mm=L1
724
C
B
24
Q=Last 2 student ID+ 100 KN
24
Diameter Last 2 student ID+ 40 mm
Q2Two wooden members of uniform cross section are joined by the simple scarf splice shown. Knowing that the
maximum allowable tensile stress in the glued splice is 75 psi, determine (a) the largest load P that can be safely
supported, (b) the corresponding shearing stress in the splice.
น
Last 1 student ID+5 inch=W
=9
4
L=Last 1 student ID+8 inch
=12
60°
P'
Q4
The two solid shafts are connected by gears as shown and are made of a steel for which the allowable shearing
stress is 7000 psi. Knowing the diameters of the two shafts are, respectively, dBC
determine the largest torque Tc that can be applied at C.
4
and dEF
dBC=Last 1 student ID+3 inch
dEF=Last 1 student ID+1 inch
7
R=Last 1 Student ID+5 inch
9
R
B
Tc
2.5 in.
E
TF
H
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.
Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning