Page 544 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

524 Chapter 19 Plastics and Composite Materials: Forming and Shaping

l9.27. Typical production rates are given in Table 19.2. I9.30. What determines the intervals at which the indexing
Comment on your observations and explain why there is head in Fig. 19.14c rotates from station to station?
such a wide range. l9.3l. Identify processes that would be suitable for small
I9.28. What determines the cycle time for (a) injection production runs on plastic parts, of, say, 100.
molding, (b) thermoforming, and (c) compression molding? l9.32. Identify processes that are capable of producing parts
Explain. with the following fiber orientations in each: (a) uniaxial,
|9.29. Does the pull-in defect (sink marks) shown in (b) cross-ply, (c) in-plane random, and (d) three-dimensional
Fig. 19.31c also occur in metal-forming and casting random.
processes? Explain.

QUANTITATIVE PROBLEMS

|l|9.33. Estimate the die-clamping force required for in- uniform deformation during molding, estimate the wall
jection molding five identical ZOO-mm-diameter disks in one thickness of the tubular portion of the parison.
die. Include the runners of appropriate length and diameter. |]|9.35. Consider a Styrofoamm drinking cup. Measure
|]l9.34. A 2-L plastic beverage bottle is made by blow the volume of the cup and its weight. From this information,
molding a parison 125 mm. long and with a diameter that is estimate the percent increase in volume that the polystyrene
the same as that of the threaded neck of the bottle. Assuming beads have undergone.

SYNTHESIS, DESIGN, AND PROIECTS

l9.36. Make a survey of a variety of sports equipment, such l9.44. It is well known that plastic forks, spoons, and
as bicycles, tennis racquets, golf clubs, and baseball bats, and knives are not particularly rigid. What suggestions would you
identify the components made of composite materials. have to make them better? Describe processes that could be
Explain the reasons for and advantages of using composites used for producing them.
for these specific applications. I9.45. Make a survey of the technical literature, and de-
|9.37. Explain the design considerations involved in replac- scribe how different types of (a) pneumatic tires, (b) automo-
ing a metal beverage can with one made completely of plastic. tive hoses, and (c) garden hoses are manufactured.
l9.38. Give examples of several parts suitable for insert I] I9.46. Obtain a boxed kit for assembling a model car or
molding. How would you manufacture these parts if insert airplane. Examine the injection-molded parts provided, and
molding were not available? describe your thoughts on the layout of the molds to produce
these parts.
l9.39. Give other examples of design modifications in addi-
tion to those shown in Fig. 19.31. I9.47. In injection-molding operations, it is common prac-
I9.40. With specific examples, discuss the design issues tice to remove the part from its runner, place the runner in a
involved in making products out of plastics vs. reinforced shredder, and recycle the runner by producing pellets. List the
concerns you may have in using such recycled pellets for
plastics.
products, as against “virgin” pellets.
|9.4I. Inspect various plastic components in a typical auto-
mobile, and identify the processes that could have been used |9.48. An increasing environmental concern is the very long
period required for the degradation of polymers in landfills.
in making them.
Noting the information given in Section 7.8 on biodegradable
l9.42. Inspect several similar products that are made either plastics, conduct a literature search on the trends and devel-
from metals or from plastics, such as a metal bucket and a
opments in the production of these plastics.
plastic bucket of similar shape and size. Comment on their re-
spective shapes and thicknesses and explain the reasons for |9.49. Examine some common and colorful plastic poker
their differences. chips and give an opinion on how they were manufactured.
l9.43. Write a brief paper on how plastic coatings are ap- l9.50. Obtain different styles of toothpaste tubes, carefully
plied to (a) electrical wiring, (b) sheet-metal panels, (c) wire cut them across, and comment on your observations regard-
ing (a) the type of materials used and (b) how the tubes were
baskets, racks, and similar structures, and (d) handles for
electrician’s tools, such as wire cutters and pliers requiring produced.
electrical insulation.