Manufacturing Engineering & Technology
7th Edition
ISBN: 9780133128741
Author: Serope Kalpakjian, Steven Schmid
Publisher: Prentice Hall
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Chapter 7, Problem 47QLP
In injection-molding operations (Section 19.3), it is common practice to remove the part from its runner, to place the runner into a shredder, and to recycle the resultant pellets. List the concerns you would have in using such recycled pellets as opposed to so-called virgin pellets.
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Review Problems
The extrusion die for a polyethylene parison used in blow
molding has a mean diameter of 18.0 mm. The size of the ring
opening in the die is 2.0 mm. The mean diameter of the parison is
observed to swell to a size of 21.5 mm after exiting the die
orifice. If the diameter of the blow molded container is to be 150
mm, determine (a) the corresponding wall thickness of the
container and (b) the wall thickness of the parison.
Chapter 7 Solutions
Manufacturing Engineering & Technology
Ch. 7 - Summarize the important mechanical and physical...Ch. 7 - What are the major differences between the (a)...Ch. 7 - List properties that are influenced by the degree...Ch. 7 - What is the difference between condensation...Ch. 7 - Explain the differences between linear, branched,...Ch. 7 - What is the glass-transition temperature?Ch. 7 - List and explain the additives commonly used in...Ch. 7 - What is crazing?Ch. 7 - What are polyblends?Ch. 7 - List the major differences between thermoplastics...
Ch. 7 - What is an elastomer?Ch. 7 - What effects does a plasticizing agent have on a...Ch. 7 - Define the following abbreviations: PMMA, PVC,...Ch. 7 - Explain why it would be advantageous to produce a...Ch. 7 - What are the differences and similarities of...Ch. 7 - Are molecular weight and degree of polymerization...Ch. 7 - Why do polymers need to be dried before...Ch. 7 - What characteristics of polymers make them...Ch. 7 - Do polymers strain harden more than metals or vice...Ch. 7 - Inspect various plastic components in an...Ch. 7 - Give applications for which flammability of...Ch. 7 - What characteristics make polymers advantageous...Ch. 7 - What properties do elastomers have that...Ch. 7 - Do you think that the substitution of plastics for...Ch. 7 - Is it possible for a material to have a hysteresis...Ch. 7 - Observe the behavior of the specimen shown in Fig....Ch. 7 - Add more to the applications column in Table 7.3.Ch. 7 - Discuss the significance of the glass-transition...Ch. 7 - Prob. 29QLPCh. 7 - Explain how cross-linking improves the strength of...Ch. 7 - Describe the methods by which the optical...Ch. 7 - How can polymers be made to conduct electricity?...Ch. 7 - Explain the reasons for which elastomers were...Ch. 7 - Give several examples of plastic products or...Ch. 7 - Describe your opinions regarding the recycling of...Ch. 7 - Explain how you would go about determining the...Ch. 7 - Compare the values of the elastic modulus, given...Ch. 7 - Why is there so much variation in the stiffness of...Ch. 7 - Explain why thermoplastics are easier to recycle...Ch. 7 - Give an example where crazing is desirable.Ch. 7 - Describe the principle behind shrink wrapping.Ch. 7 - List and explain some environmental pros and cons...Ch. 7 - List the characteristics required of a polymer for...Ch. 7 - How can you tell whether a part is made of a...Ch. 7 - As you know, there are plastic paper clips...Ch. 7 - By incorporating small amounts of a blowing agent,...Ch. 7 - In injection-molding operations (Section 19.3), it...Ch. 7 - From an environmental standpoint, do you feel it...Ch. 7 - Calculate the areas under the stressstrain curve...Ch. 7 - Prob. 50QTPCh. 7 - Prob. 51QTPCh. 7 - Estimate the number of molecules in a typical...Ch. 7 - Using strength and density data, determine the...Ch. 7 - Prob. 54QTPCh. 7 - Prob. 55SDPCh. 7 - Describe the design considerations involved in...Ch. 7 - Assume that you are manufacturing a product in...Ch. 7 - Assume you work for a company that produces...Ch. 7 - Prob. 59SDPCh. 7 - Make a list of products or parts that currently...Ch. 7 - Prob. 61SDPCh. 7 - Prob. 62SDPCh. 7 - Prob. 63SDPCh. 7 - Prob. 64SDPCh. 7 - With Table 7.3 as a guide, inspect various...
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- 12) Assuming injection molding pressures of 10kpsi, estimate the die clamping force required for injection molding 10 identical 1.5-in.-diameter disks in one die. Assume runner area is 5.0 in?. Discuss the affects of reorienting the disks.arrow_forward10) Die swell in extrusion is radially uniform for circular cross-sections, but is not uniform for other cross-sections. Recognizing this fact, make a qualitative sketch of a die profile that will produce each of the following extruded polymer: a. square b. triangular a) Describe the features of an extruder screw and comment on their specific functions. b) List the differences between the barrel section of an extruder and that on an injection-molding machine.arrow_forwardExplain the extrusion blow molding in detail.arrow_forward
- The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come together?arrow_forwardPLEASE SUMMARIZE IT IN YOUR WORDS!arrow_forwardAn extrusion operation is used to produce a parison whose mean diameter = 27 mm. The inside and outside diameters of the die that produced the parison are 18 mm and 22 mm, respectively. If the minimum wall thickness of the blow-molded container is to be 0.40 mm, what is the maximum possible diameter of the blow mold?arrow_forward
- Is compression molding a reversible process or irreversible process? Explain.arrow_forwardAn extruder barrel has a diameter of 4.0 in and an L/D ratio of 28. The screw channel depth = 0.25 in, and its pitch is 4.8 in. It rotates at 60 rev/min. The viscosity of the polymer melt is 100 x 10-4 lb-sec/in2. What head pressure at exit is required to obtain a net volume flow rate of 150 in3/min? Assume that you are extruding 1/2 in PVC pipe (schedule 40) using the conditions above. How long would it take to extrude a 30 foot section? Be sure to note in your solution where you got your dimensions for the PVC pipe.arrow_forwardCompare compression and injection molding for speed, cost per part, investment cost, and flexibility in types of material that can be handled?arrow_forward
- Explain and critically evaluate injection molding and provide an ICT diagram of the processarrow_forwardIn a particular extruder screw the channel depth is 2.4 mm, the screw diameter is 50 mm, the screw speed is 100 rev/min, the flight angle is 17o and the pressure varies linearly over the screw length of 1000 mm from zero at entry to 20 MN/m2 at the die entry. The plastic viscosity was 200 Ns/m2. · Estimate the operating point for the extruder when it is combined with an oval die with dimension of 20x 3 mm.arrow_forwardThe extruder head in a fused-deposition modelling (FDM) setup has a diameter of 1.25mm and produces layers that are 0.25mm thick. If the extruder head and polymer extrudate velocities are both 40 mm/s, estimate the production time for the generation of a 38mm solid cube. Assume that there is a 10-second delay between layers as the extruder head is moved over a wire brush for cleaning.arrow_forward
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