________ or ________ must be present to be classified as a molding process. correct answers Pressure, Force
What is compression molding? correct answers A molding compound is placed in an open mold cavity, the mold is closed, and then heat and pressure are applied until the material has cured/co...
IET 365 Exam 2 || Already Graded A+.
________ or ________ must be present to be classified as a molding process. correct answers
Pressure, Force
What is compression molding? correct answers A molding compound is placed in an open mold
cavity, the mold is closed, and then heat and pressure are applied until the material has
cured/cooled.
What is a key word for thermoset? correct answers Cured
What is the general rule-of-thumb for amount of pressure used in compression molding? correct
answers 2900 psi for plastics up to 1" thick, add 725 psi for every additional 1" thick of plastic
When possible use what kind of molds? correct answers Vented
What are the type of plastic(s) used for compression molding? correct answers Thermoset
Bulk Molding Compound (BMC) correct answers polyester base with fillers, resins, hardening
agents, plus other additives
What are the advantages of compression molding? correct answers 1. little waste
2. low tooling costs
3. automated or hand-operated
4. parts are true and round
5. material flow is short (less product stress)
6. multiple cavity placement not dependent on a balanced feeder system
7. cheaper than injection molding to produce higher quality short-run parts
What are the disadvantages of compression molding? correct answers 1. hard to mold complex
parts
2. inserts/ejector pins are easily damaged
3. complex shapes are hard to achieve
4. long molding cycles may be needed
5. unacceptable parts can not be reprocessed
6. trimming flash can be difficult
7. molds must be high quality steel (difficult to machine)
How to increase productivity or decrease cycle time in compression molding? correct answers 1.
pre-heat plastic
2. pre-heat molds
3. use steel molds
4. use screw extruders
5. use higher temperatures
6. use automation
, What are product examples of compression molding? correct answers automotive body panels,
distributor caps, bath tubs, dinnerware, buttons, buckles, knobs, handles, appliance housing,
radio cases, large containers
What is injection molding? correct answers A heat-softened plastic is forced from a cylinder into
a relatively cool cavity giving the item the desired shape
What are two types of injection molding? correct answers (plunger, piston, ram) and
reciprocating screw
What type of injection molder was used in lab? correct answers Reciprocating screw
What are the three zones of a reciprocating screw injection molder? correct answers 1. Feed (1/2)
2. Transition/Compression (1/4)
3. Metering (1/4)
What zone does the most plastic melt? correct answers Transition/Compression
What are the two units of an injection molder? correct answers Injection and Clamp
What is shot size? correct answers The amount of plastic that comes out of the sprue into the
mold in one cycle
What is the range of plastic that comes out of a shot size? correct answers .7 oz to 19.8 lbs
What are the major specification for injection molding? correct answers Shot size and clamp
tonnage
What is the amount of clamp tonnage? correct answers 786 lbs-force per cm squared
What is the time cycle for injection molding? correct answers 1. Fill time
2. Pack Time
3. Cooling/Dwelling Time
4. Dead Time
What is fill time in injection molding? correct answers The time it takes to displace the air in the
mold cavity with plastic material
What is pack time in injection molding? correct answers The time required to maintain enough
pressure to fill out the part and to achieve gate freeze
What is cooling/dwell time in injection molding? correct answers The time required to cool or
set enough for safe removal from the mold cavity
What is dead time in injection molding? correct answers Time required to open the mold, remove
the molded part and close the mold
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