me419homework1-spring2004

me419homework1-spring2004 - ‘ga MEI/LI? Hm“. {we N * C...

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Unformatted text preview: ‘ga MEI/LI? Hm“. {we N * C ame ' Program1 The Injection Molding Machine 1.) Once the molding cycle is about to begin, the plastic pellets enter the screw and barrel assembly through the: a. Runner b. Feed throat c. Hopper d. Nozzle e. None of the above 2.) Check valves are used on all machines to provide a way to: a. Connect the molding machine to the mold ' . b. Stop the material from flowing over the screw during injection 0. Positively shut off the material to prevent drooling (1. None of the above I 5‘ 3.) What percentage of the heat needed to melt the plastic comesfrom the shearing action of the screw? a. 10-29% b. 30-49% c. 50-69% (1. 70-90% 4.) The holding phase of the injection cycle packs additional material into the cavities until the gate freezes off at this point. a. Packing of the sprues and runners may not take place. b. Plastic can no longer be forced into the cavity. c. The mold opens and the part is ejected. d. The screw rotates counterclockwise while moving backwards. 5.) Molding a part which has an insert requires the machine to be in what mode? a. Semi-automatic b. Automatic c. Set-up d. Manual 6.) During injection, the plastic material flows from the sprue to the runner, and finally, to the cavity by what passageway? a. Barrel b. Gate 0. Nozzle d. Feed throat e. None of the above "15!. saw 7.) The function of the reciprocating screw is to: a. Plasticize or melt the plastic material. b. Convey‘the material to the front of the screw. G. Force the melted material into the mold. d. All of the above 8.) The portion of the screw where most of the shearing takes place is the: a. Feed Zone b. Transition or Compression Zone c. Metering Zone d. None of the above 9.) It is important to establish and maintain a stable process to: a. Reduce scrap b. Improve part quality 0. Reduce variation d. Improve molding efiiciency c. All of the above 10.) A hopper dryer is used to: a. Lifi the material from storage boxes b. Funnel the plastic into the barrel assembly 0. Reduce the moisture content of the material (1. All of the above e. None of the above 11.) During the cooling phase of the cycle: a. Material is conveyed to the front of the screw b. The screw rotates counterclockwise while moving backwards c. Pellets fall between the flights of the screw d. None of the above I c. All of the above 12). During machine shut-down, completely purge the barrel and: a. Coat the mold with a mold saver b. Turn off the hydraulic pump and barrel heaters c. Leave the screw in the forward position d. All of the above 6. None of the above 13.) The nozzle vis'used to: a. Prevent the material from drooling _ b. Connect the machine to the mold c. Control the temperature of the mel (1. None of the above " e. All of the above T 14.) To ensure a consistent molding cycle, be sure to accurately control the: a. Pressure b. Time c. Temperature d. Speed e. All of the above 15.) In order for the molding machine to warm up and reach operating temperature, the hydraulic motor must be allowed to run for? ' a. 1-2 hours b. 2-3 hours c. 10-15 minutes d. None of the above 16.) Material is conveyed along the screw through the (in order): a. Feed, metering, transition zones b. Metering, transition, feed zones 0. Transition, feed, metering zones d. Feed, transition, metering zones 17.) The barrel heater bands are used to: a. Contain the screw assembly b. Assist in machine set-up c. Control the molding temperature d._ Only b and c e. All of the above 18.) The purpose of the screw drive motor is to: a. Push the screw forward for injecting material b. Turn the screw in a counterclockwise direction c. Move the screw backwards for the next cycle d. All of the above 6. None of the above TRUE OR FALSE Answer each of the following questions by placing a T (True) or F (False) in, the blank. If your answer is false, please provide the correct response in the available space. 19.) The hydraulic cylinder is used to retract the entire barrel assembly from the mold and to move the assembly into the mold to begin molding. ................... .; ................................................................................................... .. __ 20.) The cavity of the mold defines the inside details of the part. ............................................................ .. __ 21.) During injection, the screw rotation stops and the screw acts like a ram. ...................... ............... .. _ 22.) A reciprocating screw rotates counterclockwise while moving backwards and forward. ............... .. _ 23.) The fixed platen moves left to right by the clamp cylinder piston. ................................................ .. _____ 24.) The higher the screw L/D ratio, the less mixing that takes place. .................................................... .. _ 25.) Difi'erent types of nozzles exist to run materials with special properties. .......................................... .. _ 26.) The injection phase of the cycle allows more material to be packed into the cavities. .................... .. _ 27.) The manual mode of operation enables the machine to make one complete cycle. ......................... .. _ 28.) To prevent bridging in the feed throat area, a cool water jacket is used to reduce the temperature. ._ 29.) The runners provide an opening for material to enter the cavities. ................................ .. ................ .. _ 30.) Moisture has no effect on processing of a plastic resin. ............................................. .................... .. f 31.) The reciprocating screw injection molding machine is the most common machine used today. 32.) The sprue bushing connects the machine nozzle to the mold. ......................................................... .._ 33.) Pressure is not considered important when developing a consistent molding cycle. ........................ .. _ 34.) 70-90% of the heat needed to melt the material comes from the shearing action of the screw. ...... .._ 35.) Once the mold opens and the parts are ejected, the machine is ready to cycle again. ...................... ..___ Program 2 The Injection Molding Process 1.) During the cooling phase, a cold mold will: a. Increase the overall cycle time of the part b. Produce parts with a dull surface finish c. Produce parts with less molded in stress d. Will allow the plastic to flow easier into the mold 2. When referring to injection time, we can distinguish 2 stages: first and second stage. First stage time is the amount of time required: a. For gate seal off b. To fill the part c. To cool the part (1. None of the above 3.) The most common heat profile usedin injection molding is: L a. Straight r ' b. Reverse c. Forward d. None of the above 4.) Using screw back pressure on an injection molding machine: a. Will have no efi'ect on the properties of a filled material b. Will increase the mixing action of the screw c. Is recommended for screws with high L/D ratios. (1. Will not allow color concentrates to disperse evenly 5.) A low clamp tonnage will: a. Require less energy to operate b. Reduce the machine wear c. Reduce the mold wear d. None of the above e. All of the above 6.) When selecting barrel temperature settings, it is a good idea to: a. Run at the highest processing temperature recommended by the material supplier b. Use a forward heat profile regardless of the recommended settings. c. Use a straight heat profile regardless of the recommended settings. d. Run at the lowest processing temperature recommended by the material supplier. 7.) Improper drying of the material will: a. Cause cosmetic defects on the molded part b. Improve the processing characteristics of the material c. Enhance the physical properties of the molded part (1. All of the above » 8.) When exposed to heat, plastics such as Nylon and PET will: a. Soften as they reach their processing temperature range b. Melt quickly once they reach their melting temperature c. Undergo both a chemical and physical change d. Experience a wide processing range 9.) During the cooling stage, a hot mold will: a. Produce parts with a high gloss or surface finish b. Produce molded parts with less stress. 0. Increase the overall cycle time of the part d. All of the above 10.) Engineering resins typically require molds operating at: a. 180 to 220 degrees Fahrenheit b. 70 degrees Fahrenheit or below c. 300 degrees Fahrenheit or above I d. None of the above TRUE OR FALSE Answer each of the following questions by placing a T (True) or F (False) in the blank. If your answer is false, please provide the correct response in the available space. 11.) Injection time is the time required for the gate to seal off and for part weight to remain constant. 12.) Thermoplastics undergo both a physical and chemical change when exposed to heat. ............... .. _ 13.) A small amount of Screw back pressure may be used with filled materials to improve mixing. _ 14.) Excessive flash can be caused by insufficient clamp tonnage. ................................................... .. __ 15.), Commodity resins typically run molds at 180 to 220 degrees Fahrenheit. ................................. .:. __’__ 16.) It is more economical to reduce the first stage time than to reduce the cooling time. ............... ... .__ 17.) First stage pressure is the pressure required to fill the part without any packing. ....................... .. _;__ 18.) You should use a forward heat profile when running a material such as nylon. ........................... .. __ 19.) In all cases, it is important to use a high' screw speed to improving the melting rate of the material. _ 20.) The mold temperature may need to be increased if parts begin sticking in the mold. ................. .. ____ Program 3 Injection Molds 1. What type of gate improves the flow of material by dispersing the material into the cavities of thin parts in a wide pattern? a. Direct Sprue Gate b. Edge Gate c. Fan Gate (1. Tab Gate e. None of the above 2.) What type of machining method is the most accurate? 3. Grinding I b. Milling 0. Turning d. None of the above 3.) The part of the injection mold which connects the mold to the machine is the... a. Locating Ring ' b. Leader Pins c. Sprue Bushing d. Clamp Slots 4.) The most effective method used to cool mold coresis... a. Bubbler b. Baffle c. Spiral Tube d. None of the above 5.) How much pressure must an injection mold be designed to withstand? a. 50 - 1,000 PSI b. 1,000 - 5,000 PSI 0. 5,000 - 10,000 PSI (1. 5,000 - 45,000 PSI 6.) One of the leader pins on an injection mold is purposely offset to... a. Ensure proper assemblyafter mold maintenance b. Assist the mold in closing properly and accurately c. Allow mold makers to incorporate side actions (1. None of the above 7.) What method(s) of machining can be performed with the steel in its hardened state? a. Grinding ' b. Electrical Discharge Machining ’ c. Milling d. All of the above e. Only A and B 8.) During the cooling phase, how can~ molders be sure that adequate cooling of parts is taking place? a. Run the water lines through the mold plates only A b. Run the water lines through the cavity and core c. Strategically locate channels throughout the mold. d. Locate water lines on the stationary side of the mold 9 9.) When removing a plastic part that has become jammed or stuck in the mold it is best to use... a. A plastic rod b. An aluminum rod 0. A brass rod (1. A copper rod e. Any of the above 10.) Molds should be thoroughly cleaned and greased... a. When they are new and have just been built b. At least once per shift during operation 0. About once a month during operation (1. Never 11.) Injection molds are built of a solid construction... a. So that the mold will fit into the machine b. Because of the tight part tolerances c. Because they are subjected to high injection pressures- d. All of the above 12.) The advantage of electrical discharge machining (EDM) is that... a. it is very accurate b. it has the ability to machine complex shapes c. it has the ability to machine steel in both its hardened and soft state d. All of the above ' e. Only B and C 13.) What machining methods are performed prior to heat treating the steel? a. Grinding ' ' b. Milling c. Turning d. All of the above e.) Only B and C 10 TRUE OR FALSE Answer each of the following questions by placing a T (True) or F (False) in the blank. If your answer is false, please provide the correct response in the available space. 14.) Water lines should not be located uniformly throughout the mold. ............................................. .. _ 15.) Different methods of machining accomplish the same results. ..................................................... .. _ 16.) Most plastics will flash if a gap of one thousandth of an inch exists ............................................. .. __ 17.) The direct sprue gate is the simplest design used on injection molds. ......................................... .. _ 18.) The carbon electrodes represents what the part feature will look like once molded ................... .. _ 19.) The melded part finish is not dependent on the surface finish of the mold itself. ...................... _ 20.) Return pins are use to ensure proper alignment of mold halves. ................................................. .. _ 21.) A balanced runner system is used to ensure that all cavities will fill at the same time. .............. .. _ p 22.) Tab gates are used to pick up strains and imperfections in the material. ...................................... .. _ 11' ...
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This note was uploaded on 08/08/2008 for the course ME 419 taught by Professor Turng during the Spring '04 term at Wisconsin.

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me419homework1-spring2004 - ‘ga MEI/LI? Hm“. {we N * C...

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