Podcast
Questions and Answers
What is one advantage of epoxide resins over other plastic materials?
What is one advantage of epoxide resins over other plastic materials?
In which situation is it not economical to use plastic tools?
In which situation is it not economical to use plastic tools?
What is a disadvantage of using plastic tools compared to metal tools?
What is a disadvantage of using plastic tools compared to metal tools?
What is a common application of plastic tools in various industries?
What is a common application of plastic tools in various industries?
Signup and view all the answers
What feature do most unit heads include to enhance drilling capabilities?
What feature do most unit heads include to enhance drilling capabilities?
Signup and view all the answers
What characteristic of thermo-setting plastics prevents them from being welded using conventional processes?
What characteristic of thermo-setting plastics prevents them from being welded using conventional processes?
Signup and view all the answers
Which welding process uses hot gas to join plastic parts?
Which welding process uses hot gas to join plastic parts?
Signup and view all the answers
How does heat transfer occur in welding processes that utilize an external heat source?
How does heat transfer occur in welding processes that utilize an external heat source?
Signup and view all the answers
What is a key benefit of welding compared to cementing and riveting in plastic applications?
What is a key benefit of welding compared to cementing and riveting in plastic applications?
Signup and view all the answers
What types of processes generate heat within the workpiece for welding plastics?
What types of processes generate heat within the workpiece for welding plastics?
Signup and view all the answers
What happens to plastic workpieces during the welding process?
What happens to plastic workpieces during the welding process?
Signup and view all the answers
What is a common filler material used in hot-gas welding?
What is a common filler material used in hot-gas welding?
Signup and view all the answers
What is a significant drawback of hot gas welding?
What is a significant drawback of hot gas welding?
Signup and view all the answers
How is the joint completed in hot gas welding?
How is the joint completed in hot gas welding?
Signup and view all the answers
The hot tool welding process primarily relies on what method to join materials?
The hot tool welding process primarily relies on what method to join materials?
Signup and view all the answers
Which type of joint is commonly made using hot gas welding?
Which type of joint is commonly made using hot gas welding?
Signup and view all the answers
What happens to the edges of materials before they are hot gas welded?
What happens to the edges of materials before they are hot gas welded?
Signup and view all the answers
What are the cold rollers used for in the hot gas welding process?
What are the cold rollers used for in the hot gas welding process?
Signup and view all the answers
In hot tool welding, what occurs after the hot blade has softened the surfaces?
In hot tool welding, what occurs after the hot blade has softened the surfaces?
Signup and view all the answers
What is a negative consequence of low joint strength in a welding process?
What is a negative consequence of low joint strength in a welding process?
Signup and view all the answers
Which of the following is NOT a characteristic of hot tool welding?
Which of the following is NOT a characteristic of hot tool welding?
Signup and view all the answers
What is one of the main benefits of using the hot machining process?
What is one of the main benefits of using the hot machining process?
Signup and view all the answers
Which of the following is NOT a method of special processing discussed?
Which of the following is NOT a method of special processing discussed?
Signup and view all the answers
What characteristic of heat-resistant materials poses a challenge during machining?
What characteristic of heat-resistant materials poses a challenge during machining?
Signup and view all the answers
Which specification is relevant for Plastic Extruders?
Which specification is relevant for Plastic Extruders?
Signup and view all the answers
In what scenario are conventional machining methods most challenging?
In what scenario are conventional machining methods most challenging?
Signup and view all the answers
What is a consequence of machining heat-resistant materials?
What is a consequence of machining heat-resistant materials?
Signup and view all the answers
Which of the following benefits is associated with foam moulding?
Which of the following benefits is associated with foam moulding?
Signup and view all the answers
What is a disadvantage of the plastic casting process?
What is a disadvantage of the plastic casting process?
Signup and view all the answers
How does work-hardening affect the machining of heat-resistant materials?
How does work-hardening affect the machining of heat-resistant materials?
Signup and view all the answers
What parameter must be considered in the selection of cutting tools for hot machining?
What parameter must be considered in the selection of cutting tools for hot machining?
Signup and view all the answers
What is essential for achieving extremely close dimensional accuracy in mould design?
What is essential for achieving extremely close dimensional accuracy in mould design?
Signup and view all the answers
What is the main function of the plunger in a plastic mould?
What is the main function of the plunger in a plastic mould?
Signup and view all the answers
Which of the following statements about mould design is false?
Which of the following statements about mould design is false?
Signup and view all the answers
In an injection mould, what does the single parting line indicate?
In an injection mould, what does the single parting line indicate?
Signup and view all the answers
What role do temperature control channels play in a mould?
What role do temperature control channels play in a mould?
Signup and view all the answers
What is NOT part of the basic components of a mould?
What is NOT part of the basic components of a mould?
Signup and view all the answers
What does the term 'knockout pin' refer to in mould design?
What does the term 'knockout pin' refer to in mould design?
Signup and view all the answers
Which of the following is critical to avoid problems in shape generation during mould design?
Which of the following is critical to avoid problems in shape generation during mould design?
Signup and view all the answers
What does the support plate in a mould primarily function as?
What does the support plate in a mould primarily function as?
Signup and view all the answers
Which component primarily assists in the removal of the fabricated parts from moulds?
Which component primarily assists in the removal of the fabricated parts from moulds?
Signup and view all the answers
Which method is primarily used for producing large mass plastic tools such as forming dies and punches?
Which method is primarily used for producing large mass plastic tools such as forming dies and punches?
Signup and view all the answers
What is a key advantage of using plastic tools for short runs and prototypes?
What is a key advantage of using plastic tools for short runs and prototypes?
Signup and view all the answers
Which alloy is NOT commonly formed using plastic tools?
Which alloy is NOT commonly formed using plastic tools?
Signup and view all the answers
What process is used to create precision thin-section metal parts by depositing metal onto a form?
What process is used to create precision thin-section metal parts by depositing metal onto a form?
Signup and view all the answers
What addition is typically made to casting resin to enhance its properties?
What addition is typically made to casting resin to enhance its properties?
Signup and view all the answers
In hot tool welding, what is the purpose of the heating wedge?
In hot tool welding, what is the purpose of the heating wedge?
Signup and view all the answers
What is the role of the roller in the hot tool welding process?
What is the role of the roller in the hot tool welding process?
Signup and view all the answers
How is heat transferred in the hot press welding method?
How is heat transferred in the hot press welding method?
Signup and view all the answers
What specific characteristic makes hot tool welding suitable for elastic materials?
What specific characteristic makes hot tool welding suitable for elastic materials?
Signup and view all the answers
What does the term 'scarfed edges' refer to in the context of hot press welding?
What does the term 'scarfed edges' refer to in the context of hot press welding?
Signup and view all the answers
In the hot plate welding process, what is the main function of the resistance element?
In the hot plate welding process, what is the main function of the resistance element?
Signup and view all the answers
What is the purpose of allowing the workpieces to stay under pressure after reaching welding temperature in hot press welding?
What is the purpose of allowing the workpieces to stay under pressure after reaching welding temperature in hot press welding?
Signup and view all the answers
Which of the following welding processes requires one of the pieces to be a body of revolution with a circular section at the joint?
Which of the following welding processes requires one of the pieces to be a body of revolution with a circular section at the joint?
Signup and view all the answers
What primary action occurs in ultrasonic welding that distinguishes it from other welding methods?
What primary action occurs in ultrasonic welding that distinguishes it from other welding methods?
Signup and view all the answers
Which welding method includes the use of a viscous filler material that aids in forming a strong bond?
Which welding method includes the use of a viscous filler material that aids in forming a strong bond?
Signup and view all the answers
In high-frequency induction welding, what is primarily applied to complete the joint after heating the plastics?
In high-frequency induction welding, what is primarily applied to complete the joint after heating the plastics?
Signup and view all the answers
What is a significant limitation of friction welding in plastics?
What is a significant limitation of friction welding in plastics?
Signup and view all the answers
Which welding technique allows crossover of dissimilar plastics during the joint formation?
Which welding technique allows crossover of dissimilar plastics during the joint formation?
Signup and view all the answers
What is primarily responsible for generating heat in nuclear welding?
What is primarily responsible for generating heat in nuclear welding?
Signup and view all the answers
Which of these materials cannot typically be joined using high-frequency induction welding?
Which of these materials cannot typically be joined using high-frequency induction welding?
Signup and view all the answers
What is a potential outcome of using the extruded-filler welding process?
What is a potential outcome of using the extruded-filler welding process?
Signup and view all the answers
Which of the following materials is NOT commonly used for moulds?
Which of the following materials is NOT commonly used for moulds?
Signup and view all the answers
What is a typical characteristic of the steel used for moulds as described?
What is a typical characteristic of the steel used for moulds as described?
Signup and view all the answers
What is the primary advantage of using flash type cavity design?
What is the primary advantage of using flash type cavity design?
Signup and view all the answers
Which type of component is usually made from plate steel?
Which type of component is usually made from plate steel?
Signup and view all the answers
What is the recommended hardness for drill rods used in mould pin production?
What is the recommended hardness for drill rods used in mould pin production?
Signup and view all the answers
Which component is typically obtained by carburization in mould design?
Which component is typically obtained by carburization in mould design?
Signup and view all the answers
Which of the following is considered a disadvantage of flash type cavity design?
Which of the following is considered a disadvantage of flash type cavity design?
Signup and view all the answers
What is the primary material that cavity designs utilize for creating mould frames?
What is the primary material that cavity designs utilize for creating mould frames?
Signup and view all the answers
What is the main disadvantage of using hardening on frame components?
What is the main disadvantage of using hardening on frame components?
Signup and view all the answers
Which property of materials generally makes them suitable for mould production?
Which property of materials generally makes them suitable for mould production?
Signup and view all the answers
What is the minimum recommended wall-thickness for mouldings?
What is the minimum recommended wall-thickness for mouldings?
Signup and view all the answers
What is an appropriate rib height in relation to its thickness?
What is an appropriate rib height in relation to its thickness?
Signup and view all the answers
Why is it better to avoid sharp corners in mould design?
Why is it better to avoid sharp corners in mould design?
Signup and view all the answers
What is a recommended maximum variation in wall thickness of a moulding?
What is a recommended maximum variation in wall thickness of a moulding?
Signup and view all the answers
What factor primarily determines the curing time of a plastic product?
What factor primarily determines the curing time of a plastic product?
Signup and view all the answers
What should the length-to-diameter ratio for through holes typically not exceed?
What should the length-to-diameter ratio for through holes typically not exceed?
Signup and view all the answers
What geometric feature is recommended to enhance the strength of a moulded part?
What geometric feature is recommended to enhance the strength of a moulded part?
Signup and view all the answers
What is the disadvantage of using thick corners in mould design?
What is the disadvantage of using thick corners in mould design?
Signup and view all the answers
What is one of the functions of providing adequate fillets in mould design?
What is one of the functions of providing adequate fillets in mould design?
Signup and view all the answers
What is the recommended depth-to-diameter ratio for blind holes larger than 1.5 mm?
What is the recommended depth-to-diameter ratio for blind holes larger than 1.5 mm?
Signup and view all the answers
Study Notes
Processing of Plastics
- Plastics deform at elevated temperatures, behaving like highly viscous liquids. Welding requires pressure.
- Thermosetting plastics cannot be welded conventionally.
- Thermoplastics can repeatedly transition to highly elastic and plastic states without losing properties.
- Welding is superior to cementing and riveting for permanent connections in terms of speed, labor cost and joint quality.
- Welding processes are classified based on heat source.
- External heat sources like hot gas, hot filler metal, and hot tools. Heat is transferred by convection, conduction and radiation.
- Generated heat inside the workpiece from sources like RF current, ultrasound, friction, etc.
Hot-Gas Welding
- Hot gas heats the edges and filler rods to a viscous state.
- Similar to manual gas welding of metals.
- Drawbacks include low joint strength, limited plasticity, slow welding speed, especially in thick sheets, and operator skill dependence.
- Can be used to weld films, creating lap joints without filler rods, enhancing efficiency.
Hot Tool Welding
- Hot tool transfers heat to the workpiece via direct contact.
- Several variations exist. Some involve placing a hot blade between parts, while others use a hot wedge that's moved along the weld line.
- Suitable for thicker parts as well as for lap and butt joints over a surface area.
- Applicable for plastics that are unsuitable for rf induction heating (e.g., PTFE, polyethylene, polystyrene)
Friction Welding
- Converts mechanical energy to heat at the welded surfaces.
- Similar to metal friction welding.
- Limitations: One of the parts must be a rotational body, and at the joint the cross section must be a circle or annulus; a flash forms during pressure application.
Ultrasonic Welding
- Uses ultrasonic energy to weld plastics.
- Similar process as metal ultrasonic welding.
- Suitable for acrylics, PVCs, and polystyrene.
- No edge preparation or filler needed.
- Applicable to dissimilar plastics
High Frequency Induction Welding
- Uses an electric field between electrodes.
- Similar to the method for metals.
- Filler rod is in viscous fluid state
Extruded-Filler Welding
- The filler rod is in a viscous fluidic state and it melts the edges of the plastic.
- Suitable for films and heavy gauge sheets
Nuclear Welding
- Uses neutron irradiation to generate heat for fusion joining.
- Not suitable for materials that become radioactive upon irradiation.
Infrared Welding
- Uses infrared to transfer heat for welding.
- Suitable for joining polyethylene films.
Joining Thermosets
- Thermosets do not soften upon heating.
- Joining involves adhesive methods or mechanical fasteners.
- Solvent bonding involves surface roughening, solvent wiping, and surface pressing until bond strength is achieved.
Design of Plastic Parts
- Mould design minimizes problems, considering shape and dimensional control.
- Uniform wall thickness is important for curing time.
- Avoiding undercuts and providing adequate fillets minimizes stress concentration.
- Proper rib and/or dome configurations increase the rigidity of parts.
- Simple part shapes facilitate removal from molds.
- Holes should have sufficient wall thickness to prevent cracking.
- Tolerances are necessary for manufacturing variations in tools, materials, or machining.
- The amount of tolerance is based on part dimensions and intended use.
Warpage Allowance
- Warpage is a measure of the deformation of a part.
- This is an undesirable effect, especially in thin parts.
- A good measure to use for warpage is + or - 0.075mm per mm.
Mould Material
- Steel alloys are commonly used in mold manufacturing.
- Other materials like Aluminum, Berrylium Copper, and Zinc may be used, based on application.
Mould Design
- There are different types of cavity designs for molds.
- These designs are called Flash type, Positive type, Semi-positive type, and Landed Plunger type, and Sub-cavity type.
- These designs differ in the way in which parts are loaded into the mold.
- Each design entails varying degrees of complexity and the selection depends on the complexity of the component.
Surface Cleaning and Treatments
- Cleaning is needed for part assembly, to prevent component failure due to accumulated debris, and to allow a better quality for decorative application.
- Cleaning methods include mechanical methods such as barrel tumbling and abrasive blasting, chemical methods such as alkaline and solvent cleaning, and vapor degreasing.
- Mechanical cleaning removes scale, dirt and debris.
- Chemical cleaning removes oils and greases and is suitable for parts of aluminum, lead, and zinc.
- Electrolytic and ultrasonic methods are used for intricate shapes.
Coating and Plating
- Metallic coatings like copper, chrome, cadmium and nickel are applied electrochemically.
- Hot-dip coatings (e.g., tin, zinc, lead, and aluminum alloys) involve immersing the part in molten metal.
- Conversion coatings like phosphate or chromate form a protective layer on the part surface
Hot Machining
- Localized heat allows for easy chip formation, reducing workpiece strength and enabling easier machining.
- It is primarily applied to heat resistant metals for better machining performance, reduced wear, better surface finish, and less shock to cutting tools.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the various processes involved in the processing of plastics. This quiz covers topics such as welding methods, thermoplastics, and thermosetting plastics, providing insight into their behavior at different temperatures. Additionally, explore the advantages of welding over other methods for permanent connections.
