3.1 Processes,techniques and specialist tools Flashcards
What influences the properties of metals such as hardness or ductility?
The grain structure of metals
Metals are made up of millions of tiny metal grains.
What is the process of altering metal properties through controlled heating and cooling called?
Heat treatment
Heat treatment affects properties like hardness and ductility.
What is the effect of hardening medium and high carbon steels?
Increases hardness and brittleness
Hardening involves heating, holding at a temperature, and quenching.
What process reduces excess hardness and brittleness in hardened metals?
Tempering
Tempering increases toughness and ductility.
At what temperature is metal heated during the tempering process?
Below the critical point
The exact temperature determines the amount of hardness removed.
What does case hardening do to steels with less than 0.4 percent carbon content?
Hardens the surface while retaining inner core properties
It improves surface hardness and resistance to surface indentation.
What is the first step in the case hardening process?
Carburising
Carburising changes the chemical composition of the surface to absorb more carbon.
What is the role of the ceramic box in the carburising process?
Holds carbon for diffusion into low carbon steel
The box is heated to about 930-950°C.
What happens to the depth of the carbon layer during carburising?
It increases with longer exposure time
The carbon atoms diffuse into the material’s structure.
What temperature is the product heated to after carburising?
About 760°C
This is followed by quenching to seal the hard surface case.
What is the purpose of quenching in the case hardening process?
To fast cool the metal and seal the hard surface case
Quenching does not affect the inner core properties.
What is annealing?
The heating and slow cooling of work-hardened metal to make it easier to work, less brittle and more ductile.
Annealing is a crucial process in metallurgy to improve the workability of metals.
What is the purpose of normalising in metallurgy?
To give low carbon steels a uniform, fine-grained structure, making the metal more ductile with increased toughness.
Normalising is often carried out after the metal has been hot worked into a shape.
What are the steps involved in the normalising process?
- Heating to about the same temperature as for hardening.
- Quick quenching.
- Left to cool.
This process enhances the toughness of the metal.
Define an alloy.
A metal made of two or more metals or combining two or more elements, one of which must be a metal.
Alloys typically exhibit enhanced properties compared to the original metals.
What is the process for producing alloys?
The metals are melted together in specific quantities and poured into bars or ingots.
Alloys can be produced in a furnace or in a casting process.
What is the four-colour printing process used in flexography and offset lithography?
Cyan, magenta, yellow, and key (black) (CMYK).
These colours are printed in various quantities to achieve the desired print colour.
What is offset lithography?
A versatile printing process capable of producing one colour to multiple colours using different roller machines.
It can handle complex printing tasks including varnishing and duplex printing.
What types of products is offset lithography used for?
Books, documents, magazines, posters, and packaging.
It is suitable for medium and long print runs.
List the advantages of offset lithography.
- Consistently high-image quality.
- Higher volume print runs of 1000 or more.
- Long life of printing plates.
These advantages make offset lithography popular for large-scale printing.
What are the disadvantages of offset lithography?
Expensive setup and running cost for small quantities.
This can make it less viable for small print jobs.
What type of inks does Flexography use?
Fast drying water-based inks
Flexography is known for its quick drying capabilities, making it suitable for various applications.
How is ink transferred in the Flexography process?
Ink is transferred to the roller then to the material via pressure from the printing roller
This method allows for efficient and effective printing on different materials.
What is a key characteristic of the Screen Printing process?
The screen has open areas for the ink to pass through
Each color requires a different screen, which is a defining feature of this technique.
What type of printing process is Gravure?
Rotary printing process
Gravure involves engraving or etching images onto a rolling cylinder for printing.
Name three uses of Gravure printing.
- Newspapers
- Comics
- Catalogues
Gravure is widely used for high-volume printing applications.
What is a common use of Screen Printing?
Small print runs of items such as posters, display boards, and textile t-shirts
This method is favored for its versatility in producing unique designs.
What are two advantages of Flexography?
- High print speed
- Suited for long runs
These advantages make Flexography a popular choice for large-scale printing projects.
What is a disadvantage of Flexography?
The cost of the printing plates is relatively high
However, the plates can last for millions of print runs.
What is a key advantage of Screen Printing?
Minimal setup costs due to the use of basic screens and printing inks
This makes it accessible for small businesses and custom projects.
What is a disadvantage of Screen Printing?
A slow process with a reasonably high cost per product
This can limit its use for larger production runs.
List two advantages of Gravure printing.
- Excellent print quality
- High printing speed
Gravure is often used for high-volume production due to these benefits.
What is a disadvantage of Gravure printing?
Expensive setup costs for making the cylinders
This can be a barrier for smaller projects or businesses.
Fill in the blank: Gravure is used for high volume printing such as _______.
[packaging, gift wrapping, wallpaper]
These applications benefit from the efficiency of the Gravure process.
True or False: Screen Printing can be used for CMYK printing.
False
While it can print in multiple colors, it is not as efficient for CMYK as other processes.
What is a disadvantage of Fine text lettering in Screen Printing?
Not as sharp as other processes
This can affect the quality of designs requiring fine detail.
What are the five types of metal casting?
Sand
Investment
Gravity die
Pressure die
Plaster if paris
What are the advantages and disadvantages of sand casting metal?
X labour intensive
X not high quality finish
/ good for one off production
/ good for small batch production
What is the process of investment casting
Wax patterns are used which melt on contact with the molten metal to give high quality, intricate shapes
what metals does gravity die metal casting use?
Metals with lower melting points like aluminium or aluminium alloys
What batch size is a pressure die useful for?
Large
