Manufacturing Week 7 & 8 Flashcards
(16 cards)
What are the 4 types of casting?
Sand, die, investment and pressure casting
True or False: Freezing of Pure Metal takes place at a varying temperature?
False
What are the 3 basic types of cast structures?
Columnar dendritic; equiaxed dedritic; and equiaxed nondentritic
What is the use of risers in casting?
To serve as reseviors, supply molten metal to the casting as it shrinks during solidification
What is the range of Reynold’s Number in gating systems?
2,000 to 20,000
Why must the metal flow rate not be too low or too high?
High enough to avoid premature chilling and solidification; not so high as to cause turbulence
Solidification time is given by which equation?
Chvorinov’s Rule
Hot tears occur in casting when?
The casting cannot shrink freely during cooling
Molding is casting, adapted to materials that are?
Very viscous when molten, e.g. thermoplastics and glasses
What can be used to control cooling at critical sections to avoid hot tearing?
Exothermic (heat-producing) compounds
What are the 4 types of molding?
Injection, blow-molding, polymer extrusion and thermo-forming
What are the 3 types of polymers?
Thermosets, thermoplastics and elastomers
What is the process of Polymer Extrusion
Raw materials (pellets, granules or powder) are placed into a hopper and fed into barrel. Screw blends the material and conveys it towards the die. Heat and friction of barrel liquefies material.
What is the blow ratio, and what is its common value?
Ratio of the blown diameter to the extruded tube diameter; 3
What is blow molding?
The extruded piece is clamped in a mold cavity much larger than itself and blown outward to fill the cavity
Thermoforming is a process for?
Forming thermoplastic sheets or films over a mold through the application of heat and pressure
