Self Study Flashcards
What are sliding bearings?
Bearings where two surfaces move relative to each other without benefit of rolling contact.
What does a shaft do?
the component rotates and transmits power from a driving device through a machine
What is Turning and Boring used for?
To machine internal and external surfaces of components with rotational symmerty
7 Turning/Boring operations
Turning Facing Parting off Boring Drilling Form Cutting Thread Cutting
In Turning what is the swing?
The maximum diameter of work which can be rotated
Typical accuracy of turning and boring?
0.01 mm but is dependent on material and diameter
How does milling take place?
The workpiece is clamped to a movable table and the tool is rotated about either a vertical or horizontal axis
What is milling?
Multiple point cutter removes metal normally to create a flat surface although free form surfaces can be created using computer and numerical control
Accuracy of milling
typically 0.05 mm but depends on the size and material being machined
What is drilling and reaming used for?
Create blind of through holes by cutting process.
Holes are drilled in rough machining and reaming gives the final finish to achieve close tolerances
Explain the process grinding
Abrasive material removal which is generally a finishing process. It is only suitable for hard materials
Typical accuracy of grinding
0.005mm
Why do discontinuous chips occur?
The material fractures ahead of the tool, indicating a poor choice of cutting condition
3 things about continuous chips
- Represent the ideal cutting for ductile materials
- Results in long tool life and good surface finish
- Very long chips can be dangerous and difficult to handle so chip breaker are often employed to break the chip up, this reduces the chance of injury and makes the chips easier to dispose
5 reasons coolants area used
- to reduce friction
- to reduce the tool/work temperature
- to wash away chips
- to inhibit corrosion
- to reduce built up edges on tools
4 desired characteristics of cutting tools
- have high hardness
- be tough
- have excellent abrasion resistance
- be able to withstand high pressures
What is high speed steel used for and why?
single point tools and twist drills
mostly in job shop type environments where productivity rats are not high.
HSS retains its hardness up to 600C
3 things about cast alloy tips
can be brazed or mechanically fastened to a holder
normally a high cast alloy which produces very hard carbides can retains its hardness up to 900°C
they are cast in ceramic mould because the material is difficult to machine
4 Things about cemented carbide tips
Sintered from powder
Retains hardness up to 1000°C
Less brittle than cast alloy tips
commonly used where high production rates are required
Define the clarification of task
functions and constraints are documented in a detailed design spec
Define conceptual design
involves the establishment of function structures in the search for solution principles and their combination into design variants
Define embodiment design
determines the layout and forms and develops the artifact in accordance with technical and commercial considerations
Define detail design
lays down the final form, arrangement, dimensions and materials of all individual parts
manufacturing instructions are produced
What are the elements of a design specification
Requirements constraints criteria context of use open remarks or questions
Define abstracting
ignoring what is particular or incidental and emphasizing what is general and essential
4 reasons the weighting an rating method bad?
- subjective and arbitrary
- numerical answers can be given too much importance. the number implies a precision that isn’t there
- the multiplication makes the method sensitive to small changes
- users an become good at making sure the rating give the answer they want
What is shearing?
when a shape is cut from sheet metal by shearing the sheet between a punch and die
Difference between punching and blanking
Punching the slug is discarded
Blanking the slug is retaining
5 types of shearing operations
Parting perforating notching slitting lancing
What do grip rings do?
improve the finish on the edge of a blanked part
it prevents movement of the sheet and allows the clearances to be reduced whilst producing a very smooth edge
Three problems with sheet bending?
minimum bend radius
springback
bending forces
define the minimum bend radius
the smallest radius which the sheet can be bent to without tensile fracture occurring on the outside of the bend
Typical values of the minimum bend radius
when t is the thickness it varies from 0 to 6t
