SUBTRACTIVE Flashcards
Define: Turning?
Workpiece is rotated and cutting tool is moved to remove a layer of material
Define: Machining?
Material is removed from a raw workpiece to achieve a desired geometry.
Define: Cutting off?
Workpiece is rotated and cutting tool is moved radially inwards to cut off a piece.
Define: Slab milling?
Rotating cutting tool is orientated parallel to surface. Layers are removed from the top.
Define: End milling?
Rotating cutting tool is perpendicular to the workpiece. Moves parallel to the top surface at a certain depth.
Define these symbols (cutting equations):
V, Vc, Vs, t0, tc, alpha, phi, Fc, Ft, R, F, N
V = tool velocity
Vc/Vs = cutting/shearing velocity
t0/tc = cut depth/chip thickness
alpha/phi = rake/shear angle
Fc/Ft = cutting/thrust force
R/F/N = resultant/friction/normal force
F and N are components of R along the tool face.
What is the equation for cutting/shearing/friction power?
FcV / FsVs / F*Vc
Approximate tool life equation?
V* T^n = C
Examples of designing for machining
- Provide easy tool access
- Avoid long thing sections (vibrations)
- Deep pockets also cause vibrations
- Holes don’t change directions internally
- Design parts that are easy to fix in place\
- Avoid outside round edges (difficult to machine without CNC)
Reasons why mechanical machining might not be suitable for a workpiece?
- Strength / Hardness too high
- Too brittle
- Too flexible
- Too complex geometry
- Special surface finish required
- Temperature rise during machining not acceptable
These are motivations for why one might choose some advanced machining methods as opposed to traditional machining methods.
If presented with a ‘what proportion of energy does the friction/shear take up’ question what should the approach be?
Simplify the fraction Uf/Ut (or Us/Ut) and then find variables.
Equation for Ut? (U total)
Fc / w * t0
Merchants equation? (for phi?)
phi = 45 + alpha/2 - beta/2
How to find beta?
mu = tan(beta) —> from mu = F/N
