Theoretical surface finish

Surface finish is dictated by the following equation

http://www.harrisonep.com/electropolishing-ra.html

Ra value is a measurement of surface finish, its the average of measurements taken from the peaks and valleys of a surface due to the cutting operation relative to a mean line.

http://www.rubert.co.uk/Ra.htm

This graph above shows a graphical representation of this data.

6061 T6 Surface finish calculation

Using the 6061 T6 aluminum speeds and feeds dictated in a previous post and the equation below its possible to estimate the surface finish of the cutting operation.








http://www.kanabco.com/vms/eng_surface/eng_surface_04.html

Tool data from
http://www.niagaracutter.com/solidcarbide/metric/nc_metric_catalog.pdf
3 flute 10mm solid carbide end mill

r = tool tip radius (Inches) 0.02 inches (2.D.P)
f = feed rate per tooth (Inches) = 0.003 inches (3.D.P)

Ra=((0.02-sqrt(0.02^2-(0.003/2)^2))*1000000)/2
     =((0.02-sqrt(0.0004-(0.00000225)))*1000000)/2
     =((0.02-sqrt(0.00039775))*1000000)/2
     =((0.02-0.01994367067517913062473309999688)*1000000)/2
     =(0.00005632932482086937526690000312*1000000)/2
     =(56.32932482086937526690000312)/2
     =28μin    
1 Microinch = 0.000001 inches therefore 28μin = 0.000028 inches
                                                                             = 0.0007112 mm
                                                                        Ra = 0.7112 µm

MDF theoretical surface finish calculation




r = tool tip radius (Inches) 0.02 inches (2.D.P)
f = feed rate per tooth (Inches) = 0.0079 inches (4.D.P)

Ra=((0.02-sqrt(0.02^2-(0.0079/2)^2))*1000000)/2
    = 196μin (3.S.F)
    = 4.9784µm