Lesson 14 of Process Industrial Engineering FREE ONLINE Course (Module)
Surface Finish - An Area of Inquiry for Industrial Engineers
Industrial engineers have to find alternative ways that reliably produce to the specification of the design but give productivity. They have to first know alternatives to produce to specification.
Surface Finish, Integrity and Flatness
MEASUREMENT OF SURFACE FINISH
Types of measurements
Waviness refers to variations in the surface with relatively long wavelengths or, equivalently, lower frequencies. Waviness may result from clamping errors, errors in the tool or cutter geometry, or vibrations of the system. Spindle tilt in face-milling operations also produces a waviness or shape error.
Roughness is the term for surface profile variations with wavelengths shorter than those characteristic of waviness. Roughness has a geometric component dependent on the feed rate, tool nose radius, tool lead angle, and cutting speed, as well as a natural component resulting from tool wear, inhomogeneities in the work material, higher frequency vibrations of the machining system, and damage to the surface caused by chip contact.
The average roughness Ra is defined as the average absolute deviation of the workpiece from the centerline:
Rp is the maximum deviation of a peak above the centerline encountered within the sampling length
Similarly, Rv, the maximum depth of valley below the centerline,
Rt, the maximum peak to valley deviation or total profile height, is equal to
Rt = Rp + Rv
The bearing ratio tp is a function of the depth p below the highest peak and is
defined as the ratio of the total length of the profile below the depth p to the total trace length L:
Ra is the most commonly specified roughness parameter and is well suited for monitoring the
consistency of a machining process.
SURFACE FINISH IN TURNING AND BORING
For turning and single-point boring, the geometric roughness is easily calculated from the tool angles and feed.
SURFACE FINISH IN MILLING
SURFACE FINISH IN GRINDING
Measured roughness values in cylindrical plunge grinding are usually well characterized by an
vw: the workpiece velocity
vs: the wheel velocity
a: the depth of cut
RESIDUAL STRESSES IN MACHINED SURFACES
WHITE LAYER FORMATION
SURFACE BURNING IN GRINDING
MEASUREMENT OF SURFACE FLATNESS
SURFACE FLATNESS COMPENSATION IN FACE MILLING
Industrial engineer have to examine, whether cutting conditions are being kept substantially below the maximum cutting parameters recommended in theory or best practice by shop personnel because of the intention to reach the surface finish specified. They have to understand the theory behind surface finish achievement and the theory of cutting conditions that give maximum material removal rate and then come out with the best cutting conditions. They they have to organize the experiment to do most productive combination and if any problem persists, they have to find out whether any improvement in other machine variables is going to eliminate the problem. It is the industrial engineer's job not to give up utilizing the best cutting variables and achieve maximum productivity while achieving the specified surface finish. Hence, industrial engineers have to be aware of various solutions to improve surface finish.
Other compensation methods
Tool Path Direction Compensation
Depth of Cut Compensation
The milling path along a plane can be compensated normal to the plane by cutting shallower on
convex surface sections (high spots) and deeper on concave surface sections (low spots).
Tool Feed Compensation
Spindle-Part Tilt Compensation
The spindle-part tilt compensation (SPTC) method is used to prevent contact of the face-milling
cutter trailing edges with the machined surface.
Updated on 31 July 2021, 22 January 2021
First published on 11 July 2020