Unit 5: Surface Finishing & Plastics

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Sections

Quick Formula Reference
Grinding Ratio
G = Volume removed / Volume wear
Material Removal Rate
MRR = v × f × d
Surface Speed
vs = πDsNs / 1000
Practice Problems
50+ ProblemsSurface Finishing & Plastics
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Surface Finishing

Section 1 of 7

Surface Finishing Fundamentals

Surface finishing processes improve surface quality, dimensional accuracy, and functional properties of manufactured parts.

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Rough PartFinishing ProcessFinished Part

Objectives

  • Improve surface quality
  • Achieve dimensional accuracy
  • Enhance functional properties
  • Improve appearance

Process Categories

  • Abrasive processes (Grinding)
  • Chemical processes (Etching)
  • Thermal processes (Flame polishing)
  • Mechanical processes (Polishing)
Surface Finishing - Complete Exam Guide

Surface Finish Theory & Measurement

Surface Roughness Parameters:
  • • Ra (Average): Arithmetic mean of surface deviations
  • • Rz (Ten-point): Average of 5 highest peaks and 5 deepest valleys
  • • Rmax: Maximum peak-to-valley height
  • • Rq (RMS): Root mean square of surface deviations
Abrasive Processes Classification:
  • • Bonded Abrasives: Grinding wheels, mounted points
  • • Coated Abrasives: Sandpaper, belts, discs
  • • Loose Abrasives: Lapping compounds, polishing pastes
  • • Free Abrasives: Ultrasonic machining, abrasive flow

Grinding Calculations & Parameters

Grinding Ratio: G = Volume of work removed / Volume of wheel wear
Material Removal Rate: MRR = v × f × d (mm³/s)
Specific Energy: u = P / MRR (J/mm³)
Surface Speed: vs = πDsNs/1000 (m/s)
Contact Length: lc = √(d × D) (mm)

Process Selection & Exam Problems

Surface Finish Requirements:
  • • Rough Machining: Ra = 6.3-25 μm
  • • Finish Machining: Ra = 1.6-6.3 μm
  • • Grinding: Ra = 0.4-1.6 μm
  • • Polishing: Ra = 0.1-0.4 μm
  • • Lapping: Ra = 0.025-0.1 μm
Problem: Calculate grinding time for 100mm length, feed=0.01mm/pass, 20 passes
Solution: T = (100 × 20) / (feed rate × table speed)
✨Surface Finishing Basics Quiz
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What is the primary purpose of surface finishing?

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