Nov 15 Machining - ME 250 Nov 15, 2007 Machining Machining...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
ME 250 Nov 15, 2007 Machining Machining A broad term that refers to the removal of material from a workpiece. Three categories ¾ Metal cutting using single/multi point cutting tools ¾ Abrasive processes e.g., grinding ¾ Non-traditional processes that utilize methods such as chemical, electrical, hydrodynamic, etc. Metal cutting A material removal process in which a sharp cutting tool is used to mechanically cut away material so that the desired part geometry remains – Most common application: to shape metal parts – Most versatile of all manufacturing processes in its capability to produce a diversity of part geometries and geometric features with high precision and accuracy Note Casting and forging can also produce a variety of shapes, but they lack the precision and accuracy of machining Service life Æ replacement parts Replacement Æ interchangeable parts Interchangeability Æ dimensional accuracy Dimensional accuracy Æ machining Machined surfaces on drawings a) Rotational – axis symmetric b) Non-rotational – Prismatic (mostly flat surfaces) – Free form (spline surfaces) Classification of Machined Parts
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Free form surfaces Die surfaces are free form / complex Machining Operations and Part Geometry Each machining operation produces a characteristic part geometry due to two factors: 1. Relative motions between tool and workpiece Generating – part geometry determined by feed trajectory of cutting tool 2. Shape of the cutting tool Forming – part geometry is created by the shape of the cutting tool (a) straight turning, (b) taper turning, (c) contour turning, (d) plain milling, (e) profile milling. 1. Motion generating shape (a) form turning, (b) drilling, and (c) broaching 2. Tool (form) generating shape Shape by tool geometry + motion Producing Round Shapes • Turning • Drilling • Boring • Reaming • Tapping
Background image of page 2
Turning • Engine lathe • Turret lathe • Copying lathe • CNC lathe Engine lathe Turret lathe Tailstock replaced with a turret Copying lathe Tool is fed radially inward Facing (Fig 22.6) Turning Feed direction parallel to part axis Most common lathe operation
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Instead of feeding tool parallel to axis of rotation, tool follows a contour creating a contoured shape Contour Turning Cutting edge cuts an angle on the corner of the cylinder, forming a "chamfer" Chamfering Tool is fed radially into rotating work at some location to cut off end of part Cutoff Pointed form tool is fed linearly across surface of rotating workpart parallel to axis of rotation Threading 1. cutting speed 2. material removal rate 3. cutting time Cutting conditions in turning Cutting speed in turning Rotational speed N is related to cutting speed v, at the surface of the cylindrical workpiece by v = π D o N Where N = rev/min D o = m (ft) v = m / min (ft/min)
Background image of page 4
Material removal rate in turning v = cutting speed ( π D o N) in mm/sec f = feed (mm) d = depth of cut (mm) The material removal rate, MRR, refers to the volume of material removed (mm 3 / sec), and is computed as MRR = v f d Machining time If f is the feed (mm/rev) then
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/04/2008 for the course ME 250 taught by Professor Dutta during the Fall '07 term at University of Michigan.

Page1 / 14

Nov 15 Machining - ME 250 Nov 15, 2007 Machining Machining...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online