19-20 machining - ME250 Design and Manufacturing I...

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Machining processes ME250 Design and Manufacturing I
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2 Introduction Turning Drilling Milling Machining centers Product design considerations Summary Outline
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3 Introduction Machining processes Material removal process in which a sharp cutting tool mechanically cuts material so that the remaining shape becomes a part. Commonly used to shape metal parts Can produce complex shapes with high tolerance; higher than casting
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4 Machined products Introduction
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5 Machined products Introduction Rotational: cylindrical or disk-like shape Nonrotational (aka prismatic): block-like or plate-like shape
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6 Machined products Introduction turning only turning + milling + drilling
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7 Machined products Introduction
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8 Introduction Parameters determining cutting conditions Feed: speed by which new material to be cut is “fed” to a tool Cutting speed: tool cutter (point) speed Cutting depth: depth with which new material is removed Typically, feed X cutting speed X cutting depth = material volume removed per unit time
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9 Rotating work cut with a stationary, single point tool Turning: external cut Boring: internal cut Turning
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10 Engine lathe Turning
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11 Cutting conditions of turning Cutting speed v [mm/min] Diameter of work before cutting D 0 [mm] Diameter of work after cutting D f [mm] Depth of cut d [mm] = ( D 0 D f )/2 Rotational speed: N [rev/min] = v / p D 0 (N as D for const v ) Feed f [mm/rev] Turning
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12 Cutting conditions of turning Feed rate f r [mm/min] = Nf Time to machine length L [mm] at constant N In actual operation need “approach” and “ overtravel ” for smooth finish at both ends of a work Material removal rate (unit must match) Turning [min] m r L T f 3 [mm / min] MRR vfd f d Length v per minute
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13 Cutting conditions of turning Time to machine volume V [mm 3 ] Use this equation when turning non-uniform diameter with constant cutting speed v (i.e. variable N along the length) Special case: when turning uniform diameter D 0 with length L and depth d , Turning m V T MRR 0 V D Ld p 0 m r D Ld V L L T MRR vfd Nf f Equation for constant N
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14 Example D 0 = 125 mm D f = 120 mm L = 900 mm v = 2.5 m/s f = 0.3 mm/rev A = O = 5.0 mm Max allowable cutting depth d max = 2.0 mm Time between each pass T r = 3.0 sec Time to complete?
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19-20 machining - ME250 Design and Manufacturing I...

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