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Shaping, Planing and Slotting Operations Chapter 7 © rkm2003 Production of Flat Surfaces Typical components with flat surfaces © rkm2003 Production of Flat Surfaces.. Cut E A' A Fe ed B' B C © rkm2003 Depth of cut Motions for producing Flat Surface D e c e i p Work Reciprocating Machine Tools • different from rotary machine tools • A single-point tool moves linearly relative to the work part • Shaper Shaping tool moves • Planer Planing workpiece moves • Slotter © rkm2003 Shaper/Shaping Machine Shaper/ Tool head d or f Tool Workpiece Vise Table f or d Ram v Base © rkm2003 Column Shaper/Shaping Machine Shaper/ Main Parts Base Column – drive, support & guide ram Table – hold & feed workpiece Ram – tool head, clapper box Types of Shaping M/c • Horizontal Shaper • Vertical Shaper (Slotting M/c) © rkm2003 Shaping Operation Cutting action and functioning of clapper box in a shaper Clapper box Tool cleared from machined surface Lifted clapper box Workpiece (a) Forward/Cutting stroke © rkm2003 (b) Return stroke Shaping Operation.. © rkm2003 Shaping Operation .. Machining of inclined surface on shaping machine Tool head & slide (axis parallel to machined surface) Clapper box (axis away from toolhead) θ Movement of the slide for feed Inclined machined surface © rkm2003 Tool holder located at a convenient angle Tool θ Workpiece Depth of cut Operating Conditions in a Shaping Machine N L (1 + m) cutting speed v = 1000 m/min where N = the number of double strokes or cycles of the ram per min (one double or full stroke = one cutting and one return stroke) L = Length of the ram stroke in mm m = return stroke time/cutting stroke time © rkm2003 Operating Conditions in a Shaping Machine .. Cutting Stroke Return Stroke Workpiece c © rkm2003 Lj c Clearance Length of stroke L Length of Stroke L = Lj + 2 c Operating Conditions in a Shaping Machine .. Feed f • Feed f is the relative motion of the workpiece in a direction perpendicular to the axis of reciprocation of the ram • Feed is expressed in mm/double stroke or simply mm/stroke because no cutting is done in return stroke © rkm2003 Operating Conditions in a Shaping Machine .. Depth of Cut d • Depth of cut d is the thickness of the material removed in one cut, in mm • Depth of cut may be given by the tool head slide or by lifting the table © rkm2003 Machining Time f w mm mm L mm Width cut in 1 stroke = f Total width = w No. of strokes to m/c total surface = w/f Strokes/mm = N Time for machining surface is t = w/(f N) min © rkm2003 Machining Time Time for machining w x L surface w t= fN min From cutting speed N L (1 + m) 1000 v v= ⇒N = 1000 L(1 + m) Machining time © rkm2003 w L w (1 + m) t= = f N 1000 v f min Material Removal Rate • Material removal rate (MRR) MRR = f d L N(1+m) mm3/min where d is depth of cut in mm f is feed in mm/stroke; N is strokes/min L is length of stroke in mm m is ratio of return stroke time to cutting stroke time © rkm2003 Planer © rkm2003 Planer/Planing Machine Housing Tool heads Tool head Reciprocating table Bed © rkm2003 Guideways Tool head Types of Planing Machines • Open Side Planer • Double Housing Planer • Edge planer • Universal planer, • Pit type planer © rkm2003 Operating Conditions in a Planer • Operating conditions in planer are similar to Shaping Machine Cutting Speed: Workpiece reciprocates cutting time=return time Cutting Tool: Multiple cutting tools cut simultaneously Job: Large size or multiple workpieces © rkm2003 Size of Shaping and Planing Machines • Largest Size of Workpiece that can be Machined Lxwx h © rkm2003 Difference between Shaper and Planer • • • • • Size of Workpiece Movement of Tool and Workpiece Construction Cutting and Return Speeds Number of toolheads © rkm2003 Slotting Slot made by slotting Ram Tool Table Typical Job © rkm2003 Column Tool holder Base Slotter/Slotting Machine Example 7.1 Find the machining time required for machining the surface 600 × 800 mm, on a shaping machine. Assume, cutting speed as 8 m/min. The return to cutting time ratio is 1:4, and the feed is 2 mm/double stroke. The clearance at each end is 70 mm. • Solution Lj = 600 mm, w = 800 mm, v = 8 m/min, m = ¼, f = 2 mm/stroke, c = 70 mm © rkm2003 Example 7.1 .. • Given clearance at each end: c=75 mm • length of stroke: L = 600 + 2×70 = 740 mm N L (1 + m) 1000v v= ⇒N = = 8.65 strokes/min 1000 L(1 + m) Assume 8.65 strokes/min available • Machining time for 800 mm width © rkm2003 w t= = 46.25 min f N Example 7.1 .. • Alternately: L w (1 + m) t= 1000 v f 740 × 800 × (1 + 0.25) = 1000 × 8 × 2 = 46.25 min Assumptions: N? © rkm2003 Examples • Example 7.2: Estimate the time required to machine a cast iron surface 250 mm long and 150 mm wide on a shaper with cutting-toreturn ratio of 3/2. Use a cutting speed of 21 m/min, a feed of 2 mm/stroke and a clearance of 25 mm. The available ram strokes on the shaper are: 28, 40, 60 and 90 strokes/min. Also, determine MRR assuming depth of cut as 4 mm. • Solution • Given data: Lj = 250 mm, f = 2 mm/double stroke, w = 150 mm, • c = 25 mm, v = 21 m/ m/min, d = 4 mm • The cutting-to-return ratio of 3/2 gives m = 2/3 © rkm2003 Examples • Given clearance is 25 mm, hence, • L = 250 + 2 × 25 = 300 mm. • We know that (Equation (1)) • SPEED v = NL(1+m)/ 1000 m/min • From the above equation, we find number of double strokes N per minute required as • N = 42 strokes/min © rkm2003 Examples • Nearest available ram strokes is 40 strokes/min. Since calculated value is more than 40, this is chosen. Normally, we should not exceed the specified cutting speed, as it will affect the tool life adversely. Hence, select N = 40 strokes/min. • With a chosen value of N, we cannot use Equation (5) for time calculation. Hence, substituting all the values in Equation (6), we get • t = 150 / (40×2) • = 1.88 minutes © rkm2003