Manufacturing Various Shapes Manufacturing Processes Outline Milling Slab

Manufacturing Various Shapes Manufacturing Processes

Outline Milling Slab Milling Face Milling End Milling Other Broaching Sawing Machining Gears

Milling – Types of Milling Slab Milling Face Milling End Milling Various Special Operations

Various Milling Tools

Action of a Milling Cutter

Conventional Milling and Climb Milling

Slab Milling Axis of tool rotation is parallel to the workpiece surface Cutters may have straight or helical teeth

Slab Milling Tools

Face Milling Axis of cutter rotation is perpendicular to the workpiece surface Leaves feed marks that vary with the feed rate

Face Milling Tools

End Milling Axis of cutter rotation is usually perpendicular to the workpiece surface Ball mill cutters have hemispherical ends and can be used to mill curved surfaces

End Milling Tools

End Milling Tools (left to right) roughing end mill, centercut end mill, ball mill. Center-cut end mills can be fed into the workpiece like a drill.

End Milling Tools Close-up view of a roughing end mill (left) and a center-cut end mill (right) Result of using a noncenter-cut end mill while feeding into the workpiece; the center has been clogged with wood. A metal workpiece would cause the tool to shatter.

End Milling

Freeform Surfaces Example of a surface that can be milled with a computer-controlled ball mill

Milling Freeform Surfaces

Milling and Feed Marks

Milling and Feed Marks The difference in feed marks between a larger cutting increment (left) and a smaller cutting increment (right).

Other Milling Operations and Tools

Milling Feed and Speed V = πDN V = Cutting speed, ft/min or m/min D = Cutter Diameter N = RPM of the cutter f= v/Nn f = Feed, in/tooth or mm/tooth v = Linear speed of the workpiece into the cutter N = RPM of the cutter n = Number of teeth on the cutter edge Make sure to account for unit differences.

Milling Feed and Speed

Milling Feed and Speed Example: Workpiece Material: titanium alloy Cutter Diameter: 3 in. Cutting Teeth: 10 Conditions: general V(titanium, general) = 175 -200 ft/min (from table) = 2100 -2400 in/min N = V/πD N = (2100 -2400)/(π*3) = 223 -255 RPM f(titanium, general) =. 005 -. 006 in/tooth (from table) v = Nnf v = 223*10*(. 005 -. 006) = 11. 2 -13. 4 in/min

Milling Material Removal Rate MRR = wdv w = Width of the cut d = Depth of the cut v = Linear speed of the workpiece into the cutter

Milling Material Removal Rate Example: Cut Width: 4 in Cut depth: . 2 in Workpiece Speed: 11. 2 in/min MRR = wdv MRR = 4*. 2*11. 2 = 8. 96 in 3/min

Milling in General Design Considerations: - Use standard milling cutters; avoid expensive special cutters - Use chamfers instead of radii (fillets) - Avoid internal cavities and pockets with sharp corners - Use materials rigid enough to minimize clamping and cutting deflections

Milling in General Avoiding Vibration and Chatter: - Mount cutters close to the spindle base to reduce tool deflection - Use rigid tool holders and fixtures - If vibration and chatter occur, change the tool shape and use cutters with fewer cutting teeth or random tooth spacing

Broaching Used to machine internal and external surfaces of varying shapes Produces parts with fine surface finish and dimensional accuracy

Broaching Machine

Cutting Action of a Broach

Broaches

Broaching Design Considerations: - Design parts so that they can be clamped securely in broaching machines and withstand cutting forces - Avoid blind holes, sharp corners, dovetail splines and large flat surfaces - Use chamfers instead of round corners when possible

Sawing Used to separate large pieces of material by removing the connecting material Wastes little material because the width of the cut is thin

Sawing

Machining Gears are cut from gear blanks (disks) The following may be used to cut gear teeth: - A form cutter - Broaches (often for internal teeth) - A single-point cutting tool guided by a template - A pinion-shaped cutter - A rack-shaped cutter - A hob

Machining Gears

Summary Many types of complicated and irregular shapes can be created by milling, broaching and sawing Gears can be shaped by these and similar means