Abrasive-Flow Machining

Transcription

1 1 Polishing Using Magnetic Fields Figure Schematic illustration of polishing of balls and rollers using magnetic fields. (a) Magnetic float polishing of ceramic balls. (b) Magnetic-field-assisted polishing of rollers. Source: R. Komanduri, M. Doc, and M. Fox. 10b.30 Abrasive-Flow Machining Figure Schematic illustration of abrasive flow machining to deburr a turbine impeller. The arrows indicate movement of the abrasive media. Note the special fixture, which is usually different for each part design. Source: Extrude Hone Corp. 10b.31

2 2 Robotic Deburring Figure A deburring operation on a robot-held die-cast part for an outboard motor housing, using a grinding wheel. Abrasive belts (Fig ) or flexible abrasive radial-wheel brushes can also be used for such operations. Source: Courtesy of Acme Manufacturing Company and Manufacturing Engineering Magazine, Society of Manufacturing Engineers. 10b.32 Economics of Grinding and Finishing Operations Figure Increase in the cost of machining and finishing a part as a function of the surface finish required. This is the main reason that the surface finish specified on parts should not be any finer than necessary for the part to function properly. 10b.33

3 3 Examples of Parts Made by Advanced Machining Processes (a) (b) Figure 26.1 Examples of parts made by advanced machining processes. These parts are made by advanced machining processes and would be difficult or uneconomical to manufacture by conventional processes. (a) Cutting sheet metal with a laser beam. Courtesy of Rofin-Sinar, Inc., and Manufacturing Engineering Magazine, Society of Manufacturing Engineers. (b) Microscopic gear with a diameter on the order of 100 µm, made by a special etching process. Courtesy of Wisconsin Center for Applied Microelectronics, University of Wisconsin-Madison. 10b.34 T A B L E P r o c e s s C h e m i c a l m a c h i n i n g ( C M ) E l e c t r o c h e m i c a l m a c h i n i n g ( E C M ) E l e c t r o c h e m i c a l g r i n d i n g ( E C G ) E l e c t r i c a l - d i s c h a r g e m a c h i n i n g ( E D M ) W i r e E D M L a s e r - b e a m m a c h i n i n g ( L B M ) E l e c t r o n - b e a m m a c h i n i n g ( E B M ) W a t e r - j e t m a c h i n i n g ( W J M ) A b r a s i v e w a t e r - j e t m a c h i n i n g ( A W J M ) A b r a s i v e - j e t m a c h i n i n g ( A J M ) General Characteristics of Advanced Machining Processes C h a r a c t e r i s t i c s S h a l l o w r e m o v a l ( u p t o 1 2 m m ) o n l a r g e f l a t o r c u r v e d s u r f a c e s ; b l a n k i n g o f t h i n s h e e t s ; l o w t o o l i n g a n d c o s t ; s u i t a b l e f o r l o w p r o d u c t i o n r u n s. C o m p l e x s h a p e s w i t h d e e p c a v i t i e s ; h i g h e s t r a t e o f m a t e r i a l r e m o v a l a m o n g n o n t r a d i t i o n a l p r o c e s s e s ; e x p e n s i v e t o o l i n g a n d e q u i p m e n t ; h i g h p o w e r c o n s u m p t i o n ; m e d i u m t o h i g h p r o d u c t i o n q u a n t i t y. C u t t i n g o f f a n d s h a r p e n i n g h a r d m a t e r i a l s, s u c h a s t u n g s t e n - c a r b i d e t o o l s ; a l s o u s e d a s a h o n i n g p r o c e s s ; h i g h e r r e m o v a l r a t e t h a n g r i n d i n g. S h a p i n g a n d c u t t i n g c o m p l e x p a r t s m a d e o f h a r d m a t e r i a l s ; s o m e s u r f a c e d a m a g e m a y r e s u l t ; a l s o u s e d a s a g r i n d i n g a n d c u t t i n g p r o c e s s ; e x p e n s i v e t o o l i n g a n d e q u i p m e n t. C o n t o u r c u t t i n g o f f l a t o r c u r v e d s u r f a c e s ; e x p e n s i v e e q u i p m e n t. C u t t i n g a n d h o l e m a k i n g o n t h i n m a t e r i a l s ; h e a t - a f f e c t e d z o n e ; d o e s n o t r e q u i r e a v a c u u m ; e x p e n s i v e e q u i p m e n t ; c o n s u m e s m u c h e n e r g y. C u t t i n g a n d h o l e m a k i n g o n t h i n m a t e r i a l s ; v e r y s m a l l h o l e s a n d s l o t s ; h e a t - a f f e c t e d z o n e ; r e q u i r e s a v a c u u m ; e x p e n s i v e e q u i p m e n t. C u t t i n g a l l t y p e s o f n o n m e t a l l i c m a t e r i a l s t o 2 5 m m a n d g r e a t e r i n t h i c k n e s s ; s u i t a b l e f o r c o n t o u r c u t t i n g o f f l e x i b l e m a t e r i a l s ; n o t h e r m a l d a m a g e ; n o i s y. S i n g l e o r m u l t i l a y e r c u t t i n g o f m e t a l l i c a n d n o n m e t a l l i c m a t e r i a l s. C u t t i n g, s l o t t i n g, d e b u r r i n g, d e f l a s h i n g, e t c h i n g, a n d c l e a n i n g o f m e t a l l i c a n d n o n m e t a l l i c m a t e r i a l s ; m a n u a l l y c o n t r o l l e d ; t e n d s t o r o u n d o f f s h a r p e d g e s ; h a z a r d o u s. P r o c e s s p a r a m e t e r s a n d t y p i c a l m a t e r i a l r e m o v a l r a t e o r c u t t i n g s p e e d m m / m i n. V : d c ; A : A / m m 2 ; m m / m i n, d e p e n d i n g o n c u r r e n t d e n s i t y. A : 1 3 A / m m 2 ; T y p i c a l l y 2 5 m m 3 / s p e r A. V : ; A : ; T y p i c a l l y m m 3 / m i n. V a r i e s w i t h m a t e r i a l a n d t h i c k n e s s m / m i n. 1 2 m m 3 / m i n. V a r i e s c o n s i d e r a b l y w i t h m a t e r i a l. U p t o 7. 5 m / m i n. V a r i e s c o n s i d e r a b l y w i t h m a t e r i a l. 10b.35

4 4 Chemical Milling Figure 26.2 (a) Missile skin-panel section contoured by chemical milling to improve the stiffness-to-weight ratio of the part. (b) Weight reduction of space launch vehicles by chemical milling aluminum-alloy plates. These panels are chemically milled after the plates have first been formed into shape by processes such as roll forming or stretch forming. The design of the chemically machined rib patterns can be modified readily at minimal cost. Source: Advanced Materials and Processes, December ASM International. 10b.36 Chemical Machining Figure 26.3 (a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process. (b) Stages in producing a profiled cavity by chemical machining; note the undercut. 10b.37

5 5 Range of Surface Roughnesses and Tolerances 10b.38 Chemical Blanking and Electrochemical Machining Figure 26.5 Various parts made by chemical blanking. Note the fine detail. Source: Courtesy of Buckbee-Mears St. Paul. Figure 26.6 Schematic illustration of the electrochemicalmachining process. This process is the reverse of electroplating, described in Section b.39

6 6 Examples of Parts Made by Electrochemical Machining Figure 26.7 Typical parts made by electrochemical machining. (a) Turbine blade made of a nickel alloy, 360 HB; note the shape of the electrode on the right. Source: ASM International. (b) Thin slots on a 4340-steel rollerbearing cage. (c) Integral airfoils on a compressor 10b.40 disk. Biomedical Implant (a) (b) Figure 26.8 (a) Two total knee replacement systems showing metal implants (top pieces) with an ultrahigh IML molecular 451 weight polyethylene insert (bottom pieces). (b) Cross-section 10b.41 of the ECM process as applied to the metal implant. Source: Biomet, Inc.

7 7 Electrochemical Grinding Figure 26.9 (a) Schematic illustration of the electrochemical-grinding process. (b) Thin slot produced on a round nickel-alloy tube by this process. 10b.42 (a) Electrical-Discharge Machining (b) (c) Figure (a) Schematic illustration of the electrical-discharge machining process. This is one of the most widely used machining processes, particularly for die-sinking operations. (b) Examples of cavities produced by the electrical-discharge machining process, using shaped electrodes. Two round parts (rear) are the set of dies for extruding the aluminum piece shown in front (see also Fig. 15.9b). Source: Courtesy of AGIE USA Ltd. (c) A spiral cavity produced by EDM using a slowly rotating electrode, similar to a screw thread. Source: American Machinist. 10b.43

8 8 Examples of EDM Figure Stepped cavities produced with a square electrode by the EDM process. The workpiece moves in the two principal horizontal directions (x-y), and its motion is synchronized with the downward movement of the electrode to produce these cavities. Also shown is a round electrode capable of producing round or elliptical cavities. Source: Courtesy of AGIE USA Ltd. Figure Schematic illustration of producing an inner cavity by EDM, using a specially designed electrode with a hinged tip, which is slowly opened and rotated to produce the large cavity. 10b.44 Source: Luziesa France. Wire EDM Figure (a) Schematic illustration of the wire EDM process. As much as 50 hours of machining can be performed with one reel of wire, which is then discarded. (b) Cutting a thick plate with wire EDM. (c) A computer-controlled wire EDM machine. Source: Courtesy of AGIE USA Ltd. (b) (c) 10b.45

9 9 10b.46 Laser-Beam Machining Figure (a) Schematic illustration of the laser-beam machining process. (b) and (c) Examples of holes produced in nonmetallic parts by LBM. 10b.47

10 10 General Applications of Lasers in Manufacturing TABLE 26.2 Application Laser type Cutting Metals PCO2, CWCO2, Nd : YAG, ruby Plastics CWCO2 Ceramics PCO2 Drilling Metals PCO2, Nd : YAG, Nd : glass, ruby Plastics Excimer Marking Metals PCO2, Nd : YAG Plastics Excimer Ceramics Excimer Surface treatment, metals CWCO2 Welding, metals PCO2, CWCO2, Nd : YAG, Nd : glass, ruby Note: P pulsed, CW continuous wave. 10b.48 Electron-Beam Machining Figure Schematic illustration of the electron-beam machining process. Unlike LBM, this process requires a vacuum, so workpiece size is limited to the size of the vacuum chamber. 10b.49

11 11 Water-Jet Machining (a) (b) Figure (a) Schematic illustration of water-jet machining. (b) A computer-controlled, water-jet cutting machine cutting a granite plate. (c) Examples of various nonmetallic parts produced by the water-jet cutting process. Source: Courtesy of Possis Corporation. 10b.50 Abrasive-Jet Machining Figure Schematic illustration of the abrasive-jet machining process. 10b.51