Improved Methods for the Prediction of Chatter in Turning, Part 2. Determination of Cutting Process Parameters

pp. 12-20. (Feb 1990). The dynamics of the structure of a lathe at the cutting point are directly identified under normal machining operation using an improved version of a method originally proposed by H. Opitz and H. Weck. The improved method is based on the interrupted cutting of a specially designed, surface-modulated workpiece that provides a strong, broadband excitation. This interrupted cutting has been theoretically shown to permit the identification of the structure's dynamics from input-output measurements, despite the intrinsic coupling of the structure with the cutting process during machining. All three components of the cutting force and the tool's acceleration are measured simultaneously. (Edited author abstract) 25 Refs. 49, I. E. Minis, E. B. Magrab, I. O. Pandelidis, "Improved Methods for the Prediction of Chatter in Turning, Part 2. Determination of Cutting Process Parameters," Journal of Engineering for Industry, Transactions ASME. 112(1), pp. 2127. (Feb 1990). The dynamics of the metal cutting process are identified by a new and simple experimental method that permits the direct determination of the cutting transfer functions from input-output measurements. A specially designed stiff force dynamometer rigidly mounted to the machine tool's turret is used for the measurement of the cutting force. An external force is applied to the base plate of the dynamometer in such a way that the measurements of both the tool's displacement and the corresponding cutting force are uncoupled from the influence of the machine tool structure's dynamics. The cutting transfer functions are obtained in the vicinity of the structure's first resonance, under a wide range of cutting conditions. (Author abstract) 21 Refs. 50, I. E. Minis, E. B. Magrab, I. O. Pandelidis, "Improved Methods for the Prediction of Chatter in Turning, Part 3. A Generalized Linear Theory," Journal of Engineering for Industry, Transactions ASME, 112(1), pp. 28-35. (Feb 1990). The linear theory of chatter has been generalized to any machining configuration without a priori assumptions on either the direction ol7 the cutting force or the modal directions of the machine tool structure. Furthermore, the effects of the tool's orientation on the stability of the machining system are directly expressed by its closed loop characteristic equation. Using experimental measurements for the dynamics of both the machine tool structure and the cutting process obtained previously under actual cutting conditions, the proposed theory is applied to two cases of orthogonal turning. The resulting predictions of the critical depth of cut are in excellent agreement with the measurements of actual chatter for a wide range of cutting conditions. (Author abstract) 14 Refs. 51, A. M. Dolgikh, "Improvement of Electrolytic Diamond Cutting (combined) M e t h o d s , " Soviet Journal o j Superhard Materials, 11(6), pp. 66-70. (1989). The technological possibilities of combined schemes of electrolytic diamond cutting are analyzed. It is established that cutting with an ultrafine tool with an internal cutting edge does not give the required effect. Cutting with a tool having a cutting edge on the periphery with centrifugal injection of the medium is more efficient. A new scheme of cutting with such a wheel with rotary gas saturation of the medium is proposed. A mathematical model for control of the oscillatory motion of the rotor-pendulum is given. It is concluded that the oscillatory motion in the cathode zone ensures that the catting process is fairly efficient and involves the minimum consumption of diamond and electrical energy: (Author abstract) 3 Refs~ 52, I. Fukumoto, T. Ayabe, "Improvement of Ground Surface Roughness in AI-Si Alloys," Wear, 137(2), pp. 199209. (May 1990). A1-Si alloys are difficult materials to cut, having nodules of silicon (hard phase) distributed at random over a matrix of aluminum (soft phase). These alloys having a silicon content over 11%, to include eutectic and hypereutectic alloys, have proven to be very hard to wear down, making them potentially useful in precision-engineered instruments and machines and for pistons in automobiles. However, the grinding process used to give these articles a highly polished surface finish must be considered owing to the great difficulty in grinding these types of alloys. AI-Si alloys containing 11-26 wt.% Si were used in this study to ascertain the grinding characteristics of these alloys over a range of differing parameters. Different grinding wheels and different fluids were used in the grinding process to determine the most efficient method of grinding AI-Si alloys. Power spectrum analysis was used to determine the roughness of the materials after the grinding process, and an autoregression model was adapted to the power spectrum analysis data to calculate roughness curves for each of the alloys. (Edited author abstract) 9 Refs. 53, P. De Donato, J. M. Cases, M. Kongolo, L. Michot, A. Burneau, "Infrared Investigation of A m y l x a n t h a t e Adsorption on Galena. Influence of Oxidation, pH and Grinding," Colloids and Sulfaces, 44(207-228), (Mar 1990). A dynamic method (chromatographic saturation front analysis), batch adsorption tests and Fourier-transform infrared diffuse reflectance spectroscopy have been used to investigate the adsorption/abstraction of amylxanthate on galena surfaces, The galena was either pretreated in order to obtain 'clean' galena (i.e. unoxidized), and then oxidized by dissolved oxygen in aqueous solutions, or wet ground under controllable conditions (pH 4 and natural pH 9.3). The amount of amylxanthate abstracted is drastically reduced, if dissolved oxygen is eliminated. Air during wet grinding provokes an oxidation of the galena surface. Acid wet grinding favours the adsorption/abstraction of xanthate. (Edited author abstract) 27 Refs, 54, E. J. Danielewicz, G. H. Sherman, A. Sona, "Innovative Optics for Shaping and Focusing Industrial CO 2 Lasers," SPIE - Beam Diagnostics and Beam Handling Systems, Vol 1024, Hamburg (Germany, F.R.), 21-22 Sep 1988. pp. 150158. Society of Photo-Optical Instrumentation Engineers, Bellingham, WA (USA). The recently developed capability to diamond turn ZnSe, has led to a number of useful optical components for high power CO2 lasers which were not previously available on a cost effective basis. For example, aspheric lenses can provide tighter focused spots; axicons can convert solid beams to donut shaped beams and vice-versa, or can be used as beam integrators; multifaceted prisms and pyramids can easily divide a beam into several parallel beams. This paper explains the working principles of these diamond-turned optics and gives examples of material processing applications. 55, I. Uchida, T. Kohno, T. Onishi, Y. Okazaki, N. Ozawa, K. Takeuchi, "In.process Measurement a n d WorkpieceReferred Form Accuracy Control. II. The Application of K-HIPOSS and a Parallel Leaf-spring Micro-tool Servo," J. Jpn. Soc. Precis. Eng. (Japan), 56(1), pp. 134-9. (Jan. 1990). For part.1 see ibid., 54(8), pp. 1463 (1988). Following the precision machining method with a control system (workpiece-referred form accuracy control: WORFAC) proposed in the previous part, the system and an experiment with an in-process measurement sensor, K-HIPOSS, and a parallel leaf-spring micro-toot servo are described. Compared to the standard HIPOSS model, K-HIPOSS features a long working distance and a wide dynamic range

72

J A N U A R Y 1991 VOL 13 NO 1