Technological Features in Processing of Conical Lenses

The paper presents the technology of obtaining flat-conical lenses (axicons) by the method of free grinding a work-piece to a flat tool through a layer of abrasive suspension. For this, theoretical and experimental studies of the regularities of stock removal from the base of the cone and its lateral surface have been carried out. The processing modes have been identified that ensure both uniform operation of the flat surface of the part and enhanced removal of the allowance in the edge or central zone of this surface. During the study of the processing of the conical surface, the set-up parameters of the technological equipment have been established, at which there is a minimum deviation of the generatrix of the cone from straightness and maximum productivity of the process. The stages of processing conical lenses are proposed, which allow to assign the optimal sequence of operations in the manufacture of this type of parts from blanks of a cylindrical shape in cases where the ratio of the height of the cone to the diameter of its base H/d £ 0.5. The main stages of processing include: grinding of the bases of cylindrical blanks with maintaining their mutual parallelism with a given accuracy; polishing one of the cylinder bases to achieve the required roughness and deviation from non-flatness; fastening a cylindrical blank to an auxiliary plane-parallel glass plate using molecular cohesion forces; mechanical fastening of a cylindrical work-piece with a collet adapter mandrel for a plane-parallel glass plate; applying the nearest sphere to the second base of the cylindrical blank; drawing a conical surface on the spherical part of a plano-convex lens; grinding and polishing the conical surface to achieve the required roughness and straightness of the cone generatrix. The degree of efficiency of the setup parameters of the machine has been revealed depending on the technological heredity of the work-piece from the point of view of the distribution of the allowance to be removed over the machined surface.

Solution Treatment Process of Haynes 230 Cylindrical Blank Used for Hot Flow Spinning

Hot flow spinning is one of the most effective methods to manufacture the cylindrical parts of nickel-based superalloy. However, crack occurs easily in the hot flow spinning process of Haynes230 alloy when the cylindrical blanks are obtained by forging and wire-electrode cutting billet due to the severe segregation of carbides existed in the microstructure of the Haynes230 forging billet. The solution treatment process of Haynes230 blank is put forward to obtain the cylindrical blank with homogeneous and fine grained microstructure used for hot flow spinning. The influence of solution treatment process on the microstructure and hardness of Haynes 230 was investigated; and the relationship between grain size and solution temperature was analyzed. The results show that the grain size of Haynes230 alloy increases with the increasing of solution temperature and the holding time. The abnormal growth of grains occurs under excessively high solution temperature and long holding time. The grain growth activation energy of Haynes230 is about 296.0kJ/mol. The hardness of Haynes230 alloy decreases with the increasing of solution temperature, but negligibly changes with the holding time. The severe segregation of carbides can be eliminated and the cylindrical blank with homogeneous and fine grained microstructure used for hot flow spinning of Haynes230 alloy can be obtained after solution treatment at 1230°C for 60 min heat preservation.

Die Forming Simulation of PM Parts Based on AMESim

The mathematical model of cylindrical compact simulation is established by using the mathematical model of the net pressure P1 and the loss pressure P2 in AMESim environment, basing on the physical model of the powder metallurgical cylindrical blank. The simulation model of multi-step P/M parts is established by disassembling and transformation of parts, which is successfully introduced to the hydraulic system simulation. The corresponding velocity and displacement curves are obtained by running batch the three parts of B, C, A, following the principle that the speed of different height step mode is equal to the pressing rate. When the piston reaches a certain equilibrium displacement, , , and respectively range from 20 to 100, from 20 to 50, and from 50 to 2000. According to the corresponding suppression curve obtained, corresponding optimized parameters could be got to meet the requirements of the pressing speed with the AMESim optimization function.

Development of a Novel Ablative Composite Tape Layup Technology for Solid Rocket Motor Nozzle and Liquid Engine Liners

Solid rocket motor nozzles and liquid engine throats use ablative composite materials to protect the structures from the extremely severe operating conditions of high temperature, pressure and particle impingement. These ablative nozzle liners are processed from carbon phenolic/silica phenolic prepregs using a complex processing cycle. The process starts from impregnating the fibres with phenolic resin followed by either moulding or wrapping/winding prepreg tapes over metallic mandrels followed by polymerization under pressure. Traditionally, prepreg is cut into straight tapes and wound on mandrels to form the divergents. For throats and convergents, prepreg patterns are cut and stacked for curing. Plies of shape conforming to the development of base cone are cut from the prepreg and wound on the mandrel. After polymerization, the final required configuration is machined from this cylindrical blank after the liners are cured. The new method, described in this paper, replaces the straight-cut prepreg tapes by bias-cut prepreg tapes. These can be used for ablative liners in which the plies are at an angle to the direction of the flow. Bias tapes are cut at 45° to the warp and weft directions of the fabric to the required width and formed to the required frustum of cone. Since the cone is formed from straight cut bias tape, the fibre construction will be uniform around the circumference unlike the pattern cut tape. The efficiency of this process depends on the wrapping ratio which is in turn a function of the diameter, ply angle and tape width. To get the best wrapping ratio, shaped mandrels are used which brings down the material wastage and machining allowances. This paper describes the attempts to develop the Bias wrapping technology for angle wound liners. The details of process trials, challenges faced and how they were overcome, advantages of the process over conventional process etc are explained. Exhaustive material characterization of the material was done. Property comparison and validation of performance in subscale tests and a full scale static test are also discussed. The analysis indicates that this new technology has good potential in replacing the traditional tape-winding technology for rocket motor nozzle liners.

Assessing the Metal Consumption for Manufacturing a Conical Part by Hollow Billet Crimp-Expansion and Sheet Blanks Drawing Crimping

The process of hollow conical forming is described for two schemes: crimp-distribution for hollow billets and stretching from sheet billet with subsequent crimping for cylindrical blank. The item thickness varying was investigated for these schemes. Dependency of technological allowance ratio on crimping coefficient and expansion ration for items allowance was investigated. The effectiveness of stretching from sheet billet with subsequent crimping was proven.

A Study of the Effects of Reversal Cycles in the Gear Rolling Process by Using Finite Element Simulations

The manufacturing of machine components with sustainable and innovative methods is an interesting topic for research. Gears are some components which have complexity in both design and production technology. Therefore applying innovative methods on gear manufacturing can be of interest to industry. One of the most promising production methods for gear wheels is Gear Rolling. The gear wheel is formed during a certain rolling process from a cylindrical blank into the final designed shape. The process of gear rolling with rotational gears is progressing by running several rolling cycles with one, or two dies in contact with a work-piece. A specified rotational speed and radial feed speed is applied to the dies in order to form the required geometry on the blank. In this paper, the authors have simulated the process with the finite element code, DEFORM 3D. Especially the effects of reversal cycles on final gear wheel geometry have been evaluated from the simulations. Different settings for the rotation direction of the dies have been used and the effects are evaluated with specific quality criteria.

Ultra-Precision Machining of Off-Axis Convex Ellipsoidal Surface Using Two Different Accurate Spiral Tool Paths

The off-axis parabolic mirror plays more and more important role in high-tech areas since the advantages of reducing space and improving the quality of imaging. Two ultra-precision manufacturing methods are often applied to machining the off-axis ellipsoidal mirror, which one is revolving the cylindrical blank around the axis of ellipsoidal surface and another one is revolving around the axis of cylindrical surface. But which machining method can produce a better result has no rounded comparisons and analysis according to previous research. In this paper, the tool path generation method is presented and the corresponding tool paths of each manufacturing method for the off-axis ellipsoidal mirror are calculated respectively. The motion characteristics are also analyzed and compared correspondingly. Finally, the effects of diamond tool parameters are further analyzed in theory to avoid the tool interference. The studies processed in this paper provide a theoretical basis of choosing the ultra-precision manufacturing method for the off-axis ellipsoidal mirror and can improve the efficiency and precision of processing.