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This study considers the operation assignment and capacity allocation problem in flexible manufacturing systems. A set of operations is selected to be processed and assigned to the machines together with their required tools. The purchase or usage of the required tools incurs a cost. The machines have scarce time and tool magazine capacities. The objective is to maximize the total weight of the assigned operations minus the total tooling costs. We use Lagrangean relaxation approach to obtain upper and lower bounds on the optimal objective function values. The computational experiments show that our approach provides near optimal bounds in reasonable solution times. Journal of the Operational Research Society (2010) 61, 872-877. doi: 10.1057/jors.2009.19 Published online 20 May 2009 Keywords: Lagrangean relaxation; flexible manufacturing systems; tool assignment; computer numerically controlled machines

An algorithm is developed for the execution of motions on the computer numerical control (CNC) hypoid generating machine using the relations on the cradle-type machine. The algorithm is based on the condition that, since the tool is a rotary surface and the pinion/gear blank is also related to a rotary surface, it is necessary to ensure the same relative position of the head cutter and the pinion on both machines. The algorithm is applied for the execution of motions on the CNC hypoid generator for the manufacture of spiral bevel gears, based on the machine tool setting variation on the cradle-type hypoid generator conducted by optimal polynomial functions up to the fifth-order. By using the corresponding computer program, the motion graphs of the CNC hypoid generator are determined for the manufacture of spiral bevel gears, based on the optimal variation in the velocity ratio in the kinematic scheme and on the variation in the cradle radial setting on a cradle-type generator. [DOI: 10.1115/1.4001130]

Straight bevel gears are usually manufactured with various machines and systems, and the tooth profiles are produced by grinding or machining by means of a tool with many cutting edges. In recent years, the straight bevel gear has been manufactured by an end mill using a computer numerical control (CNC) milling machine because the use of the auxiliary apparatus, special cutters, and special machine tools is not needed. Using this method, the gear manufacturing with high accuracy is an important problem. In this paper, the coordinate measurement of the straight bevel gear manufactured in this method is performed and the gear accuracy is evaluated. The tooth profiles of the straight bevel gear generated by a quasi-complementary crown gear instead of a conventional complementary crown gear are introduced. For this study, the tooth profiles of the straight bevel gear were modeled using a 3D computer-aided design system and the gear was manufactured by an end mill using a CNC milling machine based on a computer-aided manufacturing process. Afterward, the coordinates of many points on the gear tooth surfaces were measured at random using a coordinate measuring machine. This coordinate measurement provides the information about the factors related to the gear accuracy such as pressure angle, tooth angle error, workpiece setting angle, apex to back, and so on. Therefore, the values of the above factors were estimated and were compared with the theoretical ones, respectively. [DOI: 10.1115/1.2988480] Keywords: accuracy, straight bevel gear, end mill, CNC milling machine, coordinate measurement

The major advantages of a new plasma-assisted fuel reformation system are its cost effectiveness and technical efficiency. Applied Plasma Technologies has proposed its new highly efficient hybrid-type plasma-assisted system for organic fuel combustion and gasification. The system operates as a multimode multipurpose reactor in a wide range of plasma feedstock gases and turndown ratios. This system also has convenient and simultaneous feeding of several reagents in the reaction zone such as liquid fuels, coal, steam, and air. A special methodology has been developed for such a system in terms of heat balance evaluation and optimization. This methodology considers all existing and possible energy streams, which could influence the system's efficiency. The developed hybrid-type plasma system could be suitable for combustion applications, mobile and autonomous small- to mid-size liquid fuel and coal gasification modules, hydrogen-rich gas generators, waste-processing facilities, and plasma chemical reactors. Index Terms--Coal, combustion, liquid fuel, plasma, reformation, waste processing.

The method for loaded tooth contact analysis is applied for the investigation of the combined influence of machine-tool settings for pinion teeth finishing and misalignments of the mating members on load distribution and transmission errors in mismatched spiral bevel gears. By using the corresponding computer program, the influence of pinion's offset and axial adjustment error, angular position error of the pinion axis, tooth spacing error, and machine-tool setting correction for pinion teeth finishing, on tooth contact pressure, tooth root stresses, and angular displacement of the driven gear member from the theoretically exact position based on the ratio of the numbers of teeth is investigated. On the basis of the obtained results, the optimal combination of machine-tool settings is determined. By the use of this set of machine-tool settings, the maximum tooth contact pressure and transmission errors can be significantly reduced. However, in some cases, by the use of appropriate machine-tool settings for the reduction of tooth contact pressure, the angular displacement of the driven gear increases. Therefore, different optimized combinations of machine-tool settings for pinion tooth finishing for the reduction of the sensitivity of gears to misalignments in regard to maximum tooth contact pressure and transmission errors should be applied. By the use of the combination of machine-tool settings to reduce the sensitivity of gears to misalignments in regard to transmission errors, a slight reduction of maximal tooth contact pressure is achieved, too. [DOI: 10.1115/1.2936903]

A method for rapid computer numerically controlled (CNC) machining is being developed in an effort to automatically create functional prototypes and parts in a wide array of materials. The method uses a plurality of simple two-and-a-half-dimensional (2 1/2-D) toolpaths from various orientations about an axis of rotation in order to machine the entire surface of a part without refixturing. It is our goal to automatically create these toolpaths for machining and eliminate the complex planning traditionally associated with CNC machining. In this paper, we consider a problem that arises in automating this process--visibility to the surface of a model that is rotated about a fourth axis. Our approach involves slicing the computer-aided design (CAD) model orthogonal to the axis of rotation. The slice geometry is used to calculate two-dimensional visibility maps for the set of polygons on each slice plane. The visibility data provides critical information for determining the minimum number and orientation of 2 1/2-D toolpaths required to machine the entire surface of a part. [DOI: 10.1115/1.2039100] Keywords: visibility, rapid prototyping, machining, slice geometry

Miniaturized machine tools, referred to as mesoscale machine tools (mMTs) henceforth, have been proposed as a way to manufacture micro/mesoscale mechanical components. A thorough study of the dynamic behavior of the mMT is required for the successful development of its machine structure. This paper demonstrates the development of an mMT, the performance evaluation of its mesoscale milling process, and the characterization of its dynamic behavior. The mMT is developed by using an air turbine spindle and three piezoelectric linear stages, and its volumetric size is 150 x 70 x 140 mm. A series of micro/mesoscale milling experiments are conducted, and the performances in the developed mMT testbed are evaluated. The dynamic characteristics of the mMT can be different from those of conventional machine tools because the mMT is a miniaturized structure and comprises different machine components. Therefore, the effect of the miniaturization of a structure on the change of its dynamic behavior, called scaling law of the structural dynamics, is studied numerically and experimentally. The dynamic characteristics of the developed mMT that are estimated from the scaling law of the structural dynamics are much different from those obtained from an experimental modal analysis, and the flexible joints of the developed mMT are mainly responsible for this significant difference. Therefore, the joint dynamics of the mMT are studied by introducing an equivalent lumped parameter model thus enabling simple identification of the joint dynamics and the effective modification of its critical joints to enhance a machining performance. [DOI: 10.1115/1.2123007] Keywords: mesoscale machine tool (mMT), scaling law, structural dynamics, joint dynamics, lumped parameter model, experimental modal analysis, finite element (FE) method

A study conducted to find a set of efficient points for a bicriteria problem on a single CNC machine for minimizing the manufacturing cost and minimizing the makespan, by determining processing times under controllable conditions is presented. The results of the study demonstrate how the process planning and scheduling decisions can be integrated.

Abstract This paper describes error compensation methods for parallel kinematics machines (PKMs). First, joint errors and link deformations caused by external forces and heat are discussed. Because a linear scale [...]

A method for the determination of optimal machine tool setting for manufacturing modified (mismatched) hypoid gears based on improved load distribution and reduced transmission errors is presented. The applied load distribution calculation is based on the conditions that the total angular position errors of the gear teeth being instantaneously in contact under load must be the same, and along the contact line of every tooth pair instantaneously in contact, the composite displacements of tooth surface points--as the sums of tooth deformations, geometrical surface separations, gear body bending and torsion, deflections of the supporting shafts, misalignments, and composite tooth errors--should correspond to the angular position of the gear. The tooth deformations consists of the bending and shearing deflections of gear teeth and of the local contact deformations of the mating surfaces. The tooth deflections are calculated by the finite element method. As the equations governing the load sharing and load distribution are nonlinear, an approximate and iterative technique is used to solve this system of equations. The method is implemented by a computer program. Using the program that was developed the influence of machine tool setting parameters for pinion manufacture on maximum tooth contact pressure, load distribution factor, and transmission errors is investigated. By successively choosing the optimal value for every machine tool setting parameter, and by applying the optimal set of these parameters, the maximum tooth contact pressure is reduced by 5.8%, the load distribution factor by 5.9%, and the angular position error of the driven gear by 65.4%, in regard to the hypoid gear pair manufactured by the machine tool setting determined by the commonly used method.

Research describes the usage of titanium nitride coated solid carbide drills to evaluate through-tool coolant drilling of aluminum/silicon carbide metal matrix composite materials. Data indicate that the technique is superior in terms of tool wear, cutting forces, surface finish, and burr heights compared to conventional coolant or dry drilling.

Research evaluates the machining performance of a new powder metallurgy material, MnX along with three other conventional materials. Test data reveal that the new material performed superiorly in terms of cutting forces, tool wear, and surface finish especially at higher cutting speeds.

Numerous control strategies have been developed to compensate for the effects caused by friction in linear guideways of feed-drive systems. For ultraprecision machining applications, these offer a wide variety of powerful, nonlinear algorithms, but generally use rather complex computing algorithms, exhausting system resources. By the use of a special sophisticated aerostatic bearing technology, no friction and, therefore, no stick-slip exist within linear guideways. This entails a lack of damping in the feed direction, which is a considerable setback for the classic cascaded control concept usually implemented in commercially available servo systems. This paper presents an approach to obtain superior behavior of the controlled system by combining the cascaded concept with a control design in the state space. Both simulation and implementation results are presented, together with tuning methods and aspects. Index Terms: Air bearing, automatic tuning, cascade control, machine-tool control, state feedback, ultraprecision manufacturing.

Military planes are one of the most challenging aircrafts to build for engineers as the passing of the time makes their requirements more complicated and far more advanced. One fine example of this is the building of British Aerospace's Eurofighter, which requires tighter tolerances and higher operating speeds. These demands have driven engineers to use fewer and more complicated parts, which in turn heightens the pressure on tooling and machining operations.

We present a distributed approach to tool management in flexible manufacturing systems (FMS). Tool sharing among cells in FMS enables greater utilization of tool resources, but requires greater coordination of tool use by different cells, especially when tooling requirements change unexpectedly. We discuss how concepts from distributed artificial intelligence (DAI) such as negotiation can provide solution methods. In particular, we propose polite methods by which an agent can solve such a problem through negotiation with other agents. We present simulation results for a tool scheduling problem in which polite tool sharing is used for handling unexpected "rush" jobs. Index Terms - Distributed artificial intelligence (DAI), flexible manufacturing systems, rescheduling, tool scheduling.