Standard Grinding Wheel Research Articles

Investigation of Technological Parameters for Machining Toroidal Section of Solid Ceramic End Mills

Solid ceramic mills are a promising technological solution for cutting heat-resistant materials. Although nanostructured cutting ceramics has a number of valuable physical and mechanical properties providing high operational performance of mills, it has low strength. The design of a solid ceramic mills is formed by smooth surfaces without stress concentrators to ensure operability and to reduce the probability of failure. The most important structural element of solid ceramic end mill is a helical groove with a negative rake angle needed to increase surface strength. This groove can be machined with standard grinding wheels of type 1A1 or 1V1. However, the application of grinding wheels of a standard shape requires the use of reduced cutting parameters to prevent chipping on the forming sections of the cutter. Chipping can be caused by too short length of the contact line and the stress concentration at the end point of the profile of the grinding wheel, which is typically fully responsible for shaping the front surface and its transition to the tooth back. In this paper, in order to increase the contact line, we develop a new approach to designing grinding wheels for machining helical grooves of solid mills and determining rational technological and operational parameters for there use. A new approach is developed based on the fundamental principles of analytical geometry and linear algebra, numerical methods and basic axioms of the shaping theory. In this study, we have identified the key relationships between parameters determining the position of the grinding wheel relative to the workpiece and the geometrical parameters of a solid ceramic mills. The developed approach allowing to determine the specific design of the grinding wheel, depending on the initial parameters of the mill and the trajectory of the axis of the wheel relative to the mill, was implemented in the MathCAD environment.

On the use of grains recovered from spent vitrified wheels in resinoid applications

Vitrified grinding wheels are used in various end applications. They are easy to dress and have better mechanical properties. In general, grinding wheels are used till the stub portion. After usage, this stub portion is discarded as waste. Grains in this portion are fresh. Recovering and reusing the grain in the stub portion are both economically and environmentally beneficial. This work deals with the recovery and reuse of abrasive grains from vitrified brown alumina grinding wheel rejects. Grains are recovered using mechanical crushing processes. The recovered grains are used for production of resinoid cylindrical grinding wheel of 350 mm outer diameter. Performance of this grinding wheel was compared with standard grinding wheel of brown alumina grain in a CNC cylindrical grinding machine. The experiment was conducted by varying three feed rates (0.25, 0.5, and 1 mm/min). The trial wheel exhibits lower wheel wear and higher grinding ratio in all feed rates, without any loss in material removal rate. The difference in performance of the grinding wheel is correlated to the difference in toughness of the grains. It is shown that grains from vitrified rejects of brown alumina can be recovered and advantageously used in resinoid applications. This helps in reusing the otherwise wasted abrasive, thereby reducing pollution to the environment.

Способ затылования резьбовых фрез

The paper presents a form-relieving method for thread mill teeth by means of a grinding wheel rotated about two axes, which significantly simplifies design process for tool manufacturing, since combining rotation angles makes it possible to use the same standard grinding wheel to profile thread mills of several size classes, accounting for acceptable accuracy class for the thread being processed. The algorithm and software proposed, based on the mathematical technique we developed, allow the user to compute the grinding wheel positioning angles to obtain the desired relief angles for a thread mill. We present an example of computing the grinding wheel rotation angles for a set of input data

Simulation of thermal strength of the process of flat grinding of workpieces in intermittent circles

The present article is concerned with numerical schemes of the radial Py and the tangential Pz components of the grinding pressure and with the average contact temperature T, °С. These characteristics give an opportunity to assess the level of the thermal power strain at every path of the operational cycle of the flat pendulum grinding using a standard grinding wheel (SW), an intermittent grinding wheel (IGW) and a composite grinding wheel (CGW). Value forecasting of forces Py,pz and the temperature T will make it possible to manage the grinding process and will give the opportunity to avoid the defects precipitation at the grinding finish of the workpiece.

A Novel Method of Twist Drill Fluting Fulfilling Required Web Thickness and Rake Angle

As substitute of the meshing theory based fluting method, other analytical, machining movement simulation or empirical method are developed in last decades. Currently, a kind of flute prevails. It is ground by using 1V1/1A1 standard grinding wheel and should fulfil requirements of designated web thickness and radial rake angle. This paper presents a novel method by straightforwardly determining install position of the grinding wheel. Based on the relative movement with variables’ parameterization, equations to keep web thickness are firstly derived. Then, a family of flute cross-sectional curves is computed automatically with respect to grinding process parameters and wheel geometry. The calculation process is characterized by concise in principle and easy to use. Its validity is verified by good agreement between the results computed and manufactured example.

A new algorithm to solve the grinding wheel profile for end mill groove machining

Groove is one of the key structures of end mills. Some of them could be machined by standard grinding wheels (1A1 or 1V1 type), some others must design new wheel profiles. Based on the enveloping and analytic geometry theories, a novel algorithm was proposed to calculate the wheel profiles for special groove machining. The machining process was analyzed, the contact line principles were discussed, and the calculation procedure was detailed. In addition, the algorithm was implemented on a personal computer by using the MATLAB programming language. Therefore, the desired wheel profile could be computed automatically with four input parameters, namely, the groove lead, the wheel axial vector, the point coordinates on the wheel axis, and the discrete points on the groove profile (or groove profile expression). The proposed algorithm and the corresponding program were finally verified by three different examples. The results demonstrated good agreements with the practical wheel profiles.

A novel composite diamond-containing dispersed material of natural and synthetic diamonds powders and abrasive tools made of it

A two-stage process of producing a novel composite material based on fine-dispersed powders of natural diamonds and mesh grinding powders of synthetic diamonds. At the first stage of producing the components mixture is compacted and at the second stage it is sintered in a gas-thermal reactor of the physicochemical synthesis plant at a temperature of 1100–1200°C and below ambient pressure in the methane atmosphere. The values of the morphometric characteristics and the uniformity of abrasive powders in these characteristics produced from the new diamond-containing material, their physico-mechanical and electrophysical properties were studied. The results of the use of these composite powders in grinding wheels for machining a hard alloy are discussed. A substitution of powders of the new composite material for synthetic diamond mesh powders in the cutting layer of a standard grinding wheel makes it possible to essentially (more than by a factor of 3) increase the wear resistance of the tool.

A novel approach to determination of wheel position and orientation for five-axis CNC flute grinding of end mills

In practice, the flutes of end mills are ground using CNC grinding machines via controlling the grinding wheel’s position and orientation to guarantee the designed flute parameters including rake angle, flute angle, helix angle, and core radius. However, for the previous researches, the designed flute profile was ground via building a specific grinding wheel with a free-form profile using two-axis CNC grinder. And, the free-form grinding wheel will greatly increase the manufacturing cost, which is too complicated to implement in practice. In this research, the flute-grinding processes were developed with a standard grinding wheel via five-axis CNC grinding operations. The mathematical representation of machined flute parameters was deduced in terms of the grinding wheel’s position and orientation. The geometrical constraints to avoid interference and abnormal flute profile for the five-axis CNC fluting were first developed in this work. Finally, the difference between the designed flute parameters and the machined flute parameters were formulated as a constrained optimization problem so as to determine the wheel’s position and orientation. The set of effective initial points for this optimization model was found mainly distributed the first quadrant of the contact area. The fminsearch function in Matlab toolbox was recommended to solve the optimization model due to its capability of handling discontinuity problem. The solution obtained in optimization model and the corresponding machined flute parameter were verified and compared with Boolean simulation in CATIA to confirm the validity and efficiency of the proposed approach. The results showed that the accuracy of machined flute parameters could achieve 1e-3 mm and 1e-2°, which satisfied the machining tolerance. This study provides a general solution for the CNC fluting operations and could be extended to grind complex surface of end mills in the future study.

Influence of the Macro-topography of Grinding Wheels on the Cooling Efficiency and the Surface Integrity

The surface integrity of ground workpieces is not only influenced by the chosen parameters, but also by the coolant supply. Coolant supply in grinding is mainly governed by the nozzles used and their parameters. However, the cooling efficiency in grinding can also be enhanced by altering the macro-topography of the grinding wheel itself. In this paper three different grinding wheels using the same nozzle parameters are compared with respect to their cooling efficiency and hence their impact on the surface integrity of the ground workpieces. Besides a standard grinding wheel with continuous layer, a slotted grinding wheel as well as a segmented grinding wheel are presented and their respective cooling efficiency is evaluated. It is shown that by altering the macro-topography of a grinding wheel the resulting surface integrity can be influenced positively as well as negatively.

Five-axis rake face grinding of end-mills with circular-arc generators

The rake angles and the cores of the end-mill cutting tools are very important for they control the cutting forces during machining, the strength of the cutting edges, the rigidity of the end-mills and the chips removal capability. Thus, grinding end-mill flutes with accurate rake angles and accurate cores is very crucial in cutting tools’ industry. Flutes grinding is normally accomplished using two axis CNC grinding machines; however, this requires grinding-wheels with free-form profiles, expensive and uneasy to make, and the produced cutting edges and the normal rake angles along these edges are inaccurate. Hence, this work extends the five-axis CNC grinding approach developed by the first author to grinding of circular-arc ball end-mills. The generic mathematical equations of the grinding-wheel orientations and locations are first derived. Then, the grinding-wheel path is generated and the produced flute surface is precisely modeled. With standard grinding-wheels, computer simulation for the grinding approach is conducted and proved to produce precise end-mill cores, accurate cutting edges and accurate rake angles along these edges.

Исследование условий повышения точности геометрической формы поверхностей, шлифованных разнозернистым и стандартным кругами

Исследование условий повышения точности геометрической формы поверхностей, шлифованных разнозернистым и стандартным кругами

Superabrasive grinding wheels in the machine tool system: Restrictions by the rigidity criterion

The paper provides some findings of the investigation aimed at determining the required values of the rigidity index of superabrasive grinding wheels as one of the machine tool elements in the course of machining. Standard grinding wheels are shown to have a certain rigidity margin; critical values of this parameter are discussed.

Performance of a new segmented grinding wheel system

This paper investigates the mechanical and thermal effectiveness of a new segmented grinding wheel system with controlled radial coolant supply. The applicability of the system was examined in terms of grinding forces, specific energy and ground surface integrity in plunge grinding of AISI 4140 steel. It was found that compared with a standard grinding wheel, the new system enhanced the grindability with a lower specific energy and less application of coolant. It was also found that the new grinding system could effectively maintain the sharpness of active cutting edges, evidenced by the minimisation of ploughing and rubbing deformation in ground workpieces. The cleaning capacity of the wheel was improved and chip loading on wheel surfaces was avoided. Meanwhile, the new wheel system generated better surface integrity without tensile residual stresses.

Processing Design in Machining Ball-End Cutter with a Parallel Grinding Machine

Processing Design in Machining Ball-End Cutter with a Parallel Grinding Machine

A Standard Grinding Wheel Assessment Method to Support a Sophisticated Grinding Knowledge Based System

A Standard Grinding Wheel Assessment Method to Support a Sophisticated Grinding Knowledge Based System