New design for end grinding wheels

A new grinding-wheel design is developed by analysis of the nonuniform abrasive action in the case of plane grinding by the end of the wheel; the wheel parameters are established.     

A study on wear mechanism and wear reduction strategies in grinding wheels used for ELID grinding

Metal-bonded superabrasive diamond grinding wheels have superior qualities such as high bond strength, high stability and high grindability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the grinding wheel. Electrolytic in-process dressing (ELID) is an effective method to dress the grinding wheel during grinding. The wear mechanism of metal-bonded grinding wheels dressed using ELID is different form the conventional grinding methods because the bond strength of the wheel-working surface is reduced by electrolysis. The reduction of bond strength reduces the grit-depth-of-cut and hence the surface finish is improved. The oxide layer formed on the surface of the grinding wheel experiences macrofracture at the end of wheel life while machining hard and brittle workpieces. When the wheel wear is dominated by macrofracture, the wheel-working surface is free from loaded chips and worn diamond grits. When the oxide layer is removed from the wheel surface, the electrical conductivity of the grinding wheel increases, and that stimulates electrolytic dressing. The conditions applied to the pulse current influence the amount of layer oxidizing from the grinding wheel surface. Longer pulse ‘on’ time increases the wheel wear. Shorter pulse ‘on’ time can be selected for a courser grit size wheel since that type of wheel needs high grinding efficiency. Equal pulse ‘on’ and ‘off’ time is desired for finer grit size wheels to obtain stable and ultraprecision surface finish.     

An accurate method for five-axis flute grinding in cylindrical end-mills using standard 1V1/1A1 grinding wheels

Flute grinding is a critical process in end-mill manufacturing. The wheel geometry and position during the grinding process govern the flute profile and determine the flute parameters (i.e. rake angle, core radius, and flute width). Accuracy of these parameters should be ensured to obtain optimal cutting performance. For a given wheel geometry, the current technologies can only determine the wheel position for the desired rake angle and core radius without consideration of the flute width. This disadvantage seriously restricts the improvement of machining quality and the flexibility of flute grinding. To cope with this problem, this paper presents a novel method of five-axis flute grinding using standard 1V1/1A1 wheels to ensure the accuracy of the three flute parameters. Based on the theories of analytic geometry and envelope, equations for calculating the flute parameters are first derived. Afterwards, a system of nonlinear equations is created to calculate the wheel position for flute grinding. The validity of the proposed method is verified by 3D simulations and machining experiments. Lastly, the sensitivity of the valid flute width with respect to the wheel geometric parameters is further investigated in this work.     

The optimal diamond wheels for grinding diamond tools

Grinding is the most suitable process for manufacturing good quality diamond tools. In this paper, diamond wheels have been studied. From the grinding of polycrystalline diamond (PCD) insets, the effects of certain factors such as the bonding material, the grit size and structure of a diamond wheel have been investigated. It is concluded that vitrified bond diamond wheels are the most suitable for grinding PCDs and the recommended grit size is mesh number 1000, which can get a good surface quality within an appropriate time. The wheel structure is another important factor. Rougher wheels (mesh #800, #1000) with the softer grade scale P yield a higher material removal rate (MRR) than scale Q. However, a finer wheel (mesh #1200) needs a tougher structure to promote its grinding ability and to have a higher MRR.     

高速砂轮基体截面的优化设计

运用ANSYS提供的参数化语言(APDL)建立高速砂轮基体的模型,并以最大的环向应力减去最小环向应力之差最小化为目标函数,求解高速砂轮基体优化设计的问题,给出了优化后砂轮基体的截面形状和应力分布结果.结果表明:经过优化设计后,可以明显降低最大环向应力值,同时大大缩小了环向应力变化范围.     

In-process dressing of fine diamond wheels for tool grinding

In tool grinding operations, especially ceramic cutting tool materials, two aims are important: high production efficiency and high-precision cutting edges with minimum surface and subsurface damage. Using conventional grinding conditions, these two aims cannot be combined without essential restrictions. In-process dressing enables efficient use of fine-grained grinding wheels to obtain superior cutting edge quality.     

A novel KFCM based fault diagnosis method for unknown faults in satellite reaction wheels

Reaction wheels are one of the most critical components of the satellite attitude control system, therefore correct diagnosis of their faults is quintessential for efficient operation of these spacecraft. The known faults in any of the subsystems are often diagnosed by supervised learning algorithms, however, this method fails to work correctly when a new or unknown fault occurs. In such cases an unsupervised learning algorithm becomes essential for obtaining the correct diagnosis. Kernel Fuzzy C-Means (KFCM) is one of the unsupervised algorithms, although it has its own limitations; however in this paper a novel method has been proposed for conditioning of KFCM method (C-KFCM) so that it can be effectively used for fault diagnosis of both known and unknown faults as in satellite reaction wheels. The C-KFCM approach involves determination of exact class centers from the data of known faults, in this way discrete number of fault classes are determined at the start. Similarity parameters are derived and determined for each of the fault data point. Thereafter depending on the similarity threshold each data point is issued with a class label. The high similarity points fall into one of the 'known-fault' classes while the low similarity points are labeled as 'unknown-faults'. Simulation results show that as compared to the supervised algorithm such as neural network, the C-KFCM method can effectively cluster historical fault data (as in reaction wheels) and diagnose the faults to an accuracy of more than 91%.     

New systematic and time-saving procedure to design cup grinding wheels for the application of ultrasonic-assisted grinding

Since glass and ceramic materials have beneficial properties, they have gained more importance in numerous technical applications during the last 30 years. For example, nowadays, ceramics are used as artificial hip joints or as mechanical seals for highest relative speeds. Glass components are used for multitude of optical applications like cameras and reflectors. But besides a lot of advantages, the processing of these materials is very difficult. In particular, this contains the manufacturing of small components like microreactor plates or glass wafers with hundreds of small holes, too. Using ultrasonic-assisted grinding, the treatment can significantly be optimized and higher removal rates can be realized. For the generation of ultrasonic waves, often piezoactors are used that excite the grinding tools with vibrations of 20 kHz and amplitudes of a few microns (Markov 1966; Kuttruff 1988). Using an ultrasonic wave, the tool geometry is strongly restricted to guarantee the hybrid functionality (Siegert 2002; Dawe Instruments Ltd. 1967; Derks 1984). The paper describes a new way to calculate the design of tools suitable for their use in ultrasonic-assisted grinding. As a machining process, the manufacturing of spherical optics with cup-grinding wheels is selected.     

A method for proximate testing of railroad wheels

A new method for nondestructive testing of railroad wheels using natural vibrations that are excited by a hammer impact is proposed. The method is based on the effect of the generation of the dominant frequencies of natural vibrations in the presence of cracks. A physical substantiation of the method and the results of experimental studies are presented. The place of the proposed method in the general system of nondestructive testing of railroad wheels is determined. In addition, methods for nondestructive testing based on using natural vibration frequencies are briefly reviewed.     

High-porosity wheels based on cubic boron nitride for defect-free grinding

Boron-nitride wheels with large pores are characterized by high permeability and permit defectfree grinding.     

More efficient profiling and use of diamond grinding wheels

We consider the contact-erosion profiling of diamond wheels with metal binders, by means of a composite disk electrode. The productivity may be increased by increasing the height of the electrode profile, without loss of accuracy.     

A novel CNC grinding method for the rake face of a taper ball-end mill with a CBN spherical grinding wheel

A novel method using a CBN spherical grinding wheel to grind the rake face of a taper ball-end mill and the configuration of corresponding CNC tool grinder are presented. This method utilizes the self-adaptation characteristics of a sphere to decrease the number of simultaneous cooperative axes of a CNC tool grinder and to smooth the rake face on the transition area between the taper and the ball-end of the mill. In order to obtain an accurate normal rake angle, which is one of the key factors affecting tool cutting performance, a moving coordinate system based on the required normal rake angle and the cutting edge was established. Then, by the proposed moving coordinate system, an algorithm to determine the position and orientation of a spherical grinding wheel, the basis of CNC code generation, is proposed and the relevant formulations are deduced. The 3D simulation of rake face grinding for a taper ball-end mill with constant helical angle indicates that the number of simultaneous cooperative axes of the CNC tool grinder is decreased from five to four and the smooth transition of the rake face is realized by the proposed method herein.     

A precision grinding method for screw rotors using CBN grinding wheel

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88.     

Force modeling and machining characteristics of the intermittent grinding wheels

In the surface grinding operations, the grinding fluid cannot be supplied sufficiently in the cutting zone. Temperature generated in the cutting zone increases rapidly and causes thermal damage such as burning on the surface of a workpiece. To reduce thermal damage, the intermittent grinding wheels, which have an excellent cooling effect, have been applied. This paper describes machining characteristics by using intermittent grinding wheels. The grinding force of the intermittent wheels has been simulated by the SIMULAB, which is a program for simulating dynamic systems. Using the intermittent grinding wheels, the characteristics of grinding force, temperature, surface roughness, and geometric error have been evaluated experimently.     

Improved contact-erosion shaping of diamond wheels and diamond profile grinding

Contact-erosion profiling of diamond wheels based on metallic binder by means of a composite electrode is considered. This method increases the productivity, without reducing the precision, by increasing the profile height of the electrode (tool).