Optimizing the Sharpening Process of Hybrid-Bonded Diamond Grinding Wheels by Means of a Process Model

The grinding wheel topography influences the cutting performance and thus the economic efficiency of a grinding process. In contrary to conventional grinding wheels, super abrasive grinding wheels should undergo an additional sharpening process after the initial profiling process to obtain a suitable microstructure of the grinding wheel. Due to the lack of scientific knowledge, the sharpening process is mostly performed manually in industrial practice. A CNC-controlled sharpening process can not only improve the reproducibility of grinding processes but also decrease the secondary processing time and thereby increase the economic efficiency significantly. To optimize the sharpening process, experimental investigations were carried out to identify the significant sharpening parameters influencing the grinding wheel topography. The sharpening block width lSb, the grain size of the sharpening block dkSb and the area-related material removal in sharpening V’’Sb were identified as the most significant parameters. Additional experiments were performed to further quantify the influence of the significant sharpening parameters. Based on that, a process model was developed to predict the required sharpening parameters for certain target topographies. By using the process model, constant work results and improved process reliability can be obtained.

EFFECTS OF GRINDING WHEEL WEAR ON THE THERMO-MECHANICAL LOADS IN THE GRINDING PROCESS

A large amount of the energy produced during grinding is converted into heat. Since not all of the heat can be dissipated by the cooling lubricant, thermally induced displacements in machine components occur, which has a negative influence on the component quality. The generation and distribution of heat is influenced by the change of the grinding wheel topography due to wear.Therefore, the wear mechanisms of grains were identified and quantified and their effect on heat generation was investigated. For this purpose, creep feed grinding investigations on bearing steel were conducted with electroplated CBN grinding wheels with different grain specifications.

Kornbruchverhalten beim Abrichten von CBN/Fracture behavior of CBN during dressing – Analysis of the single grain dressing process of CBN

Die Schleifscheibentopographie, welche durch den Abrichtprozess erzeugt wird, ist ein wesentlicher Einflussfaktor für das Prozessergebnis beim Schleifen. Das Bruchverhalten der Kornwerkstoffe beim Abrichten hängt nicht nur von den Abrichtparametern, sondern auch von dem Korntyp der Schleifscheibe ab. Daher wurden Abrichtversuche an einzelnen CBN-Körnern durchgeführt, um den Einfluss der Abrichtparameter und des Korntyps auf das Prozessergebnis zu ermitteln.   The grinding wheel topography generated by the dressing process is a factor of major impact on the result of the grinding process. The fracture behavior of the grains of the grinding wheel during dressing not only depends on the dressing parameters but also on the grain type of the grinding wheel. Therefore, dressing tests of single CBN grains were conducted to determine how the dressing parameters and the grain type influence the process result.

Prediction of Ground Surfaces by Using the Actual Tool Topography

This paper presents a prediction model for ground surfaces that uses the actual grinding wheel topography to perform a grinding simulation. Precise knowledge of expected machined surfaces plays an important role in process planning. Here, the main criterion is the achievement of the components’ function after manufacturing. Therefore, it is essential to consider the surface roughness to enable a function-orientated workpiece surface. The presented approach uses a real grinding tool topography, which is measured by a 3D laser triangulation sensor in the machine tool. After a data processing step, the measured topography is imported into a material removal simulation. A kinematic simulation of the realistic ground surface enables the data-based confirmation of the envelope profile theory for the first time.

Einfluss der Schärfparameter auf die Schleifscheibentopographie*/Influence of the sharpening parameters on the grinding wheel topography

Einen wesentlichen Bestandteil der Schleiftechnik ist der Konditionierprozess zur Herstellung der Schleifscheibenform und -schnittigkeit. Durch das Schärfen wird die Bindung zurückgesetzt und der notwendige Schleifkornüberstand und Spanraum geschaffen. Ein CNC-gesteuerter Schärfprozess kann zur prozesssicheren und ressourceneffizienten Einstellung der gewünschten Schleifbelagstopographie genutzt werden. Umfangreiche Schärfuntersuchungen sollen hierbei Aufschluss über die Wirkzusammenhänge zwischen Schärfeinstellgrößen und Schärfergebnis geben.   An essential part of grinding technology is the conditioning process for the generation of the grinding wheel shape and of a sharp topography. Through the sharpening process the required cutting grains are exposed from the bond and sufficient chip space is ensured by putting back the bonding. A CNC-controlled sharpening process can lead to an improvement in process reliability and the economic efficiency. Extensive experimental investigations were carried out to determine the relationship between the sharpening parameters and the sharpening result.

Methods of grain separation from single-layer grinding wheel topography

The paper presents results of research concerning methods used for determining grain separation from measured data representing single-layer grinding wheel topography. The methods apply information concerning determined threshold level (Threshold method) or concerning watershed segmentation (Watershed method). A method for determining the average level of bond was also proposed.

A New Grinding Force Model for Micro Grinding RB-SiC Ceramic with Grinding Wheel Topography as an Input

The ability to predict the grinding force for hard and brittle materials is important to optimize and control the grinding process. However, it is a difficult task to establish a comprehensive grinding force model that takes into account the brittle fracture, grinding conditions, and random distribution of the grinding wheel topography. Therefore, this study developed a new grinding force model for micro-grinding of reaction-bonded silicon carbide (RB-SiC) ceramics. First, the grinding force components and grinding trajectory were analysed based on the critical depth of rubbing, ploughing, and brittle fracture. Afterwards, the corresponding individual grain force were established and the total grinding force was derived through incorporating the single grain force with dynamic cutting grains. Finally, a series of calibration and validation experiments were conducted to obtain the empirical coefficient and verify the accuracy of the model. It was found that ploughing and fracture were the dominate removal modes, which illustrate that the force components decomposed are correct. Furthermore, the values predicted according to the proposed model are consistent with the experimental data, with the average deviation of 6.793% and 8.926% for the normal and tangential force, respectively. This suggests that the proposed model is acceptable and can be used to simulate the grinding force for RB-SiC ceramics in practice.