Influence of dressing strategy on tool wear and performance behavior in grinding of forming tools with toric grinding pins

The performance of grinding tools in grinding processes and the resulting surface and subsurface properties depend on various factors. The condition of the grinding tool after dressing is one of these factors. However, the influence of the dressing process on the condition of the grinding tool depends on the selected process parameters and is difficult to predict. Therefore, this paper presents an approach to describe the influence of the dressing process on tool wear of toric grinding pins and the resulting subsurface modification. For this purpose, toric grinding pins with a vitrified bond were dressed with two different strategies and the wear and operational behavior were investigated when grinding AISI M3:2 tool steel with two different grinding strategies. In general, the investigations have shown that the dressing process influences the performance and wear behavior differently depending on the grinding strategy used. The degree of clogging is influenced by the geometric contact sizes. In the case of small engagement cross sections with simultaneously large contact lengths the thermal tool load is distributed over a small annular area of the tool and favors clogging. Crushing and additional transverse loading of the grains result in an almost clog-free tool surface. This also leads to a lower G-ratio. Crushing leads to an intensified decrease of the torus radii. The influence of the dressing strategy can also be observed in the induced residual stresses. Toric grinding pins dressed by crushing induce lower compressive residual stresses into the workpiece, which can be attributed to the self-sharpening effect. This effect reduces the mechanical and thermomechanical load of the workpiece during machining.

Optimization for Morphology of Grinding Layer on Textured Laser Cladding Grinding Tool

In order to improving the grinding performance of laser cladding textured grinding tool (LCTGT) under high speed grinding process, the topography shape (height, width and height/width ratio) of laser cladding grinding layers on LCTGT were designed with RSM (response surface method) through optimizing laser cladding processing parameters and laser cladding layers structure parameters that based on Archimedes helix coefficients. The LCTGTs were produced with optimized laser cladding parameters and structural parameters for laser cladding grinding layers. The results showed that laser cladding parameters of 397W of laser power, 3.56 mm/s of the laser scanning speed and 0.91 r/min of powder feeding rate and structure parameters of laser cladding layers of 6-10-10 can meet requirement.

Process Related Characteristic-Based Topography Evaluation of Wear Conditions On Grinding Wheels

Non-productive auxiliary processes affect the single part and small badge production of milling tools. The key production process grinding is inevitably linked to the auxiliary conditioning process. The time demand of those process steps decreases the overall productivity of the manufacturing process. However, today the machine operator decides on conditioning cycles individually by the use of experience. Until today, there is no objective data based approach available that supports the initiation of these conditioning processes or the adaption of the grinding process itself in order to improve its process efficiency. For this purpose, a process related topography evaluation method of the grinding wheel surface is developed within this study. For the measurement an optical method based on laser triangulation is used. The measurement system is implemented into a common tool grinding machine tool. In addition, characteristic topography values are defined that show the wear conditions of the grinding tool. Moreover, the data is summarized in a database of wear conditions. The developed measurement method can save grinding and dressing tool resources, process times and minimizes scrap parts. In addition, an adaptation of the process and a targeted launch of auxiliary processes can be enabled. The novel characteristic-based topography measurement creates the opportunity to enhance the tool life of the grinding wheels up to 30 % without losing productivity.

Operational Behavior of Graded Diamond Grinding Wheels For End Mill Cutter Machining

The varying related material removal rate during deep grinding of cemented carbide end mill cutters results in an unevenly wear of the grinding wheel. This causes a reduced geometrical precision of the manufactured tools. Consequently, the intervals between dressing steps are reduced and the dressing infeed increases. The aim of this research project is therefore to design a tailored grinding tool with uniform wear behavior. To address this situation, the grinding tool load is determined simulatively along the width of the grinding wheel. From this an equation is derived to adapt the bonding layer properties to the local load differences. First investigations show that two different concentrations zones in the abrasive layer of the grinding wheel improves the wear behavior already. This indicates that a further reduction of the wear difference is possible by a more uniform gradient. A simulation is performed to define a knowledge based gradient with more than two concetration zones. This allows a more precise load optimized adaptation of the grinding layer properties to the geometry to be ground in terms of wear behavior. Grinding tools manufactured on this basis are used for flute grinding of end mill cutters. A reduction of the wear difference over the grindig wheel width of 52% and an improved cutting edge quality of these are demonstrated.

Optimization of in-Process Conditioning Parameters During Face Plunge Grinding of PcBN

Polycrystalline cubic boron nitride (PcBN) is an extremely hard material. Machining of the material is performed by grinding with diamond tools. Due to its high hardness, the grinding tools underlie a severe microscopic and macroscopic tool wear. This wear leads to a short tool life and results in high effort in conditioning the abrasive layer. Contrary to the usual conditioning of diamond grinding wheels with diamond dressing tools, this study investigates a conditioning process based entirely on the use of white corundum cup rolls. These conditioning tools allow the in-process face plunge conditioning of vitrified bond diamond grinding tools. The circumferential speed of the conditioning tool and the average grain diameter of the corundum are identified as the main factors influencing the topography of the generated grinding layer. To describe the performance of the conditioning process, a specific conditioning removal rate Q’sd is derived. This parameter represents a cumulated variable that allows a comparison of different conditioning strategies. It is shown that an increase in Q'sd significantly counteracts microscopic wear on the abrasive layer. Therefore, optimized process parameters enable the process of in-process conditioning to significantly reduce the wear on the grinding tool without increasing the process time or the non-productive time.

Mechanism and Experiment Study of Non-Contact Ultrasonic Assisted Grinding

Ultrasonic-assisted grinding processing can effectively reduce the surface roughness and enhance the processing efficiency in the processing of hard and brittle materials. However, the most common ultrasonic assisted grinding is a type of contact ultrasonic grinding where the grinding tool directly contacts the workpiece, which means that it is necessary to accurately control the pre-pressure of the grinding tool on the workpiece. The control of pre-pressure will inevitably increase the complexity of the grinding device, and it is easy to wear the workpiece because of improper pre-pressure control. In this paper, a non-contact ultrasonic grinding method is proposed and the machining mechanism of non-contact ultrasonic grinding is revealed. The resonant frequency of the ultrasonic vibration system and vibration amplitude of the grinding tool working face were simulated and experimentally tested, respectively. Then, the experiment of non-contact ultrasonic grinding of a sapphire wafer was carried out. The result showed that non-contact ultrasonic grinding of the sapphire wafer could reduce the surface roughness by 48.6%. Compared with traditional contact grinding of sapphire wafer under certain pre-pressure conditions, the experimental results show that non-contact ultrasonic grinding has better effects in reducing surface roughness, improving processing efficiency, and improving the quality uniformity of the workpiece machining surface.