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.

Capacity of globoidal gear-honing

A capacity is characterized by a value of material removal per time unit. A globoidal gear-honing capacity was defined by general normal changing before and after processing. In the course of an experimental part fulfillment the removals were defined depending on the properties of material worked, the abrasive layer characteristics of a globoidal hone and working modes. The experimental results are presented in a graphical form.

Optimization of Micropencil Grinding Tools Via Electrical Discharge Machining

Micropencil grinding tools (MPGTs) are micromachining tools that use superabrasives like diamond and cubic boron nitride (cBN) grits to manufacture complex microstructures in a broad range of hard and brittle materials. MPGTs suffer from a rather low tool life, when compared to other more established microprocessing methods. It was documented that when used on hardened steel workpieces, MPGTs suffer from a large amount of adhesions, mostly located at the pivot point of the tool. These adhesions lead to the clogging of the abrasive layer and ultimately in tool failure. Another problem this machining process suffers from is the formation of substructures (smaller channels inside the microchannels). The pivot is usually less prone to abrasive wear, has higher protrusion, and is therefore responsible for the deepest substructures. These substructures can easily take up half the depth of cut, obstructing the function of machined microchannels—it is one of the major flaws of this micromachining process. A micro-electrical discharge machining method (μEDM) can solve these issues by manufacturing a cavity at the pivot of these tools. A novel method that uses measurement probes to position the substrate above the μEDM electrode is implemented and a parameter study to determine the cavity manufacturing parameters is conducted for substrates with diameters < 40 μm. The goal is to demonstrate the first ever complete and reliable manufacturing process for MPGTs with a cavity and to demonstrate the advantages they provide in a machining process when compared to regular MPGTs.

Dynamic Grinding Hub Monitoring during a High Performance Grinding Process with Ceramic CBN on Cold Work Steel

Grinding is a material removing process with undefined cutting edges. The high numbers of grains participating during the chip formation are continuously subjected to non-uniform wear and topography changes. This behavior typifies a highly non-stationary process. Capturing the whole process in a simulation and predicting the work results is difficult. For this reason are In-process monitoring techniques a suitable approach to address this issue. In this paper a wireless In-process monitoring system is presented. The system is mounted on the grinding hub and detects the dynamic behavior of the wheel during the grinding process. A full bridge with strain gauges located close to the abrasive layer has been used to give instantaneous feedback concerning normal force and wheel deformation during each wheel revolution. This technique enables a continuously monitoring and improving of the grinding process, hence a more efficient and sustainable use of the abrasive layer. Experiment results are presented which demonstrate the ability of the ‘intelligent’ wheel to monitor grinding processes and to improve the machine performance.