Mohammad Rabiey

AN INNOVATIVE CONCEPT AND ITS EFFECTS ON WHEEL SURFACE TOPOGRAPHY IN DRY GRINDING BY RESIN AND VITRIFIED BOND CBN WHEEL

In the dry grinding process, as there is no coolant lubricant to transfer the heat from the contact zone, minimizing the grinding specific energy and grinding forces is a matter of importance. Some of the results of the systematic research works, based on a novel concept to make a step forward for pure dry grinding, are presented. The new concept is based on the fact that the optimisation of the chip formation reduces the friction and rubbing in the process. Such optimisation was achieved by a special conditioning process. The result showed a drastic reduction in grinding forces and no burning or damages on the surface of workpiece using the novel method comparing to conventional wheel with the same material removal rate. A theoretical discussion is also presented to support the experimental results.

Macro-topography effects on dry grinding with CBN wheels

Grinding involves high specific energy compared to other machining processes due to the negative rake angle of grains. Almost all this energy is converted to friction, generated high heat, which can have harmful effects on workpiece surface quality specially in case of dry grinding. Based on the optimisation of chip formation process, using a new concept of special structuring by special dressing of the vitrified grinding wheels, the heat generation is reduced. The results show a significant reduction of grinding forces in the new method compared to the conventional one at the same material removal rate without burning or thermal damages on the surface of workpiece.

Influence of Picosecond Laser Touch Dressing of Electroplated Diamond Wheels on the Dressing of SiC Vitrified Bond Wheel

Touch dressing of electroplated diamond wheels is a challenging technique used for precision form grinding. This paper presents an investigation to explore the capabilities of modern laser technology for touch dressing. A pulsed picosecond laser (ps-laser) beam (Yb:YAG) is used to cut diamond grains within a definite grain protrusion without noticeable thermal damage neither on the nickel bond material nor the diamond itself. A systematic study on laser irradiation parameters on cutting quality is presented. Series of experiments by dressing of SiC wheels using an ultrashort pulsed laser source as well as conventional touch dressed diamond wheel are carried out and both methods are compared. Significant advantages of the novel laser method are presented.

The Effect of Special Structured Electroplated CBN Wheel in Dry Grinding of 100Cr6

In many grinding applications, the material removal rate (MRR) is constrained by undesired thermal surface damages like burns and tensile residual stresses as well as dimensional inaccuracy. In dry grinding, due to lack of coolant, the limitation to achieve higher MRR is more critical as the major part of the heat, generated on the contact zone, is transferred to the workpiece. That is why the lower heat generation is a most important target by dry grinding. This paper presents some of the very interesting results by a comparison between a structured electroplated CBN wheel and a conventional one during surface grinding of steel. One of the grinding wheels has the normal structure and the other has special macro-structure topography developed for dry grinding. The results show a considerable reduction in grinding forces and less thermal damages using the novel electroplated CBN wheel comparing to conventional wheel.

Effects of ultrasonic vibration on grinding of 100Cr6

A new grinding method that superimposes ultrasonic vibrations on the workpiece is contrived. An ultrasonic-assisted grinding unit is used for a series of experiments under different vibration and grinding conditions to examine the behaviour of grinding forces and surface roughness. Compared to conventional grinding, a decrease of the thermal damage on the workpiece and a reduction of cutting forces have been achieved. The effects of Ultrasonic-Assisted Grinding on both dry and wet grinding were also examined. It is found that superimposing ultrasonic vibrations, especially in dry grinding, is one of the most effective methods for grinding soft steels.

Grinding of Soft Steel with Assistance of Ultrasonic Vibrations

Compared to other machining processes, conventional grinding has a low material removal rate and involves high specific energy. A major part of the specific energy in grinding is changed to heat which makes harmful effect on surface quality. A recent and promising method is the use of ultrasonic assistance to increase the material removal rate along with decreasing the thermal damage on the workpiece and reducing cutting forces. The advantages of Ultrasonic Assisted Grinding (UAG) were proved mostly for the brittle material. Our investigations show the improvement on the surface roughness, reduction of the grinding forces and thermal damage in case of using UAG comparing to Conventional Grinding (CG) for a soft material of 100Cr6. The designed and developed ultrasonically vibrated workpiece holder and the experimental investigation show a decrease of up to 40% of normal grinding forces.