Electro-discharge Dressing Research Articles

Experimental Investigation on Bronze-Bonded CBN Formed Grinding Wheel by Means of Electro-Discharging Dressing

High-efficiency and precision machining of complicated components can be realized by using metal-bonded CBN grinding wheel. However, the difficulty in dressing those superabrasive grinding wheels is one of the main obstructions to popularize its application in industry. Different from the traditional methods, the aim of the paper is to investigate the electro-discharge dressing of bronze-bonded CBN formed grinding wheel. Based on the analysis of electrical discharge parameters and grinding performance, the results show that electro-discharge dressing of CBN formed grinding wheel is feasible. With the increase of pulse duration, pulse voltage and pulse current, the dressing efficiency is increasing, more abrasive grains are protruding, but surface topography of grinding wheel is worsen. Therefore, grinding tests show that, in order to get the dressing quality better and keep the dressing efficiency higher, the bigger electrical discharge parameters are chosen for rough dressing process and the smaller ones are chosen for finishing process.

Development of a novel custom micro-tool for effective cutting of a precision microgroove array on a microscope slide

This study presents a novel, economical and efficient fabrication technique for precisely generating multiple microgrooves on a microscope slide to allow for microscopic examination of urine sediment cells. This study incorporates two important phases: a precision wheel-tool array is fabricated and then the developed tool is used in fast on-line grinding of multiple microgrooves. The wheel-tool blank is made of diamond grit of 0–2 µm grade via co-deposition. Subsequently, it is trued, sliced and sharpened by means of micro wire electro discharge dressing. The finished wheel-tool is utilized on-line to grind multiple microgrooves using ‘high-speed and fast-shallow grinding’. A ductile grinding regime is established to obtain a nano-metric surface finish for the multiple microgrooves generated on the microscope slide. The depth and width of the grooves in the array are both 10 µm and a surface finish of Ra equal to 0.010 µm is simultaneously achieved. This multiple microgrooving technique can supply high-quality fast grinding in the fabrication of bio-medical devices, such as those used for stationing and counting urine sediment cells.

Study of an on-line precision microgroove generating process on silicon wafer using a developed ultra-thin diamond wheel-tool

This study presents a novel and economical method for precisely developing an ultra-thin diamond grinding wheel-tool and using the finished wheel-tool to on-line fabricate crisscross microgrooves on silicon wafer. The wheel-tool blank is made of diamond grain of 0–2 μm grade via a designed micro co-deposition. A non-continuous cathode design, in which current crowding effect can be suppressed, is used to obtain a diamond wheel-tool with good surface characteristics. With abrasive content of 8 g/l, a suitable interval chip-pocket of 2–3 μm can be generated. The grinding wheel blank is thinned and dressed simultaneously down to a thickness of 15 μm using micro wire Electro Discharge Dressing (w-EDD). The finished wheel-tool is directly utilized to grind the crisscross microgrooves on the silicon wafer using ‘high-speed and fast-shallow grinding’ technique. A grinding depth of 0.5 μm per stroke is exactly controlled to ensure that the removal mechanism transfers to a ductile grinding mode. The width, depth and surface roughness R a of the microgrooves are 15 μm, 9 μm and 0.087 μm, respectively.

Electrodischarge dressing (EDD) applied to contour grinding

Superabrasive grinding is a high efficiency process used in special applications such as high speed grinding, creep feed grinding, and Quick-Point. Although the maximum efficiency is obtained by metallic bonded wheels due to their wear resistance, their hardness makes almost impossible to dress them properly. Vitrified bonded wheels are now being used instead of metallic bonded ones since they have superior self-dressing capability. With the aim of obtaining maximum efficiency of these special grinding processes, in the last years a number of non-conventional dressing processes have been developed allowing the use of metallic bonded wheels. In this work, a methodology to introduce the electro-discharge dressing (EDD) of superabrasive conductive metallic bonded wheels is presented. The efficiency of EDD process to regenerate shaped wheels applied in Quick-Point or peel grinding has been studied by grinding hard metal rollers. Results show that EDD is able to remove the run-out and regenerate cutting capability.

Analysis of the electro discharge dressing (EDD) process of large-grit size cBN grinding wheels

The application of non-conventional truing/dressing (T/D) methods to the recovery of conductive-bond superabrasive wheels has been a matter of great interest in the last years, especially in the case of small-grit size wheels. However, when it comes to the dressing of large-grit size superabrasive wheels, applied in roughing operations, little information is available. The electro discharge dressing (EDD) process can be optimally applied in these cases. In this work a description of the particular mechanisms involved in bonding material removal in the EDD of large-grit size cBN wheels is presented. Indicators are defined in order to quantify the stability and efficiency of the process, and the influence of the main process variables (wheel speed, electrode size and electrical settings) is analyzed. Practical application shows that very important improvements in the grinding performance of the wheels can be obtained by maximizing grit protrusion while avoiding grain loss using this technique .

Optimisation of grit protrusion in the electro-discharge dressing process of large grit size CBN grinding wheels

The technology of superabrasive grinding has been developed in order to achieve high-quality finish in extremely hard and brittle materials. New application fields have appeared, but new problems must also be faced. The truing/dressing process has a direct influence on the grinding performance of the wheel. Mechanical dressing exhibits clear limitations, and therefore much research work has been done dealing with non-conventional dressing techniques. The problem is specially important in the case of CBN wheels, which require large space between grits in order to efficiently accommodate the swarf produced in the grinding of more ductile materials. Important limitations also appear in the case of large grit size wheels. In this paper, the electro-discharge dressing (EDD) process of 126# grit size CBN metallic bonded wheels has been analysed. The performance of the method is evaluated by measuring grit protrusion and relating this parameter to grinding forces.

Surface characteristics in the precision grinding of Mn–Zn ferrite with in-process electro-discharge dressing

Mn–Zn ferrite is used as a material of hard disk magnetic heads, but is difficult to grind because of its high hardness and brittleness. Therefore, a super-abrasive diamond wheel is used for the precision surface grinding of this material. However, the conventional dressing method cannot be applied to a super-abrasive diamond wheel. This study describes a newly proposed method for carrying out effective in-process electro-discharge dressing (IEDD) of a super-abrasive diamond wheel. Using IEDD, the surface roughness of Mn–Zn ferrite was improved, and the grinding force was reduced. IEDD is a good method to obtain efficient grinding and surface grinding of ferrite .

Precision Grinding of Mn-Zn Ferrite with In-Process Electro-Discharge Dressing

Ferrite is widely used as a material for magnetic heads for hard disks, but it is difficult to grind because its high hardness and brittleness. Therefore, a superabrasive diamond wheel is used for precision surface grinding of this material, However, the conventional dressing method cannot be applied to a superabrasive diamond wheel. This study describes a new method for carrying out effective in-process electro-discharge dressing (IEDD) of a superabrasive diamond wheel. Using IEDD, the surface roughness of the Mn-Zn ferrite was improved, and the grinding force was reduced. IEDD is a good method for obtaining efficient surface grinding of ferrite.

Precision surface grinding of Mn–Zn ferrite with in-process electro-discharge dressing (IEDD)

Ferrite is widely used as a material for hard disk magnetic heads, but is difficult to grind because of its high hardness and brittleness. Therefore, a superabrasive (diamond) wheel is used for precision surface grinding of this material. But the conventional dressing method cannot be applied to the diamond wheel. This study describes a newly proposed method for carrying out effective in-process electro-discharge dressing (IEDD) of a diamond wheel. Using IEDD, the surface roughness of Mn–Zn ferrite was improved and the grinding force was reduced. IEDD is a good method to obtain efficient grinding and surface grinding of ferrite.

Crack generation and the effect of in-process electro-discharge dressing in grinding single crystal MgO

Single crystal MgO is widely used in material with high temperature resistance, but is difficult to grind because of brittleness and crack generation. Therefore, a diamond wheel with superabrasive surface is required for surface grinding of this material. But the conventional dressing method cannot be applied to the diamond wheel with superabrasive. This study describes a newly proposed method for carrying out effective in-process electro-discharge dressing (IEDD) of a diamond wheel with superabrasive. Using IEDD, the surface roughness of single crystal MgO was improved, the grinding force was very low and crack generation was reduced. IEDD is a good method to obtain efficient grinding and surface grinding of single crystal MgO.