Abstract: Diamond grinding wheel has good grinding performance and is widely used in grinding difficult-to-machine materials. However, the hardness of diamond grinding wheel is extremely high, and dressing is quite difficult, and it is easy to get stuck when dressing. So, what should diamond grinding wheels be dressed with? Soft elastic dressing method is more suitable for dressing metal-bonded diamond micro-powder grinding wheel, because metal-bonded diamond micro-powder grinding wheel has both metal plasticity and high hardness, so dressing is quite difficult. The dressing method of diamond grinding wheel will be introduced below. A complete collection of dressing methods for diamond grinding wheels

1, grinding and dressing method

1. 1 grinding principle and dressing method

During dressing, ordinary abrasive grinding wheel and diamond grinding wheel are used for grinding, the diamond grinding wheel rotates, and the ordinary abrasive grinding wheel also makes feed movement. The abrasive particles on the surface of diamond grinding wheel begin to rotate slowly under the action of friction force, and at the same time produce a certain extrusion force on the metal bond until the bond cracks. With the constant action of friction, the cracks in the bond further expand, and finally the bond breaks, so that dull diamond particles fall off the surface of the grinding wheel and sharp diamond particles are exposed.

1.2 characteristics of grinding and dressing method

The main advantages of grinding and dressing method are: simple structure, convenient operation, short dressing time, stable grinding speed and low grinding cost, but there is impact force in dressing process, low dressing efficiency, poor dressing accuracy, many fallen abrasive particles and difficult to control the shaping quality. It is mainly used for dressing ceramic and resin bonded diamond grinding wheels.

2. Soft elastic trimming method

2. 1 the principle of soft elastic pruning method

Soft elastic dressing method is to cover the abrasive belt on the abrasive belt wheel during dressing. During dressing, the diamond grinding wheel rotates at high speed, the winding wheel rotates slowly, and the abrasive belt moves slowly on the pulley. Using the contact force between abrasive belt and grinding wheel, the bonding agent between abrasive particles on the surface of diamond grinding wheel is effectively removed, so as to achieve the purpose of dressing.

2.2 Advantages of soft elastic dressing method

Compared with other dressing methods, soft elastic dressing method is more suitable for dressing metal-bonded diamond micro-powder grinding wheel. Because the metal bonded diamond micro-powder grinding wheel has both metal plasticity and high hardness, it is quite difficult to dress, mainly because the abrasive particles on the surface of the dressing tool wear quickly, and secondly, the dressing space of the dresser is easily blocked and it is impossible to dress any more. The dressing tool of soft elastic dressing method-abrasive belt is always in contact with the new dressing wheel with sharp abrasive particles, which can form a good dressing environment and effectively remove the bonding agent between abrasive particles on the surface of diamond grinding wheel, with low grinding force and high grinding surface quality.

3. EDM dressing method

3. 1 EDM dressing principle

In the process of dressing diamond grinding wheel, the grinding wheel rotates at high speed, and the diamond grinding wheel is connected to the positive electrode of power supply, and the tool electrode is connected to the negative electrode of power supply. Spray grinding coolant between diamond grinding wheel and tool electrode, and apply voltage between tool electrode and grinding wheel to generate spark discharge between grinding wheel metal bond and dressing electrode. The high temperature of instantaneous discharge vaporizes the metal bond, effectively removes the metal bond on the surface of the grinding wheel, and fully exposes the diamond abrasive particles, thus finishing the grinding wheel.

3.2 Features of EDM Dressing

Online dressing can be realized, and the grinding accuracy of the grinding wheel can be easily ensured. After dressing, the grinding force of the grinding wheel is small, the shaping accuracy is high, and the shaping and grinding can be completed at the same time. However, the dressing speed is slow, and the performance of abrasive particles will change due to the high discharge temperature. Effectively controlling the surface temperature of grinding wheel is the key to dressing diamond grinding wheel by EDM.

4. Laser dressing method

4. 1 the principle of laser trimming method

Laser dressing method is to focus the laser beam into a small spot by using an optical system and act on the surface of the grinding wheel. Except a small part of the laser beam is reflected, most of the laser beam is absorbed by the metal binder, and the temperature rises rapidly, resulting in the evaporation and removal of the metal binder in the area irradiated by the laser beam. The removal of adhesive materials usually goes through several processes: radiation, absorption, temperature rise and gasification. When the grinding wheel is repaired by laser, controlling the laser power and density reasonably can remove the diamond abrasive particles and binder materials on the surface of the grinding wheel at the same time, thus achieving the purpose of grinding wheel shaping. By adjusting the laser processing parameters, the bonding material on the surface of the grinding wheel can also be selectively removed, so that the diamond abrasive particles have a certain protruding height, thus achieving the purpose of grinding the grinding wheel.

4.2 Advantages of laser fine-tuning method

Laser dressing is a non-contact dressing method. There is no mechanical force during dressing, no loss of dressing tools, short laser action time, small action area, no damage to diamond abrasive particles and bonding agent, and high dressing efficiency. However, the dressing process is complicated and the cost is high.

5, electrolytic dressing method

5. 1 Principle of electrolytic beneficiation

Electrolytic dressing method is mainly used for metal bonded diamond grinding wheels. During electrolytic dressing, the metal bond grinding wheel is connected with the positive pole of DC power supply as the electrolytic anode, and the tool electrode is connected with the negative pole of DC power supply as the electrolytic cathode. Spraying grinding fluid with electrolytic action between anode and cathode as electrolyte, so that diamond grinding wheel, electrolyte, tool electrode and power supply form an electrolytic loop. During trimming, the electrolyte is filled in the gap between the cathode and the anode. Current flows from the grinding wheel to the dressing wheel through the electrolyte. Under the action of electrolyte, the metal components of the metal bonding agent on the surface of diamond grinding wheel are dissolved in the electrolyte and combined with hydroxyl ions in the electrolyte to generate tiny solids, which are taken away by the flowing electrolyte, greatly reducing the bonding strength of the surface layer of diamond grinding wheel. At this time, the mechanical dressing method can greatly improve the dressing performance. Therefore, electrolytic dressing is a compound dressing method which is mainly based on electrochemical action and supplemented by mechanical action.

5.2 Characteristics of electrolytic beneficiation method

Electrolytic dressing method can conveniently realize online electrolytic dressing of metal bonded diamond grinding wheel, dressing and dressing can be completed at the same time, and it is easy to control the cutting state of diamond grinding wheel surface. Electrolytic dressing method has the advantages of short dressing time and low grinding heat, which avoids reducing the service life of diamond grinding wheel because of too high dressing temperature. The disadvantages of electrolytic dressing method are low dressing accuracy, high dressing cost and complex process.

6. Concluding remarks

Dressing of diamond grinding wheel is the key to realize precision grinding, ultra-precision grinding, high efficiency grinding and form grinding of hard and brittle materials. There are many dressing methods for diamond grinding wheels, each with its own characteristics. This paper only introduces several dressing methods which are widely studied and applied at present and have good dressing effect. In practical application, it is necessary to comprehensively consider various factors such as workpiece and machining, and choose the best dressing scheme to achieve the best dressing effect.

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