Conditioning means both the dressing and the sharpening of grinding wheels. In many cases, only a combination of both methods will provide satisfactory results in terms of grinding wheels.
The following details relate mainly to the conditioning of the bond variants resin B, metal M and metal-vitrified MV. The requirements for dressing vitrified bonds are different from those described in the chapter „Vitrified Bonds".
Dressing in this context means the recovery of the grinding rim geometry and the correction of plane and radial runouts (eccentricity).
Conventional silicon carbide wheels are used for dressing B, M and MV bonds. The choice of the proper dressing wheel with respect to grit size and degree of hardness depends on the grit size of the Diamond or CBN grinding wheel to be dressed. The overview below shows the appropriate details.
Selecting the right silicon carbide wheel
Dressing should always be made in the wet mode. If this cannot be done, select the grit size of the dressing wheel one increment finer than shown in the table. The same applies to the dressing of grinding wheels with small rim angle, e.g. pointed profile grinding wheels.
The true running (or concentricity) of the dressing wheel should be checked before every use. The runout of a dressing wheel should never be more than 0.01 mm. Particularly for fine-grained dressing wheels (grit size 320 and finer), the true running should be as perfect as possible to guarantee the best results for the Diamond or CBN grinding wheel to be dressed.
Similar to the actual grinding process, the successful dressing of a grinding wheel depends to a large extent on the parameters selected. Here are our recommendations:
|Speed of the dressing wheel:||30 m/s|
|Speed of the DIA/CBN wheel to be dressed:||1 m/s|
|Feed per stroke during predressing (roughing):||0,02–0,05 mm|
|Feed per stroke during finish dressing (finishing):||0,01–0,02 mm|
Always use the counterrotation principle when dressing. This will increase the life of the dressing wheel, and the dressed grinding tool will be more cut-efficient.
The counterrotation principle during dressing
Always select the dressing wheel with the widest possible diameter. This will make it easier to achieve straight rims on the grinding wheel.
During dressing, the SiC dressing wheel should always remain in contact with the grinding wheel to be dressed. We recommend using only about half the dressing wheel width to run over the grinding wheel rim to be dressed.
When dressing very wide Diamond or CBN wheels, make sure that the feed is not only made at the end or outer points. The occasional feed in the center of the rim prevents convex rim topographies on the grinding wheel to be dressed.
To be noted specially for pointed profile wheels:
Feed should be made in these wheels only on the inside rim. Also, the rim of the steel body which is "ground along" should not be wider than 1 mm.
The "G" value for dressing Diamond and CBN wheels is roughly between 0.025 and 0.03. This means that 30 to 40 cubic centimeters of SiC dressing wheel are needed for removing one cubic centimeter of Diamond or CBN rim. In other words: the wear at the dressing wheel is enormous, but perfectly normal.
For grinding tools to have the best possible cutting efficiency, they need a certain amount of free-standing grinding grits. If a grinding wheel has been dressed as described in the preceding "Dressing" chapter, the amount of free-standing grits is usually insufficient. To obtain the necessary grit free-stand, the bond must be set back after dressing. This process is known as "sharpening".
Unlike the dressing with silicon carbide wheels, corundum wheels are used for sharpening. The universal grit size which can be used for this process is 320 with a hardness J (specifications by WST Winterthur Schleiftechnik).
The parameters to be selected for sharpening are similar to those for finishing dressing.
When sharpening by hand, we recommend using our sharpening stones:
|Nr. 1: red||= for grit size grinding wheel D/B 301 - D/B 46|
|Nr. 2: white||= for grit size grinding wheel MD/MB 40 - MD/MB 1|
The sharpening stone should always be wet before use. Grinding oil is not suitable for wetting the stone. Use only water or emulsion.
When grinding by hand or by machine, the direction of rotation of the grinding wheel must be the same as that used during the actual grinding process.
|Grinding rim surface after dressing
(hardly any grit free-stand, blunt)
|Grinding rim surface after dressing and sharpening (good grit free-stand, aggressive)|