Bonded 3m abrasive wheels sometimes need to be trimmed. This may be due to normal tool wear or excessive grinding load (if optimum machining parameters (eg tool speed and feed rate) are not used). Whatever the reason, you’ll want to be able to shape the tool and/or expose fresh diamond abraisives. Traditionally, this has been done in two operations: the first is a trimming operation that uses some process to shape the edge of the 3m abrasive wheels. This may be the wire EDM process used by the tool supplier, the 3m abrasive wheels designed for dressing the 3m abrasive wheels, or the use of a diamond tip. Once the tool has been formed, it needs to be trimmed to ensure that fresh diamonds are exposed. This is usually done using an alumina (Al2O3) dressing bar. The size of the Al2O3 abrasive used will vary depending on the diamond size of the 3m abbrasive wheels you are trimming. The table below shows this relationship:
The old method of dressing the 3m abrasive wheels was to open the tool spindle at a very low rpm and then manually trim the 3m abrasive wheels. This is not a good way to do this for a variety of reasons. First of all, this is not safe. Never push your hand into the machine while the spindle is running. Secondly, this is definitely not a controllable and effective way to expose fresh diamonds to the 3m abrasive wheels.
The BINIC designed fixture secures the Al2O3 trim rod to the workpiece spindle. This allows you to use the machine to safely and accurately dress and trim the 3m abrasive wheels. The image above shows a 1 inch square trim bar and its mounting in the grinding platform. First place the appropriate grit trimming rod into the holder. The tool holder is then placed in the workpiece spindle and the 3m abrasive wheels is moved over the center of the dressing bar to make it almost in contact. After adjusting the coolant line, close the door, open the spindle and coolant, and finally program the machine to feed the 3m abrasive wheels into the dressing bar. The spindle speed should be set similar to the speed during the grinding process and is usually fed into the dressing bar at a feed rate of approximately 1 mm / min. The depth you must remove from the dressing bar ranges from 1-2 mm to tens of millimeters. This will depend on the size of the abrasive cutting discs (the coarse diamond takes longer) and the amount of material that needs to be removed from the 3m abrasive wheels if you want to shape it.
The benefit of this process is that the 3m abrasive wheels can be trimmed and trimmed in the same operation. By using the precise control of the machine, it provides safer operation and better results than the old dressing method.