Briefly introduces the structure and working principle of a grinding wheel arc dresser that can be used for peach-shaped groove arc dressing of large bearings. It is driven by a two-way hydraulic cylinder, and at the same time, it adopts mechanical and electrical double limits to ensure the safety, accuracy and efficiency of the arc dressing of the grinding wheel.

The grinding of the grooves of the inner and outer rings of large bearings with CNC forming grinding wheels is a very effective process method to improve production efficiency and processing accuracy. In the process of grinding the grooves of the inner and outer rings of the bearing, the arc dressing of the forming grinding wheel is a key issue that must be solved. At this time, the practicability and convenience of the grinding wheel arc dresser are particularly important.

As the mother machine for P2 and P4 bearing grinding processing, the MGK28 series of high-precision CNC vertical universal grinders can be equipped with grinding wheel arc dressers that meet their different functions according to the needs of customers.

1 Design background

The MGK2835O high-precision CNC vertical universal grinder (manufactured by Beijing Guangyu Dacheng CNC Machine Tool Co., Ltd.) ordered by a bearing factory needs to grind large bearings. For the peach-shaped grooves of the inner and outer rings, according to the geometric shape and surface accuracy requirements of the workpiece to be processed, select the appropriate grinding wheel and perform arc trimming on it, and then the workpiece is ground to meet the quality requirements of the workpiece. On this basis, a set of grinding wheel arc dresser is designed.

2 Working principle

The structure of the grinding wheel arc dresser consists of the dresser base 1, the rotating bracket 2, the left center 3, the diamond pen base 4, the diamond pen 5. The right center 6, the hydraulic cylinder piston rod 7, the sector block 8, the non-contact switch 9, the mechanical limit rod 10 and other main parts and other auxiliary parts. The dresser adopts a simple beam structure supported at both ends, and both ends of the dresser base 1 support the rotating bracket 2 through precision bearings.

The grinding wheel arc dressing requires the diamond pen tip to make a uniform circular swing relative to the grinding wheel. In this design, a bidirectional hydraulic cylinder is used to drive to ensure the diamond pen swings evenly and smoothly. There is a hydraulic cylinder on the base 1 of the dresser, which is driven by a two-way hydraulic cylinder. The linear motion is converted into a rotary motion through a rack (hydraulic cylinder piston rod 7) gear (fixed on the right center 6), thereby driving the rotating bracket 2 to make Swing back and forth regularly. The diamond pen 5 fixed on the rotating support 2 also swings in a reciprocating circle around a preset circle center. By adjusting the electrical and hydraulic components and the CNC machining program control, the grinding wheel can be trimmed to the desired arc.

The position of the diamond pen can be adjusted back and forth through the thread on the diamond pen base 4 installed on the rotating bracket 2. The distance between the diamond nib and the center of the grinding wheel (when it is on a horizontal surface) is a-R when repairing a convex arc on the grinding wheel, and a+R when repairing a concave arc on the grinding wheel. The center distance of the arc dresser is a, that is, the distance from the center of the grinding wheel to the line connecting the left and right centers on the horizontal plane, and the radius of the arc to be trimmed is R. The dresser is mainly used to dress the peach-shaped grooves of the inner and outer rings of large bearings, which are convex arcs. The trimming adjustment of the concave arc will not be described in detail. When trimming the convex arc, the position of the diamond pen can be adjusted with the help of the tooling mandrel (fixed with the left and right centers 3 and 6) so as to make the diamond pen easier to adjust to a more accurate position. It is tightened with a set screw to fix the diamond pen to ensure accuracy, safety and effectiveness.

The swing of the diamond pen, that is, the swing of the rotating bracket 2, is jointly restricted by the mechanical limit and the electrical limit to ensure the accuracy and effectiveness of its swing angle. Among them, the mechanical limit restricts the swing range of the sector block 8 through the up and down adjustment of the mechanical limit rod 10, thereby controlling the swing position and range of the rotating bracket 2; the electrical limit uses a non-contact switch 9 as a sensor element, which is performed by the numerical control system control. The speed and direction of the swinging back and forth of the rotating support 2 are controlled by the hydraulic valve group, so that the rotating support 2 can obtain a proper swing speed and direction. The hydraulic valve group is composed of hydraulic valves such as pressure reducing valve, flow control valve and directional valve.

Working principle of hydraulic control of grinding wheel arc dresser. The hydraulic pump in the oil tank 1 is driven by a motor to provide a pressure oil source for the hydraulic system, which is adjusted by a direct-acting relief valve to control the system pressure to not greater than 0.7MPa. When the grinding wheel performs arc trimming, the direction in which the diamond pen swings back and forth, that is, the direction of movement of the two-way hydraulic cylinder 3 piston rod is controlled and adjusted by the two-position four-way directional valve 4; the speed of the diamond pen swings is the amount of flow through the oil circuit It can be controlled to realize the process of rough and fine trimming during arc trimming. The selection of rough repair and fine repair is controlled by the two-position three-way directional valve 4. During the rough repair, the oil circuit passes through the two-way flow control valve 5. At this time, the flow control is 0.6L/min; during the fine repair, the oil circuit passes through the two-way flow. Control valve 6, at this time the flow control is 0.2L/min. At the same time, the flow of the oil circuit during rough repair and fine repair can be adjusted according to the actual workpiece and the grinding process to meet the grinding processing requirements of different workpieces.

3 Operation method

When the grinding wheel arc dresser is in use, a tooling mandrel is made according to the size and accuracy of the grinding wheel arc that needs to be trimmed. The groove needs to be Ø40mm×320mm). Use the left center 3 and the right center 6 to fix the two ends of the mandrel. With the help of the mandrel, the position of the diamond nib can be accurately adjusted to meet the needs of dressing.