JPS5820754B2 - How to dress the grinding wheel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of dressing a grinding wheel having hard abrasive grains such as cubic boron nitride.

Conventionally, in grinding wheels using cubic boron nitride as abrasive grains,
A rod-shaped truing tool embedded with diamond particles is fixed on a table, and the table is traversed to truing the outer circumference of the grinding wheel to remove runout on the outer circumference of the grinding wheel. In order to make the wheels protrude, workers pressed a bar-shaped dressing tool containing alumina granules against the outer periphery of the grinding wheel. The problem was that the efficiency was extremely poor.

In the present invention, a dressing wheel is opposed to a grinding wheel after truing, a gap smaller than the grain size of loose particles for dressing is formed, and loose particles for dressing are supplied between the two while relatively rotating the two. In addition, dressing is performed by oscillating the grinding wheel and the dressing wheel relative to each other in the axial direction.

Embodiments of the present invention will be described below based on the drawings.

First, in FIG. 1, reference numeral 1 denotes a base, and a grindstone head 2 is mounted on this base 1, and a whetstone wheel 4 is fixed to one end of a whetstone shaft 3 rotatably supported on this whetstone head 2. There is.

This grinding wheel 4 has a structure in which abrasive grains 6 made of a hard material such as cubic boron nitride are fixed to the outer peripheral surface of a metal base ring 5 (see Fig. 3) with a binder made of resin or metal. be.

The other end of the whetstone shaft 3 is fixed to the whetstone stand 2.

A drive motor 7 is rotationally connected via a transmission belt 8 .

In addition, a movable table 1 is attached to the base 10 fixed on the base 1.
1 is mounted to be slidable in a direction parallel to the grinding surface of the grinding wheel 4, and this movable table 11 is connected to a hydraulic cylinder 12 as a traverse device mounted on the base 10.

A tool support 13 is mounted on the movable table 11 so as to be slidable in a direction perpendicular to the grinding surface of the grinding wheel 4.
A drive shaft 14 is rotatably supported in parallel to the grinding surface of the grinding wheel.

A truing wheel 16 and a dressing wheel 17 for truing and dressing the grinding wheel 4 are fitted onto the first drive shaft 14 at a predetermined interval.

This truing wheel 16 is made by fixing a large number of particles of hard material such as diamond to the outer periphery of a metal base ring by sintering with copper alloy, for example, and its width is the same as the width of the grinding wheel 4 in order to reduce truing resistance. It is smaller.

The dressing wheel 17 is made of a material having a certain degree of hardness, toughness, and wear resistance, such as tempered steel or hardened steel, and its width is slightly wider than the width of the grinding wheel 4, and its radius is the same as that of the truing wheel 16. An appropriate size (for example, 50 μ) that is less than the outside diameter of the loose particles for dressing described later than the radius of
It's just smaller.

18 is a motor fixed to the tool support 13, and the drive shaft 1
4 is rotationally connected and true.

The dressing wheel 16 and the dressing wheel 17 are driven one rotation so as to reduce the peripheral speed relative to the grinding wheel 4.

Next, the feed applying device 19 that applies forward feed to the truing wheel 16 and the dressing wheel 17 toward the grinding wheel 4 will be explained.

A feed screw shaft 20 is screwed into the tool support 13 and rotatably supported on the movable table 11.

A pinion 21 is rotatably supported on this feed screw shaft 20 within the force shaft, and a pawl 23 pivotally supported on a rotating plate 22 fixed to this pinion 21 is attached to a ratchet wheel 24 keyed to the feed screw shaft 20. They are removably engaged.

Therefore, when the pinion 21 is rotated by the forward and backward movement of the rack piston 26 based on the operation of the hydraulic cylinder 25, the feed screw shaft 20 is rotated in the forward direction via the pawl 23 and the ratchet wheel 24.
The tool support 13 is moved forward by a predetermined amount (for example, 10 μ).

In FIG. 3, 27 is a nozzle for supplying dressing liquid between the dressing wheel 17 and the grinding wheel 4 which has undergone truing, and is connected via a pump P to a tank 28 in which the dressing liquid is stored. .

As an example, the dressing liquid is one in which 500 g of dressing free particles 29 (about 100 μm in diameter) of alumina, silicon carbide, etc. are mixed into the grinding liquid 101.

Reference numeral 30 denotes an agitating blade that prevents separation of the grinding fluid and the loose particles 29, and is rotationally driven by a motor 31.

Next, the oscillation mechanism 40 that oscillates the grinding wheel 4 in order to uniformly dress the grinding wheel 4 will be described.

First, the grindstone head 2 has a constant pressure support 41 and a variable pressure support 42.
are fixed concentrically with the grindstone shaft 3 and facing each other.

This constant pressure support 41 has a large diameter stepped portion 4 formed on the grinding wheel 3.
3 has a pressure chamber 44 between its one side 43a and the support 41.
It is loosely fitted to the variable voltage support 42, and is also loosely fitted to the variable voltage support 42.

A plurality of recessed pressure pockets 45 are formed in the bottom of the variable pressure support 42 facing the other side surface 43b of the large diameter stepped portion 43. A periodically fluctuating pressure fluid VP is supplied through a throttle 46 provided at the tip thereof, while a constant pressure fluid CP is supplied to the pressure chamber 44 .

Next, the operation of the above embodiment will be explained based on the electric circuit for discrimination shown in FIG.

When the truing/dressing command is sent, the motor 18 is started to drive the truing wheel 16 and the dressing wheel 17 one rotation, and the contact 50 is closed to energize the relay CR1. Based on this, the switching valve is switched, pressure oil is supplied to and discharged from the hydraulic cylinder 25, the feed screw shaft 20 is rotated in the forward direction via the rack and pinion and ratchet mechanism, and the tool support 13 is moved forward by a predetermined amount to cause the truing wheel 16 to move forward. And forward feed is given to the dressing wheel 17.

When the hydraulic cylinder 25 reciprocates and returns to its original position, the contact 51 is closed and the relay CR2 is energized, and the normally closed contact Cr2 is opened and the relay CR1 is deenergized.

The switching valve is switched based on the energization of the relay CR2, and pressure oil is supplied to and discharged from the hydraulic cylinder 12, causing the movable table 11 and the truing wheel 16 to reciprocate at an appropriate feed rate in a direction parallel to the grinding surface of the grinding wheel. The grinding wheel 4 is then trued by the truing wheel 16.

When the movable table 11 reciprocates and returns to its original position, the dressing wheel 17 faces the grinding wheel 4, and a gap t is formed between them based on the difference in radius between the truing wheel 16 and the dressing wheel 17.

However, when the wear of the truing wheel 16 during truing is equal to the radius difference, the gap t becomes zero.

However, in such a case, since the dressing wheel 17 is also worn by the dressing described later, the radius of the dressing wheel becomes smaller than the radius of the truing wheel immediately before the next truing outside the drain sink.

When the movable table 11 returns to its original position, the contact 52 is closed and the relay CR3 is energized, and the normally closed contact cr3 is opened and the relay CR2 is deenergized.

The pump P is activated based on the energization of the relay CR3, the dressing liquid is ejected from the nozzle 27, and the dressing loose particles 29 supplied to the gap t are transferred to the dressing wheel 17.
The abrasive grains are backed up by the abrasive grains of the grinding wheel 4 and are bitten into the binder holding the abrasive grains and scraped off, causing the abrasive grains to protrude from the binder and dressing the grinding wheel 4.

Simultaneously with the activation of the pump P, the fluctuating pressure fluid P is supplied into the pressure pocket 45 of the variable pressure support 42 via the throttle 46, so the fluctuating pressure fluid VP is supplied into the pressure pocket 45.
A static pressure corresponding to the fluctuating pressure is generated, and in response to this pressure fluctuation, the grinding wheel shaft 3 is oscillated in the axial direction against the pressure of the constant pressure fluid CP supplied to the pressure chamber 44 of the constant pressure support 41. Ru.

Therefore, during the above-mentioned dressing, the grinding wheel 4 is oscillated, and the free abrasive grains also wrap around behind the hard abrasive grains and remove the binder, so that the grinding wheel 4 is uniformly dressed.

At the same time as the relay CR3 is energized, the timer TR1 is energized, and after a set time elapses, the timer TR1 times out and its normally closed contact tr1 opens, and the relay CR3 is deenergized and the dressing of the grinding wheel 4 is completed.

In the embodiments described above, the loose particles for dressing do not necessarily need to be mixed and fed after grinding, and only the loose particles may be fed between the grinding wheel 4 and the dressing wheel 17 using their own weight or compressed air.

The dressing wheel 17 is made of nylon on the outer periphery of the metal disc.
If a synthetic resin with excellent strength and abrasion resistance such as polyacetal is fitted, loose particles for dressing will be embedded and held in the synthetic resin, and the grinding wheel can be dressed effectively.

As described in detail above, the present invention allows the dressing wheel to face the grinding wheel after truing by forming a gap smaller than the outer diameter of the loose particles for dressing, and the free particles for dressing are disposed between the two. Since the grinding wheel is dressed by supplying abrasive and relatively oscillating both in the direction parallel to the grinding surface, dressing is performed effectively and uniformly, and the distribution of the abrasive grain protrusion is improved. It becomes uniform, the abrasive grain holding power becomes large, and the life of the whetstone can be extended.

Further, there is an advantage that not only the amount of abrasive grain protrusion necessary for discharging chips can be obtained in a short time, but also the grinding resistance can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a truing/dressing device for a grinding wheel according to the present invention, Fig. 2 is a sectional view taken along the line ■-n in Fig. 1, and Fig. 3 is a diagram showing a device for supplying loose particles for dressing. , FIG. 4 is a control electric circuit diagram. 4... Grinding wheel, 11... Moving table, 12
・・・・・・Hydraulic cylinder (traverse device), 13・
...Tool support body, 16...Truing car, 17...Dressing car, 19...
- Feeding device, 29...Free granules for dressing, P...Pump (device for feeding free granules for dressing).

Claims (1)

[Claims] 1. A method of dressing a grinding wheel bonded with a hard abrasive binder such as cubic boron nitride, in which a dressing wheel with a circular cross section is opposed to the grinding wheel, the two are rotated relative to each other, and the outer peripheral surfaces of both are A gap of an appropriate size smaller than the outer diameter of the loose particles for dressing is formed by bringing them close to each other, and while maintaining this gap, the loose particles are supplied between the two, and the dressing wheel and the grinding wheel are placed on the grinding surface. A method of dressing the grinding wheel by oscillating the grinding wheel relatively in a direction parallel to the grinding wheel.