Design of automatic sandblasting machine with synchronous conveying of shaft inner hole and outer circle

At present, there is no synchronous sandblasting equipment for inner hole and outer round products in China. If you need to blast the inner hole and outer circle, you must go through two sand blasting and two independent sand blasting machines, and the inner hole of the shaft is generally small in diameter and deep. This operation is inefficient and not effective. Improve production efficiency, obtain uniform surface roughness, and develop synchronous sandblasting of inner hole and outer circleConveying automatic sandblasting machine.

1. Working principle and process

The conveying automatic sandblasting machine is powered by compressed air. The compressed air builds up the working pressure in the sand storage pressure tank. The sand is conveyed to the sandblasting pipe through the sand valve and sprayed out through the spray gun. The spray gun is fixed on the spray gun mechanical arm. As the mechanical arm moves up and down, the grit sprayed by the spray gun is evenly sprayed on the product surface and inner hole (the small turntable drives the product to rotate at a constant speed), and the sprayed grit passes through the spiral The conveyor is transported to the vertical elevator, and then the gravel is transported to the gravel separation system by the vertical elevator for sorting. The qualified gravel continues to enter the sand storage tank for the next sand blasting.

2. The main structure of the sandblasting machine

Conveyor automatic sandblasting machine is mainly composed of sand recovery system, sand sorting system, sand blasting system, feeding system, dust removal system, and control system. The sandblasting mechanism is located above the feeding mechanism, the recycling mechanism is located below the feeding mechanism and the screening mechanism, the screening mechanism is located at the unloading end of the lifting mechanism, and the air inlet of the dust removal mechanism is set next to the sandblasting mechanism. All mechanisms are connected to the control cabinet. Electric connection. The feeding mechanism of the conveyor type automatic sandblasting machine includes a power mechanism, a belt pulley, a large turntable, a small turntable, a small turntable driving wheel, a tensioning wheel and an indexing mechanism. The large turntable is arranged on the frame, and the small turntable is evenly arranged on the circumference of the large turntable. On the upper side, the small turntable is connected with a belt pulley, and the small turntable driving wheel and the tensioning wheel are arranged on the frame outside the circumference of the large turntable. In the sand working area, the loading and unloading area and the blasting working area are arranged symmetrically at a level of 180°. The belt pulley, tensioner and small turntable driving wheel under the small turntable in the sandblasting working area always cooperate with the belt. The pulley under the turntable is always out of contact with the belt. The driving wheel of the small turntable is driven by a power mechanism. The top of the rotating shaft of the big turntable is connected with an indexing mechanism, which is fixed on the frame and driven by the power mechanism.

3. Gravel Recovery System

3.1 Horizontal screw conveyor

Conveyor type automatic sandblasting machine horizontal screw conveyor is composed of reducer, screw shaft, conveying cover, bearing with seat, etc. Its working principle is: use the rotation of the screw shaft with spiral blades to cause the grit to generate mutual contact along the spiral surface. Movement, the grit is rotated with the screw shaft by the friction force of the trough or the conveying pipe wall, thereby pushing the material forward and realizing the conveying of the grit.

3.2 Vertical lifting mechanism

The vertical elevator of the conveyor automatic sandblasting machine is composed of a reducer, a roller, a conveyor belt, a hopper, a closed shell and an anti-loosening device. The shell is welded and formed by cold-rolled steel plates. Access doors are arranged on the side, and movable doors are installed on the front and sides of the lower cover. Centrifugal gravity blanking, the conveyor belt adopts a special transmission belt with polyester core, high strength and stretch resistance. The pulley adopts a squirrel cage structure, which improves the friction between the belt and the pulley and prolongs the service life; at the same time, it avoids the scattered grit from being embedded between the pulley and the belt and affecting the transmission. A pulse wheel is installed on the lower rotating shaft of the conveyor automatic sandblasting machine hoist to detect the working status of the hoist. The pulse signal can be fed back to the PLC in time, and if there is an abnormal signal, it will alarm in time to ensure the safe operation of the equipment.

4 Gravel separation system

4.1 Gravel separator

It adopts a curtain structure with discrete sorting function. When the gravel is lifted by the elevator to the sorter, the gravel mixture is evenly sent into the sorting area through the curtain winnowing device to form a uniform sand gravel slag flow curtain. The gravel mixture is pushed by the horizontal airflow to the particles during the descending process. , Thus forming a skewed curved trajectory, the degree of skew is not the same due to the difference in the specific gravity and particle size of the particles. The dust is sucked into the dust collector for purification treatment, and qualified sand and some small debris are sorted by vibrating screen and then enter the sand storage tank for recycling.

4.2 Vibrating Screening Machine

After the dust passing through the outlet of the bucket elevator is separated, the grit enters the vibrating screen, and the reusable grit enters the vibrating screen separator for size separation. The vibrating screen separator is equipped with two layers of screens. The upper screen can separate the coarser impurities and send it to the waste hopper. The lower screen can separate the unqualified grit smaller than the size requirement and send it to the waste hopper.

The upper surface of the second layer of screen is grit that meets the size requirements, which are sent to one by one sand storage tank to continue recycling. The sand storage tank is connected to the automatic sandblasting machine through a pneumatically controlled discharge valve. When the upper tank of the automatic sandblasting machine lacks gravel, the discharge valve is automatically opened to add the sand stored in the sand storage tank to the conveying automatic sandblasting machine.

5. Sandblasting system

The conveyor-type automatic sandblasting machine is a frame-type assembly structure, which drives the inner and outer wall spray guns to move up and down vertically. The height of the outer wall spray gun is adjusted according to the height of the outer wall of the parts. The reciprocating movement uses the SIEMENS servo motor to drive the precision ball screw. Circular orbit support and guidance.

6. Feeding system

6.1 Intermittent rotation structure of large turntable

The large turntable of the conveyor automatic sandblasting machine is driven by the reducer to rotate the indexer 90° into and out of the sandblasting chamber body. After the accuracy is in place, the cylinder door seals the sandblasting chamber body at the same time. At this time, sandblasting and loading and unloading of the workpiece are carried out at the same time to improve work efficiency. The table top of the turntable is made of 20 mm thick steel plate, and a high wear-resistant rubber protective layer is fixed on the surface of the turntable, which can effectively improve the service life of the table. The large turntable is equipped with a high-precision splitter and a geared motor, and the repetitive positioning accuracy of the large turntable's rotary station is ≤±0.05°.

6.2 Small turntable structure

There are a total of 8 rotating tables on the big turntable, which are arranged symmetrically, and the small turntable in the sandblasting zone is driven by a triangle belt to rotate. There is a center positioning hole on the surface of the turntable, which can realize the center positioning of the fixture.

7. Dust removal system

The dust removal equipment of the conveyor automatic sandblasting machine is three-stage dust removal, which are first-level cyclone dust removal, second-level filter cartridge dust removal, and third-level HEPA high-efficiency filtration. The dust removal system is outside the sandblasting equipment, and is connected with the dust suction port of the sandblasting chamber body and the air suction port of the curtain separator through the dust removal pipeline. The dust removal efficiency of the first-stage cyclone dust collector can reach 90%, which reduces the burden of the rear dust collector, extends the service life of the filter element, and reduces the operating cost of the equipment.

8. Control system

The electrical control system of the conveyor automatic sandblasting machine adopts a programmable controller, and is equipped with a servo motor to realize the precise positioning of the revolving door, and realizes the detection and control of the entire system action (switching quantity, analog quantity, pulse counting, etc.) through program control. The system is equipped with sound and light alarm function. When there is an error in the mechanical operation device or the electrical circuit system fails, the system will automatically alarm and stop the sandblasting operation. The operation control of the motor has protection functions such as overheating, slipping, overloading, and reverse.

9. Test and analysis

9.1 Test process

1) Add enough gravel to the conveyor automatic sandblasting machine, and perform the idling operation of the equipment without connecting to the air source, run it for a period of time under normal working conditions, and perform a load test after the operation is normal; 2 1) Connect the sand blasting air pipe to the air compressor air pipe to check whether the air pipe is unobstructed; 3) Start the sand blasting program, and record the operating parameters and surface roughness during operation.

9.2 Test results

Through repeated tests, the equipment operating data is obtained under the premise of ensuring the uniform surface roughness and achieving the expected effect: the pressure at work is 1 MPa, the air flow is 10 m3/min, the frequency of the large turntable is 50 Hz, and the frequency of the small turntable is (25 ±5) Hz, sand volume is 20 kg/min, spray gun speed is (25±5) Hz. The roughness detection value after sandblasting is shown in Figure 3. The selection of measuring points is that the same circumferential interface selects 4 points for 90° measurement.

10. Conclusion

After the conveyor automatic sandblasting machine is put into operation, the surface roughness, safety protection and efficiency of the product surface after sandblasting fully meet the technical and production requirements of the product. The conveyor automatic sandblasting machine can blast different grit and different specifications of products, can achieve precise control of the surface roughness after sandblasting, improve production efficiency, reduce labor intensity, and increase enterprise benefits. It has a very broad application prospect.