in Vol. 18 - March Issue - Year 2017
Introduction of the QR32 Series Crawler-Type Shot Blasting Machine
QR32 tumble belt type shot blasting machine
Equipment working principle
Table 1: Main technical parameters
Shandong Kaitai Group, China
Technics and technology of abrasion investment casting
Abstract: The QR32 series crawler-type shot blasting machine is suitable for surface cleaning of small castings, forgings and other parts. A rubber belt winding in three rollers is driven by power mechanism and moves in both positive and negative directions in the cleaning chamber. When the workpieces placed on the belt are cleaned, the impeller head projects pills that impact on the workpiece surface. The positive movement of the belt rolls the workpiece continually, so that the entire surface of the workpiece is exposed in the projectile beam to eliminate "the shot blasting blind corner". After cleaning, the workpiece can be automatically unloaded by the belt reverse movement. This equipment is suitable for different production scales that can be used not only in a single but also multi-station environments. The characteristics of the shot blasting chamber, impeller head, separator, dust removal system, etc are also introduced in this paper. It is proven by the application that this equipment has advantages of reasonable structure, low-energy consumption, and good cleaning effect, etc. Keywords: Crawler-type; Shot blasting machine; Casting; Forging; Surface cleaning
The Q32 series Crawler-type shot blasting machine is routine equipment produced by Kaitai Company that is suitable for the surface cleaning of small castings, forgings and surface rust cleaning, as well as strengthening of some parts such as springs, gears, crankshafts, and connecting rods etc. Through shot blasting treatment, the surface corrosion, the oxide skin and casting molding sand of the workpiece surface can not only be removed, but the internal stress can be reduced as well in order to improve surface paint adhesion, corrosion resistance, and anti-fatigue strength etc. Being suitable for different production scales, this type of equipment can be used alone, as well as in various combinations. The machines can also be composed with the continuous conveyor to form a cleaning production line. For large, medium and small production scale modalities, the machine is the ideal equipment for surface cleaning processes.
2. Working principle and technical parameters
2.1 Working principle
This equipment is mainly composed of a loading and unloading system, cleaning chamber, impeller head, elevator and separating system, electronic control system and dust removal system, etc. In the cleaning chamber, the rubber belt, winding in three rollers, is driven by a power mechanism to rotate in positive (counter clockwise) or reverse rotation. When the machine is operating, it is necessary to open the door of the cleaning chamber and to place the workpiece on the rubber belt between the two up-rollers by the loading system automatically. After the workpiece reaches the specified quantity, the door and should be closed and the machine then started; now, the impeller head projects pills to impact the surface of the workpiece. When the rollers rotate counter-clockwise, the workpiece is continuously rolled by the action of belt movement. In the rolling-over process, the workpieces are impacted by the pills projected by the impeller head. In this condition where the workpiece is impacted during rolling-over, the hitting probability is almost the same whether the workpiece is large, small, thin, thick, round or flat, which can eliminate "the shot blasting blind corner".
After the pills are splashed, they pass through the small holes in the belt and fall to the steel mesh at the lower part of the chamber to be screened, finally arriving in the collecting pills bucket. The pills are transported in a level direction by the screw conveyor to the bottom of the elevator, and are then lifted in a vertical direction to the separator of pills and sand located at the top. The cleaned pills then inflow into the storage bucket and enter the impeller head through the pill valve to continue circulation. The dusty gas is sucked into the dust collector by fan and filtrated to be discharged into the atmosphere. Blasting time is controlled by time relay. After the shot-blast cleaning is finished, the pills are then screened and the shot chamber door is opened automatically; the belt reverses rotation and the workpieces are unloaded at once. So far, when a work cycle is completed, there has been no manual operation in the whole process, and it is fully closed operation.
2.2 Main technical parameters
The main technical parameters of this equipment are shown in Table 1.
3. Equipment structure characteristics
3.1 Cleaning chamber
The function of the cleaning chamber (welded together by using steel plates) is to isolate the working area and prevent pills and dust from splashing. At the same time, the cleaning chamber is the installation foundation of multiple parts. For example, the impeller head is mounted on its top; the crawler roller and its transmission mechanism are located inside the cleaning chamber; the screw conveyor at the bottom is fixed to the cleaning chamber also. Therefore, the cleaning room not only requires good sealing performance and impact resistance, but has certain stiffness and geometric accuracy as well. In order to meet these requirements, the cleaning chamber steel plate components are cut by a CNC laser-cutting machine and the base of the bearing seats are welded using a special mould positioned to ensure that crawler roll and screw conveyer etc. are in the correct installation position. The sealed door is adapted in the cleaning chamber, and the wear guard plate is installed in the cleaning chamber indoor wall to prevent breakdown of the wall. Due to the necessity of withstanding vertical impact, the top guard has selected 65Mn steel used as the protection plate.
3.2 Impeller head
This machine is equipped with a QY360 type impeller head, and a double disc with symmetrical distribution groove for mounting blades is adopted in this impeller head, so it has good rigidity and stability. Blades can be inserted outward from the impeller center. When the double disc rotates, the blades are automatically positioned and locked under the action of centrifugal force, so other mechanical devices are not needed.
If the blades need to be disassembled, the outer ends of the blade are merely tapped and removed easily from the center of the double disc. It is convenient to check the wear situation of impeller and directional set. The impeller head has the advantages of simple structure, and convenience of assembly and disassembly blades.
The separator belongs to whole curtain winnowing type. It works based on the gravity separation principle; that is, the mixture of pills and residue is subjected to horizontal airflow to form a skewed trajectory during the falling process. Because of the difference of specific gravity and particle size, the degree of deviation is different; thus, the flow curtain of pills, metal oxide fragments and dust is effectively separated into three parts. The pills material for reuse fall into a pills bucket to be used by the impeller head; entering into the waste pipe, dust particles are excluded; dust is inhaled by the dust collector. The baffle of the feed inlet in winnowing device can be adjusted to change the thickness and evenness of the pills and sand flow curtain. Adjustment of the butterfly valve on the pipeline can be carried out to improve the separation effect. Impurities entering into the impeller head are reliably set to be no more than 1%, and pill waste is set as not more than 1%.
3.4 Dust removal system
The dust removal system consists of dust collector, fan, pipeline, deposition tank and so on. A two-stage removal dust process is adopted in this equipment to improve the dust removal effect and prolong the service life of the filter bucket. Because of the larger gravity, large particles in the dust fall first when they pass through the deposition tank to avoid the accumulation of pills in the pipeline, and finally, they will be filtered through the filter bucket.
As a standardized product, more than 1 thousand machine sets have been generated and sold by Kaitai Company: the product and company are praised widely by users. The QR32 series crawler-type shot-blasting machine is mainly used for surface cleaning, removal of rust and strengthening of small castings and forgings of various shapes. Practice has proven that the equipment has the following advantages: 1) equipment is miniaturized. The elevator and the cleaning chamber are directly connected together, and the separator and settling box are located at the upper part of the cleaning chamber; therefore, equipment covers an area of small, low manufacturing costs; 2) a high degree of automation. The whole process from loading, blast cleaning, pills material circulation and unloading is automated; 3) good cleaning effect. In this machine, belt transmission is used to drive workpieces, so they are constantly tumbling, and all surfaces are evenly cleaned. A satisfactory effect can be obtained for blind corners presenting cleaning difficulty.
Yuan cunbo, Xu yinlian
Shandong Kaitai Shot Blasting Machine
Machinery Co. Ltd., Shandong Binzhou 256217
Mechanical Engineering School, the
University of Jinan, Shandong Jinan 250022