Have questions? SBM sales representatives are available for live chat now WELCOME TO SBM MACHINERY!

Coal Grinding Mill

Coal Grinding Mill

Details of this product

Coal Grinding Mill four-valve combination

The double-motor-driven Coal Grinding Mill is one of the grinding equipments currently put into production in China. The technical requirements for the diameter, processing precision and heat treatment hardness of the four-lobed composite ring gear of the milling equipment are very high. SBM developed a practical processing method based on the four-lobed structure combined with the large ring gear manufacturing process for the four-lobe structure combined with the large ring gear.

1. Four-lobed combination large ring gear structure and performance parameters

The four-clip combined large ring gear is composed of four sets of gears to form a whole circular structure, and the large ring gear often adopts a double web structure to improve the overall rigidity of the large ring gear.

The four-ring large ring gear is made of ZG40CrNi2Mo, the quenching and hardness requirement is 310-350HBS, the modulus is mn=36mm, the pressure angle α n=25°, the helix angle & beta;=7.25°, the tip diameter is da=13281.536mm, Tooth width b=1100mm, net weight 110t, gear precision Q10-AGMA390.03, dimensional accuracy IT7, tooth surface roughness Ra3.2μm.

2, four-petal combination large ring gear processing difficulties

(1) Elimination of casting, heat treatment residual stress and mechanical processing stress deformation;

(2) Control of wall thickness consistency of the ring-to-mouth joint surface joint plate;

(3) Control of the joint precision of the four-petal interface;

(4) Control of the accuracy of the large ring gear.

3, four-petal combination large ring gear process technology solutions

(1) Ring gear deformation control

The shape of the four-lobed ring gear is a wide-groove structure with double webs. During the casting and heat treatment of the blank, the cold and heat shrinkage of each part of the blank is uneven, so that the volume change of the metallurgical structure inside the casting and the internal stress of the blank are large. . In order to eliminate the stress, in the process of the large ring gear, the secondary machining technology is adopted, the four-gear gear joint surface is disassembled after the rough milling, and the vibration aging and artificial aging treatment process are added to make the rough/finishing process alternately. Eliminate casting, heat treatment residual stress and machining stress; adopt multi-point support on the workpiece clamping method to enhance the rigidity of the large ring gear; use multi-step machining, select small-travel amount and high-speed cutting processing method in the finishing process. Greatly reduce the deformation of the large ring gear.

(2) Control of the consistency of the ring gear wall thickness

In order to ensure the equal strength of the split section of the four-lobed ring gear, it is critical to control the blank sub-line datum. Firstly, the four-lobed ring gear is not used as the reference. At the same time, two scribing discs are used to ensure that the horizontal center line of the four-ring ring gear is aligned, and then the center position of the ring gear is determined according to the unprocessed inner circle. Bonding surface 90 & deg; center line and 45 & deg; symmetrical center line, while taking into account the symmetry uniformity of the rib plate distribution to draw the inner and outer round lines; after heat treatment, the joint surface of the joint will appear upturned and sagging phenomenon, then the four-ring gear ring will be put together first. Re-test the line, for the tooth surface allowance, ensure that the length of each chord is equal to the length of the arc, adjust the radius of the workpiece and then split it into four lobes. Strictly control the two 90° of each ring of the four-toothed ring gear. The cumulative error of the joint angle is such that the four-ring large ring gear has the same arc length and the uniform surface thickness of the joint surface is uniform.

(3) Control of the joint precision of the ring gear joint

1 The four-lobed large ring gear is subjected to a large alternating load in the operation of the Coal Grinding Mill, especially at the 1/4 joint joint surface. Therefore, the appropriate tool and cutting amount should be selected to control the flatness and roughness of the joint surface of the four-ring large ring gear. It adopts carbide end mill with a speed of 500r/min, a feed rate of 400mm/min and a cutting depth of 0.2-0.3mm. Use the feeler gauge to check the joint clearance of the four-ring ring gear. The depth of the 0.04mm feeler plug into the joint surface does not exceed 25mm, which creates conditions for the processing and installation of the refined joint bolt holes.

2 The four-lobed ring gear has a span of 13m. According to the central plane, the joint hole is machined on the CNC boring and milling machine, and the coordinate values ​​and aperture tolerances of each hole are strictly controlled.

At each joint of the four-toothed ring gear, 12 sets of couplings are connected. Among them, 4 sets are used for the positioning of the refined bolt with the matching accuracy of H7/h6. The special locking nut device is used, and the locking torque is higher than the traditional hydraulic pressure. The pre-tightening force of the wrench is more accurate and labor-saving.

The special lock nut device is shown in Figure 3. The principle that the thrust of the plurality of jack bolts and the reaction force of the main bolt caps generate the same large clamping force on the joint surface, the joint surface of the joint is tightly closed, and the friction torque of the small diameter high pressure strong bolt is small, and the friction torque is small. Small tightening torque is pre-tightened. The combination of multiple bolts can generate a huge clamping force, so the locking of the jacking bolt can be completed by using a manual torque wrench, and the pre-tightening force control can be realized to effectively prevent the nut from loosening.

In the process of roughing/finishing the four-ring large ring gear, the disassembly and assembly according to the installation, disassembly and pre-tightening torque specifications of the special lock nut device are strictly carried out to ensure uniform bearing capacity of each joint surface.

(4) Four-ring large ring gear finishing and tooth surface roughness control

1 finishing process

The large-toothed ring loading method adopts a claw reverse-supporting large ring gear, and does not process the inner circle. At the same time, the high-horn horn such as the end of the inner subsidy block on the reference end face is used to form the truck into all the processing surfaces. After finishing the car, it will not be split and will be transferred directly to the fine hobbing process. It not only ensures the consistency of the machining standard, but also avoids the deformation of the ring gear caused by repeated fitting and turning of the workpiece.

2 hobbing process

Firstly, the matching workbench is used to ensure the stable support of the large ring gear, and the T-shaped groove layout of the worktable is used to supplement the end face of the large ring gear, the reference end face and the large end face of the inner flange to increase the height horn fulcrum to ensure the contour support pad. After the plate is smoothly positioned, the card is loaded, and the number of fulcrums is not less than 2/m along the circumference. During the milling process, the surface of the table and the large ring gear are always monitored, and the warping deformation of the Shanghai Shibang ring gear is controlled at any time.

Since the upper limit of heat treatment of the large ring gear reaches 350HBS, the carbide milling cutter is selected for rough milling, and most of the tooth surface is removed to ensure that the center of the milling cutter coincides with the center plane of the tooth groove where the joint surface is located. The four-lobed gear teeth are split after rough machining for sufficient aging treatment; the semi-finishing milling still uses the carbide disc milling cutter to mill and leave the fine hobbing allowance, strictly correct the hob cutter The turret and the end face bounce meet the standard requirements, and the carbide roller is used to finish the tooth shape. Select the appropriate cutting amount: cutting speed is 50~60r/min, the range of cutting is 70~400mm/min; in the milling process, according to the inspection results of the tooth surface roughness, adjust the cutting amount of fine hobbing in time, and control the finishing pass Quantity until processing to the paper size. After finishing, the measured tooth surface roughness is between Ra3.2 and Ra1.6 & mu; m, and the accuracy reaches IT7.

During the machining process, each time the large ring gear is removed once, the group and corresponding marks shall be made on the end face of the large ring gear of each valve, and the tooth mark shall be printed at the position of the tooth tip after rough milling to ensure four petals. The ring gear is accurately reset.

After that, Shanghai Shibang concluded that the manufacturing quality of the four-cutter large ring gear of the mining Coal Grinding Mill has an important impact on the smooth running of the Coal Grinding Mill transmission. Through the research on the four-lobe large ring gear of the mining Coal Grinding Mill, the deformation of the four-ring large ring gear, the wall thickness consistency of the joint plate of the joint surface, the joint precision and the gear precision are effectively controlled, and the transmission precision of the large ring gear is improved. It meets the requirements of drawing design. At present, this technology has been widely promoted in the manufacture of other four-lobed large ring gears, and the application effect is remarkable.

Get Price And Support

Simply complete the form below, click submit, you will get the price list and a SBM representative will contact you within one business day. Please also feel free to contact us by email or phone. ( * Denotes a required field).