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The chipper is a special equipment for cutting wood and non-wood materials into pieces of wood and scrap. Generally, the medium density fiberboard requires the shape of the wood chip to be 16 to 30 mm in length, 15 to 25 mm in width, and 3 to 5 mm in thickness. To assess the process performance of a chipper, it is mainly based on the length of the chip that is cut. Namely: a large number of wood chips cut by the chipper should have the same length and size, which meets the predetermined requirements. The more wood chips with uniform length, the better the process performance of the machine. For the width and thickness of the chips, the chipper is generally difficult to control directly during the cutting process.
There are many types of chippers, but the actual situation at home and abroad, in the medium density fiberboard industry, commonly used in the following two types.
1), disc chipper
The cutting mechanism of the disc chipper is a large-quality steel disc. The flying knife is mounted on the side of the disc and forms a cutting pair with the bottom knife and the side knife on the same side of the machine base. The raw material is cut into pieces, and the number of flying knives depends on the diameter of the cutter. It is 3 pieces, 20 pieces or even more. When the number of blades exceeds 6 pieces (including 6 pieces), it is customary to call it multi-knife. Disc chipper.
2), drum chipper
The cutting mechanism of the drum chipper is a cylindrical knife roll (drum). A number of flying knives are mounted on the surface of the knives parallel to the axis. The number of flying knives depends on the diameter of the knives. Up to 8 pieces. The bottom of the machine is equipped with a bottom knife. The flying knife and the bottom knife form a cutting mechanism, and the input raw materials are cut into wood chips. The drum chipper has a compact structure and a wide range of cutting materials. Its cutting materials are mainly small-diameter wood, wood processing residues and wood harvesting residues. Depending on how the knife roll and feed are configured. Drum chippers are divided into horizontal forced feed and tilt forced feed.
1. Basic structure and assembly and disassembly precautions: drum type chipper consists of machine base assembly, knife roll assembly, upper feed roller assembly, lower feed roller assembly, conveying assembly, hydraulic system and electrical control system Part of the composition.
Frame assembly.
a. The basic mechanism: the frame assembly is composed of the inner and outer wall panels of the machine base, the bottom knife seat support, the bottom knife seat, the bottom knife, the bottom knife pressing plate, the bottom knife bolt, the clip key, the lower comb board, the scraping rod, the screen mesh and the like.
The base is welded by high-strength steel plate, which is the supporting foundation of the whole machine. The bottom seat support and the base weld are integrated to form the bottom knife seat. The bottom knife is fixed to the bottom knife seat by a special bottom knife bolt through the bottom knife pressing plate. The bottom knife seat can be freely extracted through the hole on the side of the machine wall panel. When working, it locks the bottom knife to the base by two clamping keys. The cut shavings fall through the screen holes and are discharged from the bottom of the base. The large shavings larger than the mesh holes are broken again by the scraping rods mounted on the machine base.
b. Precautions and requirements for assembly and disassembly: The bottom knife bolt is a special high-strength bolt and should not be replaced by ordinary bolts.
When the bottom knife bolt is tightened, apply a torque wrench to tighten the value according to the instructions.
When the bottom bolts are tightened and disassembled, they must be alternated from the middle to the sides.
Before assembling the clips, apply a proper amount of lubricant to the upper and lower contact surfaces. When locking, both sides must be carried out simultaneously or alternately.
After the bottom knife is sharpened, it must be adjusted on the special bottom knife adjustment device to ensure the required installation width of the design.
Knife roll assembly.
a. Basic structure: The knife roll assembly is composed of a knife roll, a main shaft, a main bearing, a press block, a flying knife, a flying knife bolt, a locking device and a large pulley.
The knife roll is the working part of the chipper. It is a rotating body welded by high-strength steel plate. It has good rigidity and a certain moment of inertia and is subjected to dynamic balance test. The knife roll and the spindle are connected by a locking device. Both ends of the main shaft are supported by self-aligning roller bearings, and the bearing seats are respectively fixed on the left and right wall plates of the machine base.
Two or more flying knives are fixed to the knife roll by a special pressure cutter bolt through a pressure block.
b. Precautions and requirements for assembly and disassembly: Flying knife bolts are special high-strength bolts and should not be replaced by ordinary bolts.
Before assembling the flying knife, it is necessary to remove the debris on the surface of the knife seat. When tightening the flying knife bolt, apply the torque to move the hand to meet the specified value of the instruction manual.
After the flying knife is sharpened, a group of flying knives mounted on the same knife roll must be equal. It is also adjusted on a dedicated flying knife adjustment device to ensure the required installation width of the design.
After the flying knife is installed, the knife roller must be turned in reverse to check if it is rubbed against the bedknife.
Upper feed roller assembly.
a. The basic structure; the upper feeding roller assembly is composed of an upper feeding roller seat, an upper feeding roller, an upper feeding roller shaft, a swing shaft, a locking device, a chain transmission device and a speed reducer.
b. Precautions and requirements for assembly and disassembly: During assembly, the relative position of the feed roller on the shaft must be strictly controlled to ensure the relative position of the feed roller and the feed roller seat on both sides, the sprocket and the chain transmission.
The locking device must be evenly tightened according to the instructions to ensure the locking of the outer and feeding rollers, the inner and the shaft.
Lower feed roller assembly.
a. Basic structure: The lower feeding roller assembly is composed of a lower feeding roller, a feeding roller shaft, a supporting roller, a locking device, a speed reducer and the like.
b. Precautions and requirements for loading and unloading: Same as above feeding roller assembly.
2, the relevant experience calculation formula of the drum chipper:
a. Calculation of production capacity: The theoretical production capacity of the forced feed drum chipper can be calculated as follows:
Q=3.6×b×h×V×K1×K2×K3×K4×10-3
Where: Q - volume, m3 / h;
B——the width of the feed port section, mm;
H——the height of the feed port section, mm;
V——feeding speed, m/sec;
K1——machine time utilization factor 0.7~0.9;
K2 - working time utilization factor 0.8 ~ 0.9;
K3——filling port fullness factor 0.3~0.7;
K4——The cross-sectional real product coefficient of the material to be processed under compression, the branch material is 0.2-0.3, the sheet and slats are 0.3-0.5, and the small-diameter logs are 0.4-0.7.
b. Empirical calculation of power:
N=19×Z×n×d2×L×K×10-6
Where: N - power. kW;
Z——the number of flying knives;
N——knife roller speed, r/min;
D——the maximum diameter of the material to be cut, cm;
L——the length of the wood chip, cm;
K——Unit energy consumption, that is, the work required for cutting 1 piece of m3 wood chips per piece, generally K=4～6kW·h/m3, the upper limit can be taken for hard materials, and the lower limit can be taken for soft materials.
Factors affecting the quality of wood chips
1) Raw material quality The quality of raw materials directly affects the quality of wood chips. Therefore, it is required that the raw materials have the best shape and regularity, a certain moisture content, no decay and less skin. The moisture content of the raw material is preferably not less than 35%. Otherwise, not only will the amount of debris increase, but also the power consumption will be high, and the service life of the cutting tool will be shortened. The epidermis of the bark is mainly bast fiber, which is a gelatinous substance and contains more pectin, sand and silice. When cutting, not only the amount of debris is large, but also the tool wear is severe.
2), chipper type disc chipper is suitable for the production of large-scale raw material shavings with large log diameter, and equipped with screening machine and crusher. The drum chipper is suitable for small and medium-sized fiberboard manufacturers, and the raw materials are cut by small-diameter materials, branches and slabs, and the skin of the materials. The lower part of the drum chipper is provided with a sieve plate, and the cut wood chips can no longer be screened.
3), tool selection The sharpness of the tool directly affects the quality of the chip. The flying knife blade has two kinds of single-blade and double-edged blades, and the drum-type chipper has a four-sided blade. Single-blade inserts cut the material into pieces; double-edged inserts are suitable for cutting hard and frozen materials. The grinding angle of the blade should be determined according to the material of the material to be cut. When cutting hard or frozen materials, the grinding angle should be large, and the cutting angle of the cutting tool should be small. This will ensure good cutting quality and reduce energy consumption. In order to ensure the sharp edge of the blade, the blade is required to be periodically ground and replaced. Under normal circumstances, the flying knife should be replaced every 4~8h, and the bottom knife should be replaced every half a month.
4) The length and thickness of the blade for the installation of the blade are determined by the mounting position and angle of the blade. The width of the blade is naturally broken. It depends on the shear strength of the material, which is generally less than The length of the shavings. Therefore, the installation requirements of the blade are relatively high, and it is a non-negligible adjustment technology. Whether using a drum chipper or a disk chipper, all the blades are required to have the same amount of protrusion, and accurately maintain the flying knife and the bottom knife. distance.
Although the chip length of the drum chipper is controlled by the feed speed and the speed of the knife roll, the distance between the fly knife and the bottom knife is still an important factor affecting the size and uniformity of the chip. For the drum chipper widely used in China's fiberboard enterprises, it is advisable to keep the distance between the flying knife and the bottom knife at 0.8~1.5mm.
Chipper brief
Chipper brief