Ring die is the key to the pellet machine parts, is the most main grain machine parts, according to the statistical, ring die loss fees account for more than 25% of the entire production workshop maintenance, at the same time, to squeeze out particles has a direct impact on the quality of feed. Therefore, understanding the characteristics of the ring die and the ring die and correct selection of reasonable and effective maintenance, for feed producers is crucial. In the face of ring die characteristics and selection, use and maintenance to make some analyses, for your reference. 1 the characteristics of the ring die 1.1 ring die material and heat treatment of ring die materials mainly include carbon structural steel, alloy steel and stainless steel 3 classes. 45 steel, carbon structural steel, such as the heat treatment hardness is commonly HRC45 ~ 50, it belongs to the lower grade material of ring die, its wear resistance and corrosion resistance are poor; Alloy structural steel, such as 20 crmnti, 40 cr, 35 crmo, heat treatment hardness over HRC50, and has good comprehensive mechanical properties, this kind of material made of ring die high strength, wear resistance, but the disadvantage is that poor corrosion resistance; Stainless steel material X46Cr13 (German brand), 4 cr13 and 3 cr13, stiffness and toughness of the material are better, heat treatment hardness greater than HRC50, and has good abrasion resistance and corrosion resistance, long service life. In order to control ring die after heat treatment hardness uniformity, each ring die after heat treatment, every part of the third section in the circumferential direction, take not less than 3 points average hardness measurement, the hardness value of the various parts should be no greater than the difference between the HRC4. In addition, the response to the hardness of ring die blank control, its hardness is between HB170 ~ 220 advisable, if too high hardness, drilling, the drill is easy to break and cause death hole, spend low is hard

Influence of die hole finish. In order to control the uniformity of blank inner material, conditional word, internal inspection should be made for each blank to prevent blank internal defects such as cracks, porosity, sand inclusion. 1.2 ring die structure, compression ratio and roughness of the common ring die are straight type hole, stepped hole, outer taper hole and inner cone hole, etc. Stepped hole is divided into release type ladder hole bore (commonly known as the decompression or release) and compression type ladder hole, as shown in figure 1, the different forms of die hole is suitable for different kinds of feed raw materials or different feed formula. Ring die compression ratio is an effective length of the ring die and the ratio of the smallest diameter of ring die, it is an indicator of the strength of pellet feed extrusion. The compression ratio, the greater the extrusion of pellet feed more strong. For straight shape hole ring die compression ratio, effective length of loop die is the total thickness of ring die, minimum diameter is the diameter of the die itself; For release type ladder hole and outer cone hole, the effective length of die hole which is a total thickness of the ring die, less release hole length or the length of the outer cone hole, small diameter of pore size to calculate the compression ratio of aperture; For compression type ladder hole and inner cone hole, this kind of situation is special, generally the entire ring cavity thickness as effective length of die hole, minimum diameter in small diameter of pore size, of course, so that calculate the ring die before the meaning of the compression ratio and there is a difference between two cases. Roughness is important index to measure the quality of ring die. Under the same compression ratio, the greater the roughness, feed extruder, the greater the resistance discharge more difficult, also affect the quality of the particle surface roughness too. Suitable roughness value should be between 0.8 ~ 1.6. 1.3 ring die working area, hole arrangement and opening rate

The inner diameter of the ring die work area of the ring die pupil the product of the effective width, the effective width of the ring die of the distance between two more routine slot. Under the same work area, ring die is inversely proportional to the diameter and the effective width. Ring die hole when the arrangement is generally arranged along the circumference, and most in the width direction and the mutual interactions between holes, make whole drilled holes in the approximate equilateral triangle arrangement. If the diameter of the holes for the d, between holes and hole wall thickness for a, ring mold opening rate of bits, then according to the principle of an equilateral triangle, it is easy to calculate: bits of material 0.9 d2 (d + a) / 2, for example, ring die hole diameter is 4.5 mm, if the pores between the wall thickness of 2.6 mm, then you can calculate the ring die opening rate of 36%. Can be seen from the above formula, under the condition of the die hole diameter must be, to improve the opening rate of ring die, must reduce the die hole between the wall thickness, but the minimum wall thickness must meet the needs of the ring die strength. The general rule is, die hole diameter, the greater the ring die opening rate is higher. 1.4 ring die linear velocity loop die linear speed ring mould the tangent velocity, the high and low affect extruding zone material layer thickness and material through the die hole of the time, thus influence granulating machine yield and grain quality. Linear speed is high, has the potential to squeeze the material in the formation of the fault, granulating discontinuous, make soft particles, powder, and materials for the moisture content is higher also easy skid, even cannot granulating; Lower ring die linear velocity while make particles are of good quality, but the larger impact on production. Commonly used ring die velocity between 6 ~ 9 m/s.