A ring mold features
1.1 ring mold materials and heat treatment
Ring mold material, carbon structural steel, alloy steel and stainless steel 3. Carbon structural steel, such as 45 steel, the hardness of heat treatment is generally HRC45 ~ 50, it belongs to the lower grade material of the ring mold, wear resistance and corrosion resistance are poor; alloy structural steel, such as 20CrMnTi, 40Cr, 35CrMo, etc. heat treatment hardness above HRC50, and has good mechanical properties, the ring die by such materials, high strength, corrosion resistance, wear resistance or, but the disadvantage is bad; stainless steel X46Cr13 (German grade) 4Cr13 , 3Cr13 such as stiffness and toughness of these materials are good heat treatment hardness greater than HRC 50, and has good wear resistance and corrosion resistance, long service life.
In order to control the heat treatment of the ring mold hardness uniformity, after the heat treatment of each ring mold in three equal portions of the circumferential direction at each site, taking not less than 3:00 of the average measured hardness, the hardness of the various parts of the difference should not more than HRC4.
In addition, the response to the hardness of the ring die blanks to control its hardness HB170 ~ 220 is appropriate, if the hardness is too high, drilling when the drill bit easy to break and cause death hole, the hardness is too low to affect the finish of the die hole. In order to control the rough internal homogeneity of the material conditional, then respond to each blank internal flaw detection, to prevent the rough internal cracks, pores, coarse defects.
1.2 ring mode pore structure, the compression ratio and roughness
Common ring mold hole straight holes, stepped holes, outside the tapered hole and tapered hole and so on. The ladder-shaped hole is divided into the release step hole (commonly known as decompression hole, or the release of the hole) and compressed ladder Kong, Figure 1 shows, a different form of die holes for different types of feed ingredients or feed formulations.
The ring die compression ratio is the ratio of the effective length of the ring mold hole and the minimum diameter of the ring die hole, it is an indicator to reflect the particle feed extrusion strength. Compression ratio increases, more solid extruded pellet feed. For straight-hole ring mold compression ratio, the effective length of the ring die hole is the total thickness of the ring mode, the minimum diameter shall die hole diameter; for release ladder hole and outer tapered hole mode the effective length of the hole is the total thickness of the ring mold minus the release of the length of the hole or outside taper length, small diameter of the aperture is the calculation of compression ratio of the aperture; for compression ladder hole and tapered hole This situation is rather special, general thickness of the ring mold as the effective length of the die hole, take small diameter minimum diameter aperture ring die, of course, so the calculated compression ratio of the meaning and the first two cases there is a difference.
The roughness is also a measure of an important indicator of the quality of the ring mold. Under the same compression ratio, the greater the roughness value the greater the resistance, feed extrusion, the material is more difficult, too large roughness also affects the quality of the particle surface. Appropriate roughness value should be between 0.8 and 1.6.
1.3 ring die area, the arrangement of the holes and open porosity
Circumference of the ring mold work area inside diameter of the ring mold and the effective width of the product, the effective width of the distance between the two more process slots of the ring mold. In the same work area, is inversely proportional to the diameter and the effective width of the ring mold.
The ring mold drilling arrangement is generally arranged along the circumference, and in the width direction of the holes between the row and row intersect, so that the drilled holes was approximate equal an equilateral triangle arrangement. If the set hole diameter d, wall thickness between the holes with the holes a of ψ ≈ 0.9d2 / (d + a ring mold opening rate of ψ, according to the principle of an equilateral triangle, is not difficult to calculate: ) 2
For example, the hole diameter is 4.5mm ring mold, take the wall thickness between the holes is 2.6mm, you can calculate the ring mold opening rate of 36%.
It can be seen from the above formula in the case of a certain diameter of the die hole, to improve the opening rate of the ring mold, you must reduce the wall thickness between the die hole, but the minimum wall thickness must meet the needs of the intensity of the ring mold.
The general rule is that the die hole diameter, the greater the higher the open porosity of the ring mold.
1.4 ring mold line speed
Tangent speed in the ring mold, ring mold line speed, the level of impact to the material thickness and material of the extrusion region through the time of the die hole, thereby affecting the production and grain quality of the pellet mill. Line speed is too high, there may squeeze the area of ??materials to the formation of the fault is not continuous, granulation, the particles of the system out of soft, powder, slippery and high moisture content material, can not even granulation ; lower linear velocity of the ring mold the system out of particles of good quality, but a greater impact on yield. Ring mold line speed is generally between 6 ~ 9m / s.
1.5 ring mold installation
Installation of ring die face the mounting cone mounted hoop mounting. Face the style is simple to install, ring die is not easy to tilt, but the ring mold mounting bolts are easy to cut, not for large models of pellet mill. Performance of ring mold centering cone mount, transmission torque, the ring mold mounting bolts is not easy to cut, but carefully assembled and mastery of certain skills, or ring mold is easy to orange juicing machine
the ramp. Install more suitable for small models of pellet mill hoop-style, easy installation, take a short drawback is that the ring mold itself asymmetric, not off the surface.
2 ring mode selection of
It can be seen through the characteristics of the ring mold, the choice of a ring mold factors to be considered are many. However, in practical work, usually a number of factors is already designed well, such as the installation of the ring mold, ring mold line speed and ring die area, and other, which has decided to purchase particles machine, generally does not change. Other factors to ensure that by choosing a professional manufacturer of ring die, such as the material of the ring mold, heat and wear resistance of die holes open porosity and roughness, these factors professional ring mold manufacturer can usually achieve the best performance requirements, users do not freeloaders to buy the manufacturers of the technology and equipment protection ring mold can. For example, the die hole processing and heat treatment quality depends on specialized gun drill and vacuum heat treatment equipment in order to ensure that ordinary drilling and heat treatment method is difficult to be processed into high-quality ring mold.
Commonly faced in the feed mill is the appropriate choice of how to produce their own feed varieties and recipes form of die holes and ring die compression ratio. In general, the straight-shaped hole and release of stepped hole suitable for the processing of compound feed; outside the tapered hole for processing defatted bran high-fiber feed; within the tapered hole and light weight compression ladder hole should be processed grass powder class feed. Release ladder hole design of the reasons mentioned above, due to the feed of certain species, especially the small diameter of the feed, less than the minimum requirements to ensure a reasonable compression ratio conditions, the wall thickness of the ring mold, resulting in ring mode strength is not enough, ring mold burst phenomenon, forced to take the thicker the measures under the premise of ensuring the effective length of the die hole, increasing the thickness of the ring die and at the same time increase the decompression hole (the release of holes) in the production of the Central Standing Committee.
Choice of compression ratio for the ring mold, the raw material used in each formula is not the same, different granulation process is also different, specific and appropriate compression ratio but also on various feed manufacturers in the production of groping, only under past experience gives an approximate range. Generally, livestock and poultry feed should be selected between 9 and 13 compression ratio; fish feed should be selected between 13 and 16 compression ratio; shrimp species should be selected between 20 to 25 of the compression ratio; heat-sensitive class The feed should be selected between 7-9 compression ratio; forage and straw feed should be selected between 6 and 9 compression ratio. In addition, feed producers according to their quality requirements slightly increase or decrease the actual compression ratio, such as selection of a slightly lower compression ratio increase production, reduce energy consumption, reduce the wear of the ring mold favorable, but also reduces feed quality such particles are not strong enough, powder and high; the contrary, the particle quality, such as smooth particle appearance, density increases, the rate of chalking small, but it will increase production costs.
3-ring mode of use
Correct to adjust the gap between the ring die and roller is the key to use the ring mold. In general, the gap between the ring mold and the pressure roller is appropriate between 0.1 ~ 0.3mm. Under normal circumstances, the new pressure roller and ring die match should adopt a slightly larger gap, the old pressure roller and the old ring die match should adopt the smaller the gap, large-aperture ring mode should be chosen slightly larger gap, the small aperture of the ring mode should use the smaller the gap, easy granulation of materials should take a big gap, and hard-to-pelleting materials should take a small gap. For the operator, have practical experience in the operation, the gap of the ring mold able to select and adjust.
In addition, the ring mold during use, but also note the following: ① newly purchased ring mold, usually in the boot before with oil "wash mode, to remove the burr in the die hole. If purchased in the regular factory φ2.5 above the die hole ring mold from time to die holes in the φ2.5 the following ring mold, generally require oil in the normal pre-production mold cleaning a few minutes to ten minutes for ring mold of the die hole roughness poor, sometimes in the fuel mix into the 20% to 50% of fine sand grinding in order to carry out normal production. ② ring mold during use, be sure to avoid the material mixed with large pieces of gravel, sand, iron, bolts and iron hard particles, so as not to accelerate the wear of the ring mold or ring mold caused too great a shock , resulting in a ring mold burst. If the iron into the mold holes must be out of or drilled. ③ symmetrically on both sides of ring mold in the production of a certain period of time in turn installation to use, so that the ring mold wear uniform. ④ ring mold must not be installed after the tilt, or will produce uneven wear; bolts fastening ring mold must achieve the required pallet wrapper torque in order to avoid the bolt cut and damage to the ring mold.
4 ring mold maintenance
Reasonable maintenance of the ring mold is one of the necessary measures to ensure that the ring mode to work properly and prolong its service life, usually work to do the following: ① When the need to replace the ring mold, non-corrosive The oil squeezed out of the original feed, in order to re-use the material smoothly and prevent corrosion of die hole. ② ring die after a certain time, you should regularly check the ring mold inner surface of the local bulge, and check the die hole conductivity discharge port polished, sealing, or varus, if the application grinder or other tools in the work of the ring mold surface protruding part of the polished and then chamfer the mouth of a conducting ring mold to make the necessary repairs to extend the life of the ring mold. Repair should pay attention to the work of the ring mold surface of the lowest place overrun bottom of the tank should be higher than 2mm and after the repair still pressure rollers eccentric shaft adjustment margin, or ring mold should be scrapped. If the majority of die hole to be material to plug not material, soaking in oil or oil-cooking approach can be taken so that the material softening, re-granulation; If you still can not granulating, you can use the drill will drill the hole clogging mold materials out then oily materials plus fine sand grinding. ④ ring mold must be stored in a dry, clean place, and do a good job specifications logo, if stored in damp places, may cause corrosion of the ring mold, thereby reducing the life of the ring mold or discharge effect.