Selection of ring die pellet mills

Ring die is an important part of the pellet mill, it is as important as the human heart. The quality of ring die influences machine's production per hour,power consumption and product quality seriously. only to choose a good ring die,can they ensure the pellet mill's normal and steady production.

 

Ring die generally made of carbon steel, alloy steel or stainless steel by forging, machining, drilling and heat treatment process. At present,popular ring dies in the market vary, the main reason is the different in material and process selection and control.The ring die produced by some small factory mainly made of carbon steel or alloy steel by forging, drilling holes with twist drill,then through the ordinary heat processing.Ring dies produced in this way usually have this or that problems.For example, the new model needs a  longer time to wash the die, high energy consumption, low output, poor quality of the pellets and die burst and so on. In addition, there is a more serious problem that the service life is short,no wear resistance, which greatly affected the production efficiency of the pellet mills.

　

So how to choose a suitable ring die will be very critical.

   

Selection of ring die:

1. In the premise of selection of quality ring die,we should choose appropriate form of die hole, opening rate and compression ratio (compression ratio = effective length of die hole  / diameter of die hole) according to the material variety, formula and production. In the premise of guarantee the strength of ring die, try to improve the rate of ring die holes. For some varieties of materials, in the ensurance of reasonable compression ratio,if the ring die wall is too thin,so that ring die strength is not enough.In this case,there will be die burst phenomenon in the production.At this point,the thickness of ring die should be increased and add pressure-relief holes in the premise of ensuring the effective length of die hole.

    

2 The working gap between the ring die and the press roller has an important influence on the effective use of the ring die. Generally speaking, the gap between the ring die and roller is between 0.1-0.3. Based on practical experience,while pulling the ring die rotating by hand, the state that the pressure roller seems to turn but in fact not is better. So how to adjust the gap between the ring and the roller? Through our experience we know that, when installed new die, first of all, loose press roller and adjust bolt to make the outside round surface of the press roller close to the ring die inner circle surface; secondly, adjust the eccentric axis of press roller orderly and makes the gap between the roller and the ring die proper, preload adjust bolt, pull the ring die, and gradually adjust the gap, make the press roller in the working state that seems to turn but in fact not,then fasten  the adjustment bolts. When new die installed, usually requires the gap between the die and roller slightly larger than you need, which is conducive to the smooth transition between the new die and the old roller. After the breaking-in period between the new die and the old roller, then adjust the space to what you need. In use we usually protect ring die rather than press roller, because the price of ring die is ten times or even dozens of the price of press roller.So when in use, in the situation of selecting reasonable gap,the hardness of the press roller can not too high. That is to say, the wear resistant of the press roller can not be better than the ring die. In the production process of the ring die, the materials to be used are required to clean, avoiding materials mixed with gravel, sand, iron pieces, bolts and iron bits and other hard particles. As these inclusions accelerat the wear speed of the ring die, and a lot of hard inclusion will cause the ring die be stressed for many times, and make the ring die fatigue. when the force is more than ring die's strength limit, the ring die will burst.

 

3. When the operator installs or replaces the ring die, for the ring die assembly through the cone, when installs, we should avoid bumps and scratches of conical surface, and make necessary clean and oiling for the conical surface and the rim drive cone. When replacing the ring die, do not bump and scratch cone when remove, and oiling as protection. For pellet mills that need to replace the ring die frequently, regular inspections on the transmission flange is needed in order to prevent the fracture of the die centring pin caused by the excessive wear. For excessive wear will affect the matching between the ring die and the rim. If the matching is not tight, when the ring die works, it will produces shear stress to the centring pin and makes it break. When this happens, do not mistakenly believe that it is the strength of the pin that is not enough for changing the pin of high strength, that will ultimately lead to the damage of ring die and recurrent fracture of the safety pin. Therefore, it is quite necessary to do inspection and regular protection for the ring die's cone and the transmission flange of the cone. It is also necessary for hoop type ring die to protect and inspect the surface and the component assembly.After a period of time, the press roller will wear which would influence the matching precision with the ring die, thus affecting the production of the ring die. Then we should make necessary repairs or replacement of new ring die.

 

In summary, only correct selection, rational use and effective maintenance on the ring die of the pellet mill, can we reduce costs, improve efficiency and create more economic benefits for the enterprise. You can know more: biomass pellet mill, wood pellet mill, straw briquetting machine, dryer machine etc. mechanical equipment.

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