Roller is the most important working parts of the mill. It is directly involved in the completion of part of the rubber mixing operation, the impact on the performance of the mill is also the largest. Therefore, the roller design, manufacture and use should attach great importance.
1. Materials and technical requirements
The basic requirements for the mill roll are: to have sufficient mechanical strength and rigidity to ensure that the roller is not damaged during normal use; the working surface of the roll should have a high hardness, abrasion resistance, chemical resistance And anti-peeling, so as not to damaged by knife when in the rubber cutting and some agents with corrosion; with a reasonable geometry, as far as possible to eliminate local stress concentration; has good thermal conductivity, in order to facilitate the compound Of the heating and cooling.
Roller materials are generally chilled cast iron. It is characterized by a hard surface layer, the internal toughness, strength, wear-resistant corrosion resistance, good thermal conductivity, easy manufacturing, low cost. Experimental small-scale open mill roller also used in the carbon-alloy steel.
2. Structure and size of each department
As the different use of open mill, the working surface of the roller shape is not the same. For the plastic mixing, mixing, heat refining, compression of the roller are smooth; for breaking rubber, washing rubber, grinding roller groove with a special groove, for refining the roller is Smooth with a drum.
Roller structure is devied into two kinds, one for the hollow structure, and the other for the circumferential drilling structure.
(B) Roller bearings
Open roll mill roller bearing load is very large (such as φ650 * 2100mm open mill maximum load of 1960KN), and the sliding speed is low, the temperature is high. Therefore, requiring wear-resistant bearings, bearing capacity, long service life, manufacturing and installation convenience.
Roller bearings are mainly used in sliding bearings and rolling bearing two kinds of structural forms.
1. Sliding bearings
This roller mill roller is widely used type. Which is characterized by simple structure, easy manufacturing, low cost. Sliding bearing lubricants for the dry butter or thin oil. Bearing body material is made of cast iron or cast steel, the tensile strength of not less than 200Mpa, generally with HT200 cast iron; bushing with metal (bronze) or non-metallic (MC nylon) manufacturing. The disadvantage of nylon bushing thermal conductivity is poor, large thermal expansion.
2. Rolling bearings
In recent years, large-scale open mill on the use of double row roller bearings. It is characterized by long service life, little friction loss, energy saving, easy installation, easy maintenance, lubricating oil consumption compared with the general sliding bearing can be reduced by 75%. But the high cost, supporting difficulties, so seldom use it.
(C)The nip adjustment device
According to the requirements of different mixing process, open mill should always change its roll distance when in work. Therefore, the front roll on both sides of the rack to be equipped with a pair of distance control device, adjustable range is generally 0.1-15mm. Roll distance can not be too large, so as to avoid gear ratio due to poor engagement and damage.
1. Type and structure
Commonly used pitching device according to different power sources, can be divided into manual, electric, hydraulic transmission.
Manual-type device is characterized by a simple structure, reliable work. But the labor intensity, suitable for medium and small size open mill.
Electric adjustable device is characterized by easy operation, reliable work. Drawback is the structure of complex, generally large-scale open mill is generally used.
Hydraulic pressure control device is characterized by a simple device than the electric adjustable, easy to operate, beautiful appearance. The disadvantage is not easy to maintain, sealing requirements, can not automatically return.
Therefore, the current open mill more to manual and electric-based, part of the form of hydraulic transmission.
2. Adjustment screw, nut material
In the design, the safety factor of the nut is n = 2, and the safety factor of the screw is n = 2.3. The safety factor of the nut and the roller are generally considered.
Screws and nuts with mechanical pitch are generally of trapezoidal or rectangular threads, and the number of thread-work buckles shall not be less than 10, and its helix angle a should be less than the friction angle p, ie a <p, so that it can work reliably and reversely Self-locking. Screw material commonly used 45 steel, nut materials commonly used bronze or cast iron.