What are the methods for rational selection of slewing bearings?

Reasonable selection of slewing bearings
Construction Machinery, Issue 8, 1996

As an important basic component of construction machinery, slewing bearing has been widely used in the past ten years with the rapid development of the main engine industry. In addition to excavators, tower cranes, car cranes and various cranes, it is also widely used in light industry. Machinery, metallurgical machinery, medical machinery, industrial robots, tunnel boring machines, stacker reclaimers, rotating stages, etc. In short, it is an important force-transmitting component necessary for all machines that need to make relative rotational motion between the two parts, and also need to bear axial force, radial force and overturning moment.

China’s slewing bearing industry has been more than 20 years since its establishment. It has grown from nothing to small and gradually matured. At present, it has the comprehensive development capability of design, manufacture and testing of slewing bearings that meet the needs of various types of mainframes, and has made certain contributions to the development of the mainframe industry. In particular, Maanshan Slewing Bearing Factory, in cooperation with the Beijing Construction Machinery Comprehensive Research Institute of the Ministry of Construction in 1984, successfully developed a single volleyball slewing bearing with international advanced level in the 1980s, breaking the three-piece crossover of China’s slewing bearing industry. The backward situation dominated by rollers and double volleyball has greatly narrowed the gap with developed countries and led to the rapid development of China’s slewing bearing industry. In the past 11 years, Maanshan Slewing Bearing Factory has provided more than 20,000 sets of four types of slewing bearings for domestic and foreign users. The products cover 25 provinces, municipalities and autonomous regions in China, and are used for more than 200 kinds of mainframes in more than ten industries.

With the rapid development of various host industries, whether it is self-development, or the introduction of technology, joint ventures, and cooperation, the requirements for slewing bearings are increasing. As a professional manufacturer of slewing bearings, we will strengthen the development of new products, continuously improve product quality, and meet the development of the mainframe. Need, it is our responsibility to be incumbent, but also the fundamental requirement of market competition and self-development. However, how the host correctly selects the structural type of the slewing bearing (single volleyball, cross roller, double volleyball, three-row column, etc.) and size (track center diameter D0, rolling body diameter d0), but due to external load The mechanism of the complex force system and the bearing capacity of the raceway is not deeply understood. There are some unreasonable conditions in the selection, which affect the economic benefits of the host industry and even lead to major quality accidents, which cause the main engine industry and the slewing bearing industry. Pay attention to it. This article explores the rational selection of long-term slewing design and production experience for the host selection service to overcome the blindness of use and ensure the reliability of the host.

▲ Selection of slewing bearing structure type
There are four types of structures for common slewing bearings: single volleyball, cross roller, double volleyball, and three-row. In order to make the selection scientific and reasonable, the data comparison is first carried out.
1.1 Single volleyball and cross roller type rated static capacity, rated dynamic capacity comparison
The rated static capacity C0 and the rated dynamic capacity Ca determine the bearing capacity and service life of the slewing bearing. The single volleyball Q1600*50 and the cross roller J1600*36 with the same external type and installation dimensions are as follows. :
→ Single volleyball type Q1600*50 rated static and dynamic capacity (C01, Ca1)
C01=f0·d02·Z·sinα
=38×502×89×sin50°=6476906(N)
Where f0 – the hardness coefficient of the raceway, 38N/mm2 at 55HRC
Z—— the number of rolling elements
Α——raceway contact angle, generally mechanically take α=50°
Ca1= 95·f1·fs·fc·fα·fd·Z2/3·fH
=95×0.299052×3.74244×0.837510×0.651309×872.672×19.9339×0.732247
= 738760(N)
The meanings and sub-expressions of the symbols in the formula are omitted.
→ Static and dynamic capacity (C02, Ca2) of cross roller type J1600*36
C02= f0·d0·L0·(Z/2) ·sinα
=76×36×0.8×36×(122/2)×sin45°
=3398783(N)
Where L0 – effective contact length of rolling elements
Ca2=410·f1·fc·fα·f07/9·d020/27·(Z/2)3/4 ×fH
=410×0.390100×0.874740×0.682713×13.6484×46.9444×21.8272×0.732247
= 978133(N)
From the above calculations, the static load capacity of a single volleyball is 90% higher than that of the cross roller type, but the dynamic load capacity is 25% smaller. Any two volleyball and cross roller type comparisons with the same basic parameters can be selected. Consistent.

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