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Measurement of Cone Shaft and Cone Sleeve of High-speed Wire Rolling Mill’s Roller
ABSTRACT
To obtain good assembly performance when transferring roll moment, a cone fit is adopted between cone shaft and cone sleeve of roller of high-speed wire rolling mill. This paper introduces an automatic cone measuring method, dissertates the principle of taking reference cylindrical surface of the roller as measuring reference to measure cones, and the main characteristics of the associated horizontal automatic cone measuring instrument. Measuring error of the instrument is also analyzed. The instrument uses grating transducers for cone diameter measurements and for axial positioning of transducer. The measuring error for diameter measurement is 1.4μm,the axial positioning error is less than 0.01mm, and the relative error for taper measurement is less than 2×10-3.Since the instrument is equipped with data acquisition system, many parameters and actual profile of the measured cone can be obtained according to the collected measuring data. Furthermore, virtual assembly of corn shaft with cone sleeve can be carried out on the computer, and the actual assembly effect of cone shaft with cone sleeve can be observed so that selective assembly with higher accuracy can be realized to the fullest extent.
Keywords: rolling mill, roller, grating transducer, stepping motor, virtual assembly
1. INTRODUCTION
Compared with smooth cylindrical fit, cone fit has advantages of automatic alignment, higher coaxiality, easy to adjust the degree of tightness, closer fit, easy to disassemble, etc. Therefore, it is widely used in mechanical facilities. Now, the rolling speed of high-speed wire rolling has exceeded 100m/s. To adapt to this speed, cone fit with good performance must be adopted between cone shaft and cone sleeve of high-speed wire rolling mill’s roller otherwise the roller of the mill will have some run-out so that the rolling speed and rolling benefit can’t be ensured.
The inspection of the cone has two methods: composite inspection and monomial inspection. Cone gauges are used for composite inspection while goniometers, indexes, sine bars, angular blocks are used in monomial inspection for measuring parameters of cone tolerance[2]. This paper introduces an automatic cone measuring method, together with an associated horizontal automatic cone measuring instrument. The instrument measures cone shaft and cone sleeve under the condition that taking reference cylindrical surface of the roller as measuring reference. Parameters of the roller are: the maximum diameter of measured cone shaft is 241mm,the length range of measured cone shaft is 647mm~985mm, the maximum diameter of measured cone sleeve is 192mm, the length range of measured cone sleeve is 647mm~985mm and the normal taper of measured cone is 1:12. The tolerance requirement of the cone is that the allowable variation in diameter should be within 1±0.003mm when axial displacement is 12mm[1].
2. PRINCIPLE OF MEASUREMENT
Two grating transducers are located at both side of the cone, they are parallel and at right angle with the axis of the cone. The measurement begins at the bigger end of measured cone to ensure the measuring accuracy. The size of the diameter measured equals to the sum of the two transducer readings. One measurement is done for every 0.9o rotation of the cone, i.e. 400 measurements are done for a full circumference. One circumference measurements are done for every 1mm axial interval. The measuring procedure ends when measurements for the circumference at the smaller end of the cone have completed .At the section which is L apart from bigger end (the diameter is D) of the cone, Assume that the theoretical diameter of the section is d, measured diameter is
C = (D ? d ) / L (1)
d = D ? C - L (2)
D = d ? d = d ? (D ?-L) = d + L ? D (3)
Where C is the normal taper of the cone,
d is the measuring error of diameter
sleeve of the roller, the allowable variation in diameter should be within10.003mm when axial displacement is 12mm. Therefore,the measuring error of the instrument for measuring diameter should not exceed 3 m.
3. COMPOSITION OF THE INSTRUMENT
Fig.1 automatic cone measuring instrument
The instrument consists of four parts: mechanical system, measuring system, dada acquisition system and data processing system, control system for axial movement and radial rotation.
(1) Mechanical system
Mechanical system of the instrument includes bed plate, left and right supports for supporting roller, and workbench of measurement. Mechanical system has two functions. The first is to support measured cone to rotate, and the second is to support grating transducer to do rectilinear movement along the cone axis. When in measuring operation, support the cone on two supports with two centers at the beginning, then start the motors to locate transducer in its axial place with horizontal grating, and alternatively, to locate transducer in its radial place by driving the cone to rotate with a deflectable rod.
(2) Measuring system
Measuring system is mainly made up of grating transducers and measuring circuit. It is used for axial locating and diameter measurements. Grating transducer has characteristics such as high accuracy, fine resolution, broad measuring range, strong ability to resist disturbance, etc. The accuracy of ordinary grating transducer can reach to 0.5μm /300mm; the resolution can reach to 0.05μm. The measuring circuits for grating transducer include subdivision circuit, direction identification circuit, counting circuit, and display circuit. In our design, the resolution and measuring accuracy of the grating transducer for diameter measurements are 0.5μm and 1μm/20mm; the resolution and measuring accuracy of the grating transducer for axial locating are 0.5μm and 1μm/20mm, respectively.
(3) Dada acquisition system and data processing system
The function of dada acquisition system and data processing system is to collect measured data such as diameters，angles, axial positions, and then input these data to the computer through standard RS-232C seria interface for data processing, so that measuring results and actual cone profile of the measured cone can be obtained.Since the Baud rate of serial communication is set to 9600bps, the system can transmit 1200 bytes in a second. The total number of measured data is about 400×100=40000 while 9 bytes are needed to store one measured ata..So the time required to do whole measurement is approximate 40000×9/1200=300s, or about 5 minutes.
(4) Control system for axial movement and radial rotation
Fig.2 the interface of control operation
The function of control system is to control stepping motors by which the rotation and axial rectilinear movement can be implemented. The core of control system is a parallel interface board. Figure 2 shows the interface of control operation. By operations within this interface, starting and stopping of motors, control of rotating direction and speed and locating of the transducer along cone axis, can be realized. The stepping angle of stepping motor is 0.045o; Accuracy of 0.01mm can be obtained for rectilinear movement control by means of driving mechanisms such as gears, ballscrews, etc.
4. EVALUATION OF THE MEASURED CONE
Once the measurement is finished, evaluation of the measured cone can be made from 400×100 measured data. According to the definition of taper, there are two methods which can be used to get the actual taper of the measured cone.
(1) Both 400 measured data measured on sections of bigger end and smaller end of the cone are processed separately with least square method.
D' and d ' , the diameters of two circles determined by least square method, can be found out. Then, we can find out L, the axial distance between these two sections, from locating dimensions. According to equation Ca= (D'?d ' ) / L' , the actual taper of measured cone can be calculated.
(2) Total 400×100 data are processed with least square method and the equation of the tapered face determined by least square method can be calculated. After two appropriate sections are chosen, we can calculate and d”, the diameters of two sections and L" ,the distance between twosections, and then, the actual taper of measured cone can be calculated according to equation Ca = (D"?d " ) / L" .
This instrument adopts the second evaluation method. Other parameters such as standard deviation of taper, maximum deviation of taper and minimum deviation of taper can also be calculated while further data processing work is done. To enhance the visualizability of measuring results, processing of visualization has been adopted. The actual profile of tapered face can be displayed on the screen of computer in the form of grid according to measured data. Figure 3 is the actual profile of a tapered face. If you click any point on the profile, the axial position and the diameter of the section at which the point is locating, and deviations, can be printed，on the screen immediately. Besides, you can drag the actual profile with mouse so that you can observe the condition of an arbitrary position on the profile.
This instrument can make virtual assembly of cone shaft and cone sleeve by computer. Numbering for cone shafts and cone sleeves and then save their measuring results. When they are to be used, virtual assembly can be made by computer by making use of saved result. Taking notice of the actual assembly effect of cone shaft and cone sleeve, selective assembly of cones with high accuracy can be realized to a great extent[3].
Fig.3 actual profile of a tapered face
5. CONCLUSIONS
The measurement of cone shaft and cone sleeve of roller introduced in this paper takes reference cylindrical surface of roller as the reference of measurement. This is accordance with actual condition of cone fit, so that it has great advantage in principle.The horizontal automatic cone measuring instrument has characteristics such as simple in structure, convenient in adjustment and operation, high accuracy, broad measuring range, etc. The instrument has heavy load bearing capacity, large rigidity and enhanced adaptability. Grating transducers are used in measuring system for diameter measurement and axial positioning, and radial angular positioning is completed with stepping motor. So, the error for measuring diameter is less than 1.4μm and the relative error for measuring taper of cone is less than 2×10-3.
Horizontal automatic cone measuring instrument is automated in great extent. The adoption of digital grating transducers which have high accuracy is propitious to the computer aided data acquisition and data processing. Large amount of digital information can be obtained from collected data after procedures of error separation, error correction and statistic analysis. With visualization technique the profile of measured cone can also be displayed on computer’s screen. It is of great importance that, using collected data, virtual assembly of cone shaft and cone sleeve can be realized so that selective assembly of cones with high accuracy can be realized to a great extent.
REFERENCES
[1] Rakesh Gupta. Prototyping and Design for Assembly Analysis Using Multimodal Virtual Environment[J]. Computer Aided Design. 1997, (29): 585-597
[2] Xu Kun, Wang Shao Tuan. Measurement of Cone’s Taper Angle in Same Direction. Tractor @ Farm Transporter. 2002, l3(3): 47
[3] Du Ming Fang, Zhang Yong Ming. Measurement and Data Processing of Circular Cone. Metrology & Measurement Technique. 2002, 29(4):10-11
[4] Li Xiao Qing, Zhang Fu Run, Yang Chu Min. Development of Special Measuring Tools for Small Diameter on Male Cone of Large-Sized Cone Parts. Tool Engineering. 2003, (5):44-46
[5] Yu Xin Hai, Chen Ping. Measurement of Large Diameter Cone with Universal
Measuring Microscope. Practical Measurement technology. 2000,26(4):34-35
[6] Shi Jian Yao, Yang De Wang. Measurement of Cone Diameter and Error Analysis. Practical Measurement technology. 2000, 26(5):34-36
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