Influence of spindle speed on inner diameter accur

2022-09-21
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The influence of spindle speed on the accuracy of inner diameter of spinning workpiece

Abstract: This paper discusses the influence of spindle speed change on the accuracy of inner diameter of workpiece in the spinning process test of a specific workpiece. When the longitudinal feed speed is constant, the spindle speed increases, that is, the feed quantity becomes smaller, and the inner diameter accuracy will be improved

key words: spindle speed feed inner diameter accuracy

I Process analysis

a process test part, the material is LF21, and the shape and size are shown in the figure below:

the previous manufacturer's processing method was turning with aluminum rods, but this processing is extremely uneconomical, and the material utilization rate is only 8%, which not only causes a lot of waste of raw materials, but also a long processing time. In view of the uncertainty of this matter,

in order to save raw materials and processing hours, stamping or cold extrusion methods have been considered to process this part, and process tests have been done in this regard, but these two processes have not met the requirements of the dimensional tolerance of the inner diameter of the workpiece on the drawing. Using spinning process, on the one hand, raw materials can be saved, and parts that meet the technical requirements of the drawing can be spun

II Process flow

spinning process flow is:

blanking → stamping preform → spinning → stress relief → machining → inspection

stamping preform blank is shown in the following figure:

use preform blank to form the workpiece required by the drawing in one strong spin. The key technology is how to determine reasonable process parameters to ensure the internal diameter of the mouth Φ 84h7+0.035 and surface finish ra=3.2um

III Process test

the qx62-90 double wheel spinning machine developed by our institute is selected as the process test equipment, and its technical parameters are:

center height: 300mm

spinning pressure: transverse 70kN; Longitudinal 90kn

stroke: transverse 220mm; Longitudinal 500mm

spindle speed: 30045071010001320rpm

according to the characteristics of parts and previous spinning process experience, we preliminarily selected the following process parameters:

spindle speed: n=1000rpm

longitudinal feed speed: f=300mm/min

gap: △ 1=2mm, △ 2=1.45mm

roller diameter: Φ 200mm

fillet radius of spinning wheel: r=6mm

core mold diameter: Φ 83.9+0.02mm

for the parts tested with this process parameter, it is found that the expanding phenomenon is particularly serious, the mouth size is out of tolerance (i.e. bell mouth), and each workpiece has ellipse phenomenon, and the mouth inner diameter ellipse long axis size Φ 84.16mm, stub shaft size Φ 84.07mm。

this kind of problem can be solved by repairing the core mold. The pre meeting representatives reach such resonance and reduce the outer diameter of the core mold. However, it is very difficult to repair the core mold, the test cycle is long, and we need to explore many times to ensure a reasonable dimensional tolerance, so we decided to change the process parameters to solve the above problems

according to the spinning process theory on the data, the smaller the longitudinal feed, the worse the die sticking and the larger the expanding diameter; On the contrary, the larger the longitudinal feed, the better the die sticking, and the expanding phenomenon can be improved. Therefore, if the spindle speed decreases, it is equivalent to an increase in the feed per revolution, under the condition that the vertical feed speed of the spinning wheel is forced by the merchants to keep the transformation of green industry unchanged. In order to improve the expanding phenomenon of the workpiece inner diameter, we reduce the spindle speed and increase the longitudinal feed per revolution of the roller

we change the spindle speed and reduce the spindle speed from n=1000rpm to 710rpm, that is, the longitudinal feed per revolution is increased from 300/1000=0.3mm/r to 300/710=0.42mm/r, and other process parameters remain unchanged, then the inner diameter accuracy of spinning parts should be improved. However, the actual process test results are just the opposite, that is, the phenomenon of expanding diameter and ellipse is more serious. The measurement results are: inner diameter size: ellipse length ③ clamp specific 1. Generally, excellent medium carbon steel and alloy structural steel shafts are adopted Φ 84.28mm, stub shaft Φ 84.15mm, which is also much beyond our expectation. At first, I thought it was just an accidental phenomenon of a single part, but after continuous testing of many pieces, I found that this phenomenon still exists

this aroused our interest, and we decided to continue to explore the law. Regardless of the surface finish of the workpiece, the spindle speed is further reduced from n=710rpm to 450rpm, that is, the longitudinal feed per revolution is increased from 300/710=0.42mm/r to 300/450=0.67mm/r, and other process parameters remain unchanged. The process test results show that the phenomenon of expanding and ellipse is more serious, and the inner diameter is the long axis of ellipse Φ 84.40mm, stub shaft Φ 84.22mm。

increase the spindle speed to n=1320rpm, that is, the longitudinal feed per revolution is 300/1320=0.23mm/r, which not only improves the surface finish, but also improves the inner diameter accuracy. The measurement result is: inner diameter size: elliptical long shaft Φ 84.03mm, stub shaft Φ 84.00mm。

from this, we can see that there must be some laws in this specific spinning process that we have not noticed before. We can summarize it as the following conclusion: if the longitudinal feed speed of the spinning wheel is set to the same value and the spindle speed is set to different values, that is, if the feed per revolution of the spindle is larger, the expanding and ellipse phenomenon will not be improved, but will become more serious. This is contrary to the rule that we used to say in books, "the larger the feed, the better the pasting"

IV Process test results

why does the spindle speed decrease and the larger the feed rate, the phenomenon of expanding diameter and ellipse can not be improved, but will become more serious? The results of this process test are shown in the table below. Process test results

for this specific spinning process, we can find that the linear speed of the workpiece is different under the above spinning process conditions. It can be understood as follows: when the spindle speed is high, the spinning linear speed is high, then the forming rate of the material applied by the spinning wheel to the local deformation area of the workpiece is fast, in other words, when the spindle speed is high, it is equivalent to the increase in the number of spinning wheels participating in the forming of the workpiece, The increase of the area of the deformation area per unit time makes the material have higher plasticity, and effectively limits the circumferential flow of the material during deformation. The deformation conditions of the workpiece are improved, the expanding phenomenon is reduced, the workpiece is well pasted, and the inner diameter accuracy is improved. It ensures that the workpiece has high dimensional accuracy and surface quality

it is generally believed that the spindle speed has no significant influence on the spinning process. Increasing the speed can only improve the surface finish of parts and improve productivity. Now it seems that this statement is not comprehensive. For the spinning process of this specific part, the spindle speed has a significant impact on the inner diameter tolerance and the phenomenon of expanding and ellipse, that is, the linear speed during spinning directly affects the inner diameter accuracy of the workpiece. Due to the limitation of conditions, we cannot test the parts with other sizes. Maybe the size changes, and the influence of the spindle speed on the inner diameter tolerance, expanding and ellipse is not significant, but for the products of this process test, the influence of this parameter cannot be ignored

having mastered the above rules, in the process of spinning this product, we no longer consider simply reducing the spindle speed to improve the accuracy of the inner diameter of the workpiece, because this will not solve the problem, but affect the surface finish of the workpiece after spinning. We try to increase the longitudinal feed speed of the roller at a relatively high speed of the spindle

in this process test, we spin the qualified samples with the following process parameters

spindle speed: n=1320rpm

longitudinal feed speed: f=300mm

longitudinal feed rate: 0.23mm/revolution

gap: △ 1=2mm, △ 2=1.45mm

roller diameter: Φ 200mm

core mold diameter: Φ 83.9+0.02mm

the fillet radius of the roller: r=6mm

the test results show that the performance and size of the parts produced by this process fully meet the use requirements, and the inner diameter can be controlled within Φ 84h7+0.035mm, wall thickness 1.5 ± 0.01mm, outer surface finish ra= 3.2 um

when this process is used in production, the productivity can be increased by 50% and the material utilization rate can be increased to 90%. Therefore, it is more economical to process such parts by spinning

v Conclusion

after the above process tests, it is known that for some specific parts, when the longitudinal feed speed is unchanged and only the spindle speed is changed, the spindle speed will increase, that is, when the feed volume becomes smaller, the inner diameter accuracy will be improved

References:

(1) spinning technology, machinery industry press 1986, wangchenghe et al.

(2) strong spinning and its application, National Defense Industry Press 1963 (end)

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