By analyzing the relationship between these parameters and their influence on the structure and performance, some valuable conclusions are drawn.
Keywords: transmission system; Power gap; Torque; reduction ratio
The main transmission system is the core link of the transmission system of milling machine. Main drive of traditional milling machine
The power system adopts step-by-step transmission mode, and its calculation and design methods have been discussed in detail.
State. With the development of machine tool technology, the main transmission system of CNC milling machine and machining center
Continuously variable transmission has been widely used. Although some large machine tool design manuals are not suitable
The analysis, calculation and design methods of step-by-step transmission mode are discussed, and some design schemes are formed.
Principle, but the processing requirements for spindle stepless speed change system are varied, with
With the development of machine tool technology, the design of machine tool products tends to be more and more reasonable.
When designing the main drive system, main technical parameters and characteristic parameters such as height are needed.
Gear reduction ratio, spindle rated speed, power loss, etc. Are calculated.
The relationship and influence between them and their influence on the structural performance are analyzed. in the past
The introduction and discussion of this aspect in the technical literature is more general and simple, and relevant conclusions are drawn.
This is also simple and can't meet the requirements of analysis and design, so it needs to be constantly.
In-depth study, improve the calculation and design method of main drive. Over the years, I have been responsible for many projects.
Design of CNC milling machine and machining center products, design of various main transmission systems.
In-depth analysis, accumulated more analysis and design experience, the main drive system.
The main design parameters and characteristic parameters are deduced, calculated and analyzed.
Analysis, draw some applicable conclusions, as follows.
Characteristics of 1 spindle stepless transmission system
Spindle stepless transmission system is mainly composed of stepless speed regulating motor, transmission device and machine.
Mechanical transmission mechanism.
1. 1 Main mechanical characteristics of continuously variable speed motor and its drive
Continuously variable speed motor has a speed inflection point, that is, rated speed. Its characteristics are: less than
Rated speed is in constant torque range, and rated speed is greater than constant power range, such as
As shown in figure 1. The rated speed is generally 500 rpm, 750 rpm, 1000 rpm, 1500 rpm, 2000 rpm, etc. According to the principle of cost, they are usually used as follows.
1500rpm. If the motor with rated speed above1500rpm is directly used,
There is no mechanical deceleration, the output constant power range and low-speed torque are small, and it is impossible.
Meet the requirements of normal use in various occasions.
1.2 types and characteristics of mechanical transmission mechanism in spindle stepless speed change system
(1) Direct 1: 1 Drive
The motor can be directly connected with the spindle assembly or driven by a synchronous belt,
Simple structure, easy to obtain high speed, but low torque, generally only suitable for high speed and
Light cutting occasions.
(2) direct deceleration or acceleration
Synchronous belt transmission mode or gear transmission mode is often used, and the structure is simple.
Single. For deceleration drive, the constant power range can be expanded, and the spindle torque can be increased, but expanded.
And the maximum rotation speed is limited. For the uplink drive, you can get
High speed, but it narrows the constant power range and reduces the low-speed torque.
(3) high and low two-stage variable speed transmission
Generally, the gear two-speed transmission mechanism is adopted, which can match the more economical rated speed.
A larger stepless speed regulating motor can not only achieve higher speed, but also greatly broaden the constant speed.
Power range, improve low-speed torque, meet the requirements to achieve higher speed, can be carried out.
The occasion of large cutting capacity processing.
(4) Three-stage variable speed transmission of high, medium and low gear.
Adopting gear three-speed transmission mechanism, the rated speed is more economical.
Stepless speed regulating motor can not only obtain higher speed, but also greatly broaden the constant power range.
Greatly improve the low-speed torque, suitable for high-speed and large cutting.
In the case of batch processing, its mechanical properties are almost the same as those of stepped variable speed gears. but
The structure is complex, and the maximum speed is more limited because of the multi-stage transmission mode of gears.
At present, this transmission mode is rarely used.
As can be seen from the above introduction, various transmission modes have their own advantages and disadvantages, and the key is based on.
According to different usage requirements, choose different transmission modes.
1.3 on high and low two-stage variable speed transmission mode
From the above analysis, it can be seen that the adoption of high and low two-stage variable speed transmission mode not only
High rotating speed can be obtained, the constant power range is greatly widened, and the improvement range is greatly reduced.
Speed torque, and the structure is simpler than three-step transmission, so it is an ideal transmission side.
Type. Especially for the consideration of the price of electronic control system, we often use spindle motor with rated speed of 1500r/min. When the rated speed is greater than or equal to.
1000r/min spindle motor, and requires a larger output constant power range.
For large spindle low-speed torque and high spindle speed, high and low gears must be adopted.
Variable speed transmission mode.
At the same time, it can be seen that the calculation and design of high and low two-step transmission mode are important.
It is much more complicated than direct drive. Different parameters will lead to different mechanical properties.
Different, adapt to different use requirements. Therefore, the calculation of each design parameter is derived.
Formula, analyze the influence of parameter selection on mechanical properties, and analyze parameter selection and conclusion.
Structural design, which is aimed at the design of spindle stepless speed regulation system, is very important for how to pass
Through calculation and design, the predetermined technical requirements of CNC machine tools are achieved, and better control is realized.
It is of great significance to make manufacturability and performance-price ratio.
2 Calculation and Analysis of High and Low Two-stage Transmission System
There are many forms of high-low two-stage variable speed transmission mechanism, but its analysis and calculation are as follows.
The same. In the design of machine tool products, under normal circumstances, it is based on products.
Location, use, technical requirements and other factors, determine the main motor power and its rated speed, the main
Main parameters such as the maximum speed of the shaft and the maximum torque of the spindle, and then according to these main parameters
Calculate and determine the high and low gear reduction ratio of the main drive to ensure that
Set other parameters and structural parameters for structural design. Due to the adoption of a two-speed transmission side
Type, may produce the phenomenon of power loss in a certain speed range, this is
Power gap. Narrowing the power gap as much as possible is also to determine the high-grade and low-grade of the main drive.
One of the main basis of gear reduction ratio.
2. 1 Calculation of high-low reduction ratio
2.5 Comprehensive analysis and determination of parameter selection
The above formula reflects the relationship between the main technical parameters and the selection of design parameters.
Type selection, technical characteristics analysis, structural design and analysis play an important role.
(1) Influence of Low Reduction Ratio on Mechanical Characteristics and Selection of Reduction Ratio
According to the formula (1), the low gear reduction ratio consists of the maximum torque of the spindle and the maximum torque of the motor.
Decide. The greater the maximum torque of the spindle, the greater the reduction ratio of low gear; On the contrary, low-level reduction
The greater the speed ratio, the greater the maximum torque of the spindle. Meanwhile, according to Formula (3), the gear reduction ratio is low.
The larger the spindle, the smaller the rated speed, that is, the wider the constant power range. But according to the formula,
(5), (6) and (7) The greater the reduction ratio of low gear, the greater the power loss or power gap.
Therefore, it is necessary to comprehensively consider and analyze, and choose a larger low reduction ratio to ensure success.
There should be a large range of spindle maximum torque and constant power, but the low speed reduction ratio should not be too large.
Large, otherwise the power loss is too large, which will greatly affect the mechanical characteristics of the machine tool and will not play a positive role.
Common requirements. Generally, it is more appropriate to choose a low reduction ratio of 3.5~5, specifically.
The choice depends on the specific technical requirements and use requirements.
(2) The influence of high-grade reduction ratio on mechanical properties and the selection of reduction ratio.
The previous technical literature rarely analyzes the high-grade reduction ratio and simply points out that it is high.
The gear reduction ratio is generally 1.
According to equations (5), (6) and (7), the greater the high-grade reduction ratio, the smaller the power loss;
At the same time, according to Formula (3) and Formula (10), the larger the top gear reduction ratio, the lower the power gap speed.
The smaller the circumference. Therefore, high-grade reduction ratio is good for mechanical characteristics. And according to the formula
(2), in the case of a certain maximum spindle speed, the greater the high-grade reduction ratio, the motor
The higher the maximum speed used. We know that we don't have to choose when making design choices.
To choose the real maximum speed of the motor, as to how much to choose, we should make a comprehensive analysis. from
From the above analysis, it can be seen that the higher the maximum speed of the motor, the better the mechanical characteristics, but
The higher the maximum speed of the motor, the more important it is to the stability and machining accuracy of the mechanical structure.
The higher the demand, the higher the cost and the lower the economy, which becomes a contradiction to some extent. place
Therefore, the high-grade reduction ratio is generally selected at 1~ 1.5, and need not be limited to 1.
(3) strength gap analysis
According to formula (5), after determining the motor characteristics and the maximum spindle speed, the minimum power
It is related to the high and low deceleration ratio. Choose a large high reduction ratio and a small low reduction ratio.
The greater the ratio, the greater the minimum power, that is, the smaller the power loss. But as can be seen from the above analysis.
As we all know, the stability and machining accuracy of mechanical structure are important for high-grade reduction ratio.
Seeking height; Low gear reduction ratio is small, which will lead to small maximum torque of spindle and constant power norm.
Small perimeter affects mechanical properties. This is a contradiction. We can increase the rated power of the main motor.
Electricity to make up for the impact of power loss, which will increase costs. So, on the whole,
In this case, a power gap is allowed, and the size of the allowed power gap depends on the specific situation.
The use requirements and technical requirements generally do not exceed 1.2~ 1.5, under special circumstances.
It can be bigger.
3 Conclusion
The design of two-stage variable speed main drive system for CNC milling machine or machining center is under way.
The main design parameters, mechanical properties and application requirements must be considered comprehensively.
And analysis, not only to achieve good mechanical properties and meet the use requirements, but also to meet the requirements of the system.
Requirements for manufacturability and economic adaptability. According to the author's experience, high-grade deceleration is generally adopted.
The ratio is1~1.5; The reduction ratio of low-grade and high-grade is 3.5 ~ 5; The power gap is generally not greater than.
1.2~ 1.5。
References:
[1] Editorial Committee of Modern Practical Machine Tool Design Manual. Modern practical machine tool design manual [M]. Beijing:
Machinery Industry Press, 2006.