What Is a Capstan Lathe?

Machine tool (English name: machine tool) refers to the machine that manufactures the machine, also known as the working machine or machine tool, and is commonly referred to as the machine tool. Generally divided into metal cutting machine tools, forging machine tools and woodworking machine tools. There are many methods for processing mechanical parts in modern machinery manufacturing: in addition to cutting, there are casting, forging, welding, stamping, extrusion, etc., but all parts with higher accuracy requirements and finer surface roughness requirements are generally required in Final machining is performed on the machine by cutting. Machine tools play a major role in the modernization of the national economy.

The prototype of the 15th century machine tool, due to the need for clocks and weapons,

The quality of the machine tool itself directly affects the quality of the machine made. Measuring the quality of a machine tool is multi-faceted, but it mainly requires good workmanship, serialization, generalization, high degree of standardization, simple structure, light weight, reliable work, and high productivity. The specific indicators are as follows:

1. Possibility of craftsmanship

Process possibility refers to the ability of the machine to adapt to different production requirements. General-purpose machine tools can complete a variety of parts in a certain size range with multiple processes, and the possibility of technology is relatively wide, so the structure is relatively complex, suitable for single-piece small batch production. Special machine tools can only complete specific procedures of one or a few parts. Its process possibilities are narrow and suitable for mass production. It can improve productivity, guarantee processing quality, simplify machine tool structure, and reduce machine tool costs.

2.Accuracy and surface roughness

To ensure the accuracy and surface roughness of the machined parts, the machine tool itself must have certain geometric accuracy, motion accuracy, transmission accuracy and dynamic accuracy.

Geometric accuracy refers to the mutual position accuracy of parts and the shape accuracy and position accuracy of main parts when the machine tool is not running. The geometric accuracy of the machine tool has an important influence on the machining accuracy, so it is the main index for evaluating the accuracy of the machine tool.

Motion accuracy refers to the geometric position accuracy of the main parts when the machine tool is operating at the working speed. The greater the change in geometric position, the lower the motion accuracy.

Transmission accuracy refers to the coordination and uniformity of movement between the end effectors of the machine tool transmission chain.

The above three accuracy indicators are tested under no-load conditions. In order to fully reflect the performance of the machine tool, it is necessary to require the machine tool to have a certain dynamic accuracy and the shape and position accuracy of the main components under the action of temperature rise. The main factors affecting dynamic accuracy are the stiffness, vibration resistance and thermal deformation of the machine tool.

The rigidity of a machine tool refers to the ability of the machine tool to resist deformation under the action of an external force. The greater the stiffness of the machine tool, the higher the dynamic accuracy. The rigidity of the machine tool includes the stiffness of the machine tool components themselves and the contact stiffness between the components. The rigidity of the machine tool components itself mainly depends on the material properties, cross-sectional shape, size, etc. of the component itself. The contact stiffness between components is not only related to the contact material, the geometric size and hardness of the contact surface, but also to the surface roughness, geometric accuracy, processing method, contact surface medium, preload and other factors of the contact surface.

Vibrations appearing on machine tools can be divided into forced vibrations and self-excited vibrations. Self-excited vibration is the continuous vibration generated by the cutting process without being disturbed by any external force or excitation force. Under the continuous action of the exciting force, the vibration caused by the system is forced vibration.

The vibration resistance of a machine tool is related to the stiffness, damping characteristics and quality of the machine tool. Due to the different thermal expansion coefficients of various parts of the machine tool, different deformations and relative displacements of various parts of the machine tool are caused. This phenomenon is called thermal deformation of the machine tool. The error due to thermal deformation can account for up to 70% of the total error.

There is no uniform standard for the dynamic accuracy of machine tools, and the comprehensive evaluation of the dynamic accuracy of machine tools is made indirectly through the accuracy achieved by cutting typical parts.

3.Serialization, etc.

The serialization, generalization, and standardization of machine tools are closely related. The serialization of varieties is the basis for the generalization of components and the standardization of parts, and the generalization of components and the standardization of parts promote and promote the serialization of varieties.

4. Machine tool life

The reliability and wear resistance of the machine tool structure are the main indicators to measure the life of the machine tool. ^[2]

1. Ordinary machine tools: including ordinary lathes, drilling machines, boring machines, milling machines, planing machines, etc .;

2. Precision machine tools: including grinding machines, gear processing machine tools, thread processing machine tools and other various precision machine tools;

3. High-precision machine tools: including coordinate boring machines, gear grinding machines, thread grinding machines, high-precision hobbing machines, high-precision engraving machines, and other high-precision machine tools;

4. CNC machine tools: CNC machine tools are short for digitally controlled machine tools;

5. According to the size of the workpiece and the weight of the machine tool, it can be divided into instrument machine tools, small and medium machine tools, large machine tools, heavy machine tools and super heavy machine tools;

6. According to processing accuracy, it can be divided into ordinary precision machine tools, precision machine tools and high precision machine tools;

7. According to the degree of automation, it can be divided into manual operation machine tools, semi-automatic machine tools and automatic machine tools;

8. According to the control method of the machine tool, it can be divided into profiling machine tools, program control machine tools, CNC machine tools, adaptive control machine tools, machining centers and flexible manufacturing systems;

9, according to the processing method or processing object can be divided into lathes, drilling machines, boring machines, grinding machines, gear processing machine tools, thread processing machine tools, spline processing machine tools, milling machines, planing machines, slotting machines, broaching machines, special processing machine tools,

Each type of machine tool is usually composed of the following basic parts: support parts for mounting and supporting other parts and workpieces, bearing their weight and

The cutting process of the machine tool is realized by the relative movement between the tool and the workpiece, and its movement can be divided into two types: surface forming movement and auxiliary movement.

The surface forming motion is a motion for obtaining the required surface shape and size of the workpiece, and it includes a main motion, a feed motion, and a plunging motion. The main movement is the movement that plays the main role when stripping excess material from the workpiece blank. It can be the rotary movement of the workpiece (such as turning), the linear movement (such as planing on a gantry planer), or the rotary movement of a tool (such as

Machine tool accessories refer to all easily replaceable components except the main body of the machine.

Machine tool accessories mainly include tool holders, operating parts,

1. Virtual machine tool: Through the development of mechatronics, hardware and software integration simulation technology, to improve the design level and performance of machine tools.

2. Green machine tools: Emphasize energy saving and emission reduction, and strive to minimize the environmental load of the production system.

3. Intelligent machine tools: improve the intelligence, reliability, processing accuracy and comprehensive performance of the production system.

4. e-Machine: Improve the independence of the production system and the ability to interact with users and managers, so that the machine tool is not only a processing equipment, but also a node in the enterprise management network.

Among them, green machine tools will become research hotspots. The working mother machine that converts the blank into parts not only consumes energy during use, but also generates solid, liquid, and gas wastes, causing direct or indirect pollution to the working environment and the natural environment. According to this, green machine tools should have the following characteristics: the main parts of the machine tool are made of recycled materials; the weight and volume of the machine tool are reduced by more than 50%; the power consumption is reduced by 30% to 40% through measures such as reducing moving mass and reducing idle running power; All kinds of waste generated during the use are reduced by 50% to 60%, which guarantees a basically non-polluting working environment; 100% of the machine tool materials can be recycled after scrapping. According to statistics, the power used to remove metal during the use of the machine tool only accounts for about 25%, and various losses and auxiliary functions account for most of it. The first measure for the greening of machine tools is to build ecologically-efficient machine tools by greatly reducing the weight of the machine tools and reducing the driving power. The green machine tool proposes a brand new concept that significantly reduces weight and strives to save materials while reducing energy consumption. ^[3]

The operator must pass the examination and hold the "equipment operation certificate" of the machine before operating the machine.

The electrical machine fault diagnosis of CNC machine tools has three stages: fault detection, fault judgment, isolation and fault location. The first stage of fault detection is to test the CNC machine to determine whether there is a fault; the second stage is to determine the nature of the fault and isolate the faulty component or module; the third stage is to locate the fault to a replaceable module or print PCB to shorten repair time. In order to find the faults in the system in a timely manner, quickly determine the fault location and can be eliminated in time, it is required that fault diagnosis should be as few and simple as possible, and the time required for fault diagnosis should be as short as possible. To this end, the following diagnostic methods can be used:

Visual method

Use sensory organs to pay attention to various phenomena at the time of failure, such as the occurrence of sparks, bright lights, abnormal sounds, abnormal heating, and scorching smell. It is the most basic and commonly used method to carefully observe the surface condition of each printed wiring board that may be faulty, and whether there are signs of burnout and damage to further narrow the inspection scope.

Self-diagnostic function of CNC system

Relying on the ability of the CNC system to quickly process data, multi-channel and fast signal acquisition and processing are performed on the faulty part, and then the diagnostic program performs logic analysis to determine whether there is a fault in the system and locate the fault in time. The self-diagnostic functions of modern CNC systems can be divided into the following two categories:
(1) Power-on self-diagnosis Power-on self-diagnosis refers to the system's internal diagnostic routines that automatically execute CPU, memory, bus, I / O units and other printed circuit boards from the start of each power-on to the normal operating preparation state , CRT unit, optoelectronic reader and floppy disk drive and other equipment before the function test to confirm whether the main hardware of the system can work normally.
(2) Fault message prompts When a fault occurs during machine operation, the number and content will be displayed on the CRT display. According to the prompts, consult the relevant maintenance manual to confirm the cause of the failure and the remedy. Generally speaking, the richer the fault information suggested by the diagnostic function of CNC machine tools, the more convenient the fault diagnosis will be. However, it should be noted that some faults can directly confirm the cause of the fault according to the fault content prompt and consult the manual; while some faults do not match the fault content prompt, or one fault shows multiple fault causes, which requires maintenance personnel to Find out the internal relationship between them and indirectly confirm the cause of the failure.

Data and status checks

The self-diagnosis of the CNC system can not only display fault alarm information on the CRT monitor, but also provide machine parameter and status information in the form of multiple pages of "diagnostic address" and "diagnostic data". Common data and status checks include parameter check and The interface checks both.
(1) Parameter check The machine data of CNC machine tools are important parameters obtained through a series of tests and adjustments, and are the guarantee of the normal operation of the machine tools. These data include gain, acceleration, contour monitoring tolerance, backlash compensation value, and screw pitch compensation value. When receiving external interference, data will be lost or chaotic, and the machine will not work properly.
(2) Interface check The input / output interface signals between the CNC system and the machine tool include the interface input / output signals between the CNC system and the PLC, and between the PLC and the machine tool. The diagnosis of the input / output interface of the CNC system can display the status of all digital signals on the CRT display. Use "1" or "0" to indicate the presence or absence of the signal. Use the status display to check whether the CNC system has output the signal to the machine tool. Whether signals such as switching values on the machine side or the machine side have been input to the CNC system, so that the fault can be located on the machine side or in the CNC system.

Alarm indicator shows failure

Inside the CNC system of modern CNC machine tools, in addition to the above-mentioned "software" alarms such as the self-diagnostic function and status display, there are many "hardware" alarm indicators, which are distributed on devices such as power supply, servo drive and input / output. The indication of these warning lights can determine the cause of the failure.

Spare board replacement

Using a spare circuit board to replace a template with a suspected fault is a fast and easy way to determine the cause of the fault. It is often used in functional modules of CNC systems, such as CRT modules and memory modules. It should be noted that before the replacement of the spare board, the relevant circuits should be checked to avoid damage to the good board due to a short circuit. At the same time, the selection switch and jumper on the test board should be consistent with the original template. Some templates should also pay attention to the template Adjustment of the potentiometer. After replacing the memory board, the memory should be initialized according to the requirements of the system, otherwise the system still cannot work normally.

Exchange method

In CNC machine tools, there are often modules or units with the same functions. The same modules or units are exchanged with each other. Observing the situation of failover, you can quickly determine the fault location. This method is often used for fault checking of the servo feed drive, and can also be used for the interchange of the same module in the CNC system.

Percussion

The CNC system consists of various circuit boards, and there will be many solder joints on each circuit board. Any false soldering or poor contact may cause failure. When a circuit board, a connector, or an electrical component with a suspected fault is lightly tapped with an insulator, if the fault occurs, the fault is likely to be at the location of the tap.

Measurement comparison

For the convenience of detection, there are detection terminals on the module or unit. Using multimeters, oscilloscopes and other instruments, the levels or waveforms detected by these terminals can be used to compare the normal value with the value at the time of the failure, and analyze the cause of the failure and The location of the fault. Due to the comprehensive and complex characteristics of CNC machine tools, the factors that cause failures are various. The above-mentioned fault diagnosis methods sometimes need to be applied simultaneously, comprehensively analyze the fault, quickly diagnose the fault location, and eliminate the fault. At the same time, some failure phenomena are electrical, but the causes are mechanical; conversely, it is also possible that the failure phenomena are mechanical, but the cause is electrical; or both. Therefore, its fault diagnosis often cannot be simply attributed to electrical or mechanical aspects, but must be comprehensively considered in all directions. ^{[3] [1]}