CN115383515A - Electric heating assisted cutting system and method for online monitoring and adjustment of tool wear - Google Patents

Abstract

The invention discloses an electric heating auxiliary cutting system and method for monitoring and adjusting cutter abrasion on line. The device comprises a workpiece, an insulator, a chuck, a cutter, an insulating layer, a current transformer, an ammeter, a voltmeter, a step-down transformer, an autotransformer, a power supply, an electric brush, an industrial personal computer, an AE acoustic emission sensor, a preamplifier, a high-pass filter, a low-pass filter and a main amplifier. The AE acoustic emission sensor monitors signals with specific frequency generated in the electric heating cutting process in real time, the signals are processed by a preamplifier, a high-pass filter, a low-pass filter and a main amplifier and then transmitted to an industrial personal computer, collected signals are analyzed and processed in real time through wavelet transformation, and then the abrasion of a cutter is compensated in real time by adjusting current and cutting parameters, so that the machining precision is guaranteed. The invention solves the problem of monitoring the abrasion and the damage of the cutter in real time, and adjusts the heating current in time, so that the technology of electric heating auxiliary cutting can give full play to the economic benefit.

Description

Electric heating assisted cutting system and method for online monitoring and adjustment of tool wear

technical field

The invention relates to the technical field of mechanical processing, in particular to an electric heating assisted cutting system and method for online monitoring and adjusting tool wear.

Background technique

Conductive heating cutting technology is to pass low voltage and high current between the workpiece and the tool. During the cutting process, relying on the contact resistance between the workpiece and the tool, a large amount of Joule heat is rapidly generated, and the high temperature reduces the strength and hardness of the deformed material. Therefore, The electric heating assisted cutting technology can reduce the cutting force or torque, while ensuring the processing quality, reduce the wear of the material on the tool and improve the tool life.

Foreign scholars have conducted experimental research on conductive heating cutting of high-temperature alloys, hardened steel and other difficult-to-machine metal materials, proving the advantages of electric heating cutting, which can reduce tool wear while improving processing efficiency. However, in the process of electric heating cutting, it takes a long time to pass a large current to heat to the appropriate cutting temperature. At this time, the high temperature brings a certain degree of thermal damage to the cutting tool, which aggravates the adhesive wear of the tool and reduces the use of the tool. life. At the same time, it has a great impact on the processing quality of the parts. The tool wear is very serious when cutting difficult-to-machine materials. In order to ensure the processing accuracy, the tool has to be replaced frequently, which will greatly increase the manufacturing cost. Moreover, in order to ensure higher processing quality It is necessary to remove the tool frequently to measure the tool wear value, which greatly reduces the processing efficiency, and also brings the problem of positioning when the tool is clamped for the second time.

Therefore, it is necessary to find a real-time online monitoring technology to solve the problem of tool wear value measurement, so that the technology of conductive heating cutting can maximize the economic benefits.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention provides an electric heating assisted cutting system and method for on-line monitoring and adjustment of tool wear, which solves the problem of real-time monitoring of tool wear and damage, and adjusts the heating current in time to make electric heating assist Cutting this technology to play the greatest economic benefits.

In order to achieve the above object, technical scheme of the present invention is:

An electric heating auxiliary cutting system for on-line monitoring and adjustment of tool wear, including: workpiece, insulator, chuck, tool, insulating layer, current transformer, ammeter, voltmeter, step-down transformer, autotransformer, power supply, brush , industrial computer, AE acoustic emission sensor, preamplifier, high-pass filter, low-pass filter and main amplifier.

The AE acoustic emission sensor monitors the signal of a specific frequency generated during the electric heating cutting process in real time, and the signal is processed by the preamplifier, high-pass filter, low-pass filter and main amplifier and then sent to the industrial computer for The collected signal is analyzed and processed in real time through wavelet transform, and then the tool wear is compensated in real time by adjusting the current and cutting parameters to ensure the machining accuracy.

An insulator is set between the workpiece and the chuck, the workpiece is insulated and installed on the chuck, and the chuck is tightened to keep the workpiece fixed; the tool is installed on the tool holder of the machine tool after being insulated by an insulating material; the DC power supply Through the output of the autotransformer, the positive pole is connected to the main shaft of the lathe through the brush, and the negative pole is connected to the rear end surface of the tool.

Install the AE acoustic emission sensor on the upper surface of the tool handle, and make it close to the tool handle during installation; connect the ammeter, current transformer, voltmeter and step-down transformer into the system in series, and the tool is lightly connected to the surface of the workpiece. Light touch on, forming a closed circuit.

On the other hand, the electric heating assisted cutting method for on-line monitoring and adjusting tool wear of the present invention is realized by using the aforementioned electric heating assisted cutting system for on-line monitoring and adjusting tool wear, and the method includes the following steps:

1. Install the workpiece on the chuck after being insulated, and tighten the chuck;

2. Install the tool on the tool holder of the machine tool after being wrapped by the insulating layer, and adjust the tool angle suitable for cutting;

3. The DC power is output through an autotransformer, the positive pole is connected to the lathe spindle through the brush, and the negative pole is connected to the rear end of the tool;

4. Install the AE acoustic emission sensor on the upper surface of the knife handle, and make the AE acoustic emission sensor close to the knife handle during installation, so as to receive signals better;

5. Select the processing technology parameters by numerical calculation method, and obtain the processing technology parameters such as heating current, preheating time, cutting speed and feed rate;

6. The ammeter, voltmeter and step-down transformer are connected in series into the system, and the tool is in light contact with the surface of the workpiece to form a closed loop;

7. According to step 5, adjust the processing parameters such as heating current, speed, feed rate, etc., turn on the power switch, and after preheating for a suitable time, start the machine tool to start cutting, and use the AE acoustic emission sensor to monitor the signal of the selected frequency during the electric heating cutting process. Real-time online monitoring, the acoustic emission signal passes through the preamplifier, band-pass filter and main amplifier, and finally collects through the system;

8. Perform real-time analysis and processing of the collected signals through wavelet transform, adjust the power supply through the industrial computer, adjust the current in time to compensate for tool wear in real time, and maximize efficiency while ensuring machining accuracy;

9. After the processing is completed, turn off the power and the machine tool.

Beneficial effects of the present invention:

1. The invention is suitable for the cutting of difficult-to-machine materials such as particle-reinforced aluminum/magnesium-based composite materials, high-temperature alloys, and hardened steel, and solves the technical problems of severe tool wear and unguaranteed machining accuracy; the invention is not limited by materials, Almost all metal and non-metallic materials have acoustic emission phenomenon under certain conditions. The acoustic emission equipment is simple, and it only needs to be integrated on the basis of the original electric heating assisted cutting method to realize online monitoring of electric heating assisted cutting tool wear and damage.

2. Compared with other heating sources, such as laser, plasma, etc., the power source used for electric heating assisted cutting has low energy consumption and very low cost.

3. When the power supply heats the material in the deformation zone through the tool, the temperature rises rapidly, the thermal efficiency is high, and the heat-affected area is small.

4. Acoustic emission, as an effective non-destructive testing technology, can easily realize the online monitoring of electric heating assisted cutting, and has the advantages of high sensitivity and no need to stop during the monitoring process, which greatly saves the time of tool wear monitoring and improves the electric heating assisted cutting. cutting efficiency.

5. The acquisition signal has strong anti-interference ability, and is less affected by current parameters, cutting parameters and tool geometric parameters.

6. It can eliminate the influence of other environmental noises in the actual processing or experiment process, and has a better selective analysis of the high-frequency stage of the required acoustic emission signal, and has a wider application prospect in realizing industrial automation.

7. The present invention performs real-time analysis on the collected signals through wavelet transform, and can adjust the current and cutting parameters in time to compensate for tool wear in real time, and maximize efficiency while ensuring machining accuracy.

Description of drawings

Fig. 1 is a schematic circuit diagram of an electric heating auxiliary cutting system for on-line monitoring and adjusting tool wear provided by the present invention

in:

1-workpiece, 2-insulator, 3-chuck, 4-tool, 5-insulation layer, 6-current transformer, 7-ammeter, 8-voltmeter, 9-step-down transformer, 10-autotransformer, 11 -Power supply, 12-Brush, 13-Industrial computer, 14-AE sensor, 15-Preamplifier, 16-High-pass filter, 17-Low-pass filter, 18-Main amplifier.

Detailed ways

In order to solve the problems existing in the prior art, as shown in Figure 1, the present invention provides an electric heating auxiliary cutting system for online monitoring and adjustment of tool wear, including a workpiece 1, an insulator 2, a chuck 3, a tool 4, an insulating layer 5. Current transformer 6, ammeter 7, voltmeter 8, step-down transformer 9, autotransformer 10, power supply 11, brush 12, industrial computer 13, AE acoustic emission sensor 14, preamplifier 15, high-pass filter 16 , low pass filter 17 and main amplifier 18.

The AE acoustic emission sensor 14 monitors the signal of a specific frequency generated by the electric heating cutting process in real time, and the signal is processed by the preamplifier 15, high-pass filter 16, low-pass filter 17 and main amplifier 18 and then sent to the industrial computer 13 , the collected signal is analyzed and processed in real time through wavelet transform, and then the tool wear is compensated in real time by adjusting the current and cutting parameters to ensure the machining accuracy.

On the other hand, the electric heating assisted cutting method for on-line monitoring and adjusting tool wear of the present invention is realized by using the aforementioned electric heating assisted cutting system for on-line monitoring and adjusting tool wear, and the method includes the following steps:

1. Install the workpiece 1 on the chuck 3 after being insulated by the insulator 2, and tighten the chuck 3;

2. Install the tool 4 on the machine tool holder after being wrapped by the insulating layer 5, and adjust the angle of the tool 4 suitable for cutting;

3. The DC power is output through the autotransformer 10, the positive pole is connected to the main shaft of the lathe through the brush 12, and the negative pole is connected to the rear end surface of the tool 4;

4. The AE acoustic emission sensor 14 is installed on the upper surface of the tool handle of the tool 4, and the AE acoustic emission sensor 14 is placed close to the tool handle during installation, so as to receive signals better;

5. Select the processing technology parameters by numerical calculation method, and obtain the processing technology parameters such as heating current, preheating time, cutting speed and feed rate;

6. Connect the ammeter 7, voltmeter 8 and step-down transformer 9 in series into the system, and the tool 4 touches lightly with the surface of the workpiece 1 to form a closed loop;

7. According to step 5, adjust the processing parameters such as heating current, speed, feed rate, etc., turn on the power switch, and after preheating for a suitable time, start the machine tool to start cutting, and use the AE acoustic emission sensor 14 to select the frequency signal of the electric heating cutting process Carry out real-time online monitoring, the acoustic emission signal passes through the preamplifier 15, high-pass filter 16, low-pass filter 17 and main amplifier 18, and finally collects through the system;

8. Perform real-time analysis and processing of the collected signals through wavelet transform, adjust the power supply through the industrial computer 13, adjust the current in time, and perform real-time compensation for the wear of the tool 4, so as to maximize efficiency while ensuring machining accuracy;

9. After the processing is completed, turn off the power supply 11 and the machine tool.

The working principle of the present invention is:

The present invention designs an electric heating assisted cutting system and method for on-line monitoring and adjusting tool wear based on acoustic emission technology, uses this technology to reduce the number of times of tool change and tool wear value measurement, and maximizes efficiency while ensuring machining accuracy. During the metal cutting process, the tool will generate an elastic wave when it wears and breaks. This elastic wave is transmitted in the form of sound waves converted from the energy released by the solid when it undergoes plastic deformation and rupture. Compared with other non-destructive monitoring methods, acoustic emission (AE) monitoring has the advantages of simple sensor installation, rich signal frequency information, no influence on the processing process, and dynamic detection can be realized. Moreover, the acoustic emission method monitors the high-frequency elastic stress wave signal emitted when the tool is worn and damaged, avoiding the low-frequency area where vibration and audio signals are seriously polluted during processing, and has high sensitivity and strong anti-interference ability in the high-frequency area. At the same time, it is less affected by cutting parameters and tool geometric parameters, and is very sensitive to tool wear and breakage. The integration of acoustic emission monitoring tool wear and electric heating assisted cutting can make the technology of electric heating assisted cutting maximize the economy. benefit. Tool wear is a gradual process with slow changes. During conventional cutting, workers can estimate the degree of tool wear based on the vibration or noise of the machine tool and the cutting state. However, in the process of automatic processing, the system needs to be able to automatically judge the wear degree of the tool and replace the tool in time to avoid the decline in processing quality caused by excessive tool wear, while improving production efficiency and reducing labor costs. The acoustic emission sensor (AE) is installed on the workpiece material, and the collected signal is amplified by the amplifier and sent to the computer by the acquisition card, and the waveform is displayed after being processed by the computer. Determine the signal of a certain frequency band concerned, and perform wavelet decomposition on the signal in this frequency band, decompose the original signal into different frequency bands, and judge the degree of tool wear according to the energy of the decomposed signal. The test shows that this method has strong operability and is beneficial to popularization and application in electric heating assisted cutting.

Conductive heating cutting is to use the tool and workpiece to form a loop to pass low voltage and high current during the cutting process. Because the contact area between the tool and the workpiece and chips is very small, it can be known from the contact resistance theory that a large contact resistance will be generated in the contact area. The Joule effect of the large current heats the cutting area rapidly, reducing the material strength in the cutting area, thus making the cutting easier. Some research results show that the strength ratio and hardness ratio of tool material and processed material will change with the increase of temperature. In heating cutting, cutting effect is best if the hardness difference between tool material and workpiece material is at the maximum temperature, that is, in conductive heating cutting, there is an optimal heating temperature or current, at which temperature, the cutting tool highest durability.

The amount of heat generated in the electric heating cutting process proposed by the present invention is proportional to the time and current density of the current, and the heating temperature can be approximated as:

According to the Viedemann-Franz-Lorenz law:

In order to calculate the heating current need to calculate the size of the heating resistance. According to the characteristics of the metal cutting process itself, the heating resistance includes three parts, which are the metal material resistance Rm, the contact resistance Rt formed by the contact between the tool and the chip peak point, and the expansion resistance Rs formed due to the change of the current line density. The resistors together constitute the entire heating resistor. The three resistors can be solved through a series of complicated formulas, but the solution process is very cumbersome. For the convenience of calculation, the present invention uses Matlab software to program according to the corresponding formula, as long as the parameters of the cutting tool, the resistivity of the workpiece and the tool material and the cutting parameters are input, the calculation result of the resistance can be obtained.

Select the electric heating cutting parameters, fix the clamped workpiece on the workbench, install the tool and move the clamp to make the tool touch the surface of the workpiece lightly, so as to avoid sparking when the power is on. Preheat for a certain period of time before cutting, so that the temperature field of the workpiece is most conducive to processing, and then adjust the rotation speed, feed rate and current to perform cutting.

Claims (5)

1. The utility model provides an electrical heating assists cutting system of on-line monitoring and adjustment cutter wearing and tearing which characterized in that: the device comprises a workpiece, an insulator, a chuck, a cutter, an insulating layer, a current transformer, an ammeter, a voltmeter, a step-down transformer, an autotransformer, a power supply, an electric brush, an industrial personal computer, an AE acoustic emission sensor, a preamplifier, a high-pass filter, a low-pass filter and a main amplifier.

2. An electrically heated assisted cutting system for on-line monitoring and adjustment of tool wear according to claim 1 wherein: the AE acoustic emission sensor monitors signals with specific frequency generated in the electric heating cutting process in real time, the signals are processed by the preamplifier, the high-pass filter, the low-pass filter and the main amplifier and then transmitted to the industrial personal computer, the acquired signals are analyzed and processed in real time through wavelet transformation, and then the abrasion of the cutter is compensated in real time by adjusting current and cutting parameters, so that the processing precision is ensured.

3. An electrically heated assisted cutting system for on-line monitoring and adjustment of tool wear according to claim 1 wherein: an insulator is arranged between the workpiece and the chuck, the workpiece is installed on the chuck after being insulated, and the chuck is screwed down; the cutter is installed on a tool rest of a machine tool after being insulated by insulating materials; and a direct current power supply is output through the autotransformer, the positive pole of the direct current power supply is connected to the lathe spindle through the electric brush, and the negative pole of the direct current power supply is connected to the rear end face of the cutter.

4. An electrically heated assisted cutting system for on-line monitoring and adjustment of tool wear according to claim 1 wherein: the AE acoustic emission sensor is arranged on the upper surface of the knife handle and is tightly attached to the knife handle during installation; and connecting the ammeter, the current transformer, the voltmeter and the step-down transformer in series into a system, and lightly contacting the cutter with the surface of the workpiece to form a closed loop.

5. An electric heating auxiliary cutting method for online monitoring and adjusting tool wear, which is realized by using the electric heating auxiliary accurate system for online detecting and adjusting tool wear of claim 1, and comprises the following steps:

(1) Mounting the workpiece on the chuck after insulation, and screwing the chuck;

(2) After the cutter is wrapped by the insulating layer, the cutter is mounted on a tool rest of a machine tool together, and the angle of the cutter suitable for cutting is adjusted;

(3) The direct current power supply is output through the autotransformer, the positive pole is connected to the lathe spindle through the electric brush, and the negative pole is connected to the rear end face of the cutter;

(4) The AE acoustic emission sensor is arranged on the upper surface of the knife handle, and is tightly attached to the knife handle during installation so as to better receive signals;

(5) Selecting processing technological parameters through a numerical algorithm to obtain processing technological parameters such as heating current, preheating time, cutting speed, feeding amount and the like;

(6) Connecting the ammeter, the voltmeter and the step-down transformer in series into a system, and enabling the cutter to be in light contact with the surface of a workpiece to form a closed loop;

(7) Adjusting processing parameters such as heating current, rotating speed and feeding amount according to the step (5), turning on a power switch, preheating for a proper time, starting a machine tool to start cutting, carrying out real-time online monitoring on signals with selected frequencies in the electric heating cutting process through an AE acoustic emission sensor, and collecting the acoustic emission signals through a system after the acoustic emission signals pass through a preamplifier, a band-pass filter and a main amplifier;

(8) The acquired signals are analyzed and processed in real time through wavelet transformation, the power supply is adjusted through the industrial personal computer, current is adjusted in time to compensate the abrasion of the cutter in real time, and the maximization of the efficiency is realized under the condition of ensuring the machining precision;

(9) And after the machining is finished, turning off the power supply and the machine tool.

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