At present, for the cutting of plastic products and fiber coils represented by EPS foam, plastic carpet, etc., the manual slicing method is mainly used, and manual cutting is flexible and convenient, but the quality of manual cutting is poor, the dimensional error is large, the material waste is large, and the follow-up The processing workload is large, while the working conditions are bad and the production efficiency is low. The use of hot wire cutting can quickly cut EPS foam, plastic carpet and other plastic products, and the cut flat, can meet the rapid slicing requirements of different plastic products, which makes the hot wire widely used in cutting plastic products. occasion.
The hot wire cutter works by energizing the hot wire to make it hot. According to Joule's law e= corpse, the heat generated by the conductor is proportional to the current I, the conductor resistance R, and the energization time t. The more heat is generated, the higher the temperature of the heating wire, when it exceeds the EPS foam, plastic carpet and other plastics. The melting point of the product melts and cuts the plastic product.
The hot wire cutting machine studied in this design belongs to the class of wire cutting machine, and its development is accompanied by the development of material materials in people's life and production. It is precisely because of the EPS foam, plastic carpet and other representative plastic products and fiber coils are widely used in people's lives, which makes the hot wire cutting machine very useful, making the hot wire cutting technology develop rapidly. The most competitive with hot wire cutting machines are laser cutting machines and high pressure water jet cutting machines, each with their own technical advantages, but in some respects there are shortcomings. Their biggest drawback is that cutting and processing costs are too high and are not suitable for cutting low-cost plastic products. Nowadays, people's life and production are inseparable from all kinds of plastic products, and the types of plastic products are constantly increasing. These developments have made the hot wire cutting machine have broad development prospects.
1 Hot wire cutting machine overall design The development of hot wire cutting machine is divided into four stages: 1) The structural design of hot wire cutting machine, firstly use Solidworks to carry out 3D modeling, generate engineering drawings, and process into parts, then Assembled into a hot wire cutting machine prototype. 2) The construction of the hot wire cutting machine hardware system and the connection of each circuit. 3) The preparation of the hot wire cutting machine PLC program completes the control of the coordinated motion of the three stepping motors. 4) The production of the man-machine interface of the hot wire cutting machine makes the control of the hot wire cutting machine more convenient and intelligent.
The specific cutting process of the hot wire cutting machine. The hot wire cutting machine has three stepping motors, and the hot wire can cut the plastic products through the coordinated operation of the three stepping motors. The three stepping motors are called the feeding motor, the wire control motor and the cutting motor. When the switch is pressed, the feed motor will rotate in the specified direction of travel. There are two rollers, the upper and lower rollers forming a clamping device that is clamped and automatically forwarded when the plastic product contacts the clamping device. When a width cut hot wire is encountered, it is cut to the desired width. The plastic products continue to be transported forward. When the plastic products are delivered to the length we need, the feeding motor will stop rotating and the plastic products will stop conveying. At this time, the motor will be cut to drive the length cutting hot wire to move downwards. Cut the plastic product to the length we need. When the length cutting hot wire hits the photoelectric switch, the cutting motor will stop rotating and the feeding motor will start to rotate again. In the process of running the plastic product, the control wire motor directly drives the width cutting hot wire to continuously move up and down, which is beneficial to prevent the hot wire from sticking and not moving.
The control scheme of the hot wire cutting machine is as shown. First, three stepping motor coordinated motion control programs are written by Mitsubishi PLC programming software and downloaded to Mitsubishi PLC. Then three stepping motors will run according to the programmed program in Mitsubishi PLC. When the photoelectric switch is blocked, the photoelectric switch will send a feedback signal to the PLC, and the PLC will change the control of the three stepping motors. Two human-machine interfaces are used to communicate with the PLC. The first method is to communicate with the PLC through the touch screen, and the second is to program the LABVIEW host computer and then communicate with the PLC. The stepping motor rotates to drive the hot wire that has been heated and turned red up and down to complete the sheet cutting of the plastic products.
Directional transmission.
The width cutting structure is composed of a stepping motor, a coupling, a lead screw, a width cutting hot wire fixing device, a hot wire clamping device and the like. Its function is to keep the width cutting hot wire clamped and to reciprocate up and down.
The length cutting structure is composed of a stepping motor, a coupling, a lead screw, a length cutting hot wire fixing device, a hot wire clamping device and the like. Its function is to keep the length cutting wire in a clamped state and to reciprocate up and down.
3 hot wire cutting machine control system hardware components of the hot wire cutting machine control system need to use hardware equipment, industrial computer, Mitsubishi PLC, 5V switching power supply and 48V switching power supply, three 2HB605MAE model stepper motor driver, three stepper motor , four NPN photoelectric switches, Weiluntong TK6070IK3 touch screen, voltage regulator power supply. The industrial computer has two functions: 1) use the Mitsubishi PLC programming software GXDeveloper to write the main program to control the coordinated motion of the three stepping motors; 2) to write the human-machine interface with LABVIEW. The stepping motor driver is a device that controls the duty ratio by controlling the rotation angle and the running speed of the stepping motor to control the running speed of the motor. The voltage regulating power supply converts the 220V AC voltage into a 24V AC voltage, which supplies power to the Nichrome heating wire to heat the hot wire. The specific hot wire cutting machine control system hardware connection flow chart is as shown. 2 hot wire cutting machine structure design. The structure of the upper drum hot wire cutter is divided into three parts: 1) The design of the feed roller structure. 2) Width cutting structure design. 3) Length cut structure design as shown.
The three-dimensional effect diagram of a hot wire cutting machine is composed of a stepping motor, a coupling, a driving roller and an upper pressing roller. The function is to press the plastic product according to the hot wire cutting machine to operate normally, and the hardware device Correct wiring is very important, the line connection method is as shown. The AC1 and AC2 of the driver are respectively connected to the positive and negative poles of the 48V switching power supply, and the four ports of the driver A+, A-, B+ and B- respectively correspond to the red, blue, black and green lines of the stepping motor, pul+ and Dir+ is connected to the positive pole of the 5V switching power supply, pul- is connected to the Y1 port of the PLC, and the C0 port of the PLC is connected to the negative pole of the 5V switching power supply. In addition, the L and N terminals of the PLC must be connected to a 220V power supply.
4 hot wire cutting machine control system PLC program 4.1 initialization program In the PLC program, the first to be initialized, here is the assignment of some data registers in the program such as DO, D2, D4, D6, D10. DO assignment 400, D2 assignment 1000, D4 assignment 1000, D6 assignment 10000, D10 assignment 0. DO is the feed motor frequency, D2 is the cut motor frequency, D4 is the control motor frequency, D6 is the feed motor pulse number, D10 is the current The number of plastic products that have been cut has been completed.
When the Mitsubishi PLC is powered on, the M8002 will automatically close once, thus completing the initialization of the PLC program.
4.2 Manual Control Program The hot wire cutting machine adopts two control methods, namely manual control and automatic control. These two control methods have their own advantages in practical applications. When the hot wire cutting machine is in the test, it is more convenient to use manual control. It can make the three stepping motors move independently at any time, stop at any time, and change the direction of hot wire movement at any time. When in actual production, automatic control is necessary. Once the start button is clicked, the three stepping motors will automatically coordinate according to the program. When it is necessary to stop working, press the stop button and the hot wire. The cutter will stop moving.
Firstly, the manual control PLC programming is explained. The manual control idea of ​​each stepping motor is the same, so the manual control of the feeding motor is taken as an example, as shown.
Plug in the main power supply, switch X011 is closed, press the manual control start button on the touch screen or the LABVIEW man-machine interface of the host computer, the M0 auxiliary relay will be set to close. Then press the feed motor forward rotation button, the feed motor will continuously rotate according to the D0 output pulse frequency until the corresponding photoelectric switch is touched or the stop button is pressed to stop the rotation.
4.3 Automatic Control Program The automatic control program is as shown. The control process is: when the automatic control start button is pressed, the auxiliary relay M1 is closed, the feeding motor will rotate in the forward direction, when the number of pulses is changed, the rotation will stop, the auxiliary relay M8029 will be closed, trigger M30, and over two After the second, T0 is closed, cutting off the motor will drive the hot wire to move downwards. When it touches the photoelectric switch, the motor will stop immediately and stop rotating. At this time, the feeding motor will start to rotate again. After two seconds, the motor will be driven to move the hot wire upward. This is a cycle, and this movement will be repeated all the time. As long as the M30 is set once, a 1 is added to the D10, so that the number of products that have been cut can be recorded and displayed on the touch product or the host computer. The movement of the feed motor and the cut-off motor are related. At the same time, only one stepper motor can be operated and interlocked with each other.
However, the control wire motor rotates independently and continuously, first driving the hot wire to rotate downwards. When it touches the photoelectric switch, it stops for 2 seconds, and then drives the hot wire to rotate upwards for two seconds. This is a motion cycle and then repeats this movement straight. The reciprocating rotation of the wire control motor can effectively prevent the sticking of the plastic product and the occurrence of the bonding phenomenon of the plastic product.
5 Man-machine interface of hot wire cutting machine control system 5.1 Touch screen man-machine interface The man-machine interface of hot wire cutting machine adopts two methods: control operation by touch screen, 2) non-writing man-machine interface through upper computer LABVIEW.
The touch screen man-machine interface uses the Weiluntong TK6070IK3 touch screen, which is 7 inches in size and color display. Its application first uses the EasyBuilder8000 touch screen programming software to write a good touch screen interface. It is important to note here that when writing the touch screen interface, the address of each control button on the touch screen must be the same as the corresponding component address in the Mitsubishi PLC program, so that it can communicate correctly with the PLC. Then download the program programmed by the touch screen programming software to the Weiluntong TK6070IK3 touch screen, and connect the RS232 communication line to the PLC for communication. It is the interface after the touch screen and PLC communication are completed.
5.2 Host Computer LABVEW Human Machine Interface At present, it is very popular to use LABVIEW to write man-machine interface, because LABVIEW is simple to program and beautiful. Therefore, this hot wire cutting machine also uses LABVIEW to write the upper computer program, and the human machine interface is as shown.
Communication is much more complicated than a touch screen. First of all, to master the programming protocol communication protocol of Mitsubishi PLC, the command frame is written according to the specified command frame format, in order to communicate successfully. For example, in LABVIEW, VISA write VI input port writes 0237 30303038033032 string, all numbers are represented by ASC code hexadecimal value. 02 indicates the start character STX, the command code CMD indicated by 37 is set to start, 30303038 indicates that the address is the auxiliary relay M0 in the PLC program, 03 indicates the end character ETX, and 3032 indicates the accumulated checksum.
The programming of LABVIEW is mainly divided into three parts, 1) the writing process of the output pulse frequency of three stepping motors and the number of pulses of the feeding motor; 2) the selection part of manual control, automatic control, stop, etc.; 3) The operating status display section of the three stepper motors. The rear panel block diagram is shown as 0.
6 Conclusion) The cutting of plastic products by hot wire is faster and better than traditional manual cutting of plastic products, which reduces labor costs and improves production efficiency.
The design of the hot wire cutting machine is reasonable, the control system realizes the requirement of multi-motor synchronization, and can be controlled through two kinds of operation interfaces.
The field test shows that the hot wire cutting machine developed has the advantages of high automation, good cutting effect, convenient operation and friendly man-machine interface.
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