Length detection and cutting control of the hottes

Length detection and cutting control of CNC rebar straightening and cutting machine

in order to realize the CNC and automation of rebar straightening machine and threaded rebar straightening machine, it is necessary to accurately measure the rebar length and automatically cut the rebar according to the required length. This paper studies these two problems, and has achieved satisfactory results on the steel bar straightening and cutting machine produced by our school's machinery factory. The relative error of cutting steel bars is less than 0.5%, which overcomes the problem that the original equipment cannot be used for straightening and cutting small-diameter steel bars. The device has the functions of automatic length detection, automatic synchronous movement of the cutting table, automatic counting of the number of steel bars cut, etc. 1. Working principle diagram of steel bar straightening and shearing 1 is the mechanical transmission principle diagram of steel bar straightening and cutting machine. The straightened steel bar 1 is straightened in the rotating straightening cylinder 3 under the drive of the feeding roller 2 and the traction roller 4. The straightened steel bar moves forward through the ports of the upper and lower cutter tables. When the front end of the straightened reinforcement is not moved to the position of the retaining iron 7, although the hammer head 8 reciprocates up and down driven by the inertia wheel 9, the reinforcement is not sheared because it does not contact the upper cutter table 10. When the front end of the straightened reinforcement is pushed to the stop, which greatly improves the stability and reliability of the system, iron 7 moves the upper tool table 10 and the lower tool table 5 forward through the pull rod 6. At this time, the reciprocating hammer head 8 will shear the reinforcement through the upper and lower cutter tables (the length of the sheared reinforcement is L), completing the straightening and shearing of a reinforcement. Continuous movement can complete continuous reinforcement straightening and shearing. 2. Detection of reinforcement length. The working environment of reinforcement straightening and cutting machine is poor, and the vibration of the machine is large. When testing the size of reinforcement, in addition to ensuring the accuracy requirements, it must also meet the requirements of strong anti-interference ability, reliable operation, long service life and so on. The existing steel bar straightening and cutting machine adopts contact measurement, that is, when the steel bar moves, it drives the elastic friction wheel to rotate. The friction wheel is then connected with the pulse generator, and the length of the reinforcement is calculated from the recorded value of the pulse generator. Because the vibration of the machine itself and the reinforcement is very strong when the straightening and cutting machine is working, the wear of the friction wheel is extremely serious. If the friction wheel is not replaced regularly, the detection accuracy will be affected and the cutting error will be caused. Based on the above reasons, the non-contact detection method must be used to detect the length of reinforcement. Through experimental comparison, the scheme of alternately applying magnetic signals on the reinforcement is feasible and meets the design requirements. 5. Figure 2 of the thermal printer shows the working principle of the electrical apparatus for steel bar length detection and steel bar cut-off control. The control parameters are input to the single chip microcomputer by the keyboard, and the digital tube displays the setting parameters and the machine running state (including the number of shear reinforcement). In order to realize non-contact steel bar length detection, an excitation head and a magnetic signal reading device are installed at the outlet of the cutter head to realize non-contact detection. At the beginning of the work, the MCU is in p1 Strong adsorption, 0 port outputs high level, drives the excitation amplifier, and the current output by the excitation amplifier generates a magnetic field on the excitation head. This magnetic field magnetizes the straightened steel bar into a magnetic signal with s polarity. When the steel bar with magnetic mark moves to the position of the magnetic head, an induced pulse voltage is generated on the magnetic head, and the pulse voltage signal is amplified by the amplifier and input to the P3.0 port of the single chip microcomputer. When the MCU detects that P3.0 port is high level, P1.0 port outputs low level. That is, the excitation amplifier changes the current direction of the magnetic head, so that the reinforcement is magnetized into a magnetic signal with polarity n. In this way, the magnetization direction of the reinforcement detected by the magnetic reading head changes once, and the polarity of the excitation head changes once accordingly, and the counter automatically increases by one. As the reinforcement moves forward, there is a continuous magnetization signal with alternating magnetic polarity on the reinforcement. The length of a polarity magnetization area is the distance between the excitation head and the magnetic reading head. It can be calculated from the figure that the length of the cut reinforcement is: l= (n+1) B-A (1), where n - counter value B - distance between the excitation head and the magnetic reading head a - distance between the cutter head and the excitation head, distance a between the cutter head and the excitation head is fixed, and the distance b between the magnetic reading head and the excitation head is adjusted according to the shear length of the reinforcement. 3 cutter table speed tracking and steel bar shearing control principle when the single chip microcomputer calculates that the straightened steel bar reaches the specified length through formula (1), it is necessary to make the pull rod pull the upper and lower cutter tables to move. The existing CNC steel bar straightening machine uses the attraction action of electromagnet to make the pull rod move. There are two characteristics of this method: (1) when the moving speed of the steel bar is high and the steel bar that needs to be cut is short, the electromagnet needs to be pulled in frequently, and the coil is very easy to heat and burn the electromagnet. (2) Subsequently, social and private capital began to enter the head position uncertainty, resulting in the length of the cut-off reinforcement exceeding the tolerance. Therefore, the action of electromagnet cannot be used to control the movement of cutter table. Stepper motor has the advantages of high positioning accuracy and easy speed control. If the driving speed of the elastic pull rod on the output shaft of the continuously rotating stepping motor is kept the same, it can ensure that the reinforcement can be cut accurately according to the required length. Figure 3 is the transmission schematic diagram. The hammer head moves up and down by the action of inertia wheel. When the moving distance of reinforcement reaches the shear size, the hammer head may not be at the lower limit position; If the moving speed of the cutter head is the same as that of the steel bar (equivalent to the movement of the cutter head holding the steel bar), the steel bar can be cut accurately when the hammer head is at the lower limit position. Set in a cycle of hammer movement, the maximum distance s of the pull rod meets: