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First, the composition of the photoelectric protector Optoelectronic protectors are generally divided into two types of radiation and reflection.
The photo-shooting photoelectric protector means that the light-emitting unit and the light-receiving unit are respectively inside the light emitter and the light receiver, and the light emitted from the light-emitting unit directly hits the light-receiving unit, thereby forming a photoelectric protection device that protects the light curtain. The shoot-type photoelectric protector consists of a controller, a light emitter, a light receiver, an optical transmission line, and an optical transmission line.
The reflective photoelectric protector means that the light emitting unit and the light receiving unit are all in the same sensor, and the light emitted by the light emitting unit is reflected back to the light receiving unit through the reflector, thereby forming a photoelectric protection device that protects the light curtain. A safety protection screen is formed between the light emitter and the reflector. Whenever the security protection screen is disturbed or the equipment is not working properly, the light emitter emits a signal and transmits it to the press control system to prevent possible dangerous movements and stop the hammer from descending. Reflective photoelectric protector consists of controller, sensor, reflector and transmission line.
two. Feature points:
The instrument has a self-test function. When the transmitter has an error message, the press working status is not affected. Photovoltaic safety protects the light wave range, which is the effective sensitive area, and can be calculated by the following formula:
S = v't (seconds) = safety zone (mm)
S is the valid sensitivity zone V is the slider taxi speed T is the slider stop time (millionths of a second)
This responds to the hydraulic system and can directly control its effective sensitive area. In any case, the Rexroth high-speed response valve and servo loop allow the opto-protected light waves to appear in the mold space as much as possible. This provides a very safe working environment for operating workers. In many cases, photoelectric switches are also used to increase productivity. When the operator pulls hands back from the photoelectric safety protection light wave, the signal is generated when the workpiece is placed in the mold, and the press is started. The foot pedal and the manual switch are no longer used. . Of course, in this case, the photoelectric safety protector can still fulfill its safety protection function, and the above-mentioned photoelectric switch can improve production efficiency by 25% compared with the mechanical foot switch. Phototransmitters and reflectors are protected by a sheet metal enclosure to prevent any accidental damage.
Third, install and debug 1. Photoelectric protectors are generally installed in fixed and adjustable versions.
Fixed installation: The sensor and reflector (or transmitter and receiver) are directly fixed on the machine bed. It is usually applied to the closed press of the frame structure where the mold is relatively fixed and the light curtain is not required to be adjusted frequently.
Adjustable installation: Sensors and reflectors (or transmitters and receivers) are connected to the machine through special brackets. In this type of installation, the light curtain can be flexibly adjusted from top to bottom and left to right depending on the requirements of the die opening and the safety distance. It is generally applicable to open, closed, and four-column presses where the die change is frequent and the sizes of the die are different.
2. The determination of the height position of the light curtain and the calculation of the safety distance.
The height position of the light curtain refers to the position of the light curtain of the photoelectric protector relative to the upper and lower mold openings of the machine tool. Under the premise of ensuring the safety distance, the last light of the photoelectric protector shall not be higher than the lower edge of the die mouth, and the uppermost light shall not be lower than the upper edge of the die mouth.
The protection height of the photo-electric protector refers to the distance between the top optical axis of the light curtain and the bottom optical axis, that is, the effective height of the light curtain. The protection height is equal to the stroke of the machine slider plus the adjustment amount. The size of the protection height is related to the number of photoelectric protector beams. If the number of optoelectronic protector beams is selected too few, the height of the light curtain will not completely cover the dangerous area, and there is still the possibility of causing accidents; if it is too large, it will cause waste of funds and use. The inconvenience. Therefore, it is also important to select the specification (number of beams) of the photo-electric protector according to the protection height.
The safety distance of the photoelectric protector refers to the shortest distance between the light curtain and the working danger zone, the cutting edge of the mold, that is, the distance needed to stop the slider from the position where the hand blocks the light curtain and reaches the dangerous boundary. The safety distance is one of the necessary conditions to ensure that the photoelectric protector achieves the protection function, and the safety distance must be correctly calculated! The calculation method should be based on the press brake method.
For presses where the slider can be braked at any position in the stroke, the safety distance is calculated according to equation (1):
Ds=1.6(T1T T2) (1)
Where: Ds - safety distance, in meters (m);
1.6 - The stretching speed of the hand, in meters/second (m/s);
T1 - response time of the photoelectric protector, 0.02 seconds (s);
T2—Brake time of the press, that is, the time from the start of braking to the stop of the slider, in seconds (s), measured from the actual braking condition.
The slider cannot brake the stopped press at any position of the stroke, and the safety distance is calculated according to formula (2):
Ds=1.6Ts (2)
Where: Ds - safety distance, in meters (m);
1.6 - manpower stretching speed, in meters/second (m/s);
Ts—the time from the moment the person leaves the light curtain (ie allows the starting of the slider) to the press slider to reach the bottom dead point, ie the down stroke time of the slider, in seconds (s), can be calculated according to formula (3) or actual Determination. If the date of use of the stamping machine is less than one year, the emergency stop time stated on the label is used. If the emergency stop time exceeds one year, the emergency stop time shall be measured and compared with the value stated on the nameplate, and the larger value shall be used.
Ts = (1/2+1/N)Tn (3)
Where: N - the number of clutch engagement slots;
Tn—The time in which the crankshaft rotates once, in seconds (s).
3. In actual work, it was found that when individual users installed, they could not ensure the correct installation position, as shown in Figure 3, B, C, D, E four positions. In figure B, the installation safety distance is less than the calculated safety distance. It is assumed that if the sensor installation position is too close to the danger zone, the time for the human hand to enter the danger zone is less than the photoelectric response time T1 and the braking time of the press during the downward movement of the slider. The sum of T2 (or the slider's downstroke time TS), once the operator enters the dangerous area, even if the light curtain is blocked, the photoelectric device outputs the stop signal, and the machine tool cannot completely stop, and it may still cause a disability accident. Figure C shows that the installation of the light curtain is high, and the human hand can reach from the underside of the light curtain. D picture to install the light curtain is low, people can reach from the top of the light curtain. In Figure E, the installation safety distance is greater than the calculated safety distance, and the light curtain is too far away from the die port, allowing people to enter dangerous areas. The three conditions of C, D, and E cause that the photoelectric protector can not play a practical role in protection. It is also a virtual one. This is also a relatively dangerous and unacceptable installation. It is not difficult to imagine that if the safety distance is set too close or too far, the installation of a light curtain is too low or too high, which is likely to lead to personal injury. Therefore, the setting of the light curtain position must not be allowed to change. After replacing the mold, the installation position of the light curtain should be readjusted according to the requirements of the height of the light curtain and the safety distance so that the best use effect can be achieved.
4. According to different installation forms and determined installation positions, the controller, sensors (hair, receiver), and reflectors are fixed in place, and then the controller is connected to the machine tool electrical appliances in accordance with the requirements of the photoelectric protector instructions. If the non-return function of the return trip needs to be achieved by means of a photoelectric protector, the contact angle of the cam switch must also be adjusted.
After the installation wiring is completed, it should be checked in detail to ensure that the wiring is correct. No mistakes can be checked before commissioning.
(1) Place the switch of the controller in the “off†position to supply power to the machine. Use a multimeter to check that the power voltage connected to the photoelectric protector matches the voltage required on the product nameplate.
(2) Set the switch on the controller to the “on†position. The red power indicator and the red light on the controller are on.
(3) Light: Reflective--Adjust the position of the reflector and the sensor so that they are parallel, corresponding, and aligned. The green indicator light on the controller is on and the red light is off. Shoot-type - adjust the position of the transmitter and receiver, make it parallel, corresponding, align, to the controller on the light green indicator light, shading red light off.
(4) Inspection. Block any light beam, the green light on the controller is off, and the red light on the light is on. When the light curtain is not blocked, the bright green light is on and the black light is off. It shows that the state of the photoelectric protector is normal.
(5) The adjustment of the angle of the unprotected section. If the safety conditions permit and some sections of the slider stroke need to be unprotected, the position and angle of the cam switch must be adjusted according to the state shown in FIG. 4 . In the set non-protection interval, the photoelectric protector does not play a protective role, even if the light curtain is blocked, the slider does not stop running. In practical use, it is generally allowed to set the non-protection function within the 30° range of the slider's lower stroke and the return range of the slider, that is, the off angle of the cam switch is adjusted to 30° to 180°, so that the slider is in the down stroke of 30°. It is protected between 180° and 180°.
(6) Test run. Block the light curtain and observe that the indicator light of the controller switches normally; in the protection interval (between the lower strokes of 30° to 180°, the return cam does not protect the cam switch in the off state), the light curtain is blocked, and the machine tool slider should be able to stop immediately; When the slider is at bottom dead point (180°), it blocks the light curtain and the machine slider should be able to return. Satisfying the above three conditions, the test run will be successful before entering formal work.
Stamping operations in the form of security protection devices, according to the structure is divided into mechanical, push button, photoelectric, inductive and so on. This section focuses on the photoelectric protection device. Photovoltaic protection is currently the most effective safety protection device for protecting the personal safety of the punching machine operator. It is better than protective fences, mechanical handles, machinery dials and other protection devices to prevent the improper operation in the production process. Or a machine failure has caused a safety incident. Applicable to ordinary punch (The company is equipped with a full set of conversion devices, can make ordinary punch more safe operation.), High-performance presses, mechanical presses, hydraulic presses, laminators, shears, industrial robots, packaging equipment and Other automation equipment can also be used for multifaceted area protection or theft prevention.
August 04, 2019