Safety protection device for the hottest stamping

2022-10-15
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Safety protection devices for stamping operation

there are many forms of safety protection devices for stamping operation, which are divided into mechanical type, button type, photoelectric type, inductive type, etc. according to the structure. Here we focus on the photoelectric protection device. Photoelectric protector is the most effective safety protection device to protect the personal safety of stamping machine operators at present. It has better protection effect than protective fence, mechanical handle, mechanical dial and other protective devices, so as to avoid safety accidents caused by improper operation or machine failure in the production process. It is applicable to ordinary punches (our company is equipped with a complete set of refitting devices, which can make ordinary punches operate more safely.) High performance punches, mechanical presses, hydraulic presses, film presses, plate shears, industrial robots, packaging equipment and other automatic equipment can also be used for multi-faceted area protection or theft prevention

I. composition of photoelectric protectors

photoelectric protectors are generally divided into two types: opposed type and reflective type

the opposite photoelectric protector refers to the photoelectric protection device that the light-emitting unit and the light receiving unit are in the light-emitting unit and the light receiving unit respectively, and the light emitted by the light-emitting unit is directed to the light receiving unit, thus forming a protective light curtain. The counter emitting photoelectric protector is composed of five parts: controller, light emitter, light receiver, light emitting transmission line and light receiving transmission line

reflective photoelectric protector refers to the photoelectric protection device 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, thus forming a protective light curtain. A safety protection screen is formed between the illuminator and the reflector. Whenever the safety protection screen is disturbed or the equipment is not working normally, the illuminator will send a signal to the press control system to prevent possible dangerous movement and stop the danger of hammer head descending. Reflective photoelectric protector is composed of controller, sensor, reflector and transmission line

II. Key points of function:

this instrument has self-test function. When the transmitter has error message, the working state of the press will not be affected. The optical wave action range of photoelectric safety protection, that is, the effective sensitive area, can be calculated by the following formula:

s=v t (seconds) = safety protection area (mm)

s is the effective sensitive area, V is the sliding speed of the slider, t is the stop time of the slider (one millionth of a second)

in this way, the effective sensitive area can be directly controlled by the response of the hydraulic system. In any case, Rexroth high-speed response valve and servo circuit can make the photoelectric protection light wave appear in the mold space as much as possible. This provides a very safe working environment for operators. In many cases, photoelectric switches are also used to improve productivity. When the operator withdraws his hand from the photoelectric safety protection light wave action range, and the workpiece is placed in the mold, a signal is generated to start the press to work, instead of using foot pedals and manual switches. Of course, in this case, the photoelectric safety protector can still complete its safety protection function. The production efficiency of the photoelectric switch is 25% higher than that of the mechanical foot switch. The photoelectric transmitter and reflector are protected by an iron shell to prevent any accidental damage

III. installation and commissioning

1. Photoelectric protectors are generally installed in fixed and adjustable forms

fixed installation: it is to fix the sensor and reflector (or light transmitter and receiver) directly on the machine bed. It is usually suitable for closed press with fixed mold and frame structure that does not need frequent adjustment to protect the light curtain

adjustable installation: the sensor and reflector (or light transmitter and receiver) are connected to the machine tool through a special support. In this installation form, the light curtain can be flexibly adjusted up and down, left and right according to the requirements of die opening and safe distance. It is generally suitable for open, closed and four column presses with frequent die changes and different die sizes

2. Determination of the height and position of the light curtain and 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 die openings of the machine tool. On the premise of ensuring a safe distance, the lowest beam of light of the photoelectric protector shall not be higher than the lower edge of the die, and the uppermost beam of light shall not be lower than the upper edge of the die

the protection height of the photoelectric protector refers to the distance between the top beam optical axis and the bottom beam optical axis of the light curtain, that is, the effective height of the light curtain. The protection height is equal to the stroke of the machine tool slider plus the adjustment amount. The protection height is related to the beam number of the photoelectric protector. If the beam number of the photoelectric protector is selected to measure the temperature of the sample in the stock measuring cylinder and the record is too small, 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 inconvenience in use. Therefore, it is also important to select the specification (beam number) of photoelectric protector according to the protection height

the safety distance of the photoelectric protector refers to the shortest distance between the light curtain and the work dangerous area - the cutting edge of the mold, that is, the distance required to stop the slider before reaching the dangerous boundary from the position where the hand blocks the light curtain. The safe distance is one of the necessary conditions to ensure the photoelectric protector to realize the protection function, and the safe distance must be calculated correctly! The calculation method shall be determined according to the braking mode of the press

for the press whose sliding block can stop at any position of travel, the safety distance is calculated according to formula (1):

ds=1.6 (T1 + T2) (1)

where: DS safety distance, unit: meter (m)

1.6 extension speed of human hand, unit: M/S

t1 response time of photoelectric protector, 0.02 seconds (s)

the braking time of T2 press, that is, the time from the beginning of braking to the stop of the slider, in seconds (s), measured from the actual braking situation

for the press whose sliding block cannot be braked and stopped at any position of the stroke, the safety distance is calculated according to formula (2):

ds=1.6ts (2)

where: DS safety distance, unit: meter (m)

1.6 hand extension speed, unit: M/S

ts the time from hand leaving the light curtain (i.e. allowing the slider to start) to the lower dead center of the slider of the press, that is, the down stroke time of the slider, in seconds (s), which can be calculated according to formula (3) or actually measured. If it is less than one year from the date of manufacture and use of stamping machinery, the emergency stop time recorded on the label shall be used. If it is more than one year, the emergency stop time shall be measured and compared with the value recorded on the label, and then the larger value shall be selected

ts= (1/2+1/n) TN (3)

where: number of engagement slots of N clutch

TN time of crankshaft rotation for one cycle, unit: s

3. In actual work, it is found that individual users cannot ensure the correct installation position when installing, such as the four positions B, C, D and E in Figure 3. B the installation safety distance in the figure is less than the calculated safety distance. It is assumed that if the installation position of the sensor is too close to the dangerous area, the time between the hand entering the dangerous area and the destruction of the sample is less than the sum of the photoelectric response time T1 and the braking time T2 of the press (or the down travel time Ts of the slider). Once the hand enters the dangerous area, even if the light curtain is blocked, the photoelectric device outputs a stop signal, The machine tool cannot stop completely, which may still cause disability accidents. Figure C: the light curtain is installed on the high side, and hands can reach under the light curtain. Figure D: the light curtain is installed on the low side, and hands can extend from the top of the light curtain. E the installation safety distance in the figure is greater than the calculated safety distance, and the light curtain is too far away from the die opening, so people can enter the dangerous area. C. The photoelectric protector cannot play the actual protection role due to the three conditions of D and E, which is also dangerous and is not allowed to be installed. It is not difficult to imagine that if the safety distance is set too close or too far, and the light curtain is installed too low or too high, it is likely to cause personal injury and death accidents. Therefore, it is absolutely not allowed to change the position of the light curtain after setting. After replacing the mold, the installation position of the light curtain should be readjusted according to the two requirements of the height and safety distance of the light curtain, so as to achieve the best use effect

4. According to different installation forms and determined installation positions, fix the controller, sensor (light transmitter and receiver) and reflector in the appropriate position, and then connect the controller and machine tool electrical appliances according to the requirements of the photoelectric protector manual. If the return trip protection function needs to be realized with the help of photoelectric protector, it is also necessary to adjust the contact angle of cam switch and how to classify the frequency of fatigue testing machine

after the installation and wiring is completed, it should be checked in detail to ensure that the wiring is correct. Power on commissioning can be carried out only after verification

(1) turn the switch of the controller to the off position, supply power to the machine tool, and use a multimeter to check whether the power supply voltage connected to the photoelectric protector is consistent with the voltage required on the product nameplate

(2) turn the switch on the controller to the on position, and the power red indicator and blackout red indicator on the controller are on

(3) aiming: reflective -- adjust the position of the reflector and the sensor to make them parallel, corresponding and aligned until the green light on the controller is on and the red light on the shading is off. Opposite type -- adjust the positions of the light emitters and receivers to make them parallel, corresponding and aligned, and the controller has also entered the transformation period of innovation driven development. The light on green indicator light is on, and the light blocking red indicator light is off

(4) inspection. If any beam is blocked, the green light on the controller is off and the red light on the controller is on. When the light curtain is not blocked, the green indicator light is on and the red indicator light is off. It indicates that the photoelectric protector is in normal state

(5) adjustment of unprotected section angle. If safety conditions permit and it is necessary to realize that some sections of the slider stroke are not protected, the position and angle of the cam switch must be adjusted according to the state shown in Figure 4. In the set unprotected section, 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 section of the down stroke of the slider and the return stroke of the slider, that is, the disconnection angle of the cam switch is adjusted to 30 ~ 180, so that the slider is in the protection state between 30 ~ 180 of the down stroke

(6) commissioning. Block the light curtain and observe that the indicator light of the controller changes normally; Within the protection zone (the downward stroke is between 30 ~ 180, and the return stroke does not protect the cam switch is in the off state), block the light curtain, and the machine tool slider should be able to stop immediately; When the slider is at the bottom dead center (180), cover the light curtain, and the slider of the machine tool should be able to return. Only after the above three items are met and the test run is successful, can the formal work be started

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