Analysis on Key points of Bridge Purchase
Background:
In the corrugated board production line, the corrugated paper needs a certain time to cool and shape after heating and pasting, and then enter the cutting process. At present, the corrugated paper cutting equipment is usually located at the back end of the heating and pasting equipment, and the middle is connected by a horizontal conveying bridge to transport the heated and pasted corrugated paper to the cutting equipment. Although the layout meets the technological requirements of corrugated paper production, the horizontal conveying bridge requires a certain amount The length takes up a lot of space.#overhead bridge
1.Elements on bridge Purchase
After the single-sided board leaves the Single Facer, it is transported to the overhead bridge via the inclined Conveyor Belt (the speed is slightly higher than the running speed of the board). The conveyor belt gently clamps the board to avoid the corrugated deformation after the initial bonding.
The bridge is composed of paper device, conveyor device, cardboard alignment device, tension adjustment device and walkway on the bridge frame. Single pit board exported from single facer enters the subsequent processing after the paper feeding device, conveying device, aligning board device, tension adjusting device on the bridge conveying frame.
The of the bridge is the single-side corrugated board produced by layered wave stacking single facer enables single facer has different speed difference buffer, so that the later stage of the process can not interrupt production.
▲The slanting conveyor belt carries the single-sided cardboard onto the overpass
Single-sided board in the longitudinal elastic, and in the transverse is not easy to bend.Single-sided board from the inclined conveyor belt down, need to rhythmically guide down to the horizontal bridge conveyor belt, so that the board can be stacked evenly flat on the horizontal conveyor.The running speed of the horizontal conveyor belt is relatively slow, generally 1/10 ~ 1/7 of the speed of the production line.The of the bridge is to provide buffer stock for the single-sided board, so as to meet the needs of the occasional speed switch between single-sided and double-sided machines.#single facer
The ideal amount of paper on the bridge should be kept stable and reduced as far as possible, because the atmosphere around the bridge is often warm and wet, if the machine is against the wall, the natural air circulation around the wall will make the machine drive side humidity becomes higher due to less.Just processed cardboard to this moisture absorption capacity, so in that state, the less time the cardboard stay, the more stable the cardboard quality.Most machines have electronic control of the "bridge level control" system, such as paper before the single facer slowed down, the bridge can also quickly adjust the amount of temporary paper.But generally speaking, the bridge can balance the speed of single facer, Double Facer, so that the bridge product paper keeps in the upper and lower limit.#Corrugated Line
Before the board enters the preheater and gluing machine from the bridge, the board is unfolded and tranitted through the machine to a place several millimeters away from the lower layer of paper.This process requires the use of paper guide, the earliest type of "half-moon" steel guidance paper, but it will damage the edge of the paper, can not achieve the ideal paper guide precision, but also will produce a lot of noise.Most modern machines have one or more soft guide rollers with high surface friction coefficient, which can move on the surface paper and can be replaced at any angle in the desired direction without touching or damaging the edge of the board.
▲A bridge guide pushes the single facer board to the center line or edge
One side of the cardboard after the arrangement of another friction surface, that is, through a brake roller, the roller will eventually eliminate the paperboard stacked in the uneven phenomenon and give the paper tension, so that the paperboard then oothly into the preheating machine and gluing machine.If the tension between the single-sided cardboard and the lower layer of paper is very uneven, the cardboard will produce upward warping (often referred to as cardboard "longitudinal warping").Therefore, the brake drum and surface paper brake are effective adjustment equipment, can control the cardboard "longitudinal warping" probaa
Corrugated board production line, the s of the bridge to meet the following elements:
1. Single-side corrugated paper storage to synchronize gluing machine and single facer.
2. Adjust the tension to keep the cardboard flat.
3. Adjust the width of single corrugated and surface paper, keep the same width, to reduce trimming and waste.
When purchasing bridge, we mainly consider its operation stability, friction coefficient of friction surface, deviation correction ability etc., To sum up, the elements in the procurement of bridge are: 1).The form of bridge deviation correction.2). Tension control form.3).Stacking paper length calculation and control.
The following content will make a detailed analysis in the procurement of bridge.
2. Paper guide and tension control
Corrugated board production line tension control and automatic deviation correction has long been an important problem of corrugated board carton enterprises. In the traditional corrugated board production line, the tension and deviation correction of three-layer, five-layer and seven-layer corrugated board is basically completed by vacuum adsorption and electric regulation.Due to the use of mechanical baffle deviation correction, material rupture and paper break occur frequently, resulting in the loss of materials.More importantly, in continuous production, when the size of the base paper changes, the base paper fit dislocation will lead to the double facer on the hot plate has been dry pulp line residue;This will cause the interruption of production, until the operator will clean up the residual paste before continuous production, and ultimately reduce the efficiency of corrugated board production line.#Double facer
The tension of the base paper can be controlled directly or indirectly.Direct control is the actual paper tension value measured by the tension sensor, and then control the speed of bridge drive;Indirect control is to determine the motor speed so as to calculate the tension value of the base paper, and then control the motor speed according to the size of the difference.For the control of the tension of the base paper, the general situation is the combination of indirect control and direct control.
Multi-point air bag brake is installed on both sides of the tension system of bridge to make the tension of paper more even and the anti-slip adhesive more durable.Compared with the traditional fan tension system, it is more cost-effective and environmentally friendly.
Regarding the deviation correction control and tension control of bridge paper guide, the following two common forms are listed: first, the form of "vacuum suction air + baffle".Old models of equipment are in this form.Its disadvantage is that the suction is relatively all, easy to produce such phenomena as flute exposure;Suction control is not quantified;Manual control baffle reaction is slow, high loss, baffle easy to break the edge of the paper, paper is easy to break.
Second, the "brake + servo motor" form.The advantages of this form are: through the servo motor to achieve rapid deviation correction, automatic control can be achieved, and the cardboard alignment is fast;Through brake tension adjustment, digital control can be achieved, while reducing paper break.
A comparison of the advantages and disadvantages of the above two forms are as follows:
Table1: The advantages and disadvantages of the two tension
and deviation correction control systems are compared
▲Through the suction device and baffle to maintain a certain tension and deviation correction
▲Through servo motor and brake for deviation correction and tension control
3. Speed control system
The of the bridge is mainly to transport the two layers of cardboard produced by the single facer, which will be coated with glue after gradually cooling.Therefore, semi-finished products on the bridge should not be piled up too much, to avoid a large number of piled corrugated by extrusion and unable to timely heat dissipation, resulting in cardboard deformation.In actual production, we should:
1). Single facer shall try to keep pace with the speed of double-side locomotive;
2). Install double inclined roll device to keep the two layers of cardboard in the center position, and quickly align the two sides under the suction of bridge;
3). In the corresponding place to install ceiling fan or strong exhaust fan, speed up corrugated heat dissipation;
4). The air intake of the bridge should be adjusted based on the size of the door, the material is hard and brittle , to avoid too much or too little tension caused by breaking or moving.
The speed control of bridge not only avoids the problem of paper tearing, but also affects the accuracy of paper changing in the whole wet part and the automatic compensation of manual paper tearing.The reason is very simple, in the entire corrugated board production line, in addition to the wave bridge product paper not easy to predict, from the original paper frame to climbing belt, and from the bridge guide to the crosscutting machine distance, is almost constant.To really calculate, to put it bluntly is how to calculate the actual amount of paper bridge, and how to automatically compensate for the amount of bad paper manually torn off the bridge.At present, there are basically the following calculation methods in the market:
Using ink-jet technology, high accuracy: the principle of this way is to install ink-jet machine on the medium, and then in the vicinity of the bridge paper guide induction ink machine, from ink-jet to detection of ink all completed by the computer automatically tracking calculation, so the accuracy can be controlled within 1 meter.#Auto web guide
Used for corrugated board production line bridge length of paper meter ink-jet device, including installed on the top of the corrugated tape nozzle body, the nozzle body has the upper end for the ink pipeline to connect the mixing chamber, the lower end of the nozzle body is connected with a liquid cap with an ink hole;There is an empty cavity between the nozzle body and the liquid cap.The lower end of the nozzle body is also provided with a number of crushing holes in the form of through-hole.The mixing cavity and atomizing cavity are connected by a number of crushing holes.Through the ink-jet device can be achieved on the corrugated board production line bridge paper volume of accurate calculation, so as to effectively reduce the original paper consumption rate.#Tension control machine
Electric eye detection: the method is to install two reflective infrared detectors on the bridge and calculate thebridge retention by using the relationship between the speed and the speed ratio of thebridge belt.For example, if the distance between two electric eyes is 3 meters, and the speed ratio between the speed of the car and the speed of thebridge belt is assumed to be 6:1, the inferred result is that the distance between the two electric eyes is only 18 meters.This works for users who don't change much with paper;However, for users who use high and low materials with great changes, they may feel very strange. Why is it that some materials are accurate in calculation and some errors are as high as 20-30 meters?In fact, the reason is very simple, paper material, thickness are different, of course, the bridge shape of the wave is different in size and height, so the error value will be a lot worse.
There are infrared eyes and ink-jet dual identification system, dual control identification rate is high, but also can avoid the lack of ink or water shortage caused by the fault, but the disadvantages of the system installation cost is high and expensive.
The comparison of advantages and disadvantages of the three common speed control systems on bridge are as follows:
Table 2: The advantages and disadvantages of the three speed control systems are compared
Bridge paper volume of 70~100m is appropriate, too much will cause the bending problem of cardboard.In the production should also pay attention to the single facer produced cardboard on the bridge should not be too much accumulation, to avoid the double-sided locomotive speed too fast or broken, the machine should always observe the amount of bridge accumulation, with the double facer production speed.
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