Hydraulic and control technology, with its unique talents, was applied to the paper pressure mechanism of digital display and program-controlled paper cutters in the 1990s. With fast, safe, stable movement, large paper pressing force, low noise and automatic control, it is favored in the domestic and foreign markets. "Workers want to do their best, must first sharpen their tools", from the analysis of the current domestic digital display, program-controlled paper cutter machine transmission structure: the cutting mechanism is a worm gear drive, the structure is complex, and the transmission efficiency is low (50%), The shortage of hydraulic system utilization is insufficient. Based on the above analysis, we have carried out long-term research and discussion, and designed the paper cutter pressing and cutting work procedures as a full hydraulic control system, which will improve the performance of the domestic paper cutter to a new level.
1. Design requirements and basis
(1) Working principle.
1. Light pressure paper → cutting → return of cutting knife → return of pressure paper jack.
2. Action requirements.
â‘ Lock the cutter at the top dead center position.
â‘¡ Overload protection for cutting resistance.
â‘¢Two-handed operation, safe, flexible and reliable.
â‘£The cutting knife can stop when it moves to any position, and there should be no phenomenon of continuous knife and obvious sliding knife.
⑤Operation action can press the paper by foot, single and continuous cutting movement.
(2) Main technical parameters.
According to GB3902-83 hydraulic paper cutter manufacturing standards, take the door width of 920mm as an example. Paper pressing force of 30000N, cutting resistance: According to the article "Testing and Analysis of Cutting Resistance" in the fifth issue of "Printing Technology" in 1993, the linear cutting resistance of 120g / m2 double-sided coated paper is 15000N, and the pressure 120mm, cutting speed 40 times / min.
2. Transmission principle of full hydraulic paper cutter
According to the design requirements of national standards, the design of the transmission principle diagram, action diagram and electromagnet action sequence chart of the full hydraulic paper cutter are as follows:
1. Hydraulic pump unloading:
Before cutting, start the system motor to drive the vane pump through the belt. The pressure oil is unloaded from the filter via the vane pump → foot pedal two-position two-way valve → two-position two-way solenoid valve.
2. Foot press operation:
When the foot pedal is depressed, the two-position two-way valve is cut off, and the solenoid valve 3YA is connected. The pressure oil passes through the vane pump → 3YA → spool valve 4 → plunger speed-increasing cylinder, so that the paper pressure jack moves down and pressurizes quickly. The size of the paper pressing force can be achieved by adjusting the pressure relay. The cutting resistance and unloading of the system can be achieved by adjusting the overflow valve.
3. Single cutting action program:
①Light pressure paper: Press the two buttons in front of the worktable with both hands, the solenoid valves 2YA and 3YA are energized, and the solenoid pin is pulled out. Pressure oil → 3YA → spool valve 4 → plunger speed-increasing cylinder → swing arm 1 rotates, and the paper pressing jack quickly presses on the paper.
â‘¡Pressurization: As the pressure of the system increases, the control pipeline moves the spool valve to the right, the plunger bearing area increases, and the paper pressure reaches the design standard.
â‘¢Cutting: At the same time, the system controls the pressure oil in the pipeline to switch the pressure relay, connect the three-position four-way solenoid valve 6YA, and at the same time, the 3YA power is turned off. The pressure oil enters the right end of the cutting cylinder through the right end of 6YA, moves the piston to the left, pushes the swing arm 2, and drives the connecting rod cutting knife to cut to the bottom dead center along the cutting angle.
â‘£Cutting knife return position: When the cutting knife falls to the blade, touch the beginning of the stroke C2 to power off 6YA, and energize 3YA, 5YA, the pressure oil enters the left cavity of the cutting cylinder through the reversing valve 5YA, and the piston moves right , Drive the swing arm 2, the connecting rod cutter returns to the origin.
⑤Latch: The cutting knife returns to the original point, and the stroke switch C1 is touched to de-energize the electromagnetic pin. Under the action of the spring, the plug is inserted into the cutting knife body to prevent the cutting knife from sliding down.
â‘¥Paper pressure jack return: The latch returns and touches the travel switch C3 to power off 2YA and 3YA. The plunger speed-increasing cylinder is unloaded under the action of the paper pressure jack return spring and the system returns oil. Slide valve 4 Return to position, return to the plunger speed-increasing cylinder and return to normal position after pressing the paper jack.
⑦The cutting knife stops at any position during the movement.
When the three-position four-way solenoid valve 6YA is connected, the pressure oil enters the right end of the cutting cylinder through the valve, and the blocking object blocks the photoelectric grating in the safe area in front of the worktable during the downward movement of the cutting knife, and the photoelectric switch receives information. Turn off the three-position four-way valve 6YA, in the neutral position, the oil inlet and oil return passage are closed, so that the cutting knife can be in any position.
⑧ Overload protection: paper cutting resistance and safety system are the necessary conditions to ensure the normal operation of the machine. The overflow valve in the system mainly plays two roles. One is the unit's cutting resistance overload protection-overflow, and the other is the excess pressure oil overflows back to the tank.
4. Continuous cutting:
During continuous cutting, turn the index switch to the continuous cutting position. When the paper pressure jack return stroke switch C4 is touched, the solenoid valves 2YA and 3YA are turned on at the same time, thus starting a new round of single Cutting motion program.
3. Design and calculation of hydraulic system
When the paper pressing force is 30000N, the cutting resistance is 20000N, the paper pressing height is 120mm, the weight of the moving parts is 10KN, the rectangular guide rail is used, the friction coefficient f = 0.1, the average speed of cutting and returning is 21.2cm / s. Work pressure?
(1) 1. Cutting working pressure: when the arm is 1: 1 with the heavy arm,
F push = F cut + F lead + F inertia + F secret + F back
Look-up table 1 P ï¼ 4Mpa
2. Inner diameter of cutting cylinder
Choose 70 cylinder inner diameter.
3. Piston rod diameter: According to the pressure of the cutting cylinder 4MPa, check table 2.
Take 0.6D = 0.6 × 70 = 42mm. Choose a diameter of 45mm.
(2) Determining the flow rate of the hydraulic pump: It is known that the cutting speed is 21.2cm, whether there is a difference in the area of ​​the piston rod, or when the flow rate is constant, the movement of the piston is different.
1. Flow required by the oil cylinder:
q1 = A1 = 21.2 (D2) = 48.8L / min
q2 = A2 = 21.2 [(D2-d2)] = 28.6L / min
The average flow rate of the cylinder is
q = = 38.7L / min
q pump = q · (1 + 10%) = 1.1 q = 42.67 = 43L / min
Flow required by hydraulic pump
2. Drag the motor power of the hydraulic pump.
Pump output power
Pq = = = 3.37kw
Motor Power
P electricity = = = 3.94kw
4. Effect analysis
The whole system is simple in structure, high in transmission efficiency, fast in response, smooth in movement, and can realize automatic control of the system's overload protection. It is easy to operate and adjust, safe, inferior, and low in noise. It meets and meets the requirements of manufacturing and cutting processes. Application prospects.
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