Working Principle of the Crimping Machine – Tube Crimping Operation Methods and Maintenance & Repair

The English name for a crimping machine is typically translated as "crimping machine" or "crimper." A crimping machine is a hydraulic device used to crimp pipe assemblies. It applies compressive force through the machine’s dies to securely fasten metal fittings onto high-pressure hydraulic hoses for construction machinery or on brake lines, oil lines, air-conditioning lines, and power lines in automobiles. Crimping machines are suitable for crimping various types of mechanical high- and low-pressure oil hoses, air hoses, water hoses, cable connectors, automotive air-conditioning lines, power steering lines, oil lines, gasoline supply lines, as well as building components and daily-use hot-water and gas pipes. They are widely used in industries such as automotive, construction machinery, hydraulic machinery, and welding and cutting equipment.

The classification of crimping machines, based on their application functions, can be divided into hydraulic high-pressure pipe crimping machines, brake pipe crimping machines, air-conditioning pipe crimping machines, power pipe crimping machines, and so forth. Based on their mechanical structure, they can be categorized as straight-barrel crimping machines, double-column crimping machines, open-type crimping machines, and C-type crimping machines. According to their control methods, they can be classified as electromechanical crimping machines, PLC-controlled crimping machines, and CNC-controlled crimping machines. Among these, the electromechanical crimping machine is widely used, and its advantages and technical performance are as follows:

1. It operates on the principle of a dual-hydraulic circuit, meaning that both the piston’s reciprocating motion and the mold’s opening and closing movements are driven by hydraulic power sources. This system not only ensures smooth movement and rapid return strokes but also eliminates the issue of spring-based return mechanisms, which can cause the mold to fail to open and become locked. Moreover, the cylinder locking system is designed with continuous front-to-back passages, making it easy to clamp various specially shaped bends.

2. The hydraulic system consists of a motor, oil pump, solenoid valves, pressure regulators, and a hydraulic valve assembly, forming a dual hydraulic circuit capable of forward and backward movement. Additionally, a rapid oil-relief valve circuit has been added to the dual hydraulic circuit to achieve faster return-to-position performance. Moreover, the speed is adjustable, and both noise levels and system pressure are reduced.

3. In terms of the electrical control system, the control circuit uses a PLC circuit, which is easy to troubleshoot, convenient to maintain, and simple to replace.

4. The crimping die and die holder are manufactured using a zero-cumulative-error machining process to ensure that the spacing between the crimping lines on the finished product is uniform and free from variations in size or tapering.

5. To ensure the long-term mechanical precision and service life of the crimping machine, the locking mechanism assembly not only utilizes high-quality alloy steel materials but also incorporates a proprietary heat treatment process. Therefore, the crimping machine’s extended service life is closely linked to the rational selection of materials, the appropriate heat treatment, advanced machining techniques, and optimized structural design!
I. Working Principle of the Pipe Pressing Machine
The oil pump is installed inside the fuel tank and immersed in hydraulic oil, achieving a scientifically designed cooling and quiet operation. Driven by the motor, the oil pump delivers hydraulic oil, which pushes the plunger inside the crimping cylinder to move, causing the mold base to contract radially and thereby compressing the outer sleeve of the hose fitting. When the degree of contraction reaches the preset value indicated by the micrometer, the crimping process automatically stops. After the solenoid directional control valve switches direction, the plunger inside the cylinder moves in the opposite direction, causing the mold to open and completing the hose crimping process.
II. Installation and Commissioning of the Pipe Pressing Machine
Handling: The pipe press is best handled using a forklift, with the force applied to the bottom of the machine. It is strictly prohibited to invert the pipe press. It is also strictly forbidden to lift or carry the pipe press by its head, motor, or electrical control box.
Installation: The pipe press must be placed horizontally on a stable foundation and properly grounded.
Oil Filling: Open the oil tank cap and add 68# anti-wear hydraulic oil to the oil level indicator, filling it up to the 2/3 mark.
Power Connection: Connect the power cord to the power source specified for the tube-pressing machine. Start the motor and observe its rotation direction. The motor’s rotation direction should be consistent with the direction indicated on the motor. If the motor’s rotation direction does not match the indicated direction, please swap the positions of any two of the power cords.
Micrometer: Used to adjust the amount of contraction in the crimped hose. Turning it counterclockwise by half a turn increases the compression by 1 mm; turning it clockwise by half a turn decreases the compression by 1 mm.
Pressure Adjustment: The maximum pressure of the tube-pressing system is 31.5 MPa, and it is adjusted via the relief valve. Turning the adjustment knob clockwise increases the pressure, while turning it counterclockwise decreases the pressure. (The factory setting has already been calibrated; you can adjust it yourself if necessary.)
Mold opening speed adjustment: The speed of mold opening is controlled by a flow-diverting valve. Turning the valve clockwise increases the opening speed, while turning it counterclockwise slows it down. However, an excessively fast opening speed can increase noise levels. The optimal value should not exceed 10 MPa (already set at the factory; adjustments can be made independently if necessary).
3. Clamping Operation
When using the tube crimping machine for the first time, perform 20 to 30 no-load crimping operations. Only after confirming that all parts are functioning normally can you begin actual use.
2. When using the pipe crimping machine in winter, run it unloaded through 20 to 30 crimps to raise the oil temperature slightly.
3. Press the opening button. After the mold base opens, select the corresponding mold according to the specifications of the hose being crimped and install it onto the mold base. Then, adjust the micrometer scale.
4. Place the hose with the fitted connector into the appropriate position within the crimping machine’s die head, ensuring that the entire length is crimped in one pass.
5. Press the crimping button to perform the crimping operation until the tube crimper head stops crimping and the mold automatically opens.
6. Remove the crimped hose assembly and use a dial caliper to measure the outer diameter of the connector’s outer sleeve after crimping. If the measurement does not match the parameter table, slightly adjust the micrometer scale until the next hose assembly meets the requirements.

IV. Pressure Tube Test Example
Crimped 4-layer steel wire reinforced hose, Φ19mm (Italian Manuli 4SP standard)
According to the hydraulic hose crimping parameter table, the outer diameter of the four-layer steel wire-reinforced hose fitting’s outer sleeve before crimping is 37 mm, and after crimping it becomes 33.5 mm. Therefore, the inner diameter of the die to be used should be Ф33 mm, corresponding to a micrometer reading of 3. Install the Ф33 mm die securely onto the die holder, then turn the micrometer dial to the 3 mark. After stripping the hose and assembling it with the fitting, measure the outer diameter of the fitting’s outer sleeve once crimping is complete. If the measured value matches the post-crimping figure of 33.5 mm listed in the crimping parameter table, the crimping process is successfully completed. If the post-crimping outer diameter does not match, slightly adjust the micrometer and proceed to crimp the next hose. When crimping hose fittings: if the crimping dimension is too large, the inner rubber layer of the hose may be crushed, leading to oil leakage; if the crimping dimension is too small, it may cause oil leakage and the fitting could be dislodged by hydraulic pressure. It is crucial to master the proper crimping degree, using the shrinkage of the fitting’s inner bore as the reference. For national standard fittings, the compression should be between 0.1 and 0.4 mm; for ordinary fittings, the compression should be between 0.1 and 2 mm. Since different manufacturers produce hoses and fitting outer sleeves using varying standards—such as GB standards in most northern regions, 602 standards in southern regions, and SAE standards internationally—the specific dimensions and materials of hoses and fittings from different manufacturers may vary. Therefore, the data provided in the crimping parameter table are for reference only; the actual crimping dimensions should be determined based on pressure testing results.
V. Precautions for the Pipe Pressing Machine
1. When crimping, position the connector as close to the center of the mold as possible—do not press it onto the hexagonal nut.
2. Prevent tools and other foreign objects from entering the die head of the tube press.
3. After each work session, the eight mold holders must be fully opened to their maximum extent. This keeps the springs in an extended state, ensuring proper spring maintenance, and also releases pressure from the hydraulic cylinders, thereby extending the service life of the oil seals.
VI. Maintenance and Servicing of Pipe Press Machines
The hydraulic oil in the fuel tank should be replaced when it exceeds the service life specified by the hydraulic oil manufacturer, or if the oil level indicator shows that the hydraulic oil has turned dark due to oxidation, it must be replaced.
2. Regularly inject anti-wear lubricant onto the moving surfaces of the mold base.
3. During non-operating hours of the tube press, please cover the dust cover to prevent foreign objects from entering the die holder.