The importance of the piston
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The piston is a core moving component of fluid conveying and control equipment (such as reciprocating pumps, hydraulic valves, metering devices, etc.). Through reciprocating or rotational motion within the cylinder, it realizes the suction, compression, discharge and pressure regulation of fluids, and is widely used in industrial automation, automotive hydraulic systems, medical conveying equipment and other fields.
Its performance directly determines three key links:
① Ensuring the stability of equipment operation, the structural integrity and dimensional accuracy of the piston body, affecting the sealing effect of the cylinder body, and avoiding fluid leakage;
② Ensuring the accuracy of flow control, a stable motion state and suitable hardness characteristics can reduce flow fluctuations and meet the requirements of process parameters.
③ Extend the overall service life of the equipment. High-quality pistons can reduce the friction loss with the cylinder block, avoid equipment shutdown caused by component damage, and reduce maintenance costs. Therefore, the quality of the piston is of vital importance to the efficient operation, functional reliability and economic efficiency of fluid equipment.
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Common problems with pistons
In production assembly and practical application, piston bodies are prone to two major types of problems, which directly affect the efficiency and performance of equipment
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1. Issues with the automatic assembly of the product
Burrs at the top of the column: They cause assembly jamming, reduced efficiency, and the shedding of burrs can easily pollute the environment, and even lead to internal blockage or component wear of the equipment. ?
Column deformation (bending) : It disrupts the structural symmetry, causes the movement trajectory to shift, and may rub against the inner wall of the cylinder, leaving hidden dangers of cylinder scratches and equipment failures. ?
Product deformation (lifting) : It causes uneven fit clearance in the cylinder block and a decline in sealing, which can easily lead to leakage. At the same time, it increases the difficulty of assembly positioning, raises the defect rate and rework costs. ?
2. Functional issues regarding product usage
The bottom ribs of the product are damaged: weakening the overall strength, they are prone to breakage during reciprocating motion, leading to the failure of the piston, equipment shutdown, and affecting the production progress. ?
There are mold dirt scratches (damages) at the cylinder block position: they disrupt the flatness of the contact surface, increase movement resistance and wear, and may also lead to seal failure, causing fluid contamination or pressure loss. ?
If the flow rate of the liquid passing through is too large or too small, it will fail to meet the process requirements. In mild cases, it will cause fluctuations in product quality; in severe cases, it may lead to medical accidents or production scrapping. ?
Product lifespan issue: Frequent shutdowns for component replacement are required, which increases procurement and maintenance costs, disrupts continuous production, and causes significant losses especially in the chemical and pharmaceutical industries.
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The cause of the problem
From the three core dimensions of product design, material properties, and production processes, the root cause of the problem can be precisely located
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Automatic assembly issues (burrs, deformation) : The core problem lies in unstable production processes, such as insufficient mold precision and improper setting of injection temperature/pressure/cooling time parameters, which leads to burrs or structural deformation of the product after molding. Meanwhile, the design ratio of the wall thickness of the product cavity is not scientific, and the force application points are overly concentrated. During the forming or handling process, it is easy to cause the column to bend and the product to lift. ?
Bottom rib damage: On the one hand, the material hardness is too high (prone to brittle fracture) or too low (prone to plastic deformation), and the overall strength is insufficient; On the other hand, the connection part between the ribs and the main body of the piston is poorly designed, resulting in stress concentration. After long-term stress, it is prone to damage. ?
Dirty scratches on the cylinder block mold: The mold dirt is caused by incomplete cleaning of the mold before production. Scratches are caused by the low hardness of the material, which leads to the expansion and increase of the cavity under pressure, or the dimensional variation of the plastic part, which causes abnormal friction when fit with the cylinder body, resulting in surface damage. ?
Flow deviation: Mainly due to the excessively high or low hardness of the material, it affects the fit clearance between the piston and the cylinder, and changes the cross-sectional area of the fluid passage. In addition, the parameters at each stage of the production process (such as injection molding accuracy and cooling rate) fluctuate greatly, resulting in differences in the size and performance of the pistons in the same batch, which further aggravates the instability of the flow rate. ?
Lifespan issue: Firstly, the material hardness is too high and the wall thickness is too thick, which increases the frictional resistance during the movement of the piston and accelerates wear. Second, the material formula has not been optimized, resulting in insufficient fatigue resistance. After long-term reciprocating motion, structural aging and performance degradation are prone to occur. ?
Environmental compliance issues: If applied in fields such as medical care and food, it may also result in excessive micro-content of harmful substances (such as heavy metals and harmful chemicals) due to the formula design not fully considering environmental protection standards like RoHS and REACH, thus failing to pass market access tests.
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DOIT's solution
In response to the above pain points, DOIT has proposed precise and practical solutions from four dimensions: design, materials, manufacturing processes, and environmental protection.
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Solve the problem of automatic assembly: First, use professional detection equipment to locate the specific positions of burrs and deformations, correct the design ratio of the product cavity wall thickness, and balance the force distribution. Further optimize the injection molding process parameters, enhance the precision and cleanliness of the mold, reduce the generation of burrs, ensure the consistency of product molding, and guarantee smooth automatic assembly. ?
Solve the problem of bottom rib damage: Analyze the stress concentration area of the rib damage and optimize the connection structure between the rib and the main body. At the same time, according to the actual force requirements, adjust the hardness and strength of the material, select the formula that is impact-resistant and anti-fracture, and enhance the load-bearing capacity of the ribs. ?
To solve the problem of dirty scratches on the cylinder block mold: Appropriately increase the hardness of the piston at the material end, enhance the surface wear resistance and compressive strength, and prevent the cavity from expanding under pressure. Establish a mold cleaning control process at the manufacturing end to prevent mold dirt from adhering. At the same time, detect and correct the dimensional deviations of plastic parts to ensure a reasonable fit clearance with the cylinder body and reduce frictional damage. ?
To address flow deviation: First, based on the measured flow data, determine the appropriate material hardness range and adjust the formula to match the hardness with the flow requirement. Establish a full-process parameter monitoring system again to control the injection molding, cooling, molding and other links in real time, reduce parameter fluctuations, ensure the performance consistency of products in the same batch, and stabilize the flow output. ?
Extend product lifespan: Based on the test results of the piston's movement resistance, specifically reduce the excessively high hardness or thin the overly thick wall thickness to lower the movement friction. At the same time, optimize the material formula, add fatigue-resistant components, and enhance the structural stability and durability of the piston during long-term reciprocating motion. ?
Solving environmental compliance issues: The R&D end customizes special formulas that do not contain excessive harmful substances in accordance with the environmental protection standards of different countries and regions. A dedicated workshop for environmental protection control is set up at the production end to monitor the raw materials, production and packaging processes throughout the process, avoid pollution and ensure that the piston meets the strict environmental protection requirements of the medical, food and other fields.
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DOIT has 15 years of rich experience in rubber precision design and has successfully solved all the above problems.
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