A hydraulic cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy to produce linear reciprocating motion (or oscillating motion). It features a simple structure and reliable operation. When used to implement reciprocating motion, it eliminates the need for speed-reducing mechanisms, exhibits no transmission backlash, and delivers smooth motion; consequently, it is widely employed in the hydraulic systems of various types of machinery.

The output force of a hydraulic cylinder is directly proportional to the effective area of the piston and the pressure difference across it. A hydraulic cylinder typically consists of a cylinder barrel and cylinder head, a piston and piston rod, sealing elements, a cushioning device, and an exhaust device. While the cushioning and exhaust devices are selected based on the specific application, the other components are essential.

Let’s now take a look at the machining process for hydraulic engineering machinery cylinder barrels:

1. The hydraulic cylinder barrel is manufactured using roller burnishing. The residual compressive stresses retained in the surface layer help to close microcracks and inhibit the propagation of corrosive attack, thereby enhancing surface corrosion resistance and delaying the initiation or growth of fatigue cracks, which in turn improves the fatigue strength of the cylinder barrel. Roller burnishing also induces a work-hardened layer on the surface, reducing elastic and plastic deformation at the contact interface during grinding, thus improving the wear resistance of the inner wall of the cylinder barrel while preventing grinding-induced burns. Furthermore, the reduction in surface roughness following roller burnishing enhances mating characteristics.

2. The cylinder barrel of a hydraulic cylinder serves as a key component in products such as hydraulic cylinders, mine-used single hydraulic props, hydraulic supports, and gun barrels; the quality of its machining directly affects the service life and reliability of the entire product. Cylinder-barrel machining is highly demanding, with internal-surface roughness requirements of Ra 0.4–0.8 μm and stringent tolerances for coaxiality and wear resistance. A fundamental characteristic of cylinder-barrel machining is deep-hole drilling, a process that has long posed significant challenges to machinists.

3. Hydraulic cylinders are critical components in construction machinery. The conventional machining process consists of broaching the cylinder bore, precision boring, and grinding the bore. In contrast, the roll-burnishing method involves broaching the cylinder bore, precision boring, and then roll-burnishing the bore—three sequential steps. However, in terms of processing time, grinding one meter of the bore typically takes 1–2 days, whereas roll-burnishing the same length takes only 10–30 minutes. In terms of capital investment, a grinding machine or honing machine costs anywhere from tens of thousands to several million yuan, while a roll-burnishing tool costs between 1,000 and several tens of thousands of yuan. After roll-burnishing, the surface roughness of the bore decreases from Ra 3.2–6.3 µm before rolling to Ra 0.4–0.8 µm, the surface hardness increases by approximately 30%, and the fatigue strength of the inner surface of the cylinder barrel improves by 25%. If only the cylinder barrel is considered, the service life of the hydraulic cylinder can be extended by a factor of 2–3. Moreover, the broaching-and-roll-burnishing process is about three times more efficient than the grinding process. These data demonstrate that roll-burnishing is a rapid technique that can significantly enhance the surface quality of the cylinder barrel.

4. After roll-forming, the hydraulic cylinder exhibits no sharp micro-edges on its surface; consequently, prolonged reciprocating motion will not damage the seals or sealing elements—a critical advantage in the hydraulic industry.