As an efficient non-cutting finishing process, rolling processing relies heavily on the performance of specialized tools. Commonly used tools include rolling wheels, rolling heads, rolling dies, and auxiliary support devices. The structural design, material selection, and precision level of these tools must be customized according to the shape, material, and precision requirements of the processing object to achieve the goals of surface enhancement, dimensional correction, and shape optimization. The application of rolling processing tools covers a variety of parts such as shafts, holes, and planes. They play an important role in the fields of automotive manufacturing, engineering machinery, aerospace, etc., and can not only replace traditional grinding processes to reduce costs, but also improve the mechanical properties of parts through cold hardening.
Rolling wheels are core tools for external surface rolling. They can be categorized by shape into cylindrical, conical, arc-shaped, and special-shaped rolling wheels, suitable for processing different surfaces. Cylindrical rolling wheels are primarily used for external cylindrical rolling of shaft parts. Their working surface is cylindrical, typically with a diameter of 50-150mm and a width of 10-50mm. Uniform rolling is achieved through line contact with the workpiece. For example, an 80mm diameter, 20mm wide cylindrical rolling wheel is commonly used for external cylindrical rolling of automotive axles, reducing surface roughness from Ra3.2μm to Ra0.4μm. Arc-shaped rolling wheels have an arc-shaped working surface with a radius of curvature that matches the spherical or curved surface of the workpiece. They are used for rolling parts such as ball studs and valve spheres. For example, when machining a ball stud with a radius of 50mm, a arc-shaped rolling wheel with the same radius is selected to ensure a roundness error of ≤0.01mm. Special-shaped rolling wheels are designed for complex external surfaces such as stepped shafts and spline shafts. Multiple sets of rollers are combined to achieve multi-surface rolling in one clamping. For example, the gearbox input shaft is rolled using three sets of rollers with different diameters to roll the journal, stepped surface and spline parts respectively. The efficiency is more than three times higher than that of single-wheel rolling.
Rolling heads are specialized tools for rolling hole-type parts. They come in fixed and floating configurations, adapting to varying hole diameters and precision requirements. Fixed rolling heads, with their rollers fixed in position, are suitable for machining through-holes or blind holes with high hole precision (IT7 and above), such as cylinder bores in engine blocks. Using a 100mm diameter fixed rolling head, three to six carbide rollers apply pressure to the bore wall, increasing surface hardness from HB180 to HB250 while maintaining a roundness tolerance of ≤0.005mm. Floating rolling heads, with their rollers capable of slight radial movement, automatically compensate for workpiece installation errors. These rolling heads are suitable for rolling deep holes with aspect ratios greater than 5, such as those used in hydraulic cylinder barrels. The floating design reduces hole straightness errors by over 50%. The roller material of the rolling head is mostly cemented carbide (such as YG6X) or high-speed steel, and the surface needs to be super-finely ground (Ra0.02μm) to avoid scratching the workpiece surface. The pressure adjustment range is generally 5-50MPa and can be controlled hydraulically or mechanically.
Rolling dies are primarily used for surface rolling and shape correction of plates and profiles. These include flat rolling dies, curved rolling dies, and forming rolling dies, and are widely used in sheet metal processing. Flat rolling dies consist of two parallel rolling wheels, one above the other, and are used for flat reinforcement of steel and aluminum plates, such as in the rolling of automotive panels. Applying a pressure of 10-20 MPa, they produce a plastic deformation of 0.05-0.1 mm on the surface, eliminating surface microcracks and increasing fatigue strength by 40%. Curved rolling dies have a working surface with a specific curvature and are used for rolling curved parts such as pressure vessel heads and pipe elbows. For example, a 2000 mm diameter head is rolled using a symmetrical arc-shaped die. The surface roughness after rolling can reach Ra 0.8 μm, with a shape error of ≤ 0.5 mm. The forming rolling die can simultaneously realize the shape of the parts during the rolling process, such as rolling a flat plate into a corrugated plate. The tooth structure of the die can press out regular patterns on the surface of the plate, which not only strengthens the surface but also beautifies the appearance. It is often used in the processing of decorative parts.
Auxiliary support devices are crucial for ensuring the quality of rolling slender and thin-walled parts. These devices, including a steady rest, center rest, and guide sleeve, effectively suppress vibration and deformation during machining. The steady rest moves synchronously with the rolling tool, maintaining close contact with the workpiece surface via two or three support blocks to minimize radial runout. For example, when rolling slender shafts with an aspect ratio of 30, a double-support steady rest is used. The support blocks are made of wear-resistant cast iron, maintaining a contact pressure of 2-5N with the workpiece, keeping the shaft straightness error within 0.02mm/m. The center rest is used to secure the center of long workpieces and is suitable for rolling deep holes or long shafts, such as drill rods. Three adjustable support jaws secure the workpiece in place, preventing bending due to its own weight and ensuring uniform rolling. The guide sleeve is installed at the front end of the rolling tool to guide the tool into the workpiece or position it. For example, when rolling small holes, the clearance between the guide sleeve and the hole diameter is ≤0.01mm to prevent scratches on the hole wall caused by tool deflection. These auxiliary devices, in conjunction with the main rolling tools, can significantly broaden the application range of the rolling process and ensure the processing quality of complex parts.
