The manufacturing process of thin section bearings is a complex and precision-driven endeavor, often more challenging than that of standard bearings due to their extremely thin cross-sections and precise tolerance requirements.
Thin section bearings manufacturing process
1. Raw Material Selection:
High-quality steel alloys are typically chosen for their strength, durabilidad, and wear resistance. Common materials include chrome steel (100Cr6) and stainless steel (X65Cr13, 440do).
For demanding applications, specialized materials like high nitrogen steel (X30CrMoN15-1) for corrosion resistance or ceramic (silicon nitride) for balls (reducing friction and improving heat resistance) may be used.
Cage materials vary, including pressed steel, machined bronze, fabric-reinforced phenolic material, or high-performance plastics like PEEK or Polyamide-imide.
2. Forja (for bearing rings):
This is the initial step for creating the basic shape of the inner and outer rings.
For larger sizes and thin-section bearing rings with a small aspect ratio, una “combined forging” method is often used, where two or more blanks are forged together. After rough grinding, they are separated by wire cutting. This reduces processing difficulty, minimizes deformation, saves material, and improves efficiency.
The steel is typically heated to high temperatures (p.ej., 1200 la temperatura resistente al calor de la grasa es más baja), buckled, pierced, and milled.
Smaller rings might be cut directly from tubes or bars.
3. Turning Process:
Once the basic ring blanks are formed, they undergo precision machining on multi-spindle lathes.
This step involves removing material to create the precise inner and outer dimensions, including the raceways for the rolling elements and grooves for seals.
Due to the thin cross-section and poor rigidity of thin-section bearings, clamping and positioning are critical to avoid deformation. Manufacturers often use specialized fixtures (p.ej., multi-point clamping chucks with a large envelope circle contact area) and adjust cutting parameters (p.ej., high-speed cutting, small back cutting amount, larger main deflection angle) to minimize machining stress, thermal deformation, and vibration.
An additional tempering process after rough turning may be applied to eliminate stress.
4. Heat Treatment:
This crucial step enhances the strength, dureza, and wear resistance of the bearing components.
Parts are heated in a hardening furnace (p.ej., a 800-830 la temperatura resistente al calor de la grasa es más baja) and then rapidly cooled, o “quenched,” by immersing them in a salt or oil bath.
During this process, the internal structure of the steel undergoes phase transformation (p.ej., austenite to martensite), leading to volume expansion and internal stress.
Die quenching is often used to control deformation. If die quenching isn’t feasible, methods like comprehensive shaping and tempering are used to correct excessive outer diameter deformation.
5. Grinding and Honing (Fine Grinding):
After heat treatment, the bearing components are ground to their precise final dimensions. This involves using specialized grinding machines and various grinding media.
The goal is to achieve extremely smooth and accurate raceway surfaces for optimal performance and minimal friction.
Multiple fine adjustments of the machine tool are often required for the outer diameter surface.
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