How to ensure coaxiality and smooth operation of zinc alloy motor brackets during bearing installation at both ends of a motor?
Publish Time: 2026-02-18
In small and medium-sized motors, servo systems, and precision transmission equipment, the motor bracket is not only a supporting structure but also a key component determining the overall operational stability and lifespan. Especially when using die-cast zinc alloy brackets, their coaxiality control capability during bearing installation at both ends of the motor directly affects rotor dynamic balance, bearing wear rate, and even the overall noise level of the machine. Although zinc alloys have high density and moderate rigidity, their relatively soft nature often raises questions about their precision retention capabilities.1. High-precision die-casting molds: The source of coaxiality assuranceZinc alloy brackets are typically manufactured using high-pressure cold chamber or hot chamber die-casting processes. The core of this process lies in the precision of the mold. To ensure the coaxiality of the bearing housing holes at both ends, the mold design employs an integral core or a high-rigidity guiding mechanism, molding the two bearing mounting holes in the same mold cavity in one step, avoiding the cumulative errors caused by separate machining. High-end molds even integrate online measurement feedback systems to monitor the core position in real time during die casting, ensuring that hole position deviations are controlled within ±0.02mm. Simultaneously, the symmetrical layout of the mold's cooling channels reduces localized thermal deformation and prevents hole position misalignment due to uneven cooling. This "one-time molding, overall positioning" process lays the foundation for high coaxiality from the outset.2. Synergistic Optimization of Material Properties and Structural DesignZinc alloys possess excellent fluidity and dimensional stability, with a low shrinkage rate far lower than aluminum alloys. This results in less deformation during solidification, which is beneficial for maintaining the precision of complex geometries. The support structure typically employs symmetrical ribs, reinforcing ribs, and enclosed bearing housing designs, not only improving overall rigidity but also effectively dispersing vibration loads during motor operation. More importantly, the inner wall of the bearing housing is often designed with a small draft angle, combined with precision reaming or boring post-processing, satisfying demolding requirements while allowing for final hole diameter tolerance control at IT6 level through precision machining, with roundness and cylindricity errors less than 0.01mm, thereby ensuring the high coincidence of the inner ring axes of the two bearings.3. Precision Closed-Loop in Post-Processing and AssemblyAlthough die-cast parts themselves have high precision, key mating surfaces still require secondary finishing. Common processes include CNC boring, honing, or rolling to eliminate microscopic unevenness and precisely control hole diameter and surface roughness. Some high-end applications also employ laser alignment detection systems to verify the coaxiality of the holes at both ends before assembly and to fine-tune bearing positions by adjusting shims or interference fits. Furthermore, the excellent damping properties of zinc alloys can absorb high-frequency vibrations, reducing the resonance amplification effect caused by rotor imbalance and further improving operational stability.4. Thermal Stability and Long-Term Operational ReliabilityDuring motor operation, temperature rise causes metal expansion. Although the coefficient of thermal expansion of zinc alloys is higher than that of cast iron, the clearance changes caused by thermal expansion can be offset by properly designing bearing fit tolerances. Simultaneously, zinc alloy supports often undergo surface passivation or electrophoretic coating treatments to improve corrosion resistance and prevent loosening of the fit due to rust in humid environments. Under long-term load cycling, its creep resistance is sufficient to maintain the geometric accuracy of the bearing housing, preventing coaxiality degradation caused by plastic deformation.In summary, the zinc alloy motor bracket, through high-precision mold one-time molding, material-structure co-design, precision machining post-processing, and thermal matching optimization, constructs a complete coaxiality assurance system. It not only meets the modern motor's demands for lightweight and low cost but also demonstrates unique advantages in operational stability, noise control, and long-term reliability, making it an ideal choice for mid-to-high-end motor support structures.
