Eccentric Shaft

Hansheng Automation (Dongguan) Co., Ltd. is one of the most experienced manufacturers and suppliers of eccentric shaft in China. If you're going to wholesale bulk cost-effective eccentric shaft made in China, welcome to get pricelist and quotation from our factory. Also, customized service and OEM&ODM service are available.

We specialize in OEM manufacturing for small to medium-sized eccentric shafts, with capabilities covering outer diameters (OD) from φ10mm to φ200mm and lengths up to 500mm. We accept orders ranging from single-piece prototypes to small and medium batch production. We strictly follow your 2D/3D drawings for 100% build-to-print machining and do not make any design alterations.

Our core expertise lies in process breakdown. The larger the eccentricity, the more severe the fluctuations in cutting forces. During the CNC programming stage, we carefully plan the clamping datums and material allowance allocation for each operation. We determine which journal to machine first, how much grinding allowance to reserve, and what tooling to use to counteract centrifugal forces, before finalizing everything into an executable routing sheet.

An eccentric shaft is a critical drive component that converts rotary motion into linear or reciprocating motion. The axis of the journal is parallel to the axis of rotation but is offset by a fixed distance (eccentricity), effectively functioning as an integral cam mechanism.

Widely used in compressors, plunger pumps, and stamping presses, it is responsible for driving the piston stroke or ram movement. The mechanical output and fatigue life of the equipment are directly dictated by the precision of the eccentricity and the surface finish. Any deviation in the center-to-center distance will inevitably lead to uneven wear on the connecting rod or premature seal failure.

Exact Offset Control

The accuracy of the eccentricity depends directly on the position of the center holes. We perform end-face milling and drill two sets of center holes in a single setup on a CNC Machining Center. The reference center hole corresponds to the axis of rotation, while the eccentric center hole corresponds to the axis of the journal to be machined. The positional coordinates of both sets of center holes are directly controlled by the CNC program, keeping the positional error of a 6mm offset within ±0.005mm. By locking in the eccentricity from the very first operation, all subsequent turning and grinding processes use these center holes as locating datums, preventing any cumulative error.

Dynamic Balancing in Turning

When an eccentric shaft rotates, the centrifugal force (F = m·ω²·e) increases exponentially with the rotational speed. If unaddressed during turning, this centrifugal force causes workpiece deflection, chatter marks, and tool breakage. During the programming stage, we calculate the eccentric mass distribution and design counterweights to be installed on the drive plate in the symmetrical direction to neutralize the centrifugal force. Driven by a dead center and a lathe dog, the workpiece rotates smoothly throughout the rough and finish turning processes, keeping radial runout strictly within the correctable range for subsequent grinding.

Precision Cylindrical Grinding

While turning controls the dimensions and shape, grinding determines the final precision and surface integrity. During the turning phase, we reserve a 0.5mm rough grinding allowance plus a 0.05mm finish grinding allowance for the bearing journal outer diameter (OD). The cylindrical grinder locates the part using the two center holes and performs plunge grinding to the exact drawing dimensions. The surface roughness consistently reaches Ra 0.8μm, with a roundness of ≤0.003mm. The grinding heat-affected zone is minimal, leaving no residual tensile stress on the surface layer, ensuring the fatigue life of the bearing journals is not compromised.

For dimensions exceeding the above ranges (OD > 200mm or Length > 500mm), please contact us in advance so we can evaluate equipment compatibility.

Case Study: 6mm Offset Eccentric Shaft in 1045 Carbon Steel

Challenges

• The 6mm eccentricity needed to be precisely locked in, with no cumulative offset allowed during machining.
• The centrifugal force generated by the eccentric mass during the turning stage caused vibration, directly impacting dimensional stability and tool life.
• The final tolerance zone for the φ75 bearing journal was only 0.03mm with a surface roughness of Ra 0.8μm, which could not be achieved directly by turning alone.

Our Process & Solutions

Eccentric Positioning

We performed end-face milling and drilled two sets of precision center holes in a single setup on a CNC Machining Cente: one set corresponding to the φ110 axis of rotation, and the other to the φ75 eccentric axis. The coordinates of both sets of center holes were directly controlled by the CNC program, ensuring the 6mm center distance deviation was ≤ ±0.005mm. All subsequent operations used these center holes as locating datums, ensuring the eccentricity error did not accumulate during machining.

Dynamic Balancing in Turning

When turning the φ75 eccentric journal, the rotation of the workpiece generated continuous centrifugal force. We installed precision counterweights on the drive plate in the symmetrical direction to neutralize the dynamic unbalance caused by the eccentric mass. Driven by a dead center and a lathe dog, the workpiece rotated smoothly throughout the rough and finish turning stages, leaving no chatter marks and keeping radial runout within 0.02mm to ensure an even grinding allowance.

Allowance Allocation and Grinding

During the turning process, a 0.50mm rough grinding allowance and a 0.05mm finish grinding allowance were reserved for the φ75 journal. The cylindrical grinder located the part using the two center holes and performed plunge grinding to the final dimension of φ75 -0.03/-0.06mm. After grinding, the roundness was ≤ 0.003mm, and the surface roughness consistently reached Ra 0.8μm, with no grinding burns and no residual tensile stress on the surface layer.

Results

The 6mm eccentricity passed full inspection, the φ75 journal dimensions achieved a 100% pass rate, and the surface roughness met the Ra 0.8μm requirement. The 50-piece order was completed from material input to final inspection and delivered in 8 working days.

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