The foundry industry serves as a foundational pillar for critical sectors such as automotive, aerospace, machinery, and marine engineering. The inherent advantages of casting technology—including its cost-effectiveness, capacity for net-shape manufacturing of complex geometries, and process flexibility—make it indispensable for producing vital components. China, as a global leader in casting production, continuously sees record-high outputs. However, this growth is accompanied by escalating demands from downstream industries for higher quality and precision in casting parts. A persistent and significant bottleneck in meeting these demands lies in the post-casting cleaning and finishing stages. For numerous small and medium-sized enterprises (SMEs), the cleaning process remains overwhelmingly manual. This reliance on labor-intensive methods results in low productivity, high worker fatigue, a challenging work environment with significant dust and noise, and considerable safety hazards. While advanced automated solutions like robotic cells or high-end CNC-based systems exist, their high capital investment places them out of reach for many SMEs. This article presents the design of a dedicated, semi-automated cleaning device specifically for disc and sleeve type casting parts. The design philosophy prioritizes structural simplicity, operational reliability, and low cost, aiming to provide a viable automation upgrade that can effectively reduce labor intensity and improve production efficiency without requiring substantial financial investment.
The proposed equipment is designed to handle disc and sleeve casting parts with outer diameters ranging from approximately 100 mm to 320 mm. The core function is to automate the removal of flashes, burrs, and parting line excess from the outer cylindrical surface and, where applicable, from internal weight-reduction holes. The overall machine layout adopts a T-shaped configuration, combining the rigidity and stability of a CNC machine tool base with purpose-built, simplified non-standard components to minimize complexity and cost. The key operational concept involves fixturing the casting part on a rotating spindle and bringing a high-speed grinding wheel into controlled contact with its periphery. The machine’s main structural components include a monolithic T-shaped bed, an X-axis linear feeding mechanism, a Z-axis vertical column, a rotating spindle assembly, and a grinding head unit with its own linear feed. Manual loading and unloading are retained to keep the system simple and affordable, but the working height is ergonomically designed at approximately 840 mm from the floor to minimize operator strain during part handling. The required positioning accuracy for this roughing operation is set at ±1 mm, which is sufficient for subsequent finishing operations.
Mechanical System Design and Component Specification
The device’s architecture is broken down into several integrated subsystems. Each is designed with cost-effective manufacturing and reliable operation in mind.
| Component | Primary Function | Key Design Features & Material |
|---|---|---|
| T-Shaped Bed | Primary foundation and load-bearing structure for the entire machine. | Monolithic cast iron (HT300) construction for damping and strength. Simplified planar mounting surfaces to reduce machining cost. |
| X-Axis Feed Mechanism | Provides horizontal linear motion (X-direction) for the Z-axis column assembly. | Ball screw and linear guideway driven by a servo motor. Carries the weight of the Z-axis assembly and spindle. |
| Z-Axis Column | Provides vertical linear motion (Z-direction) for the rotating spindle assembly. | Ball screw and linear guideway driven by a servo motor. Includes mechanical hard stops and safety pins to prevent accidental drop. |
| Rotating Spindle Assembly | Holds and rotates the disc/sleeve casting part during grinding. | Servo motor driven via timing belt. Supported by a combination of angular contact and deep groove ball bearings for rigidity and thermal stability. |
| Grinding Head Unit & Feed | Houses the grinding motor and provides in-feed/out-feed motion (Y-direction) of the grinding wheel. | Powered by a standard three-phase asynchronous motor (2800 rpm) with a diamond grinding wheel. Linear motion via ball screw and guideway. |
The overall dimensions and key travel parameters of the designed equipment are summarized below:
| Parameter | Value | Unit |
|---|---|---|
| Machine Footprint (L x W) | 1400 x 1450 | mm |
| Overall Height | 1600 | mm |
| X-Axis Travel | 400 | mm |
| Grinding Head Y-Axis Travel | 240 | mm |
| Z-Axis Travel | 280 | mm |
| Target Part Diameter Range | 100 – 320 | mm |
Servo Motor Sizing: Torque and Inertia Matching
Proper selection of servo motors is critical for stable and responsive motion control. The selection process involves matching both the required torque and the load inertia reflected to the motor shaft. The fundamental motion equation governing the system is derived from Newton’s second law for rotation:
$$ 2\pi (J_m + J_L) \frac{dn}{dt} = T_m – T_L $$
where \( J_m \) is the motor rotor inertia, \( J_L \) is the total load inertia reflected to the motor shaft, \( n \) is the motor speed, \( t \) is time, \( T_m \) is the motor torque, and \( T_L \) is the load torque. The ratio of load inertia to motor inertia, \( q = J_L / J_m \), is a key performance indicator. For optimal dynamic response in medium-duty equipment, \( q \leq 3 \) is typically targeted.
X-Axis Servo Motor Calculation
The X-axis mechanism moves the entire Z-axis column assembly horizontally. Key parameters for sizing are: moving mass \( m_x = 280 \, \text{kg} \), ball screw lead \( p = 10 \, \text{mm} \), diameter \( D = 32 \, \text{mm} \), length \( L = 650 \, \text{mm} \), friction coefficient \( \mu = 0.002 \), mechanical efficiency \( \eta = 0.9 \), max speed \( v_{max} = 0.4 \, \text{m/s} \), and acceleration time \( t_a = 0.2 \, \text{s} \).
First, the total load inertia \( J_{Lx} \) reflected to the motor shaft is calculated. It consists of the inertia of the translating mass (\( J_{wx} \)) and the inertia of the ball screw itself (\( J_{bx} \)).
$$ J_{wx} = m_x \left( \frac{p}{2\pi} \right)^2 = 280 \times \left( \frac{0.01}{2 \times 3.14} \right)^2 \approx 7.10 \times 10^{-4} \, \text{kg} \cdot \text{m}^2 = 7.10 \, \text{kg} \cdot \text{cm}^2 $$
$$ J_{bx} = \frac{1}{32} \rho \pi L D^4 = \frac{1}{32} \times 7850 \times 3.14 \times 0.65 \times (0.032)^4 \approx 5.25 \times 10^{-4} \, \text{kg} \cdot \text{m}^2 = 5.25 \, \text{kg} \cdot \text{cm}^2 $$
$$ J_{Lx} = J_{wx} + J_{bx} = 12.35 \, \text{kg} \cdot \text{cm}^2 $$
The required motor speed is \( n_{x} = \frac{v_{max}}{p} = \frac{0.4}{0.01} = 2400 \, \text{rpm} \). The torque demand has three components: to overcome friction (\( T_{1x} \)), to accelerate the load mass (\( T_{2x} \)), and to accelerate the ball screw (\( T_{3x} \)).
$$ T_{1x} = \frac{m_x g \mu p}{2\pi \eta} = \frac{280 \times 9.8 \times 0.002 \times 0.01}{2 \times 3.14 \times 0.9} \approx 0.0097 \, \text{N} \cdot \text{m} $$
$$ T_{2x} = \frac{m_x a p}{2\pi \eta} = m_x \frac{v_{max}}{t_a} \frac{p}{2\pi \eta} = \frac{280 \times 0.4 \times 0.01}{2 \times 3.14 \times 0.2 \times 0.9} \approx 0.99 \, \text{N} \cdot \text{m} $$
$$ T_{3x} = \frac{J_{bx} \alpha}{\eta} = \frac{J_{bx}}{ \eta} \cdot \frac{2\pi n_{x}}{60 \cdot t_a} = \frac{5.25 \times 10^{-4}}{0.9} \cdot \frac{2 \times 3.14 \times 2400}{60 \times 0.2} \approx 0.733 \, \text{N} \cdot \text{m} $$
$$ T_{Lx} = T_{1x} + T_{2x} + T_{3x} \approx 1.733 \, \text{N} \cdot \text{m} $$
A servo motor with a rated torque greater than 1.733 N·m and a rotor inertia that yields \( q \leq 3 \) is required. A motor with a rated torque of 7.96 N·m and rotor inertia \( J_{mx} = 4.9 \, \text{kg} \cdot \text{cm}^2 \) is selected. The inertia ratio is \( q_x = J_{Lx} / J_{mx} = 12.35 / 4.9 \approx 2.5 \), which meets the criteria.
Z-Axis Servo Motor Calculation
The Z-axis moves the spindle assembly vertically against gravity. Parameters: moving mass \( m_z = 80 \, \text{kg} \), ball screw lead \( p = 10 \, \text{mm} \), diameter \( D = 32 \, \text{mm} \), length \( L = 500 \, \text{mm} \), efficiency \( \eta = 0.9 \), max speed \( v_{max} = 0.4 \, \text{m/s} \), acceleration time \( t_a = 0.2 \, \text{s} \).
Load inertia calculation:
$$ J_{wz} = m_z \left( \frac{p}{2\pi} \right)^2 = 80 \times \left( \frac{0.01}{2 \times 3.14} \right)^2 \approx 2.03 \times 10^{-4} \, \text{kg} \cdot \text{m}^2 = 2.03 \, \text{kg} \cdot \text{cm}^2 $$
$$ J_{bz} = \frac{1}{32} \rho \pi L D^4 = \frac{1}{32} \times 7850 \times 3.14 \times 0.5 \times (0.032)^4 \approx 4.04 \times 10^{-4} \, \text{kg} \cdot \text{m}^2 = 4.04 \, \text{kg} \cdot \text{cm}^2 $$
$$ J_{Lz} = J_{wz} + J_{bz} = 6.07 \, \text{kg} \cdot \text{cm}^2 $$
Motor speed \( n_{z} = 2400 \, \text{rpm} \). Torque components: to hold against gravity (replaces friction), to accelerate the load, and to accelerate the screw.
$$ T_{1z} = \frac{m_z g p}{2\pi \eta} = \frac{80 \times 9.8 \times 0.01}{2 \times 3.14 \times 0.9} \approx 1.39 \, \text{N} \cdot \text{m} $$
$$ T_{2z} = m_z \frac{v_{max}}{t_a} \frac{p}{2\pi \eta} = \frac{80 \times 0.4 \times 0.01}{2 \times 3.14 \times 0.2 \times 0.9} \approx 0.29 \, \text{N} \cdot \text{m} $$
$$ T_{3z} = \frac{J_{bz}}{ \eta} \cdot \frac{2\pi n_{z}}{60 \cdot t_a} = \frac{4.04 \times 10^{-4}}{0.9} \cdot \frac{2 \times 3.14 \times 2400}{60 \times 0.2} \approx 0.564 \, \text{N} \cdot \text{m} $$
$$ T_{Lz} = T_{1z} + T_{2z} + T_{3z} \approx 2.24 \, \text{N} \cdot \text{m} $$
A servo motor with a rated torque of 4.9 N·m and rotor inertia \( J_{mz} = 3.71 \, \text{kg} \cdot \text{cm}^2 \) is selected. The inertia ratio is \( q_z = J_{Lz} / J_{mz} = 6.07 / 3.71 \approx 1.63 \), which is well within the acceptable range.
| Axis | Total Load Inertia \(J_L\) | Max Load Torque \(T_L\) | Selected Motor Rated Torque | Motor Rotor Inertia \(J_m\) | Inertia Ratio \(q\) |
|---|---|---|---|---|---|
| X-Axis | 12.35 kg·cm² | 1.73 N·m | 7.96 N·m | 4.90 kg·cm² | 2.5 |
| Z-Axis | 6.07 kg·cm² | 2.24 N·m | 4.90 N·m | 3.71 kg·cm² | 1.63 |
Structural Analysis and Optimization of Key Components
Finite Element Analysis (FEA) was conducted on the primary load-bearing structures—the bed, the X-axis base, and the Z-axis column—to ensure structural integrity under operational loads and to guide weight optimization. The material for all major cast parts is gray cast iron HT300, with a tensile strength \( R_m \) of 300-400 MPa and a Young’s Modulus \( E \) of 108-137 GPa.
Initial Design and Analysis
The initial FEA results for the key components under their respective working loads are summarized below. Safety factors were applied to the operational loads.
| Component | Max. Von Mises Stress | Max. Deformation | Initial Mass | Observation |
|---|---|---|---|---|
| T-Shaped Bed | 36.57 MPa | ~0.018 mm | 425.1 kg | Stress and stiffness are satisfactory. |
| X-Axis Base | ~0.84 MPa | ~0.00021 mm | 88.0 kg | Highly over-designed, significant potential for weight reduction. |
| Z-Axis Column | ~5.26 MPa | ~0.073 mm | – | Deformation is relatively high for the structure’s slenderness. |
Design Optimization
Based on the initial analysis, optimization was performed with two goals: reducing the mass (and thus cost) of over-designed parts, and improving the stiffness of the Z-axis column.
1. Bed Optimization: The bed’s internal ribbing and wall thickness were reviewed. Large lightening holes were added to the central web and side walls without compromising mounting surface integrity. This reduced the mass from 425.1 kg to 341.2 kg, a reduction of nearly 20%. The maximum stress increased slightly to 30.6 MPa (still very safe), and the maximum deformation increased to 0.027 mm, which remains acceptable as it occurs away from the functional mounting areas.
2. X-Axis Base Optimization: The wall thicknesses were reduced, and lightening holes were added to the base plate. The mass was reduced from 88.0 kg to 76.3 kg. Stress and deformation remained negligible.
3. Z-Axis Column Reinforcement: To address the higher deformation, an additional reinforcing rib was added to the column’s central section. This modification significantly increased the bending stiffness. The maximum deformation was reduced from 0.073 mm to 0.046 mm, a 37% improvement, while the maximum stress also decreased to approximately 2.69 MPa.
| Component | Parameter | Initial Design | Optimized Design | Improvement / Change |
|---|---|---|---|---|
| Bed | Mass | 425.1 kg | 341.2 kg | -83.9 kg (-19.7%) |
| Max Deformation | ~0.018 mm | ~0.027 mm | Acceptable increase for mass saving | |
| X-Axis Base | Mass | 88.0 kg | 76.3 kg | -11.7 kg (-13.3%) |
| Max Stress | ~0.84 MPa | ~0.65 MPa | Remains highly safe | |
| Z-Axis Column | Max Deformation | ~0.073 mm | ~0.046 mm | -0.027 mm (-37%) |
| Max Stress | ~5.26 MPa | ~2.69 MPa | Reduced stress concentration |
Conclusion
The designed semi-automated cleaning equipment presents a pragmatic and cost-effective solution for a persistent problem in small and medium-sized foundries: the arduous and inefficient manual cleaning of disc and sleeve type casting parts. By adopting a hybrid design philosophy that incorporates the rigidity of a machine-tool structure with simplified, purpose-built components, the device achieves its core objectives. The use of servo-driven ball screw and linear guideway systems provides precise and responsive motion control suitable for the roughing operation of casting part finishing. Detailed torque and inertia matching calculations ensure the selected servo motors offer both sufficient power and good dynamic performance. Furthermore, finite element analysis guided a successful structural optimization process, reducing the weight (and thus material cost) of major components like the bed and base while simultaneously reinforcing the Z-axis column to improve its stiffness. This equipment requires minimal operator training, significantly reduces the physical burden on workers, improves the working environment by containing dust and noise to a greater degree than open manual grinding, and enhances productivity. It serves as a attainable step towards automation for SMEs, addressing the cleaning bottleneck for a common family of casting parts and providing a technological foundation for future development aimed at more complex geometries.