Abstract: Stand-rider electric pallet jacks, known for their compactness, agility, and efficiency, play a pivotal role in logistics and warehousing. With the escalating market demand and technological advancements, upgrades, modifications, and optimizations in stand-rider electric pallet jack technology are continually occurring. This paper comprehensively analyzes stand-rider electric pallet jacks used in logistics, warehousing, and handling, from their characteristics, application fields, advantages, and market development trends, combining real project cases. It delves into the development difficulties and technical measures of the steel castings steering bracket for stand-rider electric pallet jacks, aiming to better understand the application of investment casting products in the forklift sector.
1. Introduction
With the rapid development of warehousing and logistics, the efficient handling capabilities of forklifts have become increasingly prominent. Stand-rider electric pallet jacks, characterized by labor-saving, energy conservation, environmental friendliness, high efficiency, safety, reliability, mobility, and low noise, have emerged as the primary handling tools in internal warehousing and logistics. Classified as Class III powered industrial trucks, these forklifts are operated in a stand-rider manner, suitable for medium to short-distance transportation. They offer a broader field of view, reducing the risk of accidents caused by obstructed lines of sight. Steering is controlled using a maneuvering arm, with switches on the arm’s handle controlling movement. The steering bracket, the key connecting component between the maneuvering arm and the steering motor, facilitates agile turns and rapid movement.
As a crucial functional component of pallet jacks, the performance of the steering bracket directly affects the forklift’s efficiency and steering capabilities, determining its maneuverability, comfort, and flexibility.
2. Project Overview
Most functional components of stand-rider electric pallet jacks are modular and standard parts, requiring only assembly according to requirements. However, the steering bracket, being non-standard and self-developed, necessitates comprehensive consideration based on actual installation needs, functionality, material selection, casting manufacturing processes, cost analysis, and strategic supplier selection. This paper takes the development project of a steel castings steering bracket for a stand-rider maneuvering arm pallet jack as a case study to explore the design of the steering bracket. The choice of material and process for the newly designed steering bracket is crucial, not only requiring cost optimization but also emphasizing process stability, consistency, and scalability for overall assessment.
3. Construction of Steering Bracket Components
The maneuvering arm steel castings steering bracket for this pallet jack. Its upper end connects to the end of the steering tiller handle, serving as support and positioning for the maneuvering arm to execute various commands as needed. The lower end connects to the steering motor and steering wheel power unit of the pallet jack, functioning as a transitional component between the maneuvering arm and the power unit, providing 100% command conversion for power unit steering. The side end reserves slots for the control wiring of the drive system, fixing and routing the wires through the bracket for enhanced practicality and aesthetics.
Table 1: Comparison of Casting Materials and Processes
| Material & Process | Ball Iron (Resin-Bonded Sand Casting) | Steel Casting (Investment Casting) |
|---|---|---|
| Material Cost | 40.3 yuan (approx. 3.1 kg, rough surface, large machining allowance) | 41.6 yuan (approx. 2.6 kg, smooth surface, small machining allowance) |
| Dimensional Accuracy | CT-8 to CT-12 (dependent on complexity) | CT-6 to CT-7 (high precision) |
| Surface Finish | Rougher, larger machining requirements | Ra 1.6–3.2 μm, minimal machining needed |
| Casting Efficiency & Consistency | Affected by product size, quantity, automation level | High precision and consistency, suitable for complex castings |
| Cost-Effectiveness Analysis | Higher machining costs | Lower machining costs, overall cost advantage |
4. Development Difficulties and Technical Measures
4.1. Selection of Casting Material
During the initial design stages, the design team faced disagreements regarding the material and casting method for the steering bracket due to its structural complexity and functionality. Options included ball iron 450 series with resin-bonded sand casting, or steel casting material G20Mn5 with investment casting.
4.2. Determination of Casting Process
4.2.1. Ball Iron (Resin-Bonded Sand Casting)
Resin-bonded sand casting offers dimensional accuracy up to CT-8 or CT-9, with complex castings reaching CT-11 or CT-12. However, it has drawbacks such as high mold hardening strength, low give, high friction, poor repairability, and a tendency for sand holes or porosity during pouring, leading to higher defect rates.
4.2.2. Steel Casting (Investment Casting)
Investment casting involves creating a wax model, coating it with slurry to form a mold, melting out the wax, firing the mold, pouring molten metal, and cooling to obtain the part. This process offers high dimensional accuracy (CT-6 to CT-7) and exceptional surface finish (Ra 1.6–3.2 μm), significantly reducing machining requirements and costs. It is suitable for complex castings and ensures consistency.
5. Casting Cost Analysis
The project analyzed the costs of both casting processes (Table 1) and simulated machining costs, finding that steel casting saved 6.2 yuan per unit compared to ball iron. Considering all factors, steel casting with the investment casting process was more advantageous.
6. Sample Inspection Results Analysis
After determining the casting method and process, careful supplier selection was crucial to avoid delays, quality issues, and financial losses. Stringent quality checks, including magnetic particle inspection and ultrasonic testing, ensured defect-free castings.
6.1. Magnetic Particle Inspection
Magnetic particle inspection detects surface defects up to several millimeters deep by creating a magnetic field on the casting surface and using magnetic powder to reveal defects. It is sensitive to defects crossing magnetic field lines but less so to parallel defects, necessitating flexible magnetization directions for comprehensive detection.
6.2. Ultrasonic Testing
Ultrasonic testing checks for internal defects by directing high-frequency sound beams through the steering bracket. Reflections from internal surfaces or defects indicate their presence, location, wall thickness, and depth. Its high sensitivity and penetration capabilities make it suitable for detecting even fine cracks in thick sections.
7. Project Testing
After design and production, qualified steering brackets were assembled with maneuvering arm tillers and steering wheels on new pallet jacks, which passed multi-vehicle, multi-time, durability, fatigue, and continuous harsh condition tests. Improved maneuverability, compactness, and efficiency were observed, with smooth and quiet operation.
8. Conclusion
With growing logistics and warehousing demands globally, supported by policy incentives in China, the market for stand-rider forklifts is expanding. Future developments will focus on intelligence, automation, electrification, energy conservation, and leveraging big data and IoT for enhanced efficiency. Steel castings, particularly through investment casting, play a vital role in meeting these challenges, offering precision, reliability, and cost-effectiveness.