Knowledge

The selection of different structures, materials, and manufacturing processes for gear reducer housings is crucial to their performance (strength, rigidity, sealing, vibration and noise reduction, heat dissipation), cost, weight, and service life. The following is a detailed analysis:

 

I. Main Structural Forms

The design of the housing is centered around installation, maintenance, sealing, and load-bearing requirements, and mainly includes the following forms:

 

1. Integral Housing:

- Structural Features: The housing is an inseparable integral structure. It usually has a large opening (for installing the gear shaft system) and a large end cover (sometimes also called a large end cover or bearing cover).

- Application: Mainly used in small, structurally simple single-stage reducers, especially for micro-motor matching reducers.

- Advantages: Compact structure, fewer parts, good rigidity, fewer sealing surfaces (lower leakage risk), relatively low manufacturing cost (for small parts).

- Disadvantages: Extremely inconvenient to install and disassemble! Gears, bearings, etc. must be installed one by one from the shaft end, with high requirements for assembly accuracy. Inspection and maintenance of internal parts require complete disassembly, which is troublesome. Generally not suitable for large reducers or those with complex internal structures.

 

2. Split Housing:

- Structural Features: The housing is divided into two parts along the plane of the shaft line (usually through the shaft line):

. Housing cover: upper part.

. Housing base: lower part. The housing base is the main load-bearing and installation base.

- Application: The most common and widely used structural form, suitable for almost all small, medium, and large reducers.

- Advantages:

. Easy maintenance: Only the housing cover needs to be opened to inspect, maintain, and replace internal parts such as gears and bearings, with low maintenance costs.

. Convenient assembly: All shaft systems and gears can be assembled on the housing base first, and then the housing cover can be closed. The assembly process is easier than that of the integral type.

. Strong adaptability: Facilitates the design of various internal structures (multi-stage, diverse gear types), rib arrangement, bearing support, etc.

- Disadvantages:

. Long sealing surface: The separation surface between the housing cover and the housing base is the main sealing surface, requiring high processing accuracy and sealing requirements; otherwise, it is prone to oil leakage.

. Relatively lower rigidity: The split structure is naturally less rigid than the integral structure (which can be improved through structural design).

. Slightly more parts: One more housing cover and corresponding connecting parts (bolts, etc.) than the integral type.

 

3. Classification by Installation Method:

- Base-mounted: The lower part of the housing (usually the housing base) has flat feet and can be fixed to the foundation or frame with bolts. The most common.

- Flange-mounted: The input/output end or other non-bottom surfaces of the housing have flange protrusions and can be directly connected and installed with the flange of the connected equipment (such as the motor flange) through bolts. Saves space and has direct force transmission.

- Cantilever-mounted/Sleeve-mounted: Commonly used in compact reducers directly connected to motors (such as part of a cycloidal pinwheel reducer), the housing is designed to fit over the motor shaft extension and is fixed with a locking plate or flange.

- Vertical-mounted: Designed for scenarios where the input/output shafts are vertically arranged. The structure must ensure reliable lubrication and sealing in the vertical position, and the direction of the bearing axial force is also more critical.

 

 

II. Material Selection for Housings

Material selection should comprehensively consider load, size, heat dissipation, cost, processability, and lightweight requirements:

 

1. Cast iron: The absolute mainstream material.

 Gray cast iron (HT series):

- Model: HT200, HT250 (most commonly used), even HT300 (for heavy loads).

- Advantages:

- Excellent casting performance: good fluidity, low shrinkage, and capable of casting complex-shaped structures (ribs, cavities).

- Good vibration damping: effectively absorbs vibrations and noise generated by gear meshing.

- Good wear resistance and compressive strength: suitable for use as bearing housings.

- Low material and processing costs.

- Disadvantages: low tensile strength and poor toughness (susceptible to impact).

Ductile iron (QT series):

- Models: QT400-15, QT450-10, QT500-7, QT600-3 (increasing in strength).

- Advantages: Significantly superior in strength, toughness, and plasticity to gray cast iron. More resilient than gray cast iron, capable of withstanding impact and heavy loads. Still retains good castability and certain vibration-damping properties.

- Disadvantages: Slightly higher cost than gray cast iron.

- Applications: Used in applications requiring higher strength, capable of withstanding impact loads or large heavy-duty reducer housings.

 

2. Cast steel:

 Types: ZG230-450, ZG270-500, etc.

- Advantages: It has very high strength and toughness, capable of withstanding extremely heavy loads, impact loads, and alternating loads.

- Disadvantages:

. Poor casting performance: Its fluidity and shrinkage rate are inferior to those of cast iron, making it prone to casting defects such as shrinkage cavities and cracks.

. Poor shock absorption: It may generate relatively high noise.

. High cost: Both material cost and processing cost (requiring welding and heat treatment) are much higher than those of cast iron.

. Heavy weight.

- Applications: It is only used in special reducers that are subject to extremely heavy loads, large sizes, or significant impacts.

 

3. Aluminum Alloy:

- Types: ADC12 (commonly used in die-casting), A356 (commonly used in sand-casting), ZL101, ZL104.

- Advantages:

- Light weight: Its density is only about one-third that of iron, which is conducive to the lightweighting of equipment (such as in aerospace, robotics, and mobile devices).

- Good thermal conductivity: Excellent heat dissipation.

- Certain strength: The strength of die-cast aluminum alloys can be comparable to that of ordinary cast iron.

- High precision and smooth surface of die-cast parts: Suitable for mass production.

- Disadvantages:

- Lower rigidity: To achieve the same rigidity, it needs to be made heavier or reinforced with ribs.

- Poor damping compared to cast iron.

  - Large thermal expansion coefficient: Affects fit accuracy.

  - High cost and low production capacity (compared to mass sand-cast iron): Expensive raw materials and high mold costs (especially for die-casting).

  - Corrosion resistance requirements: Often requires surface treatment (anodizing, painting).

- Applications: Reducers with high lightweight requirements, small and medium-sized, medium and light loads, and mass production (especially die-casting).

 

4. Steel plate welded structure:

- Materials: Q235A, Q345, and other carbon steel or low alloy steel plates.

- Advantages:

. Suitable for single-piece, small-batch, or extra-large reducers: no need to manufacture expensive molds, high flexibility.

. High material utilization rate and short production cycle (compared with casting).

. Strong designability: easy to achieve special structures or internal reinforcement.

- Disadvantages:

. Welding seam issues: there are risks of welding stress and deformation, requiring annealing treatment. Welding seams are potential quality risk points (cracks, pores).

. Poor vibration damping and damping performance.

. Poor appearance (compared with castings): difficult to control welding deformation, rough surface.

. Higher production cost for medium and large batches than casting.

- Applications: large and extra-large reducers produced in single-piece or small-batch quantities, compact structures requiring welding, and low-volume special structures where molds cannot be made. ​​​​​​​

 

China Vigor has more than 20 years of experience, a strong technical team, and production capabilities in cast iron gear reducer housing and gear reducer casing. If you have any questions, demands, or related parts development or to improve your supply chain, please feel free to contact us at info@castings-forging.com