Cast iron casting of gearbox housings and speed reducer housings using green sand molds at DISOCO

Gearbox housings and reducer housings protect drive components while also providing the structure for installing shafts, bearings, and related parts. For designs with hollow cavities, reinforcing ribs, bases, and multiple assembly points, the quality of the casting blank is a crucial foundation for subsequent machining and assembly.

Green sand casting is suitable for parts with box-like structures and hollow cavities, such as gearbox housings and reducer housings. At Song Cong Diesel One Member Limited Company - DISOCO, a green sand casting production line system is used to manufacture parts from gray cast iron (FC) and ductile cast iron (FCD).

What requirements must gearbox and reducer housings meet?

Gearbox housing castings must simultaneously meet requirements for material, shape, metal quality, and machining allowance. These factors directly affect the ability to create assembly surfaces that meet specifications in the subsequent stages.

A gearbox housing typically has many different structural areas: walls surrounding the cavity, bearing support locations, flanges, bases, and reinforcing ribs. Therefore, when developing the casting plan, it is necessary to consider thickness variations between areas, core placement, and the fillability of the molten metal.

Notable requirements include:

• Casting structure and dimensions: ensuring the shape of the housing body, hollow cavities, and functional part locations according to the casting drawing.
• Quality in machining areas: controlling defects such as gas porosity, shrinkage porosity, or sand inclusions, especially in areas where holes and mating surfaces will be machined.
• Machining allowance: appropriate allocation at bearing mounting holes, flanges, housing parting lines, and sealing surfaces.
• Oil containment requirements: for gearboxes using lubricating oil, the quality of the housing walls and sealing surfaces must be evaluated according to design requirements.

It is important to clearly distinguish between the accuracy of the casting blank and the accuracy of the finished part after machining. Requirements such as bearing bore tolerances, concentricity, flatness, or surface roughness typically need to be achieved and verified through appropriate machining processes.

Is Gray Cast Iron (FC) or Ductile Cast Iron (FCD) suitable for gearbox housings?

The choice between gray cast iron (FC) and ductile cast iron (FCD) must be based on the mechanical property requirements, load, and operating conditions of each design.

Gray cast iron has flake graphite and is often valued for its damping capacity and machinability. Ductile cast iron has spheroidal graphite and is suitable for various strength and ductility requirements. Specific properties also depend on the cast iron grade and the metallic matrix structure.

For casting orders based on drawings, the cast iron grade and applicable standards must be agreed upon from the outset. If the material is changed, its suitability for the design needs to be re-evaluated instead of merely choosing based on cost or availability.

Why is green sand casting suitable for cast iron gearbox housings?

Green sand casting allows for the creation of housing body blanks with external structures and internal hollow cavities through the combination of molds and cores. This method has been applied in the production of gearbox housing blanks using both gray cast iron and ductile cast iron. Green sand molds use a mixture of sand, binders like bentonite, and water to create the mold.

• Forming the housing body, ribs, and base directly on the blank

A gearbox housing can include walls, reinforcing ribs, bases, and flanges within a single structure. An appropriate casting method allows these parts to be formed directly on the blank, while also allocating machining allowances in areas that require machining.

However, the design needs to be considered according to actual casting conditions. Draft angles, transition radii, and thickness variations are all factors that require discussion between the design unit and the manufacturer.

• Using cores to create hollow cavities

Gear chambers and internal voids within the housing body are created using casting cores. The accuracy and position of the core affect the wall thickness of the housing as well as the internal shape of the product. Therefore, for gearbox housing parts, core-making capability and core assembly control are crucial parts of the production plan. A product with a weight suitable for the production line still needs further evaluation regarding the complexity of the core structure.

• Organizing repetitive production based on orders

When molds, cores, and technological parameters are standardized, a green sand casting line can mass-produce casting blanks according to the same drawing. Process control helps maintain uniformity between products and batches, suitable for businesses with recurring order needs.

Quality consistency between batches also depends on controlling the sand mixture, molten metal, pouring process, and product inspection. Therefore, supplier evaluation needs to combine both equipment capabilities and quality control plans.

DISOCO's Green Sand Casting Capabilities for FC/FCD Cast Iron

DISOCO casts gray cast iron (FC) and ductile cast iron (FCD) parts according to drawings, serving the production needs for gearbox housings, reducer housings, and other drive component housings. With an automatic SINTO green sand casting line from Japan and a semi-automatic line, DISOCO can cast products weighing 1–70 kg. Additionally, DISOCO's combined casting and machining capabilities allow it to fulfill orders from blank creation to machining assembly points according to customer technical requirements.

Actual Product: FCD450 Gearbox Housing at DISOCO

DISOCO has manufactured FCD450 ductile cast iron gearbox housings, weighing 9.8 kg, supplied to FDI customers. This is a typical product in the company's range of cast iron parts for drive equipment.

Contact DISOCO to discuss green sand casting solutions for FC/FCD cast iron gearbox housings, reducer housings, and other drive component housings according to drawings.