The wooden mold for pump housings (commonly referred to as "wooden patterns") is a process equipment used in sand casting to create sand molds and cores for pump housings (pump casings). It does not directly shape the metal but forms a cavity through sand filling, compacting, and removal, followed by box closing and pouring to obtain the casting.
1. Core Components of Molds
The pump body structure is typically complex (with flow channels, volutes, flanges, and internal cavities). A complete set of wooden molds generally includes:
External mold (pattern): Used to form the outer contour and shape of the pump body. It is often designed as a split mold (e.g., upper and lower halves), requiring a properly designed parting line and draft angle.
Core box: Used for creating sand cores to form internal flow channels, holes, or complex volute cavities in the pump body. The wooden mold of the pump body often comes with multiple core boxes of different shapes.
Sliding core and core head: The detachable part (sliding core) on the outer mold is used for forming side cavities or flanges; the core head is used to position the sand core and vent gases.
2. Materials and Key Manufacturing Points
Material Selection: Prefer woods with straight grain, minimal deformation, and ease of processing, such as Northeast pine, red pine, ginkgo wood, or multi-layer plywood. The moisture content of the wood should typically be controlled between 8% and 12% to prevent deformation during later stages.
Dimensional compensation: Wooden patterns cannot be fabricated at 1:1 scale according to the part drawings. Casting shrinkage allowances must be added (typically 1%~1.2% for cast iron and approximately 1.5%~2% for cast steel), along with machining allowances.
Process: Modern wooden molds are primarily based on the 3D data of castings, with complex curved surfaces (such as spiral case flow channels) carved by CNC woodworking machines. These are then manually assembled, polished, and finally painted or waxed to prevent moisture and improve demolding performance.
3. Applicable Scenarios and Standards
Applicable: Single-piece or small-batch production, or large, complex-structured pump body castings (such as large centrifugal pump casings). Low cost, short cycle, but less durability than metal molds.
Standard: Manufacturing and acceptance generally refer to the mechanical industry standard JB/T 7699-2022 "Technical Specifications for Wooden Patterns and Core Boxes Used in Casting," which specifies the classification, dimensional tolerances, surface roughness, and structural requirements for wooden patterns