Our structural foam molding service produces thick-walled, large-format plastic parts through a low-pressure injection process that leaves a solid outer skin over a cellular core. Because the blowing gas packs the cavity instead of mechanical hold pressure, parts come out with 10 to 30 percent lower weight than solid equivalents, low moulded-in stress and freedom from sink marks on ribs and bosses. The process suits returnable packaging, equipment housings, panels and pallets, where stiffness-to-weight matters more than a cosmetic Class-A surface.
Structural Foam Molding Service: Process Window
The melt is charged with nitrogen gas or a chemical blowing agent and injected as a short shot at roughly 1,000 to 4,000 psi, against 10,000 to 30,000 psi in conventional moulding. Cells freeze against the cooler tool walls to form the skin while the core stays porous, and cavity pressures of 200 to 600 psi keep clamp demand near one ton per square inch of projected area, so large parts run on modest presses. Wall sections of 6 to 13 mm are standard, and the expanded melt reaches flow lengths that solid resin cannot, which is what makes large part molding practical on smaller equipment.
Typical Applications
- Returnable totes, dunnage trays and pallets for automated handling lines
- Equipment enclosures, junction boxes and meter cabinets
- Vehicle body panels, cargo beds and floor sections
- Appliance bases, carts and commercial floor-care housings
When Structural Web Molding Fits Better
Structural web molding, a related low pressure foam molding variant, targets very large parts on low-tonnage presses with simplified tool cooling. We recommend it for oversized panels and covers where a full structural foam tool would be underutilised, and we advise on the choice during DFM review so the process matches part size and annual volume rather than habit. Where load performance is critical, glass-filled grades recover the stiffness that foaming gives away.
Tolerances, Surface and Post-Processing
Dimensional control is moderate: expect roughly plus or minus 0.25 to 0.75 mm on large parts, with tighter control on small features. The expanding gas leaves a characteristic swirl pattern that is acceptable for industrial housings and is usually covered by texture or paint when a cosmetic surface is required. Parts can be sawn, drilled and screwed much like wood, which simplifies assembly-line fixturing.
Tooling Strategy and Verification
Aluminium tools are viable because cavity pressures stay low, cutting tooling cost and shortening lead time; steel tools are used where volumes or resin abrasiveness demand them. Gate sizing and venting are designed for foam flow to prevent burn marks and short shots. Each lot is verified for density, wall-section cuts and dimensional checks, with load or drop testing for packaging applications. Minimum orders start at 500 pieces per part number, quoted by weight band after sampling. Review our custom molding services and plastic mould range, apply our plastic part design guidelines to thick-wall geometry, and shortlist plants through our manufacturer directory.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
