As a rotational molding manufacturer, we produce seamless hollow plastic parts by rotating a charged aluminium or steel mould biaxially inside an oven while powdered resin melts onto the cavity wall. No pressure, no parting line and no weld seam means tanks, coolers, floats and playground components leave the mould stress-free and impact resistant. The process is also called roto molding, and it suits low to mid volumes from a few hundred to a few thousand units per year.
How the Cycle Works
- Charge: pre-measured powder, usually 35-mesh LLDPE, is loaded and the mould closes
- Heat: the oven holds 250 to 400 C while the arm turns at 4 to 12 rpm on both axes
- Cool: air and water mist solidification, still rotating, holds wall uniformity
- Demould: parts lift with one to two degrees of draft and need no ejector system
Design Rules That Decide Quality
Rotational moulding holds one nominal wall across a part, typically 3 to 12 mm in polyethylene, with variation around plus or minus 20 percent of nominal. Parallel walls need at least three wall thicknesses of gap, five is better, so powder can coat both sides before bridging closes the opening. Shrinkage runs two to three percent, linear dimensions are normally quoted at about plus or minus one percent, and the rest of the drawing is given a looser tolerance. Sharp inside corners run thin; generous radii and kiss-offs carry stiffness better than ribs.
Materials and Applications
LLDPE covers most polyethylene rotomolding work. XLPE adds chemical resistance for fuel and reagent tanks, PP raises temperature resistance for autoclavable containers, and PA6 suits structural fuel tanks. PVC plastisol still serves soft toys and balls. Foam-core sandwich walls are possible for insulated containers and flotation, and metal inserts can be placed in the mould before the cycle for encapsulated mounting points.
What a Rotational Molding Manufacturer Should Confirm
Tooling is the cheapest of any moulding process because the mould never sees pressure, so aluminium tools stay viable from a few thousand dollars. The trade-off is a 15 to 45 minute cycle, which keeps unit cost above injection or blow moulding. When annual volume passes roughly ten thousand units and the shape suits a parison, blow moulding usually wins on price, and tight-tolerance features are machined after moulding. See the custom molding services hub, compare processes in the compression vs transfer moulding guide, browse plastic materials, or find workshops in the supplier directory.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
