Performance of thermoplastic injection
The second major area of expertise of the LEMAN INDUSTRIE Group, developed since 1991 at the Marignier-France site, the injection of thermoplastic materials and thermoplastic elastomers offers a wide range of innovative solutions to markets with significant technological challenges and technical requirements. Intended for the molding of parts and sub-assemblies, injection, combined with the various LEMAN INDUSTRIE processes, provides innovative solutions for the production of parts with specific characteristics (fastening, insulation, sealing, technical parts, appearance parts, etc.). With the arrival of Adduxi within the Group in 2025, this expertise is further strengthened.
Extensive technicality and capabilities
LEMAN INDUSTRIE masters the design of tools and has a machine park of 100 automated injection presses, vertical and horizontal (pressure from 22 to 500T – injection 1 to 150 grams) distributed among its production sites. A large tonnage press (500T) is dedicated to multi-cavity molding. Some specific projects may be the subject of machine investments.
The demanding updating of LEMAN INDUSTRIE tools and the diversity of thermoplastic materials used (polymers and composites) guarantee a wide range of technical possibilities, a high production rate and optimum quality.
Principle of plastic injection
Plastic injection molding involves heating thermoplastic pellets until they melt, then injecting them under high pressure into a closed metal mold. The material fills the cavity, takes the desired shape as it solidifies upon cooling, and is then ejected once the part is formed. This process allows for rapid mass production of parts, with high dimensional accuracy and controlled repeatability.
How does it work ?
Tools
The mold, called a tool, consists of a fixed part and a moving part, fixed on the plates of the injection molding machine. It integrates a thermo-regulation circuit to maintain an optimal temperature (15 to 90°C depending on the materials) and an ejection battery to release the part after cooling.
The ejectors, generally cylindrical, are driven by a mechanical coupling and leave visible traces that must be anticipated during the design phase. The parting plane, the separation line between the two parts of the mold, must be strategically positioned to ensure aesthetics and functionality. For complex geometries, side drawers allow the demolding of undercut areas.
Injection
Injection relies on high pressure (up to 2 bars) exerted by a cylinder, which pushes the molten plastic material into the mold cavity via the injection nozzle. The part then has specific characteristics: injection point, ejector marks, parting line and draft.
The injection point can be central (better pressure balance) or lateral (easier to deburr, suitable for multiple cavities). The draft – 1 to 5° inclination on the walls – facilitates ejection without damaging the part. Good control of the injection parameters (temperature, speed, pressure) guarantees uniform filling, without shrinkage or deformation.
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