RTM Technology

RTM Process
RTM - Resin Transfer Moulding

For the production of fiber-reinforced components in small and medium series, the resin injection process RTM (Resin Transfer Moulding) has established itself in our company.
With the help of our RTM machinery, we have the ability to separate the resin and hardener by means of a static mixer, in order to bring them together immediately before the entry into the tool. This allows us to handle even extremely reactive resin systems. The RTM process allows us to manufacture highly reproducible components, as an exact adjustment of the volume flows is made possible by the precise control of the mixing ratio and accurate dosing of input materials.
The individual operational steps of the RTM process are shown in the following:

  • First, the later visible side of the component must be painted painted with a gelcoat.
  • Non-impregnated fibers and necessary wood or metal inserts are then placed in the two-part tool. The reinforcing fibers may be adjusted by draping or manual cropping. If you want to produce a sandwich-component, it is possible to insert a foam core of desired thickness inside the glass fiber layers.
  • The mould is now closed and the vacuum pump, as well as RTM system, is connected to the tool. By removing the air by the vacuum pump, the atmospheric pressure affects the mould and closes it completely tight.
  • At the same time, under high pressure in the tool, the impregnation of the reinforcing fibers takes place by passing over the resin through the RTM-machine. By vacuum support it is ensured that the resin is distributed evenly and without air pcoket and the inlaid glass fibers are impregnated cleanly. The resin will harden consistently with a so called exothermic reaction. A result of the now liberated temperature, the reaction process is positively influenced and the component quality improved.


On the one hand the vacuum infusion process enables a uniform distribution of the resin in the mold and on the other hand with this process
components with weight reduction, heat resistance and high strength can be produced.

Good surface quality. High fiber content. For large components.

Initially in the vacuum infusion process "dry" fibers have to be placed in a negative form. In the next step, a plastic foil is mounted over the edge of the mold. Then a vacuum is created. At the edge of the mould, on the opposite of the extraction, the resin supply is applied. By the permanently applied vacuum, the flow of the resin is initiated and supported, and enables uniform impregnation of the fabrics. Compared with the hand laminate process the vacuum infusion process has the advantages of producing reproducible components and vacuum volatile condensation products, due to the vacuum technology better and easier. Furthermore, the process is distinguished by its high fiber contents. While with the hand laminte process fiber contents of max. 30% can be achieved, the achievable levels for the vacuum infusion process may reach 50% .

Vacuum infusion process

Prepreg Technology

The prepreg technology is primarily used in applications where high demands are made on strength and weight. As with the vacuum infusion method, fiber content of 50% can be realized. A prepreg is a pre-impregnated fiber, which is the raw material for this process. Prepregs are based on phenolic or epoxy resin, which polymerize under the influence of temperature or pressure by means of a vacuum foil. They therefore have a limited shelf life. This storage period may be extended by a deep-freezing, for which we have the appropriate equipment.

As a specific process especially for rail vehicle developed there is the

Low-Temperature-Prepreg-System that meets the highest fire protection requirements.

Hand Laminating Process

Hand Laminate Process
The Process
In the production of fiber composite parts, the simplest process is the so-called hand laminating process. With this technology, the mats or fabrics consisting of glass fibers or carbon are placed on the mould and impregnated by hand, using a roller or a brush. In this case almost exclusively duroplastic matrix materials are used. These are thin in liquid form and due to this allow low viscosity and good wetting of the fibers. The wetting and placement of the fibers on the mould have to be done simultaneously with the molding process.
Advantages and Disadvantages

Advantage of the hand laminating process is the possibility to produce components with extremely complex component geometries and beeing able to use different fiber and reinforcing materials in a single component. Regarding the component size there are almost no limits. Furthermore, associated with this process there are comparatively low investment costs. In addition to different wall thicknesses within one component, undercuts with split moulds are possible. Achievable fiber volume fractions in this process are around 30% which can be increased by a subsequent pressing process during the hardening.
In decision-making, it should be noted that you have to expect high labor costs and high cycle times by using the hand laminating process. In addition, critical component quality depends on the manual skills of the processor.