Resin transfer molding

Resin transfer molding is a process in which reinforcements are manually placed into a mold and then cured to form the final part. After the reinforcing material is placed, the mold is closed, and the resin is injected into the mold by injection, infusion or vacuum, and is cured by heat release, and finally shaped.

RAW MATERIAL

The resin transfer molding process accepts many types of reinforcement materials, chopped strand or mat. At the same time, it can control the mixture of resin and catalyst to achieve ideal processing conditions.

TOOLING

RTM process requirements include: mold cavity, Flow Mat, resin and other auxiliary materials, and corresponding operating tools.

RTM flow mat: The mat is sandwiched and consists of 2 layers of fiberglass with a layer of synthetic fabric(polypropylene mat) between of them.

FINISH

RTM’s parts have a very good surface finish on either side. Also, gel coats are added to the process to achieve a modified surface, or to provide a paintable surface

FEATURES

Tolerances of parts are well improved  
In terms of part thickness, the RTM process can achieve higher and more precise dimensional control than the hand lay-up and spraying of the mold opening process. This is the result of using a matching closed mold..

Ability to make very large parts
Part size is limited only by the capabilities of the mold maker. The RTM process is suitable for very large products such as wind turbine nacelles and yacht hulls, automotive bumpers, canopies, etc. These would be difficult to produce using any other composite process.

Optimizing local material properties

The placement of reinforcing fibers prior to resin infusion allows part performance to be locally optimized. Additional (or varied forms of) fiber can be precisely positioned in areas likely to experience high stress, for example.

Process Flexibility 

In the RTM process, there are many ways to introduce the resin into the closed mold. High-pressure injection and vacuum perfusion are two effective methods. Vacuum infusion eliminates the need for high-tonnage assets (to keep mold halves closed) while allowing RTM parts to be made anywhere.

Improving Tool Life 
Using aluminum materials instead of traditional composite materials for RTM molds can improve the surface quality of parts and greatly extend the service life of molds.

Mold in B-Side Datums
For more complex part geometries that require it, the closed molds used in RTM allow part datums to be molded directly into both A- and B-Sides of a product. This improved tolerance control allows for better fits in downstream assembly operations.

Ability to Create Hollow Sections   
A variation of RTM molding uses a bladder (“bag”) that is inserted into the mold and allowed to expand before the resin is infused. This process is used to manufacture hollow products such as fan blades.