There are three moulds of FRP moulds: pultrusion mould, hand lay-up mould, filament winding mould.
The advantage of pultrusion mould is high strength in pultruded product, stable dimentions,good repeatability. It is adjustable for pultrusion length, high production efficiency.but the disadvantage is large investment, high mould cost, strict requirement in technology and materials.
The advantage of hand lay-up mould is low cost, short lead time, less limitation in the product shapes,but the disadvantage is unstable dimention of product, not good at the quality and appearance, long term in production, and cost more labors, not fitting for bulk production.
The advantage of filament winding mould is stable dimention of product, lower cost than pultruded profile, but disadvantage is long term production time.
How to select materials to make pultruded window frame mould?
Regarding the pultruded mould, the choice of the material directly affect the property of mould, especially pultruded window frame profiles, because of the large market of window frame, it requires that the mould should have longer lifetime, therefore, there are some requirements of the raw materials when choose.
- High strength, Fatigue and wear resistance
- High heat resistance and slightly deflection
- Good corrosion resistance
- Good in cutting and surface polish
- Slightly deflection of heat, stable dimentions.
How to choose parting surfaces?
Pultrusion mold usually are combined by several modules,in the mould design, the principle to choose the parting surface is; on the premise of satisfying mold manufacturing, reduce the parting surface as much as possible to ensure the close seam,because of the complex shape of FRP window frame, it is very important to select the parting surface.
Design of mould entrance
When the glass fiber enters the mold after resin immersion, the fiber bundle enters the mold under the machine traction.
Because the fiber bundle at the mould inlet is very loose, it often accumulates winding at the entrance, causing the broken fibers.in addition, in the long time that the molds be used, due to the accumulation of winding impact, often resulting in severe population wear, affecting product quality. In order to solve this problem.Peripheral down a section at the entrance of the mould for a quarter of elliptical cross section rounded corners, keep the entrance conically at the same time, in 5-8 ° Angle advisable, it is advisable to 50 -100 mm in length, it can greatly reduce the broken fibers,and improve the quality of the FRP pultrusion products.
Determination of mold size
Because the wall of FRP window frame is thicker and thinner, heat conduction is faster in the mould, therefore, the length of the mould should not be too long, which is also conducive to the smooth processing and extrusion process of the mould.
Therefore, in the design, the mold length is related to the selection of raw materials. At present, the mold length in China is generally around 900mm.
The general mould thickness is 2-3 times of the product thickness.
Mold cavity size depends on product size and shrinkage.
For FRP window frame profile, unsaturated polyester resin glass fiber system is generally adopted, the shrinkage rate is generally around 2%.
Glass fiber reinforced plastic window profiles are mostly hollow products, thus it is important to pay special attention to the mandrel design, general core mould for two-thirds of the length of the effective length of mold 2/3-3/4, and take into account in the pultrusion process mandrel fixed and adjustment and prevent eccentric, and mandrel should take into account the weight problem, comprehensive consideration, regarding mould length is 900 mm, the length of the mandrel can be designed to around 1200 mm.
