Pultrusion mold design requirements
Pultrusion mold is an important tool in the pultrusion process technology. The basic requirements for the design of forming mold are as follows:
(1) the cross-sectional area of the forming mold and the ratio of the cross-sectional area of the product shall be greater than or equal to l0. Its purpose is to ensure that the mold has enough strength and rigidity, and the other reason to ensure the even and stable heating distribution.
(2) the length of the pultrusion mold is related to the curing speed and the heating conditions of the mold. The most important is to ensure that the product is pulled out to a certain degree of curing. Mold length can be selected between 500-1500mm. In addition to thin wall thickness products and small pieces, the ordinary pultrusion mold can be designed in accordance with the 800-900mm length to achieve the normal production requirements.
In the mold machining process, we should focus on the type of cavity machining accuracy requirements, mainly include the following aspects:
(1) the deviation of the mold is an indicator that affects the quality of the product line and generally requires to be less than ±0 05mm.
(2) mold cavity roughness will directly affect the appearance of the fiberglass pultruded product, for pultrusion mold, the roughness requirements should be above 0.2. Completed mold should be smooth and bright, there are no obvious scratches, machining marks, dark spots, and it’s smooth to touch, no edge glabrous thorns, and so on.
(3) mode cavity hardness should be greater than HRC50, the index directly affect the mold service life. With higher hardness, mold can be used to produce more products, generally, pultrusion mold should have a service life of producing 5-8 million meters.
(4) cavity straightness should be < + 0.55, the index must be strictly controlled to ensure to pultrude products smoothly. Mold straightness with precision more than standard will cause the mold be plugged. The reason is mold exit wall thickness is less than entry wall thickness, so products in the mold after curing will have strong compression, and result in damaged product surface finish.