Hot forming process

Thermoforming products used in the reinforcement is different from the injection molding processing parts, injection molded parts is used in the solid reinforcement, and thermoforming products itself wall is thinner, can only use out products on the surface of the hollow steel reinforcing effect, often used in parts of the Pacific Ocean, thin wall parts or thin parts of the parts, in order to improve the rigidity, prevent deformation. For small batch of large goods, the cost of the mould is an important factor, the roll forming is a kind of alternative.

thermoforming products wall thickness uniformity is relatively less, especially in deep drawing case, products of highly direction and sharp corner uniform wall thickness is not easy. Products provided by the final wall thickness depends on the degree of an extension of the sheet thickness and sheet. Sheet is commonly used in the thermoforming 0. 1 - 10 mm, thicker sheet can reach to 20 mm, but may be too thick or thin sheet will make it difficult to molding method.

the draft thermoforming products depends on the type of mould and mould surface condition, usually in 0. 5° - 4° Range selection, with the male mold molding products, draft than with draft of cavity die molding products. ABS, for example, male mold molding, products of draft recommended 2 & deg; - 3° , and female die forming, draft desirable 0. 5° - 1° 。 Larger draft is conducive to reduce the degree of thinning products corner, make products wall thickness tends to uniform.

for double disc molding, to control the thickness of the upper and lower two pieces of bad in about 1. , within the scope of the 6 mm thickness gap is big, easy to cause quality problems, such as sag and bending. Using sheet, sheet of good extensibility, draft than allowed to take. Sheet of poor extensibility, the excessive draft, products will be broken. So if the draft ratio is determined, be about to choose good material.

if the material is certain, draft ratio will be adjusted accordingly, generally for polyolefin kind of material, draft ratio is not greater than 1. 5 is appropriate, and of thermoplastic polyurethane elastomer, draft ratio desirable 4 above. Secondly, draft ratio and molding method and the type of mould. Single cavity die vacuum forming, adopting the 1-1 draw ratio is better, the plunger to pressure and draft than desirable, double injection to control below 2:1.

shape of injection molding products processing is relatively simple, because deep drawing sheet extensibility restricts, so the products are wide caliber, shallow depth of cover, cover or box products. Products surface area without too many restrictions, low dimension, form and position accuracy of parts. Thermoforming for low pressure production process, but the sheet of vertical and horizontal extension of the plate subjected to a certain degree of orientation, and larger orientation may lead to products in use is easy to deformation, especially under the action of a force and high temperature.

draft ratio is associated with the geometric shape of products, the products surface level off, at the right is allowed within the scope of the larger draft ratio, and the drafting of larger than required products have larger draft. Female die forming, or use the male mold molding, is difficult to molding and mold release. Unless there are needed, can do on the mould structure change accordingly, which will increase the complexity of the mould and increase the cost of production. But with soft materials, if the side concave wall size small, can be forced demoulding.

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