RU2807475C1 - Method for manufacturing plastic elements with convex contour of a given shape - Google Patents

Abstract

FIELD: thermoplastics.

SUBSTANCE: invention relates to a technique for processing sheet blanks from thermoplastics, namely, to a method for moulding sheet plastic made on the basis of acrylonitrile-butadiene-styrene, or acrylic, or polyester, or polystyrene, or PVC, and can be used in any branch of mechanical engineering, in in particular, for the production of instrument housings (including radars), decorative and protective elements of a convex shape with radius bends and other means. A method has been proposed for the manufacture of plastic elements with a convex contour of a given shape, including placing a sheet of plastic on the surface of a heat-resistant material with low adhesion, heating, giving shape using a forming element, inertial cooling and removing the manufactured element from the forming element, while the heat-resistant material is placed on a flat surface , a forming element is installed above the plastic sheet, which is made in the form of a form-building mandrel of a given shape, completely corresponding to the inner surface of the element being manufactured, and such that the mandrel does not exert pressure on the plastic sheet, and the formation is carried out by wrapping the heated plastic sheet and then fixing it around the forming mandrel using heat-resistant material and clamping devices. The method ensures the production of finished parts from sheets of plastic with a precisely specified surface contour and without changing the thickness of the plastic over the entire surface of the finished part.

EFFECT: expansion of functionality.

2 cl, 7 dwg

Description

Technical field

The invention relates to a technique for processing sheet blanks from thermoplastics, namely, to a method for molding sheet plastic made from acrylonitrile-butadiene-styrene, or acrylic, or polyester, or polystyrene, or PVC, and can be used in any branch of mechanical engineering, in particular, for the production of instrument housings (including radars), decorative and protective elements of a convex shape with radius bends and other means.

State of the art

There is a known method for forming impact-resistant transparent polymer sheets (M.M. Gudimov, B.V. Perov. Organic glass. M., Chemistry, 1981, p. 160), including heating the sheet and subsequent molding between the forming elements using bending forces. In this case, molding is carried out in two stages: first, the polymer sheet is bent to a single (cylindrical) curvature; the bent sheet is then clamped into contour frames and formed to the final complex shape using pneumatic or vacuum forming.

The disadvantage of this known method is its high labor and energy intensity. In addition, the known method does not ensure reproducibility of parts with a convex closed contour and radius bends.

There is a known method for forming impact-resistant transparent polymer sheets (Patent WO 03/016025, IPC B29S 51/08, published on 02/27/2003), which includes placing a polymer sheet between the forming elements in the form of two contour halves with pinching it between them, heating and subsequent molding with using bending forces by creating a vacuum in one of the mold halves.

The disadvantage of this known method is the fact that when using it there is no possibility of obtaining a precisely specified complex curvature of the surface of polymer sheets. In addition, pinching a polymer sheet between two half-forms inevitably leads to its significant stretching during the molding process, and, consequently, to an uneven decrease in thickness over the sheet area.

Closest to the invention is a method for forming impact-resistant transparent polymer sheets (Patent RU2527463, IPC V29S 51/08, published on August 27, 2014), including placing the sheet between the forming elements, heating and subsequent molding using bending forces on the heated sheet, while a polycarbonate sheet is placed in the forming elements; silicate glasses with a given surface curvature, equidistant relative to each other, are used as forming elements, and before heating, bending forces are created on the polycarbonate sheet by means of an equally distributed mechanical load.

The disadvantage of this known method is its limited scope, namely, the inability to use it for the manufacture of parts with a convex contour of a given shape.

The essence of the invention

The main technical objective of the claimed invention is to create a method for manufacturing plastic elements with a convex contour of a given shape with uniform distribution of plastic along the contour of the part being manufactured.

The technical result is an expansion of functionality.

The technical result is achieved by the fact that in the method of manufacturing plastic elements with a convex contour of a given shape, including placing a sheet of plastic on the surface of a heat-resistant material with low adhesion, heating, shaping using a forming element, inertial cooling and removing the manufactured element from the forming element, according to the proposed solution, the heat-resistant material is placed on a flat surface, a forming element is installed above the plastic sheet, which is made in the form of a forming mandrel of a given shape, completely corresponding to the inner surface of the element being manufactured, and such that the mandrel does not exert pressure on the plastic sheet, and the formation is carried out by wrapping the heated sheet of plastic and its subsequent fixation around the forming mandrel using heat-resistant material and clamping devices.

In a particular case of implementation, the forming mandrel is made with a closed contour.

Brief description of drawings

A specific example of the implementation of a manufactured element according to the claimed method using a forming mandrel with a closed contour is demonstrated by drawings, where in Fig. 1 shows the general appearance of one of the variants of the manufactured element; Fig. 2, fig. 3 – schematic side and top views of the implementation of the method at the stage before the formation of the manufactured element; fig. 4 – schematically shows a side view of the implementation of the method at the stage of forming the manufactured element, Fig. 5–fig. Figure 7 presents the results of measurements of the thickness of the finished element, performed at its different measurement points, where the following are indicated:

1 – manufactured element;

2 – heat-resistant material;

3 – forming mandrel;

4 – sheet of plastic;

5 – flat base;

6 – clamping device;

7 – stand.

Implementation of the claimed invention

The claimed method for manufacturing an element (Fig. 1) is implemented as follows.

On the base 5 with a flat, rigid surface, a heat-resistant wrapping material 2 with low adhesion is placed and of such dimensions that they protrude beyond the dimensions of the scan of the manufactured element 1, on top of which a plastic sheet 4 is laid with a thickness equal to the required thickness of the material in the manufactured element 1 (in this example, about 2 mm). After this, a form-building mandrel 3 with a convex closed contour of a given shape is installed above the plastic sheet 4, completely corresponding to the inner surface of the manufactured element 1, so that the mandrel does not exert any pressure on the plastic sheet 4 and does not clamp the wrapping material 2 (Fig. 2, Fig. .3). This occurs due to the fact that the mandrel is installed on supports 7 installed on the base 5. The assembled package is placed in an oven heated to a temperature of 120±5°C for five minutes, while the heating time depends on the dimensions of the plastic sheet 4. Then, using a heat-resistant wrapping material 2, the heated plastic sheet 4 is wrapped around the forming mandrel 3 and fixed using clamping devices made in the form of clamps 6 (Fig. 4). Next, the molded manufactured element 1 is cooled on the forming mandrel 3 in an oven at a speed of 1°C /min to a temperature not higher than 70±5°C, to avoid the occurrence of internal stresses in the finished element 1. After cooling, the sheet 4 of plastic formed into the finished element 1 is released from the clamps 6 and removed from the mandrel 3.

Thus, in the inventive method, no mechanical forces are exerted on a solid, not heated plastic sheet 1, it is also not clamped with anything, and when molding the manufactured element 1, no additional equipment, a vacuum installation or additional accessories are used.

The use of a forming mandrel 3 with a given surface that fully corresponds to the inner surface of the element being manufactured 1 in the specified way ensures the production of finished parts from sheets of plastic with a precisely specified surface contour and without changing the thickness of the plastic over the entire surface of the finished part, which is illustrated by the results of measurements taken using a caliper ШЦЦ-I-125-0.01 GOST 166-89 and shown in the photo (Fig. 5-Fig. 7), where it can be seen that the thickness at different measurement points along the contour of the finished element 1 for the radar is 2 mm with a tolerance of ±0 .1 mm, which allows for correct operation of the device, because a constant thickness does not affect the technical characteristics on which the radiotransparency of the manufactured device body depends.

Claims (2)

1. A method for manufacturing plastic elements with a convex contour of a given shape, including placing a sheet of plastic on the surface of a heat-resistant material with low adhesion, heating, giving shape using a forming element, inertial cooling and removing the manufactured element from the forming element, characterized in that the heat-resistant material is placed on a flat surface, above a sheet of plastic, a forming element is installed, which is made in the form of a forming mandrel of a given shape, completely corresponding to the inner surface of the element being manufactured, and such that the mandrel does not exert pressure on the plastic sheet, and the formation is carried out by wrapping the heated plastic sheet and subsequent fixing it around the forming mandrel using heat-resistant material and clamping devices. 2. A method for manufacturing plastic elements with a convex contour of a given shape according to claim 1, characterized in that the forming mandrel is made with a closed contour.