SE463548B - PROCEDURE FOR MANUFACTURE OF RIGID PRODUCTS WITH HIGH-CLASS FINISHED FINISH, SPECIFICALLY MODELED PLASTIC - Google Patents

Description

46 7 J 10 15 20 25 30 35 548 2 is heated to about 200 ° C and then molded in a hydraulic press with cycle times for the pressing of about 20-60 s according to the desired thickness of the product. However, due to the fiber reinforcement in these carrier materials, visible irregularities occur on the surface of the shaped product, which simply has a poor surface finish. Various finishing work is therefore required, such as applying a primer, filling, sanding and varnishing. It also happens that a so-called activating primer is applied to the carrier material, to which in turn a soft foil is applied to obtain the desired final surface finish. In the latter case, the carrier material must always be preformed.

Another popular carrier material, which is useful for the production of the products in question, is the so-called SMC material (Sheet Molding Compound), which is usually in the form of polyester press mats with fiberglass reinforcement. SMC products are also compression molded and must be processed after molding to obtain a good surface finish. The use of SMC materials for the production of products of the type in question is described, for example, in U.S. Pat. No. 4,612,149.

Common to these two carrier materials and the methods used in the manufacture of products based on said materials is that several different operations must be performed in different steps, including eg preforming, intermediate storage, cooling, pressing, filling, grinding, varnishing , etc, partly that solvents must be used in the finishing, ie the application of primer and varnish.

It is understood that this entails clear disadvantages in the form of long total cycle times and costly finishing work.

As discussed above, these two carrier materials are formed by compression molding in a press with two tool halves. After preheating, the material is placed in the female tool's mold cavity, in which the male tool then collapses during pressing. Finally, the male tool returns, after which the shaped product is removed from the female tool, possibly by means of an ejector. Due to the fiberglass content of the carrier material, however, the product has an unsightly surface, which must be finished to achieve a good surface finish.

Another technique used in the manufacture of plastic products is vacuum forming, which means that a thermoplastic foil or plate, after heating, is sucked into a mold space in a female tool by means of vacuum channels accommodated therein, which are connected to a vacuum source. Provided that the tool itself has a good finish, the shaped product also has a high-class surface finish, which in technical terms is called class A. Due to its structure and fiber content, the carrier materials discussed above, GMT, SMC, etc, however, difficult to vacuum form. The object of the present invention is to provide a process for the production of such rigid products as stated above and which have fiber-reinforced support material but still have a high-quality surface finish, type class A.

Another purpose is that this production should take place in essentially a working step with much shorter total cycle times than has hitherto been possible.

A further purpose is that the preparation should take place completely without the use of solvents.

Therefore, according to the invention, a method has been provided in which said molding and vacuum forming are combined during the production of products with a fiber-reinforced carrier material and a foil material with a high-quality surface finish applied thereto.

The method is of the kind described in the introduction and is characterized according to the invention in that the foil material is fed into a female tool with a mold space, against whose mold walls the foil material is sucked and formed with its surface finishing side against the mold walls; that the carrier material is simultaneously or shortly thereafter fed into the female tool and placed on top of the foil material; that a male tool 465 548 10 15 20 25 30 35 4 is then brought into the mold space of the female tool so that the carrier material and the foil material are compressed and final formed; and that the male tool is finally brought out of the female tool and the finished product is taken out of it for cooling.

Additional features of the present invention are set forth in the appended dependent claims.

The invention will be described in more detail in the following with reference to the accompanying drawing, which schematically illustrates the method according to the invention.

The figure shows a device for carrying out the method according to the invention. A mold and pressing member has the general reference numeral 1 and consists of a fixed female tool 2 with a mold space 3 and a male tool in the form of a vertically movable piston 4. The shape of the stamp 4 corresponds to the shape of the mold space 3, and both of these parts have good surface smoothness .

To the left of the figure is shown a foil 6 wound on a roll 5 of a flexible, thermoformable plastic material, in this example ABS. The foil 6, which is preferably about 0.15-0.40 mm thick, is fed by means of a roller 7 into the molding and pressing means 1 via a preheating oven 8 with a temperature of about 190 ° C.

The right part of the figure shows another preheating oven 9 with a temperature of about 240 ° C, in which carrier material in the form of plates 10 is heated and softened before they are fed into the molding and pressing member 1 by means of a picking robot. ll. This entry can also be made manually or by means of other mechanical equipment. The plates 10 are relatively rigid before heating and are preferably about 3-4 mm thick. They consist of a thermoformable, glass fiber reinforced material, in this example GMT, which is discussed in the description introduction.

The process is intended for the manufacture of such rigid plastic products as vehicle body parts, moldings for the interior of vehicle interiors, and similar articles. According to this example, the final product should consist of a layer of carrier material, i.e. pressed GMT plates 10, and a foil layer 6 applied thereto and attached, which after forming and pressing has a surface finish of class A on its surface facing away from the carrier material.

The production of plastic products proposed according to the invention proceeds in the following manner.

The plastic foil 6 is heated in the preheating oven 8 and fed into the forming and pressing means 1 by means of the roller 7 and possibly by means of further feeding means (not shown). The feed is such that the foil 6 is placed over and covers the mold space 3 (dotted line). Then a clamping frame 12 is applied to the upper side of the female tool 2 so that the foil 6 is clamped and fixed around the mold space 3.

The clamping frame 12 thus extends circumferentially around and slightly outside the mold space 3.

When the foil 6 is clamped in this way, a vacuum pump 13 is actuated, which begins to have a suction effect via the female ducts 2 receiving in the female unit 2 and opening into the mold space 3. The plastic foil 6 is thus pulled down and fixed and formed with its surface finish side. facing the mold walls 3 of the mold space 15. For illustrative reasons, only two vacuum ducts 14 are shown, but the person skilled in the art realizes that there must be several such ducts in order for a sufficient suction of the foil 6 to be achieved.

Simultaneously or shortly thereafter, preferably a few seconds thereafter, the carrier material heated in the preheating furnace 9, i.e. the GMT plates 10, is fed into the mold space 3 of the mold and press member 1 and placed on top of the plastic foil 6 sucked therein. the mold space 3 so that the hot GMT plates 10 are compressed with the equally hot plastic foil 6, so that the product is given the shape determined by the appearance of the mold space 3 and the stamp 4. It should be pointed out that the piston 4 has venting needles 16, by means of which the air present in the mold space 3 is evacuated when the piston 4 strikes into it.

After completion of molding and pressing in the molding and pressing means 1, the piston 4 is pulled out of the mold space 3, whereupon also the clamping frame 12 is pulled up from the female tool 2. The water pump 13 is switched off and the finished product taken out of the mold space 3 manually or by means of a picking robot or the like (not shown). Finally, the product is taken to a suitable place for cooling. To start a new work cycle, new foil 6 is then fed over the mold space 3 and the process is repeated again.

Preferably, both the piston 4 and the female tool 2 are provided with cooling channels 17 and 18, respectively, in which a cooling medium is circulated so that these two main components in the mold and press member 1 maintain a temperature which is clearly below the aforementioned preheating temperatures and which is preferably about 20 °. 40 ° C. Furthermore, the stamp 4 advantageously has special means 19, by means of which the desired portion of the plastic foil 6 is punched out when the stamp 4 strikes into the mold space 3.

In short, the invention can be said to constitute a combination of compression molding and vacuum forming in essentially one working step and in one and the same machine. As a result, very short total cycle times can be obtained while maintaining good quality of the end product and a high-class surface finish.

In practical experiments with GMT as carrier material, it has been possible to get down to as short total cycle times as 40-60 s.

This is to be compared with previously known methods, which comprise several working steps, eg preforming, intermediate storage, pressing, primer application, filling, grinding, etc., with total cycle times of up to a few minutes. It will thus be appreciated what time savings and thus cost savings are achieved by the present invention.

In conclusion, it should be pointed out that the invention is by no means limited to the exemplary embodiment described herein, without several modifications thereof being conceivable within the scope of the inventive concept, as defined in the appended claims.

Of course, the invention is applicable to materials other than those set forth in this specification by way of example. Many other plastic materials can be used as carrier material or foil material, and foil can, if desired, be applied to both sides of the carrier material.

Under certain conditions, it is equivalent to a non-plastic material described as foil to apply non-plastic material, for example hollow material, which, however, must necessarily be able to be sucked into the mold space and attach the carrier material during pressing. In such a case, the purpose is not primarily to achieve a good surface finish, but to manufacture a rigid product in essentially one working step and without the need for solvents.

Finally, it should also be pointed out that the peripheral equipment used, namely the preheaters, feeders, etc., may be of a different type. The GMT plates can be fed in in some cases manually, and furthermore the final product can be removed from the mold space by means of an additional picking robot (not shown).

Claims (5)

463 548 8 10 15 20 25 30 35 PATENT REQUIREMENTS 1. A process for the manufacture of such rigid products as vehicle body parts, moldings for the interior of vehicle compartments, in particular plastic moldings, and similar articles, which consist of a layer of hot-formed, fiber-reinforced support material (10) and at least one of them an outer layer of a hot-formed, flexible foil material (6) with a good surface finish on its surface facing away from the carrier material (10), the two materials (6, 10) being preheated during manufacture and then brought together and placed on top and attached to each other to formation of said product, characterized in that the foil material (6) is fed into a female tool (2) with a mold space (3), against whose mold walls (15) the foil material (6) is sucked in and formed with its surface - finish side against the mold walls (l5); that the carrier material (10) is simultaneously or shortly afterwards fed into the female tool (2) and placed on top of the foil material (6); that a male tool (4) is then brought into the mold space (3) of the female tool (2) so that the carrier material (10) and the foil material (6) are compressed and final formed; and that the male tool (4) is finally brought out of the female tool (2) and the finished product is taken out of it for cooling. Method according to claim 1, characterized in that the foil material (6) is sucked into the mold space (3) by connecting channels (14) opening therein to a source of negative pressure (13). Method according to Claim 1 or 2, characterized in that the female and male tools (2, 4) are cooled to a temperature which is clearly below the preheating temperature of the two feeders (6, 10). Method according to one of the preceding claims, characterized in that air present in the mold space (3) is evacuated via venting ducts (16) in the male tool (4), when this is brought into the mold space (2) of the female tool (2). 3). 9 465 548 Method according to one of the preceding claims, characterized in that a clamping frame (12) is fitted to the female tool (2) so that the foil material (6) is fixed during this aforesaid suction into the mold space (3), and that the desired portion of the foil material (6) is punched out during the pressing by means of dedicated means (19) on the male tool (4).