JPH03226A - Extrusion molding method and extrusion molding mold mechanism - Google Patents

Abstract

PURPOSE:To save manhours and materials, and reduce the manufacturing cost of products by dividing an extrusion molding mold into two pieces and hold- fixing a various thickness of spacers. CONSTITUTION:A various thickness of iron plate spacers 2, 2' are inserted in the intermediate part of a mouthpiece A', and then an upper mold 1a and lower mold 1a' are clamped by upper mold clamping bolts (a) and mouthpiece attaching bolts (b) whereby they can correspond to the thickness dimensional alternation of products due to lot changing. During molding start, extrusion is performed by the mouthpiece A' in which the upper mold 1a and lower mold 1a' are fit to each other, and molding conditions are so set that a desired breadth and appearance can be achieved, after that, the thickness dimension is measured so as to find the dimension which may not meet the desired dimensions, and then the spacers 2, 2' having the thickness of corresponding therewith are set in the intermediate between the upper mold 1a and lower mold 1a', following this, molding is carried out in the same conditions, thus, products with an excellent appearance and accuracy can be manufactured as a result.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to the field of extrusion molding of plastics, particularly extrusion molding of irregular cross-sectional shapes, and relates to a molding method that can easily adapt to changes in molding conditions and its mold mechanism. It is.

[Prior art] Extrusion molding generally involves heating, cross-wiring, and plasticizing pellets of soft or semi-hard thermoplastic synthetic resin, such as vinyl chloride resin, and continuously extruding them from an extrusion mold with a mouthpiece shape, and then passing the pellets through a cooling water bath. The material is passed through the material and taken out continuously while fixing its shape, and then held at an appropriate temperature for an appropriate amount of time to relieve molding stress and stabilize its dimensions, resulting in a product.

The cross-sectional shape of this bisected cap is generally somewhat oversized than the required cross-section of the product, and its cross-sectional shape is not uniformly similar. This is because the viscoelasticity of the synthetic resin material depends on temperature, and the shape changes. depends on stress, viscoelasticity, and plasticity, and furthermore, this stress is caused by the balance between extrusion speed and withdrawal speed, and the cooling of each half of the extruded synthetic resin material is not uniform over time. This is because the problems are intricately intertwined and belong to the field of empirical rules that are difficult to analyze theoretically.

In other words, the reality is that industrial production of a single product is only possible after fixing one material brand and extrusion conditions and repeating test production and mold modifications many times. Moreover, it is inevitable that seasonal changes in temperature and environment, as well as slight changes in physical properties due to material lots, will result in variations in product thickness depending on the manufacturing lot of the material. There are three types, and they are replaced and adjusted each time the loft is changed.

Furthermore, in order to ensure this thickness, it was necessary to set molding conditions for a long time, resulting in material loss.

Furthermore, in foam extrusion molding, which is becoming more and more popular in order to reduce weight and cost, the behavior of the blowing agent is extremely sensitive not only to the amount added, but also to temperature and pressure. It is extremely difficult to make a decision, and we have no choice but to prepare several types of molds based on experience, and as the number of tests increases, the cost of preparing molds is putting a lot of pressure on production costs.

For example, in the extrusion molding method in which the shape of the product is fixed by extruding it from a side mold of an automobile and passing it through a cold water tank, etc., the cross section is generally not simple, that is, it has an irregular shape. In addition, the properties of the synthetic resin material used, especially its shrinkage upon cooling, vary not only with seasonal temperatures, environmental conditions, and the type of synthetic resin material, but also from lot to lot. It was extremely difficult to obtain. In particular, recently, foam extrusion molding using foaming agents has been increasing due to the demand for lighter automobiles, and in this case, the amount added, extrusion conditions, expansion and contraction due to foaming are intricately intertwined, and it is difficult to control them. Extremely.

For this reason, the general method is to prepare several types of approximate molds empirically and repeat tests to obtain a product with the desired shape, but this method also reduces the man-hours and mold preparation costs. It is also uneconomical, especially since the leftover material from test foam molding cannot be recycled, as a matter of course.

Here, Fig. 1 shows a conventional cap (^) with upper and lower upper molds (1) and lower molds (lo), where (a) shows the upper and lower mold tightening bolts divided into two halves, and (b) shows To install the cap, use two bolts, (c
) is an extrusion shaped lip.

Traditionally, two or three such caps were made,
This dealt with variations in the thickness and dimensions of extruded products for each production lot of molding material.

Figure 2 a shows the product [here, side protector (S)]
, which corresponds to the extruded lip (e).

Figure 2 shows the overall structure of the product, the side protector (S).

[Problems to be Solved by the Invention] An object of the present invention is to cope with variations in synthetic resin materials and extrusion conditions using one type of mold, and to easily and economically obtain products with desired irregular cross-sectional shapes.

That is, the mold is divided into two parts, and a plurality of spacers of various thicknesses are prepared in a shape that matches the dividing surface, and the cross-sectional shape of the molded product is thereby finely adjusted, thereby minimizing the number of extrusion trials.

Particularly in extrusion molding of materials that are a blend of foaming agents and thermoplastic synthetic resin materials, it is difficult to create products that match shape accuracy and appearance quality, but by using only one type of mold (die), manufacturing costs can be reduced. let The purpose of this invention is to obtain an extrusion molding method and a mold thereof that can shorten the time required to set molding conditions and reduce material loss associated with setting molding conditions.

[Means for solving the problem] In a method of heating and plasticizing a thermoplastic synthetic resin, extruding it from a mold having a mouth structure, and cooling it to obtain a long extruded product having a desired cross-sectional shape, the mold is moved up and down. After prototyping an extrusion molded product with an approximate cross-sectional shape using the two halves, a spacer of an appropriate thickness is sandwiched between the mating surfaces of the mold and extrusion molding is performed to obtain a product with the desired cross-sectional shape. The patented acid type 2 method, which is characterized by thermoplastic synthetic resin, is heated, plasticized, extruded from a mold with a mouth structure, and cooled to obtain a long extruded product having a desired cross-sectional shape. The extrusion mold mechanism is characterized in that the mold is divided into upper and lower halves, and a spacer of a desired thickness is clamped and fixed to the mating surfaces of the mold.

[Operation] This invention was tested using a two-piece mold whose thickness was set slightly insufficient.First, various conditions were set focusing on the product width, and then the thickness of the test product obtained was By paying attention to the excess and deficiency of the spacer and inserting a spacer of appropriate thickness, it is possible to quickly obtain a product with the desired cross-sectional shape.This eliminates the need for multiple expensive molds. Not only that, but it also produces huge savings in man-hours and construction period.

[Example] As shown in FIGS. 3A and 3S, spacers (2) made of iron plates with various thicknesses are provided in the middle part of the base (Ao).

(2'), then tighten the upper mold (la) and lower mold (l) with the upper mold tightening bolt (&) and the cap mounting bolt (b).
Tighten a) to deal with deviations (changes) in product thickness due to lot changes, etc.

As mentioned above, for example, many side protectors for automobiles have conventionally been made by extrusion molding, but this
There is a demand for lower costs, and products that use synthetic resin materials with foaming agents added are emerging.

Blends of foaming agents and thermoplastic synthetic resin materials have significantly different molding conditions due to seasonal changes in the temperature environment and variations in material kneading.

In order to create the desired shape, it takes a lot of time to set the molding conditions and a lot of material loss occurs.In particular, materials that contain foaming agents cannot be recycled, even if they are made from thermoplastic synthetic resins, which leads to the production of products. This was one of the causes of high manufacturing costs.

This invention was developed after studying how to control variations in product shape due to variations in temperature and materials in a short time.In order to create a shape in the thickness direction, we created spacers (2) and (2°) that match the shape. , upper mold (Ia>, lower mold (t
By placing it in the middle of a'), it became possible to create the desired shape extremely quickly.

The procedure is to start molding by extruding the upper die (1&) and lower die (It') using the combined die (^°), and set the forming conditions to obtain the desired width and appearance. Measure the dimensions, find out the dimensions that are less than the desired dimensions, set the spacers (2) and (2') of the appropriate thickness between the upper mold (Ia) and the lower mold (la'), and By molding under certain conditions, it is possible to produce products with good appearance and precision.

In Fig. 3a, (d) is the spacer fixing hole, and in Fig. 3, (C') is the extruded lip.The thickness of the spacers (2) and (2') is as follows in the automobile side protector. - In the example, it is about 0.2 to 0.5 cm.

[Effects of the Invention] In this invention, the extrusion mold is divided into two parts and the cross-sectional shape can be arbitrarily finely adjusted by using spacers of various thicknesses, so it is possible to quickly correct the cross-sectional shape to the optimum shape, and therefore the optimal conditions can be adjusted. By minimizing the number of trials needed to set the product, not only can man-hours and materials be saved, but the otherwise expensive mold costs can be reduced to just a few minutes. Become.

In other words, since only one die is required, the above-mentioned mold manufacturing cost is low, the manufacturing cost of the product can be reduced, and the product can be easily manufactured in accordance with the dimensions of the product drawing.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional cap, Fig. 2a is a sectional view of a product using the cap of Fig. 1, Fig. 2 is a perspective view of the product of Fig. 2a, and Fig. 3a is a perspective view of the product of the present invention. FIG. 3 is a perspective view of the cap in a state before use; FIG. 3 is a perspective view of the cap of FIG. 3a in a closed state; (1), <1h)------Upper mold ([')
, (la') - Lower mold... Upper mold, lower mold tightening bolts in half... Cap mounting bolt in half (C゛)... Extruded lip... ...Side protector, (2')...Spacer Figure 2 a i? J2 diagram b

Claims (1)

[Claims] 1. A method for obtaining a long extruded product having a desired cross-sectional shape by heating and plasticizing a thermoplastic synthetic resin, extruding it from a mold having a mouth structure, and cooling the resin, in which the mold is divided into upper and lower halves. After making a prototype of an extrusion molded product with an approximate cross-sectional shape using the molded product, a spacer of an appropriate thickness is sandwiched between the mating surfaces of the mold and extrusion molding is performed to obtain a product with the desired cross-sectional shape. Extrusion method. 2. In a mold that heats and plasticizes a thermoplastic synthetic resin, extrudes it from a mold with a mouth structure, cools it, and obtains a long extruded product having a desired cross-sectional shape, the mold is divided into upper and lower halves. 1. A mold mechanism for extrusion molding, characterized in that a spacer of a desired thickness is clamped and fixed to the mating surfaces thereof.