EP1578585A2

EP1578585A2 - Method for controlling the production of injection molded parts

Info

Publication number: EP1578585A2
Application number: EP03813907A
Authority: EP
Inventors: Christopherus Bader
Original assignee: Priamus System Technologies AG
Current assignee: Priamus System Technologies AG
Priority date: 2002-12-23
Filing date: 2003-12-22
Publication date: 2005-09-28
Also published as: KR20060020599A; DE10261498A1; AU2003296705A1; JP2006511362A; WO2004058476A2; US20060202370A1; DE10261498B4; WO2004058476A3; AU2003296705A8

Abstract

The invention relates to a method for controlling the production of injection molded parts in an injection molding die (5), which comprises a cavity (10) and, optionally, a mold core (9) of an injection molding machine, during which the temperature of the die (5) is controlled. In addition, the cavity (10) and/or the mold core (9) are/is directly heated or cooled.

Description

Process for regulating the manufacture of molded parts

The invention relates to a method for regulating the production of injection molded parts in an injection mold of an injection molding machine with a cavity and possibly a mold core, the temperature of the tool being regulated, and an injection molding machine therefor.

State of the art

In known methods for filling a mold, e.g. With thermoplastic materials, the filling process is controlled so that an initial speed-controlled phase is followed by a pressure-controlled phase that lasts until the end of the filling process. Towards the end of the speed-controlled phase or in the beginning of the pressure-controlled phase

BESTÄTIGUNGSKOPΪE Phase is reached the filling situation in which the mold cavity is completely wetted with plasticizable mass, the melt pressure inside the mold cavity being still comparatively low. This is followed by an increase in the mold internal pressure due to the continuation of the movement of an injection piston or an extruder, combined with a reduction in the specific volume or with an increase in the density of the molding compound located in the mold cavity. The extent of the compression that can be achieved in this way depends both on the prevailing temperature and on the level of the pressure acting and on the characteristic properties of the molding composition.

After the supply of melt to the mold cavity has stopped, the melt begins to solidify in the sprue. This seals the mold cavity, no further plastic melt can be fed. The temperature in the mold cavity drops until the 1 bar isochore is reached. Now the molded part begins to shrink until the molded part has reached room temperature.

The shrinkage of the molded part is determined by the pressure and temperature conditions and in particular by the viscosity of the melt in the cavity. An essential factor for the shrinkage of the molded part is the temperature distribution in the cavity at the end of the filling phase (or from the maximum pressure) until the end of the cycle. A different shrinkage from cycle to cycle results from the fluctuation of the temperature profile and from the fluctuation of the mold cavity pressure profile.

This applies to both single tools and multiple tools. In the production of all kinds of injection molded parts (plastic, metal, ceramic, etc.), multiple parts per cycle are often produced simultaneously for multiple reasons (multiple tools). The individual cavities are normally balanced with respect to geometry and gating points to such an extent that the quality of the molded parts is as uniform as possible. In the In reality, however, the shrinkage behavior of the individual molded parts is always different due to the material, temperature and the resulting viscosity fluctuations and is constantly changing.

DE 101 14 228 A, for example, discloses a method for uniformizing the shrinkage behavior of an injection molded part both between individual cavities of a multiple tool and from cycle to cycle of an injection process. The temperature and / or an internal pressure in the cavity is monitored and adjusted to a reference curve by tempering the tool from the end of the filling phase or from a pressure maximum in the cavity to the end of the injection cycle.

task

The present invention is based on the object of demonstrating further possibilities in order to uniformize the manufacture of molded parts in a simple manner and possibly to certain properties - such as a certain dimension - to regulate.

Solution of the task

To solve this problem, the cavity and / or the mandrel is heated or cooled directly.

So far, the shrinkage behavior of a molded part is only regulated with the help of mold cavity pressure and mold wall temperature by adjusting the temperature of one or more cooling circuits via the temperature of the cooling medium, but now the temperature of the cavity or the mold core is directly influenced. For this purpose, heating elements or cooling elements are directly assigned to the cavity or the mandrel. Coating of the cavity is also conceivable, for example and / or the mandrel with a thermo-ceramic coating, which is known under the name "thermoceramix.

Using these heating elements or heatable coatings, the cavity or the mold core is heated directly to a desired temperature. Excess heat can be dissipated through one or more temperature control circuits.

Analogously, processes with the reverse principle (hot tool / cold melt), such as the injection molding of thermosets. Elastomers and silicone melts are regulated using heat-dissipating methods so that the pressure and temperature conditions in the cavity or cavities remain constant. For this, e.g. cooled mold cores or heat-dissipating metal inserts or coatings can be used.

In a further exemplary embodiment, it is contemplated to create a closed control loop in which an optical view of the molded part produced is included. Regardless of the type of control of the injection molding machine, for example control of the injection parameters, control of the temperature medium, the heating elements, heat dissipation, the closed control loop can be expanded such that one or more dimensions of one or more are preferably used outside of the mold with the help of an optical instrument several molded parts as well as the surface condition or color of the molded parts may be measured and included in the control. This has the advantage that it is not only regulated relatively via constant pressure and temperature conditions, but also absolutely on the basis of certain part dimensions, or possibly on the basis of a certain surface quality.

For the sake of simplicity, the optical detection instrument should be outside the tool or the production area, for example outside on the Injection molding machine, can be arranged where the injection molded part or parts can be positioned and "scanned" using a handling system. A scanner or a CCD camera can be used as an instrument, for example.

On the one hand, this control principle offers cost advantages compared to the known visual surveillance systems (surveillance cameras) and can also be installed without personal support. The service effort is much lower, it is also conceivable as an OEM product. Handling / removal devices are already widely used in the injection molding process, so that additional optical monitoring can be integrated without much additional effort.

figure description

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing; this shows in

FIG. 1 shows a schematically represented side view of an injection molding machine according to the invention;

Figure 2 is a schematically illustrated side view of another embodiment of an injection molding machine.

An extruder unit 2 stands on, for example, a hall floor 1, with plastic reaching a screw 4 from a store 3. The plastic is pressed out of the screw 4 into channels (not shown in more detail) of an injection mold 5. The injection mold 5 has a stationary mold plate 6 and a movable mold plate 7. Both plates 6 and 7 are guided on guide columns 8.

Molded cores 9 are located on the movable mold plate 7 and cooperate with cavities 10 in the stationary mold plate 6 in order to form a mold space for producing a molded part (not shown in more detail). According to the invention 9 heating element 11 are provided in the mandrel. The cavity 10 is also assigned three heating elements 12.1 to 12.3. It is also indicated that the interior of the cavity 10 is provided with a thermo-ceramic coating 13, which can be located both on the surface, below the surface and behind the tool insert.

At least one cooling circuit 14 is located both in the stationary mold plate 6 and in the movable mold plate 7. The operation of the injection molding machine according to the invention is as follows:

The basic idea of the invention is that the temperature of a cavity or a mandrel is not only regulated via the cooling circuits and there via the temperature of the cooling medium, but also with the aid of the heating elements. If it is determined that the cavity or mandrel is too low in temperature, the heating elements are regulated higher. If, on the other hand, it is determined that the temperature in the cavity or on the mandrel is too high, the excess heat is dissipated through the cooling circuit. For example, the circulation in the cooling circuit is increased or the temperature of the cooling medium is lowered.

The aim is to keep pressure and temperature conditions in the cavity or cavities 10 constant.

The reverse principle (hot tool / cold melt) can also be used to regulate the injection molding of thermosets, elastomers and silicone melts using heat-dissipating methods. For this purpose, cooled mold cores or heat-dissipating metal inserts can be used instead of the heating elements.

A further method according to the invention is indicated in FIG. This is a closed control loop, the pressure p and the temperature T in the mold space being determined. Furthermore, the molded part itself is examined via an instrument 15. For example, the instrument 15 detects the dimension of the molded part, its surface quality or its color, the corresponding values reaching a control 16 and being compared there with stored reference values, just like the temperature and the pressure in the cavity. The result of this comparative analysis is then followed by a corresponding one Signal output to a machine controller 17, which in turn regulates the injection molding process and in particular the temperature of the melting and molding plates and the injection pressure. Control is therefore not only relative to constant pressure and temperature conditions, but also absolutely to certain properties of the molded parts.

Claims

claims

1. A method for regulating the production of molded parts in an injection mold (5) with a cavity (10) and optionally a mold core (9) of an injection molding machine, the temperature of the mold (5) being regulated,

characterized,

that the cavity (10) and / or the mandrel (9) is / are directly heated or cooled.

2. The method according to claim 1, characterized in that excess heat is removed by one or more cooling circuits (14) in the tool (5).

3. A method for regulating the production of molded parts in an injection mold (5), characterized in that in a control circuit the molded part is at least partially viewed optically with corresponding instruments (15) and the result of the analysis is compared with references and signals for a machine control ( 17) can be derived.

4. The method according to claim 3, characterized in that the dimension and / or surface quality and / or color of the molded part is / are determined.

5. The method according to claim 3 or 4, characterized in that the determination is carried out with a scanner, a CCD camera or the like.

6. The method according to any one of claims 3-5, characterized in that pressure and temperature values (p, T) in the cavity (10) are included in the control.

7. Injection molding machine for producing molded parts in an injection mold (5) with a cavity (10) and optionally a mold core (9), characterized in that the cavity (10) and / or the mold core (9) has heating or cooling elements (11 , 12.1 - 12.3) are assigned or the cavity (10) and / or the mandrel (9) has a thermo-ceramic coating (13).

8. Injection molding machine according to claim 7, characterized in that one or more temperature control circuits (14) are provided in the injection molding tool (5).

9. Injection molding machine for producing injection molded parts in an injection mold (5) with a cavity (10) and optionally with a mold core (9), characterized in that the injection mold (5) is assigned an instrument (15) for visual inspection of the injection molded part and this is connected to a control (16) containing reference values, which responds to a machine control (17).