WO2006005664A1 - Injection moulding machine with integrated position sensor system - Google Patents

Abstract

The invention relates to an injection moulding machine with at least one component which may be displaced along a linear guide (1) and a non-contact position measuring system with a positional sensor and an active position transducer for measurement of a position of said component. A disadvantage of said position sensor system is the use of an external position transducer, in other words, post-fitted to a frame or a machine bed in the injection moulding machine, which must be fixed with additional components to the moving and fixed components for measurement. The above means that, as a result of a slightly imprecise assembly, large errors in the positional measurement can be caused, which, in particular for measurement of large displacements, can lead to degrading effects. In addition, on assembly, account must be taken that the usual interfering factors in an industrial environment do not negatively influence the fixing means employed. According to the invention, said disadvantages can be avoided whereby the position sensor is integrated in the linear guide (1).

Description

 Injection molding machine with integrated displacement measuring system

description

The present invention relates to an injection molding machine having at least one component which can be moved along a linear guide and an associated non-contact path measuring system according to the preamble of claim 1.

Injection molding machines have a variety of components whose position must be determined as accurately and promptly as possible in order to be able to transmit the respective values of a control of the injection molding machine during operation, which initiates certain control sequences as a function of the determined values. The different components whose position must be recorded are, for example, movable platens, plasticizing units, screws which can be moved in the cylinder of a plasticizing unit, or else handling devices, such as robotic carriages or the like. Normally, the position of the components relative to a fixed reference frame is detected; this reference system is often a machine bed of the injection molding machine.

From the prior art it is known to measure the position of moving components with potentiometers. In this case, a slider connected to the component is pushed over a resistance path of a potentiometer when the component is moved. Vibrations and shocks to the components here load the Wegmess¬ system directly, which can lead to excessive wear and linearity deviations and defects. For this reason, a change to contactless position measuring systems took place.

Such a system is known, for example, from DE 42 33 501 C1, in which a metrological device for non-contact, continuous detection of a linear axial movement of a system rotating about a rotation axis on an injection unit of an injection molding machine is described. The measurement is carried out according to the known principle of magnetostriction. The use of non-contact magnetostrictive sensors for the displacement measurement in injection molding machines is also known for purely linear movements. Thus, various companies offer path measuring systems which are suitable for detecting tool or screw positions in injection molding machines and which operate according to the magnetostrictive principle. In this case, displacement transducers with a ferromagnetic measuring element or waveguide are essentially used, in which a magnetic longitudinal field is generated by an external moving magnet, the position transmitter. If the measuring element is traversed by a current pulse, a second magnetic field is generated radially around it. The interaction of the two magnetic fields causes a torsion pulse in the measuring element, over whose running time the exact position of the position sensor can be determined.

So far, such measuring elements are accommodated in housings in which they are protected against external influences, in particular in extruded aluminum profiles. These housings are then fastened to the machine on a reference element, that is to say, for example, the machine bed, it being necessary to ensure a substantially constant distance between position transmitter and position transducer. Usually the fastening takes place via clamps, clamps or similar fastening elements. Such Weg¬ measuring systems are z. B. from Balluff GmbH under the name "Micropulse AT" or by the Gefran SPA under the name "MK 3" (see, for example Plast¬ processor, February 3, 2003, and Elektronikpraxis Issue 10/2002 and IEE 47th year 2002, No. 11).

A disadvantage of these displacement measuring systems is that they are external displacement sensors, that is to be attached subsequently, for example, to a frame or a machine bed of the injection molding machine, which must be fastened with additional parts to the moving and fixed components to be measured. This means that large errors in the path measurement can already be called forth by a not very precise assembly, which leads to nega¬ tive effects, especially for large paths to be measured. In addition, care must be taken in the attachment, apart from the required precision, that the disturbing factors customary in the industrial environment do not adversely affect the fasteners used. The disturbing factors include, for example, shocks and jolts, which may cause which solve the fastening means or the displacement transducer relative to the fastening means can move. The displacement measuring systems, and in particular the displacement transducers, must also be protected against further external influences, such as, for example, dripping down of melt or cooling fluid.

It is thus relatively difficult and expensive to fix the Wegmesssysteme to the relatively be¬ wegten components of injection molding machines and protect so that external influences do not affect the accuracy of measurement.

It is therefore an object of the present invention to provide an injection molding machine which no longer has the abovementioned disadvantages, and in which mechanical and thermal influences can only marginally influence the measurement accuracy of the non-contact path measuring system, which results in a high recovery rate ¬ holgenauigkeit and motion quality can be guaranteed.

This object is achieved by an injection molding machine with the features of claim 1. Due to the fact that the displacement transducer of the displacement measuring system is integrated in the linear guide, along which the respective component of the injection molding machine is movable, the injection molding machine according to the invention has a high inherent strength displacement measuring system, which also ensures good calibration and is largely protected against media and other external influences is. By accommodating the Weg¬ sensor in the existing linear guide no additional Einbau¬ space must be provided. The number of parts is reduced by the invention compact design of the displacement measuring system, which costs can be reduced. Since the path measuring systems used can measure stroke paths in the range of tenths of millimeters up to several meters precisely and can repeatably control them, they can be used for path measurements of a wide variety of components on an injection molding machine.

As linear guides different systems could be considered, on the one hand classical rail systems or profile guides, but also columns or spars. The displacement transducer could be accommodated here in an inner bore which is designed so that the correct distance between the position transducer and the displacement transducer can be guaranteed. According to a particularly advantageous embodiment of the invention, the Wegauf¬ could be taken directly into a groove in the linear guide. In this case, such a groove could be provided in a region of the linear guide which experiences only a small load by the component movable on it, in order to achieve a low mechanical load on the displacement transducer. In the case of a profile as Linear¬ leadership, for example, a double-T-Profιls, the groove could be milled in generally lesser loaded surfaces in which usually already wells for mechanical attachment of the profile on the associated substrate vorgese¬ hen ,

With regard to a particularly precise determination of the position, the Wegauf¬ participants could be additionally mechanically connected to the Linear¬ leadership in addition to the volume integration. This could be done, for example, by casting or screwing. Thus Relatiwerschiebungen between the transducer and the reference component, ie the linear guide, essentially avoided the wer¬.

According to a particularly advantageous development of the invention Abdeckmit¬ tel could be provided, which further protect the transducer against environmental influences. Other such protective covers are conceivable, such as a Vor¬ see a masking tape, as it is already often brought on linear guides an¬ to fasteners with which the linear guide is connected to a machine nenbett, against pollution and other environmental influences protect.

The length of the displacement transducer should be determined as a function of the respective intended use, in particular also as a function of the strokes of the respective component to be realized in the real case.

According to a preferred embodiment, the displacement transducer could essentially extend over the entire length of the linear guide, which has the advantage of being able to absorb any displacement along this linear guide, even if this is beyond the strokes made in normal operation, for example due to a Exceptional repair goes beyond.

- A - Injection molding machines generally have many different linearly displaceable components. The movement of most of these components is along linear guides. Examples of such linearly displaceable components are an injection unit, which is usually movable relative to a machine bed and platens of the injection molding machine, a plasticizing screw of an injection unit, an injection piston of an injection unit or also movable tool mounting plates of a closing unit of the injection molding machine, as well as peripheral handling devices. such as robots for parts removal or for loading of molds in front of the injection inlet, which are linearly movable relative to the tools of a Spritzgießma¬ machine. For each or even only for such linearly movable components can be used in the corresponding linear guide Wegaufnehmer used. If several linear guides are provided for one component, for example two profiles on which the component can be displaceably mounted via sliding shoes, the displacement transducer could be integrated in only one of the provided linear guides.

If a plurality of components of the injection molding machine should be movable along the same linear guides, or if another component would be movable at least in parallel and at a short distance from the linear guide of another component, it would be advantageously possible to have both or possibly also several components Equip components with their own position sensors, these position sensor of the components with only one displacement sensor, which is integrated according to the invention in a Linearfüh¬ tion of the injection molding machine, cooperate and can be detected by this.

Such an arrangement makes it possible, for example, to determine relative distances between the respective components, which are specified by their respective position encoders. Absolute values can be recorded as well as relative values.

Advantageously, the transducer could be co-tactile by a conventional plug contact designed according to general specifications. Cheap It would be possible to attach such a plug contact in areas of the linear guide in which it is easily accessible, for example at one end of the linear guide.

For evaluation of the signals of the transducer (s) an evaluation electronics could be provided, which could advantageously work together with a regulation or control of the injection molding machine and in particular a control region for controlling the respective moving component.

According to a particularly preferred embodiment of the injection molding machine according to the invention, a displacement measuring system could be used which is based on the effect of magnetostriction and has a magnetostrictive component. As a position encoder could be used in this case, a moving position magnet, which is attached to the respective component. This is particularly easy to implement if a passive position sensor, in this case a permanent magnet, is used which requires no electrical control. The secure and location-specific attachment of the locally not very extensive position sensor is usually conditions even under industrial conditions. For example, it could be housed in a recess in a carriage of the component, which can be moved along a linear guide with a displacement transducer integrated according to the invention, as a result of which its position can be kept particularly accurate and readjustments can be substantially avoided. For the active position transducer, which comprises a magnetostrictive component, an electrical control would then be required to measure the position of the position sensor or distances between several position sensors over a pulse transit time, for example via electromagnetic pulses. Such measurements and their evaluation are state of the art. The distances between positioπsgeber and Wegauf¬ participants should not be too large in a particularly preferred embodiment, and for example in the millimeter range.

The present invention will be explained in more detail with reference to the following drawings.

The drawing shows schematically a portion of an exemplary linear guide 1, here a double-T-profile, which is often used to run components of injection molding machines, such as an injection unit, the injection nozzle is moved away from an injection port in a platen either between individual injections or for maintenance purposes. The linear guide 1 is connected to a machine bed 4 by fastening means (not shown). In its upper part, it has a groove 2.

Usually, the component via sliding blocks on the linear guide is movable. Either on these shoes or on the component directly, so beispiels¬ example at a not too far away from the linear guide point of the component, an unillustrated position sensor, preferably a permanent magnet is provided.

In Liπearführung 1 itself is not shown in the groove 2 Wegannehmer vor¬ seen, which operates on the principle of magnetostriction. This can be contacted at one end of the linear guide 1, which takes place via a plug contact. By a An¬ control of the transducer and evaluating the resulting output signals now a change in position of the displaceable on the linear guide 1 Kompo¬ nente be determined.

It should be noted that the groove 2 is mounted for receiving the transducer 2 in ei¬ nem area that is little burdened by the displaceable on the linear guide 1 component and their movement. In the drawing, the component is displaceable in the horizontal, and due to the double-T profile of the linear guide 1, an upper surface thereof is not heavily loaded. For receiving the Wegauf¬ takers a groove 2 is provided.

Not shown is a possible coverage of the groove with the transducer by a matching profile or masking tape.

LIST OF REFERENCE NUMBERS

Linear guide groove machine bed

Claims

claims 1. injection molding machine with at least one along a linear guide (1) verfahr¬ Baren component and an associated non-contact position measuring system with a position sensor and an active transducer for measuring a position of this component, characterized in that the displacement sensor in the linear guide (1) is integrated. 2. Injection molding machine according to claim 1, characterized in that the displacement transducer is received in a groove (2) in the linear guide (1). 3. Injection molding machine according to claim 1 or 2, characterized in that Covering means, in particular in the form of a cover strip, are provided for protecting the Weg¬ receiver. 4. Spritzgießmaschiπe according to any one of claims 1-3, characterized in that the displacement transducer extends substantially over the length of the Liπearführung (1) er¬. 5. Injection molding machine according to one of claims 1 - 4, characterized in that as linearly movable components an injection unit and / or a plasticizing screw and / or a movable platen and / or peri¬ phere handling devices are provided. 6. Injection molding machine according to one of claims 1-5, characterized in that a plurality of components are equipped with position sensors for measuring the respective positions and / or the respective distances, which are detectable by only one Wegauf¬ takers. - 1 - 7. Injection molding machine according to one of claims 1 - 6, characterized in that the position transducer can be contacted by a plug contact. 8. Injection molding machine according to one of claims 1-7, characterized in that an evaluation for evaluating the signals of the transducer or is provided. 9. Injection molding machine according to one of claims 1-8, characterized in that the displacement sensor comprises a magnetostrictive component. - 2 -