INJECTION MOLDING DEVICE AND METHOD
The disclosure is directed to an injection molding device comprising at least one injection mold with a first and second mold half during operation being displaceable with respect to each other in a first direction (z) between a closed position and an open position. The first and second mold halves forming in the closed position at least one cavity therebetween for receiving melted plastic material from an injection nozzle. The at least one cavity comprises first and second cavity sections which are by a constriction. Melted plastic material is injected into the first cavity section and travels from there via the constriction into the second cavity section. A first sensor arrangement is arranged in a cavity wall of the first cavity section and a second sensor arrangement is arranged in a cavity wall of the second cavity section to determine relevant parameters in relation to the constriction.
1 . Injection molding device ( 1 ) comprising
a. at least one injection mold ( 2 , 3 ) with a first mold half ( 4 ) and a second mold half ( 5 ) during operation being displaceable with respect to each other in a first direction (z) between a closed position and an open position;
b. the first mold half ( 4 ) and the second mold half ( 5 ) forming in the closed position at least one cavity ( 7 ) there between suitable to receive melted plastic material;
c. the at least one cavity ( 7 ) comprising a first cavity section ( 9 ) and a second cavity section ( 10 ) interconnected to the first cavity section ( 9 ) by at least one constriction ( 11 , 24 , 25 );
d. an injection nozzle ( 13 ) opening into the first cavity section ( 9 ) in the closed position for injection of melted plastic material ( 21 ) into the first cavity section ( 9 ) and travels from there via the at least one constriction ( 11 , 24 , 25 ) into the second cavity section ( 10 );
e. wherein a first sensor arrangement ( 15 ) is arranged in a cavity wall ( 8 ) of to the first cavity section ( 9 ) and a second sensor arrangement ( 16 ) is arranged in a cavity wall ( 8 ) of the second cavity section ( 10 ).
2 . The injection molding device ( 1 ) according to claim 1 , wherein the first sensor arrangement ( 15 ) and the second sensor arrangement ( 16 ) are interlinked to a controller ( 17 ) configured to determine during injection the viscosity of the melted plastic material in the area of the constriction ( 11 ).
3 . The injection molding device ( 1 ) according to claim 2 , wherein the controller ( 17 ) is configured to determine the viscosity as a relative value of the geometry of the constriction ( 10 , 11 ).
4 . The injection molding device ( 1 ) according to claim 3 , wherein the controller ( 17 ) is configured to determine the change of the relative viscosity between two injection cycles.
5 . The injection molding device ( 1 ) according to claim 1 , wherein the first sensor arrangement ( 15 ) and the second sensor arrangement ( 16 ) each comprise a temperature sensor ( 18 ) and/or a pressure sensor ( 19 ).
6 . The injection molding device ( 1 ) according to claim 2 , wherein the controller ( 17 ) is configured to maintain the viscosity within a predetermined range of temperature and pressure in relation to a geometry of the constriction ( 10 , 11 ).
7 . The injection molding device ( 1 ) according to claim 2 , wherein the controller ( 17 ) is configured to maintain the viscosity depending on the specific plastic material injected, such that a magnitude of an adjustment of the operation is adapted to the specific plastic material, in particular to biological and/or recycled plastic materials.
8 . The injection molding device ( 1 ) according to claim 1 , wherein the constriction ( 10 ) comprises at least one thin spot ( 11 , 24 , 25 ) extending transversal with respect to a flow path ( 14 ) of the melted plastic material.
9 . The injection molding device ( 1 ) according to claim 8 , wherein the constriction ( 10 ) comprises at least one geometry ( 11 ) for forming a film hinge in the plastic material received in the cavity ( 7 ), in particular the geometry is implemented as the at least one thin spot ( 11 ) spanning a total width w of the constriction ( 10 ) traversal with respect to the flow path ( 14 ).
10 . The injection molding device ( 1 ) according to claim 8 , wherein the constriction ( 24 , 25 ) comprises at least two thin spots ( 11 ) arranged transversal to and in flow path ( 14 ) direction behind each other.
11 . The injection molding device ( 1 ) according to claim 10 , wherein the first cavity section ( 9 ) and the second cavity section ( 10 ) are interconnected to each other by constrictions ( 24 , 25 ) in the form of
a. a first and a second outer hinge strap ( 25 ) laterally spaced apart from each other and a center axis (x) comprising two thin spots ( 11 ) arranged behind each other and transversal to the flow path ( 14 ) of the melted plastic material
and/or
b. an inner hinge strap ( 24 ) arranged on the center axis (x) comprising at least one thin spot ( 11 ) arranged transversal to the flow path ( 14 ) of the melted plastic material.
12 . The injection molding device ( 1 ) according to claim 11 , wherein at least one of the constrictions ( 11 , 24 , 25 ) comprises with respect to the flow path ( 14 ) of the melted plastic material a first sensor arrangement ( 15 ) before the constriction ( 11 , 24 , 25 ) and a second sensor arrangement ( 16 ) after the constriction ( 11 , 24 , 25 ).
13 . The injection molding device ( 1 ) according to claim 11 , wherein the injection nozzle ( 13 ) is arranged on the center axis (x).
14 . The injection molding device according to claim 1 , wherein the first sensor arrangement ( 15 ) and the second sensor arrangement ( 16 ) are arranged between 30% to 70% of the lateral width of the respective constriction ( 11 , 24 , 25 ), in particular 50% of the lateral width of the respective constriction ( 11 , 24 , 25 ).
15 . The injection molding device according to claim 1 , wherein a front face ( 20 ) of the first and/or the second sensor arrangement ( 15 , 16 ) at least partially during operation forms part of a cavity wall ( 8 ) of the cavity ( 7 ).
16 . The injection molding device ( 1 ) according to claim 1 , wherein the first sensor arrangement ( 15 ) and the second sensor arrangement ( 16 ) are arranged spaced apart by a distance (a) along a flow path ( 14 ) of the melted plastic material, wherein the distance (a) is in the range of two to five times of a functional length L of the constriction ( 11 ).
17 . The injection molding device ( 1 ) according to claim 1 , wherein at least one injection mold ( 2 , 3 ) forming part of the injection molding device ( 1 ) is a production mold or a test mold.
18 . The injection molding device ( 1 ) according to claim 1 , wherein the first sensor arrangement ( 15 ) and/or the second sensor arrangement ( 16 ) is arranged in a cavity wall ( 8 ) adjacent to or at the constriction ( 11 , 24 , 25 ).
19 . The injection molding device ( 1 ) according to claim 18 , wherein
a. the first sensor arrangement ( 15 ) is arranged a certain distance (a 1 ) apart from the constriction ( 11 , 24 , 25 ), said distance (a 1 ) is preferably greater than a diameter ( 27 ) of a sensor tip ( 26 ) of the first sensor arrangement ( 15 ); and/or
b. the second sensor arrangement ( 15 ) is arranged a certain distance (a 2 ) apart from the constriction ( 11 , 24 , 25 ), said distance (a 2 ) is preferably greater than a diameter ( 27 ) of a sensor tip ( 26 ) of the second sensor arrangement ( 15 ).
20 . A method for adjusting operation of an injection molding device ( 1 ) such that at least one mechanical property of the produced plastic part is within a predefined range, the method comprising the steps of:
a. providing an injection molding device ( 1 ) according to preceding claims.
b. determining a viscosity of the melted plastic material ( 21 ) during injection based on signals of the first and the second sensor arrangement ( 15 , 16 ) and a geometry of the cavity ( 7 ) at least partially defined by at least one geometric parameter of the constriction ( 11 );
c. adjusting the viscosity based on predetermined reference data defining a target viscosity range for producing plastic parts with the at least one mechanical property in the desired range.
21 . Method according to claim 20 , wherein the predetermined reference data is ascertained for the geometry of the cavity ( 7 ) and/or a specific plastic material by associating viscosity measurements to measurements of the at least one mechanical property of the produced plastic part in the desired range.