ARRANGEMENT FOR CONTROLLING QUALITY OF INJECTION MOULDING COMPONENTS BACKGROUND OF THE INVENTION [0001] The invention relates to a method for controlling the quality of injection moulding components, the method comprising: checking the quality of two or more consecutive injection moulding components attached to a carrier medium by means of at least one checking device prior to the injection mould- ing of a plastic product to be manufactured; comparing the quality information obtained on each injection moulding component with at least one predeter- mined quality criterion; and accepting the injection moulding components fulfill- ing the quality criteria for use in the injection moulding and rejecting the defec- tive injection moulding components.

[0002] The invention further relates to a checking device compris- ing: at least one transfer device for transferring the carrier medium and the in- jection moulding components attached consecutively thereto at least in one direction in the longitudinal direction of the carrier medium; at least one check- ing unit, through which the carrier medium and the injection moulding compo- nents are arranged to pass, and which checking unit is provided with means for checking the quality of the injection moulding components; and at least one control unit for controlling the operation of the checking device.

[0003] The invention further relates to an injection moulding ma- chine comprising: a mould having a mould cavity that is limited by at least a first mould piece and a second mould piece; at least one actuator for opening and closing the mould ; at least one feed channel for feeding plastic material into the mould ; a control unit for controlling the operation of the injection moulding machine; and a transfer device for transferring the carrier medium and the injection moulding components attached consecutively thereto into the mould cavity.

[0004] In injection moulding, different prefabricated injection mould- ing components can be inserted between the mould halves, which then are integrated in the injection moulding machine into a plastic product together with the injection moulded plastic material. Quality defects may, however, be cre- ated in the manufacture and handling of injection moulding components, which then affect harmfully the quality of the plastic product to be manufactured. De- fective injection moulding components may, thus, cause extra material and work costs.

BRIEF DESCRIPTION OF THE INVENTION [0005] It is an object of the present invention to provide a novel and improved method and checking device for controlling the quality of injection moulding components connected to each other, and an injection moulding ma- chine that utilizes the method.

[0006] The method of the invention is characterized by marking the accepted or alternatively rejected injection moulding components by providing the carrier medium with a quality mark that indicates the quality.

[0007] The checking device of the invention is characterized in that the checking device comprises at least one marking unit, through which the carrier medium is arranged to pass after the checking unit, and that the mark- ing unit comprises at least one marking device for providing the carrier medium with a quality marking indicating the quality of the injection moulding compo- nent on the basis of the check performed in the checking unit.

[0008] The injection moulding machine of the invention is character- ized in that it comprises at least one reading device, which is arranged to rec- ognize the quality marks provided on the carrier medium indicating the quality of the injection moulding components.

[0009] The essential idea of the invention is that the carrier medium and the injection moulding components attached thereto are run through a checking device in which the quality of the injection moulding components is checked. After the check, the accepted or rejected injection moulding compo- nents are marked by providing the carrier medium with a quality mark. The in- jection moulding machine has a reading device that recognizes the quality mark on the carrier medium and can direct by using a transfer device a defec- tive injection moulding component away so that only good-quality components will be used in the injection moulding.

[0010] The invention provides the advantage that the quality of an injection moulded plastic product can be improved when the quality of the one or more injection moulding components belonging to the plastic product are checked even before the injection moulding. Because the injection moulding components are checked and defective components rejected before the injec- tion moulding, both the injection moulding material and the operating time of the injection moulding machine are saved.

[0011] An essential idea of an embodiment of the invention is that the injection moulding component is cleaned in a cleaning device before the check. The cleaning device is arranged to remove dirt particles, such as dust, from the surface of the injection moulding component.

[0012] An essential idea of an embodiment of the invention is that the carrier medium is an elongated polymer film.

[0013] An essential idea of an embodiment of the invention is that patterns according to the IMD (In-Mould Decoration) technique, which are con- secutively pressed into the carrier medium, are used as the injection moulding components. The invention is especially well suited for use in connection with such in-mould coating, i. e. IMD.

[0014] An essential idea of an embodiment of the invention is that the injection moulding components are physical pieces formed in a separate manufacturing phase and that the injection moulding components are arranged one after the other and connected by means of a carrier medium into a con- tinuous elongated formation.

[0015] An essential idea of an embodiment of the invention is that the quality mark is either accepting or rejecting by type. It is then possible to mark either the injection moulding components accepted or alternatively re- jected by the checking device. The injection moulding components provided with the quality mark are processed in the injection moulding process accord- ing to a predefined control strategy.

[0016] An essential idea of an embodiment of the invention is that the quality mark is a visually readable mark, such as a colour mark, brand, opening, or notch, made into the injection moulding component or carrier me- dium.

BRIEF DESCRIPTION OF THE FIGURES [0017] The invention will be described in greater detail in the at- tached drawings, in which Figure 1 is a schematic view of an injection moulding process, to which the solution of the invention is applied, Figure 2 is a schematic cross-sectional view of a plastic product manufactured by the IMD technique, Figure 3 is a schematic transverse view of an IMD film, Figure 4 is a schematic transverse view of a carrier medium and the injection moulding components attached thereto, Figure 5 is a schematic view of a checking device of the invention, Figure 6 is a schematic top view of a carrier medium and the con- secutive injection moulding components on it, Figure 7 is a schematic top view of a second carrier medium and the consecutive injection moulding components on it, and Figure 8 is a schematic view of an injection moulding machine that is equipped with a checking device and quality mark reading device of the in- vention.

[0018] In the figures, the invention is shown in a simplified manner for the sake of clarity. Similar parts are, where possible, marked with the same reference numbers in the figures.

DETAILED DESCRIPTION OF THE INVENTION [0019] Figure 1 shows in a highly simplified manner an injection moulding apparatus having an injection moulding machine 1 and a transfer device 2 for handling a carrier medium 3. The injection moulding machine 1 comprises a mould 4 having at least a first mould piece 5 and a second mould piece 6. The mould pieces 5,6 form a mould cavity 7 that defines the shape of the plastic product to be manufactured. At least one mould piece 5,6 is ar- ranged movable so that the mould 4 can be closed for moulding and opened to remove the plastic product from the mould 4. At least one mould piece 5,6 can be moved by means of an actuator 8, which can be a hydraulic cylinder, for instance. Further, the injection moulding machine 1 has a feeding device 9 that is connected to the mould cavity 7 through at least one feed channel 10, whereby the mould cavity 7 can be filled with melted plastic material. An oper- ating unit 11 can control the operation of the injection moulding machine 1.

Control connections are illustrated with dotted lines in Figure 1.

[0020] In decorating and coating plastic products to be injection moulded, it is possible to use the IMD (In-Mould Decoration) technique, in which a carrier medium 3 with a pre-printed pattern 19 is arranged into the mould cavity 7. When plastic material 21 is injected into the mould cavity 7, the pattern 19 on the surface of the carrier medium 3 fastens to the plastic product 20 to be moulded shown in Figure 2. The carrier medium 3 can for instance be made of polyester, on the surface of which the pattern 19 is made by some printing method. The pattern 19 can be ink or a colouring agent suitable for the purpose.

[0021] To handle the carrier medium 3, the injection moulding ma- chine 1 can have a transfer device 2, by means of which the carrier medium 3 can be transferred between the mould pieces 5,6. The transfer device 2 may comprise a first roll 12 and a second roll 13 that are rotated using a first motor 14 and a second motor 15. A control device 16 can control the operation of the transfer device 2.

[0022] The transfer device 2 can further comprise a first reading de- vice 17 that is arranged to recognize positioning marks 18 made on the carrier medium 3. With the positioning marks 18, the carrier medium 3 can be driven exactly to the correct position relative to the mould 4 so that the pattern 19 can be formed at the desired point of the plastic product 20. The first reading de- vice 17 can be connected to the control device 16 that controls the motors 14 and 15 on the basis of information received from the reading device 17.

[0023] Further, the injection moulding machine 1 of the invention is equipped with a second reading device 22 that is arranged to read quality marks 23 formed on the carrier medium 3. The reading device 22 is arranged to transmit identification information to the control device 16 of the transfer de- vice 2 which then controls the transfer of the carrier medium 3 in the direction of the arrow. If a defective pattern 19 is detected on the basis of the quality marks 23, the defective pattern is transferred past the mould cavity 7. Only the patterns 19 are used in injection moulding, which have been accepted in the check performed prior to the moulding. The patterns 19 can be marked with the quality mark 23, which in the check are found to meet predefined quality criteria, or alternatively the patterns 19 can be marked with the quality mark 23, which are found defective.

[0024] Figure 2 is a cross-sectional view of a plastic product 20 manufactured using the IMD technique, and a printed pattern 19 is integrated during moulding on the surface 24 of the visible side thereof. The surface 24 may also have one or more films 25 that protect the pattern 19 from wear and environmental effects. A moulded plastic material 21 forms the back surface of the plastic product 20.

[0025] Figure 3 shows from the side a section of an IMD film that comprises a carrier medium 3 and a pattern 19 fastened thereto by printing, for instance. The pattern 19 may be made of ink or some other suitable colouring agent. On top of the pattern 19, there may be one or more films 25. The pro- tective film 25 can for example be a reinforced film that forms a wear-resistant layer on top of the pattern 19.

[0026] Figure 4 shows a second carrier medium 3 having pieces 26, such as protective windows of mobile station displays, manufactured during earlier phases and attached consecutively thereto. Further, the injection moulding components 26 attached to the carrier medium 3 may be electronic components, antennas, fastening elements, or support pieces. Any injection moulding component can be used that can be attached to a carrier medium 3 and transported into the moulding cavity 7 of an injection moulding machine 1 by means of the carrier medium 3.

[0027] Figure 5 shows in a highly simplified manner a checking de- vice 27 of the invention, comprising at least a transfer device 28, checking unit 29, marking unit 30, and control unit 31. By means of the checking device 27, it is possible to perform a quality check, such as acceptance inspection or pre- injection moulding check, on the injection moulding components 33 attached to the carrier medium 3. The carrier medium 3 is driven by the transfer device 28 through the checking unit 29. The checking unit 29 may comprise one or more cameras 34 that film the injection moulding component 33 attached to the car- rier medium 3. The camera 34 is connected to an image processing device 35, in which the information obtained by the camera can be processed. The image processing device 35 can for instance be a computer running an image proc- essing program. The image processing device 35 can be connected to the control unit 31 of the checking device 27, which in turn can control the transfer device 28 and marking unit 30 on the basis of the received information. One or more quality criteria can be set in the control unit 31 to compare the informa- tion obtained from the checked injection moulding component 33 with.

[0028] The camera 34 can be used to examine the visually detect- able shapes, dimensions and colours of the injection moulding component 33.

It is also possible to detect with the camera 34 dust and other impurities in the injection moulding component 33, such as IMD pattern 19. The camera 34 can for instance be a high-resolution digital line camera. Filming can be done while the carrier medium 3 moves, or alternatively the carrier medium 3 can be stopped for filming. In the latter case, the camera 34 can be a conventional digital camera having sufficient accuracy. If necessary, it is also possible to use several cameras 34, of which at least some can also be arranged to moni- tor a quality-wise critical detail in the injection moulding component 33.

[0029] Instead of the camera 34 or in addition to it, the checking unit 29 may comprise one or more other measuring instruments for controlling the quality of the injection moulding components 33. The checking unit 29 can for instance be equipped with other optic measuring instruments or a laser scan- ner.

[0030] After the checking unit 29, the carrier medium 3 goes through the marking unit 30. The marking unit 30 comprises a marking device 36 for making a visually readable quality mark 23 on the carrier medium 3. If necessary, there may be several marking devices 36. The marking device 36 can be a printer that makes a predefined quality mark 23 with colour. The col- our marking printer can be an inkjet or laser printer, for instance. The marking device 36 can also be a laser that burns the quality mark 26 to the carrier me- dium 3. The marking device 36 can also be a perforating device suitable for perforating the carrier medium 3. A further possibility is that the marking device 36 is arranged to form the quality mark 26 such that it fastens to the carrier medium 3 a sticker or sprays paint on it. The type of the selected marking de- vice 36 depends for instance on whether the carrier medium 3 is stopped for the time of the check and marking of the injection moulding component 33, or whether it is a continuously operating apparatus, in which case the quality marking 26 is made"on the go." [0031] The transfer device 28 can comprise a first roll 37 and a sec- ond roll 38 that can be driven with a first motor 39 and a second motor 40. The control unit 31 is arranged to control the operation of the motors 39,40. The carrier medium 3 can be run continuously in the direction A from the first roll 37 to the second roll 38. Alternatively, the running can be cyclic. Further, the car- rier medium 3 can, if necessary, be run from the transfer device 28 in the direc- tion B from the second roll 38 to the first roll 37. It is also possible that the car- rier medium 3 is not moved by rolling, but the transfer device 28 is arranged to move the carrier medium 3 in some other manner. The carrier medium 3 can for instance be supported by means of suitable support elements either entirely or at least partly into a spread shape, in which case the transfer can be done by moving the support elements in the linear direction.

[0032] Further, the checking device 27 can comprise one or more cleaning units 32 for cleaning the injection moulding components 33 attached to the carrier medium 3. The cleaning unit 32 can comprise one or more clean- ing devices 41. The cleaning device 41 can be mechanical, in which case the cleaning can be based on brushing, liquid spraying, gas blowing, or a combina- tion thereof. Further, it is possible to use an electric cleaning device, such as a plasma cleaner or ionization apparatus. Yet further, it is possible that the cleaning device is arranged to chemically clean the injection moulding compo- nents 33. In chemical cleaning, the injection moulding components 33 can be treated with a suitable reactive liquid, for instance. The cleaning unit 32 can also comprise a combination of the above-mentioned solutions. The essential thing is, however, that the cleaning unit 32 is able to remove impurities at- tached to the injection moulding components 33 without damaging the compo- nent 33.

[0033] It is possible to arrange the carrier medium 3 first on the second roll 38 and run it in the direction B through the cleaning unit 32 to the first roll 37. After this, normal cleaning, checking, and marking can be per- formed in the direction A. Further, it is possible to reverse the carrier medium 3 and, if necessary, repeat the cleaning, if impurities are still found during the check.

[0034] Further, there may be a counter 43 arranged to the checking device 27 to count the ratio of accepted injection moulding components to the rejected components. If the batch being checked contains more rejected com- ponents than allowed by a predefined ratio, the entire batch can be rejected and not transferred at all to the injection moulding machine 1. This arrange- ment saves the operating time of the injection moulding machine 1.

[0035] Figure 6 shows a carrier medium 3 from the top. In this case, an IMD pattern 19 is printed on the surface of the carrier medium 3. The quality mark 23 can be the colour mark 23a shown in Figure 6 and made with a printer or paint sprayer. Further, the quality mark 23 can in some cases also be a sticker 23b fastened to the carrier medium 3. The quality mark 23 can be a mark that is intended merely for identification, i. e. it is of the yes/no type. Alter- naively the quality mark 23 may comprise readable information, such as a bar code. It should also be noted that the quality mark 23 can be arranged to indi- cate alternatively either an accepted good-quality injection moulding compo- nent or a rejected component.

[0036] The solution shown in Figure 7 differs from the solution of Figure 6 only by the quality mark 23. As shown by Figure 7, the quality mark 23 can be an opening 23c or a notch 23d. Quality marks 23 of this type can for instance be made with a mechanical perforation tool or by beam processing.

[0037] Figure 8 shows an injection moulding machine 1 having a checking device 27 of the invention arranged thereto. The transfer device 2 of the injection moulding machine 1 is then arranged to transfer the carrier me- dium 3, and no transfer device is required for the checking device 27. The in- jection moulding components 33 attached to the carrier medium 3 can be cleaned in a cleaning unit 32 belonging to the checking device 27, after which the quality of the components 33 is checked in the checking unit 29, and the quality marking is made in the marking unit 30. After this, the carrier medium 3 continues on in the direction C toward a moulding unit 42. Before the compo- nent 33 enters between the mould pieces 5,6, the reading device 22 checks whether the component 33 was accepted in the preceding quality check. If the component 33 was rejected, the carrier medium 3 is driven on until the reading device 22 detects the next accepted component 33. The accepted component 33 is arranged between the mould pieces 5,6, the moulding is performed, the mould pieces 5,6 are opened, the plastic product is removed, and the carrier medium 3 is again transferred onward.

[0038] The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the claims.