Method for the optimal alignment of veneer sheets at a lay-up station

Abstract

The invention relates to a method for the optimal positioning of veneer sheets at a lay-up station, wherein the veneer sheets are attached for a veneer assembly composed of veneer sheets glued on top of each other. The method comprises determining an optimal position for each veneer sheet and a location for virtual alignment edges and laying up the veneer sheets as positioned in accordance with the virtual alignment edges, for a veneer assembly.

Claims

1. A method for the optimal positioning of veneer sheets at a lay-up station, wherein the veneer sheets are attached for a veneer assembly composed of veneer sheets glued on top of each other, wherein the method comprises: determining an optimal position for each veneer sheet in the veneer assembly; determining perpendicularly-arranged virtual alignment edges individually for each veneer sheet, with respect to the optimal position thereof, at least the virtual alignment edges being determined separately of the real veneer edges of each individual veneer sheet, without the virtual alignment edges extending outwardly of the respective real veneer edges; and positioning the veneer sheets with respect to each other such that the veneer sheets are aligned in accordance with the respective virtual alignment edges thereof, during lay-up of the veneer sheets to form the veneer assembly.

2. A method as set forth in claim 1, wherein determining the perpendicularly-arranged virtual alignment edges for each veneer sheet further comprises: determining the perpendicularly-arranged virtual alignment edges for each veneer sheet and a true location of the veneer sheet at a lay-up station on the basis of a camera image; and positioning the veneer sheets in accordance with the virtual alignment edges and with respect to the optimal position to form the veneer assembly by means of positioning elements in response to obtained image data.

3. A method as set forth in claim 1, wherein determining the perpendicularly-arranged virtual alignment edges for each veneer sheet further comprises: determining the perpendicularly-arranged virtual alignment edges for each veneer sheet and a true location of the veneer sheet at a lay-up station on the basis of a camera image; and positioning the veneer sheets in accordance with the virtual alignment edges and with respect to the optimal position to form the veneer assembly by means of positioning elements in response to obtained true location data.

4. A method as set forth in claim 1, further comprising trimming the veneer assembly, after laying up the veneer sheets, according to at least one of the virtual alignment edges, such that the at least one of the virtual alignment edges becomes a real alignment edge of the veneer assembly.

5. A method as set forth in claim 4, further comprising trimming all edges of the veneer assembly after laying up the veneer sheets.

6. A method as set forth in claim 1, further comprising mechanically marking the virtual alignment edges by making alignment holes or indications in each respective veneer sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described more closely with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a traditional lay-up practice in a schematic view of principle,

(3) FIG. 2 shows in a schematic view of principle one lay-up practice implemented according to the present invention,

(4) FIG. 3 shows in a schematic view of principle a second lay-up practice implemented according to the present invention,

(5) FIG. 4 shows a veneer assembly trimming operation in a schematic view of principle, and

(6) FIG. 5 shows in a schematic view an arrangement for mechanically marking the virtual alignment edges by making alignment holes according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 depicts a traditional way of laying up veneer sheets, wherein veneer sheets 1, l′, 1″ are aligned against stationary fences 13, 14 set in a perpendicular relationship with each other. This method has been in active service for a long time, but it has a problem in the sense that the veneers may end up in an undesirable position. In FIG. 1, the uppermost veneer 1 is shown in such incorrect position, the result of which is that the veneers must be sawn to a slight oversize in order to ensure a correct size for the veneer assembly after the edge sawing operation.

(8) FIG. 2 shows a method of the invention, in which the laying up of veneers is conducted manually by using laser lines to indicate the location of a virtual alignment edge. Laser pointers 3, 4 produce two laser lines perpendicular to each other, which enable the operator to align a veneer 1 arriving at the lay-up operation on top of a most recently laid-up veneer 2 in an optimal manner. The operator aligns the veneer 1 in consideration of possible defects present in the leading edge closest to himself for making maximum use of the veneer in terms of its surface area.

(9) FIG. 3 illustrates a second lay-up practice of the invention, in which the veneers are positioned automatically. In this embodiment, the production line is provided with a camera 8 placed upstream of a lay-up station, said camera checking the dimensions of a veneer and calculating whether it is sufficient for a panel, and concluding which is the optimal position to set it. A veneer with insufficient dimensions is rejected from the assembly. When a veneer conveyed by belts arrives at the lay-up station, it will be captured by grippers 5, 5′ whose position at the end of support brackets 6, 6′ is precisely known and, at the same time, a second camera 7 is used for checking a true position of the veneer, followed by calculating an alignment position for the veneer. This enables determining precisely the position of a veneer in the coordinate system of a robot. After this, the veneer is conveyed to a desired lay-up point and lowered down. In the presented embodiment, the veneer is lowered on top of a panel 9 by means of the support brackets 6, 6′. Then, the panel 9 is moved away from under the veneer, whereby one end of the veneer descends and attaches to the stack with adhesive. This is followed by withdrawing the support brackets 6, 6′.

(10) One alternative to the foregoing mode of operation is such that, as a veneer conveyed by belts arrives at a lay-up station, said veneer can be dropped onto a panel tablet traveling forward at a speed equal to that of the veneer, or onto some other veneer-receiving carrier. After the tablet has advanced across a halfway point, the grippers are able to take hold of the veneer, followed by performing necessary straightening operations, and then the tablet or another carrier can be pulled away from under for taking up the next veneer.

(11) Once completed, the veneer assembly is conveyed for a trimming operation e.g. to an edge sawing apparatus, which is used for sawing the veneer assembly to provide it with an edge consistent with a virtual alignment edge and a desired amount of tolerance. One alignment edge 10′ is preferably the edge which is leading in the advancing direction of a veneer upon its arrival at the lay-up station, and a second alignment edge 10 is the edge perpendicular thereto. From the lay-up station, the veneer assemblies depart preferably in a direction perpendicular to the original advancing direction, such that the alignment edge 10′ lies in a parallel relationship with the veneer assembly's advancing direction and can be sawn without stopping the veneer assembly. Preferably, the edge opposite to the alignment edge is also sawn at the same time by driving the veneer assembly across saw blades 12′, 12 set at a desired crosswise distance from each other. The short sides perpendicular to the alignment edge are trimmed in such a way that the conveyor can be stopped e.g. on the basis of a pulse sensor reading, or such sides can be trimmed while the action is going on by using a so-called flying saw or a saw which advances in the same direction as the veneer assembly at the same speed while having its blade advancing across the veneer assembly. During the trimming operation, the veneer assembly is held e.g. by a belt 11.

(12) A virtual edge can also be marked with some prior known method, which marking remains fixed in various operations of the process. Such a method may comprise e.g. marking a virtual edge by means of a perforation or another mechanical indication (see, e.g., element 21 or 22 in FIG. 5). The perforation can be made e.g. by drilling or punching a required number of marking holes or recesses in a veneer sheet. The marking can also be made e.g. with an ink jet printer or some other instrument (see, e.g., element 20 in FIG. 5) producing a permanent imprint.