IES20010218A2

IES20010218A2 - A method of testing co-extruded panels

Info

Publication number: IES20010218A2
Application number: IE20010218A
Authority: IE
Inventors: James Mcgee; Denis Collins; Roy Lowe
Original assignee: Athlone Extrusions Dev Ltd
Priority date: 2000-03-09
Filing date: 2001-03-08
Publication date: 2001-09-19
Also published as: GB0105826D0; IE20010217A1; GB2360092B; GB2360092A

Abstract

Co-extruded sheet samples (12) for testing are cut to a width of approximately 100 mm across the complete width of the extruded sheet. The edge of the sample (12) to be viewed is first planed to a smooth finish and the sample is placed in position on a viewing platform of a stand (11). Using horizontal and vertical adjusting knobs (22,24) in conjunction with a focusing ring of a microscope unit, a magnified image of the sample edge at a particular point is obtained on a monitor (15). The brightness of the image can be altered by changing the light intensity on a light source unit (7). When a focused image of the sample edge cross section has been obtained, a vertical adjustment knob (24) is rotated until the cross-hair pattern is lined up with the image of the top of the sample as viewed on the monitor (15). This reading on the digital readout unit is zeroed. The cross-hair pattern is then lined up with the bottom of the top layer and the thickness of the layer can be read directly from a digital readout (17). Subsequent layers may be measured in a similar manner. Layer distribution is determined by taking similar measurements across the width of the sheet by moving the carriage (25) along tracks (26) to a desired measuring position.

Description

“A METHOD OF TESTING” Introduction The invention relates to a method of testing layer distribution in a co-extruded panel. The invention also relates to an apparatus used in the method of testing.

Baths for domestic use and similar products are usually manufactured either from moulded ceramic materials, cast iron or cast acrylic sheet. Cast acrylic sheet is widely used as it can be readily thermoformed into a bath at lower cost, of lighter weight, with greater design flexibility and with lower thermal conductivity than other materials.

The term “acrylic” used in this context refers to poly (methyl methacrylate) (PMMA) materials. For the manufacture of acrylic sheet, a hulk polymerisation or cast process is used during which high molecular weights are achieved.

Relative to most other plastics materials, such acrylics are particularly suitable for bath manufacture as they have excellent scratch resistance and a high gloss surface finish. However, the manufacture of cast acrylic is both a difficult and lengthy operation so that the sheet material is consequently expensive. A co-extrusion production process overcomes some of these difficulties.

There is however a need for a method and apparatus for testing that the co25 extruded product will have a high quality surface with optimum performance characteristics.

OPEN TO PUBLIC INSPECTOR UNDER SECTION 28 AND RULE 23 JNL ΓΤοΤ,ο ι IE010218 ATHL04/C/IES -2Statements of Invention According to the invention, there is provided a method of testing layer distribution in a co-extruded panel comprising the steps of:(a) cutting a sample of the panel to a desired size; (b) mounting the sample with an edge of the panel exposed; (c) moving a camera relative to the sample to a predetermined location along the length of the sample; (d) focusing the camera on the interface between the layers of the sample at the predetermined location; (e) generating a reference level at the interface; and (f) moving the camera relative to the panel sample from the reference level to measure the thickness of a layer from the reference level.

In one embodiment of the invention, the method includes the steps of;(g) moving the camera relative to the panel sample to another predetermined location along the length of the panel sample; (h) repeating steps (d) to (f); and (i) repeating steps (c) to (h) across the width of the sample to determine the thickness of the layer across the panel.

IE010218 ATHL04/C/IES -3Preferably, after cutting of the sample, an edge of the sample to be analysed is smoothed.

In a preferred arrangement, the sample is fixed in position and the camera is moved relative to the sample.

The invention also provides apparatus for testing layer distribution in a coextruded panel by a method of the invention, the apparatus comprising: a stand for supporting a cut length of panel sample with an edge of the sample exposed; a camera, the camera being movable relative to the sample and being focussed on an interface between the layers of the sample at a predetermined location; and means for generating a reference level at the interface.

Preferably the apparatus comprises releasable clamp means for holding a sample in a fixed position in the stand.

In a preferred embodiment of the invention the camera is mounted for controlled movement in a number of directions relative to a test sample.

Ideally the camera includes a microscope for close-up focussing on the layer distribution of a sample. Preferably the microscope comprises a light ring to provide illumination of a sample.

IE010218 ATHL04ZC/IES -4Brief Description of the Drawings The invention will be more clearly understood from the following description thereof, given by way of example only , in which;Fig. 1 is a diagrammatic perspective view of a testing apparatus of the invention used in the testing method of the invention; Fig. 2 is a perspective view of the apparatus, in use; Fig. 3 is a side view of the testing apparatus of Fig. 2; and Fig. 4 is a view of an image generated by the testing apparatus of Figs. 2 and 3.

Detailed Description Referring to the drawings, there is illustrated a testing apparatus used for measuring the layer distribution in a co-extruded product such as a twin layer sheet or panel 1 as illustrated in Fig. 4 and comprising a lower layer 2 of acrylonitrile-butadiene-styrene (ABS) and an outer or surface layer 3 of acrylic material. Such sheets may be used, for example, for thermoforming baths and the like.

The testing apparatus 10 comprises a stand 11 with a viewing platform 14 for supporting a sheet sample 12 which is held in a fixed position on the stand 11 by releasable clamps 13 which are shown in the released position in Fig. 2 and 3. A microscope 5 is fitted with a light ring 6 which is fed from a light source 7 to provide even illumination of the sample 12. The microscope 5 is fitted to a closed circuit television camera 8 which is connected to a monitor 15. A line generator IE010218 ATHL04/C/IES -516 provides a reference cross-hair pattern in the monitor 15 and a digital readout unit 17 provides a readout of the layer thickness as determined on testing.

The camera 8 is mounted for movement in four directions to accurately position the camera relative to the test sample. The camera 8 is mounted on a table 20 which in turn is mounted for movement in the direction of the arrows A on an intermediate support 21 by operating a first adjusting knob 22. The intermediate support 21 is in turn mounted on a main support 23 for movement in the direction ofthe arrows B by operating a second adjusting knob 24. The support 23 extends upwardly from a carriage 25 which runs along longitudinal tracks 26 in the direction of the arrows C.

Co-extruded sheet samples for testing are cut to a width of approximately 100 mm across the complete width of the extruded sheet. The edge of the sample 12 to be viewed is first planed to a smooth finish and the sample is placed in position on the viewing platform of the stand 11. Using the horizontal and vertical adjusting knobs 22, 24, in conjunction with the focusing ring of the microscope unit, a magnified image of the sample edge at a particular point is obtained on the monitor 15. The brightness of the image can be altered by changing the light intensity on the light source unit 7.

When a focused image of the sample edge cross section has been obtained, the vertical adjustment knob 24 is rotated until the cross-hair pattern is lined up with the image of the top of the sample as viewed on the monitor 15. This reading on the digital readout unit is zeroed. The cross-hair pattern is then lined up with the bottom of the top layer and the thickness of the layer can be read directly from the digital readout 17. Subsequent layers may be measured in a similar manner.

Layer distribution is determined by taking similar measurements across the width of the sheet by moving the carriage 25 along the tracks 26 to a desired measuring IEO1O218 ATHL04/C/IES -6position. Depending on the results of the test the production process may be modified or adjusted.

The invention provides a highly efficient method of measuring layer distribution 5 in co-extruded sheets.

The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims

1. A method of testing layer distribution in a co-extruded panel comprising the steps of :(a) cutting a sample of the panel to a desired size; (b) mounting the sample with an edge of the panel exposed; (c) moving a camera relative to the sample to a predetermined location along the length of the sample; (d) focusing the camera on the interface between the layers of the sample at the predetermined location; (e) generating a reference level at the interface; and (f) moving the camera relative to the panel sample from the reference level to measure the thickness of a layer from the reference level.

2. A method as claimed in claim 1, including the steps of:(g) moving the camera relative to the panel sample to another predetermined location along the length of the panel sample; (h) repeating steps (d) to (f); and (i) repeating steps (c) to (h) across the width of the sample to determine the thickness of the layer across the panel. IE010218 ATHL04/C/IES -8A method as claimed in claim 1 or 2, wherein after cutting of the sample, an edge of the sample to be analysed is smoothed, preferably the sample is fixed in position and the camera is moved relative to the sample. Apparatus for testing layer distribution in a co-extruded panel by a method as claimed in any preceding claim, the apparatus comprising: a stand for supporting a cut length of panel sample with an edge of the sample exposed; a camera, the camera being movable relative to the sample and being focussed on an interface between the layers of the sample at a predetermined location; and means for generating a reference level at the interface. Apparatus as claimed in claim 4 comprising releasable clamp means for holding a sample in a fixed position in the stand, preferably the camera is mounted for controlled movement in a number of directions relative to a test sample, preferably the camera comprises a microscope for close-up focussing on the layer distribution of a sample, preferably the microscope comprises a light ring to provide illumination of a sample.