TRIMMING OF CONTOURED POLYMERIC PANELS

Abstract

A method for trimming a thermoformed panel comprises the steps of opening a thermoforming mold to reveal the thermoformed panel, attaching a robotic arm holding means to the thermoformed panel, removing the thermoformed panel from the thermoforming mold by the robotic arm holding means, repositioning the robotic arm holding means over a trimming table, the table comprising a cutting router affixed to the table bed, moving the robotic arm holding means relative to the cutting router in directions to trim all edges of the panel to required panel dimensions, moving the robotic arm and trimmed panel to a panel collection station, and depositing the trimmed panel at the collection station, wherein the directional movement of the robotic arm is controlled by input from 3-dimensional drawing software of the final shape of the thermoformed panel, and wherein the thermoformed panel is of a polymeric material.

Claims

1. A method for trimming a thermoformed panel comprises the steps of opening a thermoforming mold to reveal the thermoformed panel, attaching a robotic arm holding means to the thermoformed panel, removing the thermoformed panel from the thermoforming mold by the robotic arm holding means, repositioning the robotic arm holding means over a trimming table, the table comprising a cutting router affixed to the table bed, moving the robotic arm holding means relative to the cutting router in directions to trim all edges of the panel to required panel dimensions, moving the robotic arm and trimmed panel to a panel collection station, and depositing the trimmed panel at the collection station, wherein the directional movement of the robotic arm is controlled by input from 3-dimensional drawing software of the final shape of the thermoformed panel, and wherein the thermoformed panel is of a polymeric material.

2. The method of claim 1 further comprising an optional step of the robotic arm holding means positioning the panel at a drilling station and moving the panel such that holes are drilled at desired positions either partially or fully through the panel.

3. The trimmed panel of claim 1 wherein the panel is a double curvature panel.

4. The trimmed panel of claim 1 wherein the polymeric material of the panel comprises polyethylene or polypropylene or unfilled polymethyl methacrylate, filled polymethyl methacrylate or unsaturated polyester.

5. The robotic arm of claim 1 wherein the robotic arm holding means are suction cups.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a block diagram of a process for making a contoured polymeric panel.

[0009] FIG. 2 shows exemplary trimmed edge shapes.

DETAILED DESCRIPTION OF THE INVENTION

[0010] Panel Composition

[0011] Any thermoformable polymeric material may be used for the panel. In some embodiments the polymeric material is polyethylene (PE) or polypropylene (PP) or unfilled polymethyl methacrylate (uPMMA), filled polymethyl methacrylate (fPMMA) or unsaturated polyester. An exemplary filled polymethyl methacrylate is Corian® which is available from DuPont Safety and Construction Inc., Wilmington, Del.

Panel Thermoforming

[0012] Preferably, the thermoformed panel of this invention is a contoured panel, i.e., it is not flat. Exemplary contoured panels are single or double curvature panels. By single curvature is meant that the panel curves in only one direction, either upwards or downwards. By double curvature is meant that the panel curves in two directions both downwards and upwards.

[0013] FIG. 1 provides an overview of a process for making a contoured polymeric panel such as a double curvature panel.

[0014] The panel feedstock is a flat sheet of a necessary length, width and thickness such that finished panel shape and dimensions can be achieved. The shape of the panel feedstock will vary depending on the shape of the finished panel. Exemplary feedstock panel shapes are triangular, square, rectangular, pentagonal, hexagonal etc.

[0015] In step 1, the panel feedstock is placed in heating oven to preheat the panel and make the panel pliable. The temperature of the oven and dwell time of the panel in the oven will vary depending on the panel composition and thickness. Typical preheating temperatures are from 100 to 170° C. and dwell times from 5 to 15 minutes.

[0016] In step 2, the lower surface of the panel is placed on the lower half of a thermoforming vacuum molding tool and the upper half of the tool then positioned over the upper surface of the panel to close the tool. Any suitable vacuum molding tool may be used, for example an adaptive surface mold such a technique being well known in the plastic molding art. The panel remains in the tool for enough time to allow the panel to fully conform to the desired shape, this time being determined by the panel composition, panel thickness and type of tool. Typical processing conditions for this step are pressures of from 0.5-1.5 bar, preferably about 0.8 bar and press times of from 5-30 minutes. After the desired dwell time in the mold, the mold is cooled such that the temperature of the panel is well below its glass transition temperature.

[0017] In step 3, after molding has been completed, the upper half of the tool is removed to reveal the contoured thermoformed panel. The panel is then removed from the mold. This removal process is achieved by attaching a robotic arm holding means to the thermoformed panel and then removing the panel from the mold by the robotic arm holding means. In one embodiment, the robotic arm holding means comprises suction cups located at the extremity of the robotic arm.

[0018] In step 4, the robotic arm holding means repositions the panel over a trimming table, the table comprising a cutting router affixed to the table bed. The robotic arm holding means moves the panel relative to the cutting router in directions to trim all edges of the panel to required panel dimensions. The directional movement of the robotic arm is controlled by input from 3-dimensional drawing software of the final shape of the thermoformed panel, Panel edges may be straight or curved (chamfered) as shown by examples in FIG. 2. In FIG. 2, 2a is a square edge trim and 2b and 2c curved edge trims.

[0019] In step 5, the robotic arm moves the trimmed panel to a panel collection station and deposits the trimmed panel at the collection station

[0020] In an optional further embodiment, the robotic arm holding means may position the panel at a drilling station and move the panel such that holes are drilled at desired positions either partially or fully through the panel. This step may be completed before or after the edge trimming operation of step 4.

EXAMPLES

[0021] Panel composition, dimensions and processing conditions are shown in Table 1. A number of different conditions was tried for some of the panels. Trimmed panel edge quality was a visual assessment. If the trimmed edge was smooth the quality was deemed to be good.

TABLE-US-00001 TABLE 1 Step 1 Step 2 Preheating Thermoforming Trimmed Feedstock Panel Time (mins) Time (mins) Panel Panel Dimensions Panel Curvature and Temperature and Pressure Edge Composition (mm) (Single or Double) (° C.) (bar) Quality PE 900*550*12 Double 10 min @ 10-20 min @ Good 120° C. 0.9 bar PP 900*550*12 Double 12 min @ 10-20 min @ Good 140° C. 0.9 bar uPMMA 900*550*12 Double 10-15 @ 15-25 min @ Good 140° C. 0.9 bar fPMMA 900*550*12 Double 15 min @ 15-25 min @ Good (Corian ®) 145-165° C. 0.9 bar

Utility

[0022] This method of trimming highly contoured panels finds utility in external cladding panels, internal cladding panels, furniture, sculptures and other applications. The trimmed edges are of sufficient quality that adjacent panels may be adhesively bonded at the edges.

[0023] The panels may be fixed to the article structure by screws, bolts, pins, adhesives, tapes or other fixing means.