Compact Laser Machine Enables Cost Effective Panel Fabrication

Coherent OmniBeam 250

Several individual panels are typically produced on a single substrate and then cut apart using the Coherent OmniBeam 250.





September 20, 2012

By Frank Gaebler, Coherent

Bradley Nameplate is a US based manufacturer of nameplates, signage and other products fabricated from plastics, films and thin metals. A substantial part of the company’s business is instrument panel overlays, typically fabricated using thin polycarbonate. There is an increasing demand in this market for panels with small, fine features, such as arrays of ventilation holes. These small features cannot be readily produced in polycarbonate of this thickness using traditional means, such as a die cutter, a router or a knife cutter. This article explores how Bradley Nameplate has implemented a cost-effective laser cutter that enables volume production of these types of fine features in polycarbonate.

Fabricating Overlays
Overlays are plastic panels for electronic equipment that are printed with graphics, and which contain various holes for ventilation, connectors and controls (buttons, switches, etc.). These are supplied to manufacturers of instrumentation who adhere them to a metal chassis that contains all the electronic components of their product.

Bradley Nameplate typically utilizes polycarbonate sheets in the 0.25 mm to 0.5 mm thickness range as the substrate for these overlays. This material is favored because it is dimensionally stable, easy to screen print, and readily cut using a variety of techniques, including die cutting, knife cutting and laser cutting. The company’s typical production runs are in the 500 to 1000 quantity range.

These polycarbonate sheets are about 300 mm by 600 mm in size. This can fit several individual panels, which are generally around 50 mm to 75 mm high by 460 mm wide (for a standard 48.26 cm wide rack mount piece of instrumentation). The process starts with screen printing of all the graphics on the panel in mirror reversed orientation. Printing may utilize up to eight colors, and transparent inks are used for areas on the panel which will become “windows” through which a display or indicator light is viewed.

Next, any areas which correspond to the windows in the panel are cut out from the adhesive sheet. This is done because the adhesive would obscure the view through the polycarbonate to the underlying display. The adhesive contains backing layers on both sides. After cutting, one backing layer is removed, and the adhesive sheet is then aligned with and adhered to the printed side of the panel substrate. The second backing layer of the adhesive is removed by the customer when they are ready to place the panel on their chassis.

The printed panel with adhesive is then cut to make whatever holes are required for ventilation, connectors and controls. Additionally, the individual panels are cut apart, so that the final result is a printed panel, cut to finished size, with adhesive and a backing.

Cutting Options
For many years, Bradley Nameplate relied primarily on steel rule dies to cut both adhesive sheets and plastic panels. They have also used digital knife cutting systems. However, the company moved to a laser based, digital cutting tool (the Coherent OmniBeam 250) for many of the tasks that formerly employed these other technologies.

The laser is significantly more economical than die cutting for production runs of less than 1000 pieces because it eliminates tooling costs. Also, the laser can cut finer features. This is important because there is an increasing demand for panels with large numbers of small features, such as ventilation holes and LED indicator windows. In addition, the laser can more readily cut thicker (over 0.5 mm) plastic panels with greater accuracy than die cutting. Customer lead time is also reduced because cutting parameters for a new job can be set rapidly for the Coherent OmniBeam 250. In contrast, procuring a new die takes days or weeks.

When compared with a digital knife cutter, there are some tradeoffs. The biggest disadvantage of laser cutting is that it can cause some discoloration (browning) when cutting polycarbonate in particular (this isn’t true of some other plastics, such as acrylics). This problem can largely be eliminated by applying a masking film (e.g. Signmask) to the side of the plastic facing the incoming laser beam. On the other hand, knife cutting can’t readily be used for substrates that are over 0.25 mm thick. Also, the Coherent OmniBeam 250 is much faster when there is a significant amount of detail in the cutting pattern.

Bradley Nameplate also uses the laser exclusively for cutting adhesive sheets. This is because these can only be cut singly with a knife cutter. In contrast, five or more of these sheets can be stacked and laser cut in a single operation.

In conclusion, the use of a laser cutter at Bradley Nameplate has eliminated their procurement expenses for dies, and eliminated a full time position for a die cut operator. Because of this, the company achieved a payback on their capital expense for the equipment within the first year of operation, even though they only ran it for about two hours a day. In addition to fabricating instrument panels, the company has found the laser system to be a flexible tool, applicable to a wide variety of other materials, including thin films, paper, wood and other plastics.

Figures:
Coherent OmniBeam 250
Instrument panel overlays are produced on polycarbonate, and may contain numerous small holes and clear windows.

Coherent OmniBeam 250
Several individual panels are typically produced on a single substrate and then cut apart using the Coherent OmniBeam 250.

Coherent OmniBeam 250
The laser system is a quicker way to process adhesive sheets than a digital knife cutter, because several can be stacked and cut at one time.

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