Plasma Bonding Process

Dorset based inrekor Ltd was developing an innovative structural sandwich panel technology when they met with LG Motion to enhance the process, increase product range and improve throughput.

The Product

LG Motion Plasma Bonding System
With far reaching potential for lightweight and low-cost structural frame applications across all industries, particularly in vehicle chassis development, the high strength to weight ratio inrekor® panel can be applied to small and large scale manufacture with minimal tooling investment.

These panels, based upon an ARPRO® core material with external layers of steel or aluminium, combined with a patented process guarantees exceptional rigidity. The data suggests the new panel offers geometric strength of up to ten times that of traditional honeycomb panels with considerable advantages in cost, design flexibility and ease of manufacture. The finished panels are assembled and bonded to form a final three-dimensional structure such as a complete chassis floor-plan with all required design features incorporated.

With limitless design possibilities and the production-volume flexibility of the inrekor system, the external metal surfaces for two-dimensional panels are typically manufactured using the latest water jet or laser cutting methods; for high volume production, punch-pressing these skins can be extremely cost- effective.

The ARPRO cores can be supplied in flat sheet form or specially moulded for large scale production. inrekor also supply fully assembled three-dimensional assemblies or ‘flat-pack’ panels for customers to assemble on-site. The technology is fully transferable for Tier One automotive manufacturers to use directly for high volume production.

The Challenge

The critical process is joining these materials together to ensure optimum peel and tear strength. inrekor developed an plasma bonding technique. The atmospheric pressure plasma treatment activates the surfaces to be bonded prior to the application of the adhesives and the lamination is completed using a separate high pressure cold press.

This successful development then evolved into an automated process which involved LG Motion designing and supplying large frame gantry positioning system.

As part of the requirement, inrekor requested that flexibility was built into its design in terms of both motion control and mechanics to allow the machine to be adapted, if required, to suit the diverse production levels that the sandwich panel system offers.

The Solution

The system supplied was free-standing and incorporated the bed for the panels to be supported on, the XYZ Gantry system and a motion controller. The motorised gantry supports and positions the plasma head over the panel bonding area where flat sheets of core or skin material are supported on a wire-mesh bed. The vertical height of the plasma head is manually operated Z-axis stage and panels up to 3m x 2m may be processed using a simple PC programmed raster scan where the width of the plasma beam is tracked over the entire surface to be treated.

plasma head above an ARPRO® panel core

To meet the speed, cost and performance requirements, belt-driven linear actuators were selected for the XY motion. The lower X-axis is comprised of two parallel coupled actuators to prevent axis crabbing and supports a single Y-axis linear actuator for the 2 metre span. Motorised axes are open loop stepper motor driven, with in-line gearboxes for increased torque output. The motors are fitted with rear shaft handles that allow operators to manually move the plasma head if required and also assist greatly in development. Both X and Y axes include datum switches for homing the gantry before the automated scanning process begins, over-travel limit switches for safety and a cable management system. A simple stepper motor control and drive system allows the operator to set-up individual axis sequential moves using a basic like programming language.

The Result

inrekor were delighted! By working closely with inrekor Ltd from the outset of the project, the LG Motion design and application engineers delivered and installed successfully.

Within in the original brief it was made clear that future mechanical modifications should be possible and relatively straightforward. Possible upgrades included adding rotary encoders to the stepper motors to provide ‘position verification’ for improved position control, or to replace steppers with servomotors to allow higher scanning speeds. Control upgrades could be met with higher level motion controls that would permit compound X and Y moves for contoured positioning of the plasma head with the possibility to include GUI programming of complex shapes using customer supplied CAD data. Using controller I/O the plasma process could also be extended to control the plasma source as well as the Z-axis and include adhesive dispensing

Further advancing and speeding the entire process.

All of this was met by taking a modular approach to the solution and certainly assisted in meeting budgets and potentially increasing the useful life of the system. The photographs show a typical inrekor chassis and the LG Motion gantry showing the plasma head above an ARPRO® panel core.

typical inrekor chassis

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