From CAD to airbag

A new tool that generates motion control paths directly from CAD drawings is helping airbag manufacturer Automotive Safety Components International ramp up production for the fast-growing curtain-bag market.

A new tool that generates motion control paths directly from CAD drawings is helping airbag manufacturer Automotive Safety Components International (ASCI) ramp up production for the fast-growing curtain-bag market.

To protect automobile occupants in roll-over conditions, the curtain bags that cover the side window areas must stay inflated for longer than a standard airbag. ASCI achieves this by adding glue to the seam stitching.

But with demand for curtain safety accessories beginning to escalate, ASCI initiated a development project to automate the gluing process. Developing the applicator mechanism was relatively easy, but ASCI also wanted the machine to operate directly from the CAD drawings of airbags provided by automobile manufacturers.

Motion control supplier Baldor provided a solution in the form of a toolkit called MintNC. This PC-based environment imports information in industry-standard CAD formats – including G-code, HPGL and DXF – and generates the required real-time motion commands. In this instance, the package imports an airbag drawing, runs an optimisation script to turn the drawing lines into a time- and movement-efficient path, and then streams the resulting motion commands to the motion controller.

The real-time motion control system that controls glue application, consists of a NextMovePCI motion controller card plugged into the expansion bus of the host PC, connected to three FlexDrives and three BSM servo motors that control X-Y-Z axis movement.

In operation, two laser-cut halves of an airbag – one on top of the other – move into the machine, and the Z axis comes down and vacuum-lifts one half into the air. The glue gun mounted on the X-Y axes then moves in and deposits a 4mm-wide bead of glue around the edge of the bottom half.

The Z axis then drops back down and compresses the pieces together to create the join, and the glued bag moves along to the sewing stage of the process.

The new machine is a prototype, and performs a dual role for ASCI. It provides the means to automate the sampling process, allowing curtain bags to be produced automatically from a design drawing – providing a service that allows ASCI’s automobile customers to evaluate and optimise their designs extremely rapidly. It also speeds production, allowing the gluing process for these very large airbags to be performed in typically seven minutes.

This provides an efficient platform for both the manufacturing quantities required today, and the expected progression of curtain bag technology from the luxury to the mass-market vehicle sector.

ASCI is now developing the machine concept to provide its sister production sites around the world with automation for mass-volume production.

Baldor provided the motion control subsystem used in the machine, and worked on-site with ASCI to develop and optimise the control software.

The software for the real-time motion control system was simplified by means of multi-tasking facilities built into the MintMT motion language used in application. This allowed the control program to be broken down into a number of small individual tasks, such as homing the axes, controlling Z axis movement, controlling the glue-laying X-Y axes, and collision detection algorithms and other tasks associated with machine safety. Some of these tasks run in the background, while others are called as required by MintNC’s event-driven scripting environment. The human-machine interface to the machine was created as part of the front-end MintNC process.

The entire motion control subsystem was produced and optimised by Baldor in around a month. The overall machine, was developed and commissioned by ASCI in just over four months.

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