An automotive client required a metal component of exceptional strength and pressure resistance. See how ESI met the challenge.

The versatility and precision of specialized metal stamping creates countless components that keep critical safety systems functioning every day. The Knee Airbag Grommet that ESI manufactured was no exception.

About the Part

knee-airbag-grommet-automotiveGrommets are generally made of metal, plastic, or rubber, depending upon the application. They need to prevent critical tearing or abrasion in pierced material, covering the edges of the piercing and protecting it from wire, cable, or line being routed through it.

In the case of the Knee Airbag Grommet, the metal component needed to be specially crafted for the automotive industry. It demanded exceptional strength and pressure resistance in order to fit and protect airbags in Ford Transit Vans.

The grommet, measuring 34mm x 18mm x 8mm draw, and was engineered to a 0.1mm tolerance. The depth of this draw falls at the upper limit of what a conventional stamping processes can create, and had to be developed to suit the product based upon finite element analysis. The process needed to accommodate the unique material stretching of the final application.

The Challenge

The part’s unique geometry would not allow for transfer press tooling — conventional stamping and its necessary tooling and engineering was needed to develop this piece.

The part’s deep draw presented such an unusual challenge to the engineering and tooling teams that it required several FEA simulations. These simulations helped to best estimate the number of stations required, the intermediate draws, and radii on the forms.

Even with these software tools, the team still needed to further develop and fine tune the tooling. We made wire EDM strips with different gutting simulations and ran them through the form stations in the die. This time-saving method allowed for different stamping variations after the forms were finished, but prior to finishing the gutting portion of the tool.

The Solution

Ultimately, the tooling team built a 24 station progressive tool to ensure the proper development of the difficult draw required for this part.

Crafted from DDQ Steel with Zinc plating, the grommet displays exceptional strength. The finished piece was manufactured in large runs — as a supplier to the world’s third largest automotive supplier, ESI manufactures quantities of 1,000,000+ every year.

ESI’s commitment to success beyond stamping and our dedication to the operation of a finished product is clear in every piece of the shop’s custom engineering work. To learn more on this and other custom projects, contact the team today.


Equipment Used150-Ton Press
Overall Part Dimensions34mm x 18mm x 8mm Draw
Tightest Tolerances0.1mm
Material UsedDDQ Steel
Material FinishPlating
Industry for UseAutomotive - Ford Transit Van
In-Process Testing/Inspection PerformedGage at press, CMM, Vision Inspection
Volume1,000,000+ per year
Delivery/Turnaround10 weeks