Resources | Working with damped metal

Practical techniques and guidance

HOW TO USE SOUND DAMPED METAL SHEET

By its very nature, laminated steel or aluminium sheet has a viscoelastic core. For some applications, this can affect the way it should be incorporated into structures or components.

Whilst it can quite often be used “as is” as a simple substitute for existing (noisy) sheet metal components in fabrication, deep-drawing, spinning etc, for some applications there are a few manufacturing, welding and forming considerations that need to be taken into account as described below.

General fabrication
Where possible, equipment manufactured with SDS should be designed using flat sheets. The laminate can be sheared, punched, pierced, drilled, screwed, glued and riveted to form the overall shape.  If the amount of slippage, distortion or other physical characteristic is not acceptable, then fabricate with conventional steel and fit our single skin self adhesive dampers after folding, welding etc has taken place. As long as around 70% – 80% of the flat area is covered, then the damping performance will not be significantly reduced.

Welding – can I weld SDS?
SDS can be spot and resistance welded using an electrically conductive bridge between the inner and outer sheets. Welding machinery should be set for minimum air pressure, minimum current and maximum time. Other forms of welding may be used, however, SDS may distort if too much heat is applied.

Whilst tack welding may often be practical, seam welding is not recommended without prior consultation. In cases where a seam wled is required, we can supply ready-cut sheets where the laminate does not extend right to the edge of the shape. This leaves a single ply sheet margin round the edge that allows for normal seam welding without distortion whilst retaining the damping properties.

Welding should be carried out in a well ventilated area with extract hoods to disperse fumes.

Folding, Bending and Rolling
Folding & bending is the most difficult forming operation it requires the use of appropriate techniques. Springback is greater with SDS sheets than with monolithic steel sheets. Therefore, we recommend over bending, decreasing the bending radius and possibly selecting low yield strength grades (DC04). In order to avoid peeling of the sandwich near the cut edges, we suggest that the minimum distance between the bend and the edge should be at least ten times the thickness of the sheet. We can supply asymmetric laminates to faciltate bending.

SDS can be folded using progressive or hand-folding techniques. However, the maximum bend radii should not exceed three times the overall thickness otherwise bowing may occur.

SDS can be rolled. In some cases, we can supply an asymmetric laminate so the thinner skin is on the inside of the rolled piece. This helps reduce slippage between the skins.

Drilling and Punching
When drilling or punching the bottom skin should be supported to prevent the laminated layers being forced apart. With bends & rolling slippage will occur between the skins, with the outer skin sliding back over the radius of the inner skin. This can be compensated for by making any pre-punched holes elongated and/or by increasing the radius of the fold. We can also provide an asymmetric laminate with a thinner layer on the inside.

Deep Drawing and Spinning
Laminated steel can be deep-drawn, often using the same tooling as for conventional steel sheet. Some experimentation with settings may be required. Sound damped steel can also be formed via spinning to create domes etc – often using an asymmetric laminate.

Powder Coating and Painting
SDS can be painted with wet paint, two pack and special coatings without problems. Where temperatures may exceed 180C, for example during powder coating, we can supply the damped laminate with a high temperature polymer which is designed for these higher temperatures.

Working Temperature Range
The laminate can be used at continuous operating temperatures of up to 180C. If the application requires temperatures in excess of this, we can supply the material with a high temperature core that allows the material to be used at much higher temperatures. Contact us for more details.

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