Note on working on aluminum components and vehicles

The following points must be observed when working on aluminum components and vehicle bodies:

 Information on body workbay

 Information on dent removal

 Information on drawing in

 Information on temperature control

 Notes on separation of bonded joints

 Notes on separating bolted connections (flow-hole bolted connections)

 Notes on separating punch rivet joints and creating flow formed rivet joints

 Notes on various body materials

 Note on damage diagnosis

 Notes on straightening and reforming

 Notes on accident repairs

Information on body workbay

Separate workplaces are required for work on vehicles with aluminum components. Information on this is available in the XENTRY Portal  Consulting & Services  Workshop planning & Networking  Workshop planning  Services  Downloads.

Information on dent removal

On aluminum parts, it is possible to remove dents up to a certain deformation depth.

Comprehensive dent removal work can be accomplished only under the effect of heat. In the event of higher deformation, it is necessary to replace the damaged parts.

In contrast to sheet steel, the dent removal operations on aluminum plate should be started in the middle of the sheet metal. If possible, an attempt should be made to remove the dents by pressing out. Replace sharp-edged and hard dent removing tools with plastic, wood or aluminum tools.

If stretched too much, e.g. with steel tools, aluminum tends to work-harden (blocking of the displacement motion), which can lead to embrittlement or crack formation.

Information on drawing in

To draw in, first heat up the aluminum plate with a "neutral" welding flame to approx. 150 °C to 450 °C and wait until it cools down again at certain points to the draw-in point. The rapid temperature change causes the surface to contract and the aluminum plate assumes its original shape.

The heated point is flattened because the surrounding colder material expands less, preventing thermal expansion of the heated material. When it cools, the heated, flattened material contracts.

Observe the following working rules:

 The aluminum surface must be cleaned. Do not burn any contamination into the surface.

 The point to be repaired must be heated up. Thermal expansion within the area to be repaired must be limited.

Information on temperature control

The following procedures are available for checking the temperature:

 With thermal paints (e.g. colored pens), applied at a distance of approx. 25 mm from the edge of the heating zone. Observe manufacturers' specification.

 With self-adhesive temperature measuring strips whose measuring fields change color accordingly after certain temperatures are exceeded.

 Using an infrared thermometer or pyrometer. Observe manufacturers' specification.

 With a soft wooden wedge (e.g. spruce, willow). Heat up the point to be repaired. Then wipe across the heated point with the soft wooden wedge using medium pressure.

The following stripes indicate the specific temperature:

 Light brown at approx. 350 °C

 Medium brown at approx. 400 °C

 Dark brown at approx. 450 °C

 Black at approx. 500 °C

 A soft wooden wedge that has not been carbonized should be used.
Otherwise there is a risk that the temperature display may be incorrect, and the aluminum may be stripped out during restraightening.

Notes on separation of bonded joints

Before separating bonded joints (e.g. flange connections) they have to be heated first. The maximum permissible temperature is 180 °C. The ideal temperature for detaching a flange connection, e.g. with the aid of a chisel is approx. 100 °C to 120 °C.

Notes on separating bolted connections (flow-hole bolted connections)

Bolted connections that are screwed together in aluminum extruded sections can be removed using an electric screwdriver (e.g. cordless screwdriver).

Bolted connections screwed into cast aluminum components must always be unscrewed by hand.

 Flow-hole bolts are always replaced by blind rivets for repair work.

Notes on separating punch rivet joints and creating flow formed rivet joints

Only tools approved by Daimler AG may be used.

 Observe manufacturers' specification.

Riveted joints accessible on one side must be bore out, milled-off or ground open.

 It must be ensured that any chips and grinding residue are removed immediately.
Otherwise contact corrosion may occur.

Notes on various body materials

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Note on damage diagnosis

Conduct initial accident diagnosis (See "Conducing initial accident diagnosis" document).

 The respective component must always be replaced in the event of any cracks, folds or deformation (exception).
Otherwise the required minimum strength of the structural components is not ensured.

 Exception for deformation:
The front longitudinal members (E) (Aluminum extruded parts) can only be partly restraightened.
When restraightening the front longitudinal member (E) the permissible tolerances must be observed (see Checklist for damage diagnosis in event of accident, form FG 60).

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 Model 217.4
The rear longitudinal members (F) (aluminum extruded parts) can only be partly restraightened.
When restraightening the rear longitudinal members (F) the permissible tolerances must be observed (see checklist for damage diagnosis in event of accident, form FG 60).

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Notes on straightening and restraightening

Restraightening in structural areas is generally prohibited. Exceptions here are only the front longitudinal members (E) and on model 217.4, the rear longitudinal members (F).
The following procedure is to be observed for restraightening:

 The deviation of the measuring points (11, 12) must not be greater than 10 mm in the Y-direction, otherwise the front longitudinal member (E) must be replaced. Diagnosis and measuring systems must be used for the diagnosis (see checklist for damage diagnosis in event of accident form FG 60).

 Restraightening must always be conducted on a straightening system approved by Daimler AG, with the specific pulling device for model 222 and model 217 from the special tool kit.

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The following procedure is to be observed for restraightening of the rear longitudinal members (F) on model 217.4:

 The deviation of the measuring points (13, 14) must not be greater than 3 mm in the Y-direction and Z-direction, otherwise the front longitudinal member (F) must be replaced. Diagnosis and measuring systems must be used for the diagnosis (See Checklist for damage diagnosis in event of accident form FG 60).

 Restraightening must always be conducted on a straightening system approved by Daimler AG, with the specific pulling device for model 217.4 from the special tool kit

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The front longitudinal member (E) must only be restraightened when deformation is in the Y-direction.
 The front longitudinal member must be checked for cracks before and after the restraightening and must be replaced if cracks are found.
Otherwise the required minimum strength of the structural components is not ensured.
 When restraightening a front longitudinal member (E) the permissible tolerances must be observed (see checklist for damage diagnosis in event of accident, form FG 60).

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The rear longitudinal member (F) must only be restraightened when deformation is in the Y-direction and Z-direction.
 The rear longitudinal member must be checked for cracks before and after the restraightening and must be replaced if tears or cracks are found.
Otherwise the required minimum strength of the structural components is not ensured.
 When restraightening a rear longitudinal member (F) the permissible tolerances must be observed (see checklist for damage diagnosis in event of accident, form FG 60).

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Notes on accident repairs

Accident repair is subdivided into 2 stages:

 Repair stage 2 (bonded and riveted parts)

 Repair stage 3+ (welded structural parts)

 Special qualification training is required for repair stage 3+ on vehicles with aluminum bodies (aluminum welding qualification certification).

Employees not verified as having participated in special qualification training and have neither completed training for body work nor are authorized for such work may not perform any work on vehicles in repair stage 3+.

Information on the qualification training is available through the responsible Market Performance Center (MPC).

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