Note on working on aluminum components and vehicles - AH60.00-P-0034-01SL
MODEL 231
Observe following notes when working on aluminum components and vehicle bodies:
- Notes on body workbay
- Notes on dent removal
- Notes on drawing in
- Notes on temperature control
- Notes on separation of glued joints
- Notes on unfastening bolted connections (flow-hole bolted connections)
- Notes on separating punch rivet joints and creating flow formed rivet joints
- Notes on various body materials
- Notes on straightening and restraightening
- Notes on accident repairs
Notes on body workbay
Special workbays are required when working on vehicles with aluminum components. Information on this is available in GOTIS at Body and aluminum workplace gotis://K_00.0_00.1
Notes on dent removal
On aluminum parts, it is possible to remove dents up to a certain deformation depth.
In the event of higher deformation, it is necessary to replace the damaged parts. Comprehensive dent removal work can be accomplished only under the effect of heat.
In contrast to sheet steel, on aluminum plate the dent removal operations should be started in the middle of the sheet metal. If possible, attempt to eliminate the dents by pressing out. Replace sharp-edged and hard dent removing tools with plastic, wood or aluminum tools.
If stretched too highly, e.g. with steel tools, aluminum tends to work-harden (blocking of the displacement motion), which can lead to embrittlement or crack formation.
Notes on drawing in
To draw in, first heat up the aluminum plate with "neutral" welding flame to approx. 150 °C to 450 °C and then allow to cool down punctually at the drawing 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:
- Clean aluminum surface. Do not burn any contamination into the surface.
- Heat up the point to be repaired. Limit thermal expansion within repair point.
Notes 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 discolor appropriately after exceeding certain temperatures.
- With infrared thermometer or pyrometer. Observe manufacturers' specification.
- With soft wooden wedge (e.g. spruce, willow). Heat up the point to be repaired. Then wipe across the heated point with the wooden wedge with 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
The wooden wedges used should be charred, otherwise the temperature display is not correct and the danger exists of the aluminum tearing during reshaping.
Notes on separation of glued joints
Before glued joints (e.g. flange connections) can be separated, they have to be heated up first. The maximum permissible temperature is 180 °C. The ideal temperature for detaching flanged connections, e.g. with the aid of chisel, is approx. 100 °C to 120 °C.
Notes on unfastening 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 in to 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
Use only tools approved by Daimler AG.
The application for connections accessible on both sides is available in GOTIS at Blind/self-piercing riveting gotis://K_68-80_06.0
Observe manufacturers' specification.
Riveted joints accessible on one side must be bore out, milled-off or ground open.
Because of the risk of contact corrosion it must be ensured that any cuttings or grinding residue are immediately removed.
Notes on various body materials
- Aluminum sheet parts
- Cast aluminum parts
- Aluminum extrusion press parts
- Sheet steel parts
Notes on straightening and restraightening
Restraightening in structural areas is generally prohibited. A single exception hereto is the rear floor in the area of the rear longitudinal member (1).
The following procedure is to be observed for restraightening:
- The deviation for measuring points (2) may not be greater than 3 mm. For diagnosis purposes, the Gotis listed Diagnosis and measurement systems gotis://K_60-65_01.0 must be used.
- Restraightening must always be conducted on a straightening system approved by Daimler AG (Straightening systems for passenger cars (Celette) gotis://K_60-65_02.0
, Straightening systems for passenger cars (Car Bench) gotis://K_60-65_03.0
or Straightening systems for passenger cars (Car-O-Liner) gotis://K_60-65_04.0) with
pulling device 231 589 01 27 00.
- Before any restraightening work the complete rear area is to be exposed over a large area (panels, covers etc. up to the connections on the inner longitudinal member).
- Before and after completion of the restraightening work the connection areas (X, Y and Z) at the left and right are to be checked for cracks (see AH60.00-P-0014-01N General information on crack diagnosis on aluminum components).
Notes on accident repairs
Accident repair is subdivided into 4 stages:
- Repair stage 1 (screwed parts)
- Repair stage 2 (glued and riveted parts)
- Repair stage 3 (welded parts)
- Repair stage 3+ (welded structural parts)
Special qualification training is required for repair stages 3 and 3+ on vehicles with aluminum bodies (Aluminum welding qualification certification).
Employees not verified as having participated in special qualification training and have not completed training for body work nor are authorized for such may not perform any work on vehicles in repair stages 3 and 3+.
Information on the qualification measures is available through the responsible MPC.
Schematic view of repair stages