The downward vertical stroke of the tamper presses the mix to be paved under the base of the screed. It ensures a regulated feed of material to the screed and achieves the required degree of pre-compaction.
The materials from which the tamper is constructed must fulfil particularly high standards due to the continuous impact loads from its vertical reciprocating motion. A hard surface and a ductile core are among the most important properties of tamper bars. At the beginning of the manufacturing process, profile rods are cut to the required length for the tamper bars with a CNC-controlled saw. Thanks to the chamfered leading edge, the tampers ensure even mix feed and optimal compaction in later use. The service life of these components depends on their hardness. Induction hardening, the process also used for the pressure bars, ensures consistent hardness over the entire length of the bar and achieves a hardening depth of at least 5 mm. The core remains ductile and flexible, while the surface, which is in constant contact with the mix to be compacted, retains its high resistance to wear. The bores for the heating rods are drilled on a CNC deep hole drilling machine developed especially for VÖGELE. In these this bores, the heating rods heat the bars (tamper bars and pressure bars) centrally from the inside over the entire length and guarantee homogeneous heating. In this way, bitumen residues are prevented from adhering during subsequent paving (particularly during the pre-heating phase prior to starting work) and abrasive wear on contact surfaces is reduced.
In the final step this phase, all bars are straightened in a straightening jig. The maximum permissible flatness deviation is 0.5 mm.