Well over 20,000 drums per year. Just-in-time production in top quality.
Drums are the heart of every roller. As a key component of the rollers, a great deal of expertise goes into them. That is why Hamm attaches particular importance to their quality and manufactures all drums in Tirschenreuth in its own state-of-the-art drum factory. In-house manufacturing offers maximum flexibility and enables Hamm to maintain the highest quality standards.
The main plant in Tirschenreuth can produce up to 20,000 rollers per year. Since tandem rollers are equipped with two drums, Hamm requires considerably more than 20,000 drums per year. They are produced just-in-time in a drum plant with an area of over 11,000 m². Thanks to this and short scheduling times, Hamm can respond very flexibly and quickly to market demands.
Up to 120 employees work in multiple shifts at the drum plant. They turn over considerable volumes of material. Among other things, between 12,000 and 15,000 t steel is processed each year. With all components inside, fully assembled drums weigh between 1 and 8 t.
The drum – the heart of the machine.
The entire production process, from blasting the sheet metal to painting the fully assembled drum, takes between 9 and 24 hours, depending on the size and type of drum. A particularly large number of work steps are involved in the manufacture of oscillation, VIO, padfoot and VC drums.
Right from the start, the production parts belonging to the drum are assigned to a specific customer order.
Rust and scale are removed from the panels in a blasting plant.
Two to three days before the final assembly of the corresponding machine begins, the production of the drum shell from a flat steel panel starts. The extremely wear-resistant panels are up to 2.30 m wide, can be 45 mm thick and weigh up to 4 t. They are first cleaned of rust and scale in a blasting plant. In the process, the blasting material is collected and reused.
In the next step, the panels are cold-formed almost completely automatically in one of the four hydraulically operated circular-bending machines. With pressures of up to 280 bar, cylindrical blanks are produced from flat panels in a very short time. Maximum precision is required here; perfect roundness and a correct gap dimension are important. Both are of paramount importance for quality and durability.
The drum shell is then welded with a longitudinal seam in a semi-automatic submerged arc procedure – and thus largely emission-free – in one of three special machines. Depending on the material thickness, up to eight working gears are required in a computer-controlled process until the weld seam is complete.
Up to eight working gears may be required until the weld seam is complete.
The installation of the steel plates – also called circular blanks – then begins. These are welded to the drum shell at precisely specified positions by high-tech robots. The robots use sensors to determine the distance between the workpiece and the electrode extremely precisely and correct their position independently in the event of deviations. This results in weld seams with perfect strength and position, which subsequently withstand the high loads.
All padfoot drums "find their feet" in this processing state. Attached by hand, the padfeet are finally welded to the shell in a seven-axis welding robot.
Before the next machining step, all drums are stored for a certain time. In the process, they relieve the stresses that inevitably arise during the upstream welding processes. The mechanical processing only follows once they have cooled down and are stress-free.
In mechanical processing, a distinction is made between drums for earthworks or asphalt construction. In the case of drums for earthworks, a special longitudinal milling machine removes the part of the weld seam that protrudes on the outside.
Then it's off to a state-of-the-art CNC machining centre built specifically for Hamm. It is not only unique, but also the most modern of its kind in Europe. Depending on the drum type, up to 220 bores are created and threads cut in 40 to 100 machining steps. Some bores are produced as high-precision fits accurate to hundredths of a millimetre. In addition, up to 10 plane surfaces are milled to absorb the vibration or oscillation units. This is necessary to ensure that the axles for the vibration and oscillation drives subsequently fit perfectly.
The drums for the asphalt construction are further turned in their entirety. This guarantees a perfect surface and thus high surface quality when compacting asphalt.
In the pre-assembly stage, the travel drives, vibration drives and oscillation drives are assembled into complete assemblies. The employees then install these in the drums. This means that Hamm ensures that the quality of the mechanically highly stressed assemblies can be monitored down to the smallest component, and maintained at the highest level.
Drum rotating device
Using a special drum rotating device, employees lift the shafts with the eccentric masses into the drum and install the drives.
Last but not least, the drums pass through a modern and environmentally friendly paint shop. Over a distance of 40 m the drums are washed, painted in a single-layer process, and dried.
From the paint shop, the drums are sent to the final assembly. The mounting brackets and, if required, hydraulic hoses are installed. They are then ready for installation in the rollers and leave the drum plant for the assembly hall for final assembly.
