Process cycle and tool change
One of the most prominent advantages of profile pressing is the short set-up times between production cycles. When changing the profile, only one tool change is required, allowing production to continue without stopping the process completely. The press is equipped with a Die-Slide system, which makes it possible to prepare the new tool during the ongoing pressing. During the tool change, the old tool is pushed out while the new one is placed in the correct position, without stopping the process. In addition, cleaning of the removed tool can be done during the pressing cycle itself, further reducing downtime.
Tools and adjustments
The tools used for profile pressing are made from hot-work steel and hardened to achieve durability and precision. After manufacture, the tools are tested and adjusted to ensure that the flow of material through the tool is properly controlled, which is crucial for the final shape of the profile. Surface hardening, such as surface nitriding or titanium coating, is done to extend tool life and maintain product quality.
Tooling costs and lead times
Another advantage of profile pressing is the low tooling costs. Compared to other processes, such as die-casting, the tooling costs for profile pressing are significantly lower – often only a tenth of the cost. Tools are also delivered quickly, usually within 2-3 weeks of ordering, which is a major advantage in development projects. Tooling costs vary depending on the size and complexity of the profile, with simpler tools for a solid profile costing around £10,000, while more complex tools can reach £100,000 for larger, more complicated profiles.
Technological limits of profile pressing
Extrusion technology is constantly evolving, making it possible to produce aluminium profiles with more complex cross-sectional shapes. As standard, the direct extrusion process works with ingot dimensions from 5″ up to over 12″, with rectangular ingots for wider profiles. By using special tooling solutions, profiles with a width of up to 140% of the ingot diameter can be produced, meaning that a 360 mm wide profile can be produced from a 10″ ingot.
Largest and smallest profile constructions at ProfilGruppen
Machining factor and shape factor
In profile pressing, it is important to consider the machining factor, which is calculated by dividing the ingot area by the area of the extruded profile. An optimum machining factor is between 30 and 50, while too high a factor can lead to critical pressure levels that damage tools and equipment. The form factor, which is the ratio of the total perimeter to the weight of the profile, gives an indication of relative pressability. The lower the value, the easier it is to press the profile.
Alloy selection and thickness
The choice of alloy also affects the wall thickness. For example, alloy EN AW-6005 requires a 15% increase in material thickness compared to EN AW-6060, and EN AW-6082 requires 25%. Generally speaking, larger profiles require thicker material for the process to be possible.
Common faults: rear and front end faults
There are two common defects that can occur in profile pressing: back-end defects and front-end defects. Rear end failure occurs at the end of the press cycle if the inlet opening in the die is too large or if too little of the ingot is saved in the “butt end”, leading to surface defects and potentially reduced strength. To avoid this, the inlet should be maximum 90% of the container diameter. Front end failure occurs when the material left in the tool is joined to the new casting at the start of a new cycle, which can cause strength problems and often requires 1-5 meters to be cut away from the profile.
Executive summary
Profile pressing offers many advantages, including short set-up times, low tooling costs and fast tool delivery. Technological developments make it possible to produce more complex profiles with greater precision. Although there are technical limits and the risk of some errors, these can be managed with the right adjustments and tool adaptations. This process provides great flexibility and efficiency for the production of aluminum profiles.
