The Haimer Safe-Lock pull out protection system ensures safe cutting tool clamping; special drive keys in the tool holder match the spiral shaped grooves on the cutting tool shank, thus creating frictional clamping forces and a positive locking form-fit. This prevents the cutting tool from pulling out of the tool holder, and it increases the productivity through faster permissible speeds and increased tool life.
Within the last 10 years, since the introduction of the Safe-Lock system, it has been confirmed that this method of clamping the tool is often superior to conventional milling chucks and Weldon shanked tool holders. The shrink, collet and hydraulic chuck Safe-Lock tool holder portfolio has become much larger within the last few years. “We are proud that our Safe-Lock pull out protection system has established itself as the new standard in the heavy duty and rough milling industry and is also becoming more and more important in other areas such as trochoidal milling,” said Andreas Haimer, managing director of Haimer GmbH. “We are happy about our new license partners, who help expand the Safe-Lock portfolio and make it available for more end-users.”
Success in Aerospace
Safe-Lock has emerged from the requirements of heavy-duty machining, which is a daily challenge in the aerospace and energy producing industries. Innovative materials such as various titanium alloys are not only light, but also very rigid, corrosion resistant and difficult to machine. This doesn’t only affect the machine concepts and processes, but also the cutting tools and tool holders that are being used.
Many workpieces are made from a solid block—during this milling process up to 90% of the material is being removed. To optimize the process economically as well as qualitatively and to achieve a high metal removal rate, high torques and feed rates with low rpms are chosen. During this high performance cutting operation (HPC), high pulling forces occur. In combination with high cutting forces and aggressive feed rates, a flexing movement of the tool in the tool holder is created, which in the end increases the risk of tool pull out. This affects all the tool holder designs which provide accurate clamping and a high run-out accuracy, such as shrink, hydraulic or milling chucks. As a consequence Safe-Lock is now widespread within the aerospace industry.
Alexander Steurer, senior manager NC—Programming Stator Components at MTU Aero Engines in Munich, Germany, explained the decision to use the Haimer system. “Through the introduction of Safe-Lock and the shrinking technology from Haimer, we can guarantee process reliability even with milling challenging high temperature materials,” he said. “This is a prerequisite to guarantee smooth processing during manufacturing of frames and castings, given our high degree of automation. The combination of pull-out protection and highest concentricity of the Safe-Lock system leads to low vibration and as a result, a stable machining process. Due to the increased cutting depths and feeds, the metal removal rate can be increased significantly. And thanks to the improved runout accuracy of Haimer shrink fit chucks, tool life is improved by up to 50%.” The benefits of less than 3 µm runout that the symmetrical Safe-Lock design provides, coupled with optimum balance and the possibility for easy length presetting, were reasons for MTU to switch to the Haimer system.
Safe-Lock has not only found enthusiastic followers in the aerospace industry. Working at Glätzer Company (Solingen, Germany), Daniel Rautenbach, managing director of the CNC-Machining Specialists, knows how competitive and thorough the automotive industry can be. “Perfect quality and delivery reliability are the basic requirements to quote in our industry, and pricing is highly competitive,” he said. Therefore, in his business, the difference between profit and loss comes down to process efficiency.
Through one of the biggest projects in this area, Ingo Schulten, operation manager for Glätzer, became aware of the Haimer Safe-Lock pull out protection system and started using it in 2013. The specific application was a part for a pneumatically operated truck disk-brake which consisted of spheroidal-graphite cast iron, Type EN-GJS-800-2. In order to mill concave contours the contact between cutting tool and the work piece isn’t just punctual, but it actually covers between 30% or 40% of the tool.
Schulten said, “The extremely high engagement and cutting forces cause the tool to want to pull out from the holder.” The utilized Weldon Chucks ensured that the cutting tool stayed in the holder, but the side lock screw prevented the tool from achieving good runout accuracy. According to Schulten “the tool life was very unstable which even led to tool breakage”.
The milling tests with Safe-Lock convinced him and the other employees at Glätzer. “To me the switch to Safe-Lock seemed obvious, like using an electric starter instead of a crank to start a car,” said Schulten. “The cutting data improved significantly. The tool life increased by 40% consistently.”
High Speed Cutting
Safe-Lock is becoming popular in other industries and during HSC machining with high-helix end mills as well as in trochoidal milling. During trochoidal milling operations, where the cutting speed and axial depth of cut can be increased through software support, the productivity is significantly improved. Thus, milling operations are carried out three times faster with deeper depths of cut, even when it comes to hard and difficult to machine materials.
However, this also increases the danger of tool pull out. Even though only a thin chip is usually removed during trochoidal milling operations, often the entire length of the cutting tool edge is used during the process. This results in higher axial forces which force the operator to pay attention to safe cutting tool clamping. A shrink fit chuck with Safe-Lock is a solution since it offers more security than the Weldon system, is easier to install and can be clamped very precisely. The ideal balancing and runout characteristics of the shrinking technology in combination with the clamping safety of the Safe-Lock system permit the possibility of greater productivity achieved through faster permissible speeds and increased tool life all with complete tool security assurance.