Article by Haimer
The Haimer Safe-Lock pull-out protection system ensures safe cutting tool clamping. Special drive keys in the toolholder match the spiral-shaped grooves on the cutting tool shank, thus creating frictional clamping forces and a positive locking form-fit. This effectively prevents the cutting tool from pulling out of the toolholder. Furthermore, it increases the productivity through faster permissible speeds and increased tool life.
Safe-Lock has become a de-facto standard in the area of toolholding for milling operations. 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 clearly superior to conventional milling chucks and Weldon shanked toolholders. This is proven by a large number of license partners, some of which rank amongst the world’s leading cutting tool and tool holder manufactures: Walter, Widia, Sandvik Coromant, Seco Tools, Sumitomo, Kennametal, Helical, Emuge Franken, Data Flute, Niagara, OSG and Mapal. In 2017, Iscar and Ingersoll also decided to offer tools with the Safe-Lock shank. Furthermore, the shrink, collet and hydraulic chuck Safe-Lock toolholder portfolio has become much larger within the last few years. In addition to the Safe-Lock hydraulic chucks from Kennametal, Mapal is working to introduce its hydraulic chuck offering with Safe-Lock.
Andreas Haimer, managing director of Haimer GmbH, explains: “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. We are also very happy about our new license partners, who help expand the Safe-Lock portfolio and also make it available for more end users.”
MTU Aero Engines manages challenging roughing applications for the military turboprop engine TP400-D6 with Haimer Safe-Lock. MTU is responsible for the TP400-D6’s intermediate-pressure compressor, intermediate-pressure turbine and intermediate-pressure shaft and has a stake in the engine control unit. Furthermore, final assembly of all TP400-D6 production engines takes place at MTU Aero Engines in Munich. Photo courtesy of MTU Aero Engines
Successful in the Aerospace Industry
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 toolholders that are being used.
Many workpieces are made from a solid block – during this milling process up to 90 percent 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. But 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 toolholder is created which in the end increases the risk of tool pull out. This especially affects all the toolholder designs which provide accurate clamping and a high runout accuracy, like for example shrink, hydraulic or milling chucks.
As a consequence, Safe-Lock is in widespread use within the aerospace industry. Alexander Steurer, senior manager NC - programming stator components at MTU Aero Engines in Munich, explains 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. 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. Because of increased cutting depths and feeds, the mrr can be increased significantly. And thanks to the improved runout accuracy of Haimer shrink-fit chucks, tool life is improved by up to 50 percent.
The benefits of less than 3µm runout, that the symmetrical Safe-Lock design provides, coupled with optimal balance and the possibility for easy length presetting were substantial reasons for MTU to switch to the HAIMER system instead of continuing to use Whistle Notch or Weldon tooling systems. While these other systems do prevent tool pull out, both are unsymmetrical by design, hence providing insufficient runout and balance accuracy.
Glätzer CEO Daniel Rautenbach (right) and Manager Ingo Schulten are continuously extending the use of Haimer shrinking technology, with and without Safe- Lock. Photo courtesy of Haimer
Higher Productivity with Safe-Lock
However, Safe-Lock has not only found enthusiastic followers in the aerospace industry. Working at Glätzer, Daniel Rautenbach knows how fiercely competitive and thorough the automotive industry can be. The managing director of the CNC machining specialists located in Solingen explains: “Perfect quality and delivery reliability are the basic requirements in order to quote in our industry. Pricing is highly competitive.” Therefore, in his business, the difference between profit and loss comes down to process efficiency. Hence, quality without compromise is a must.
Through one of the biggest projects in this area Ingo Schulten, operation manager, became aware of the Safe-Lock pull-out protection system and started using it in the middle of 2013. The specific application was a part for a pneumatically operated truck disc-brake, which consisted of spheroidal-graphite cast iron, Type EN-GJS-800-2. To mill concave contours the contact between cutting tool and the workpiece isn’t just punctual, but it actually covers between 30 or 40 percent of the tool.
Schulten explains: “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. "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,” Schulten explained. “The cutting data improved significantly. The tool life increased by 40 percent consistently.”
Trochoidal milling makes the milling operation three times faster and deeper, even in hard materials like stainless steel or titanium. Suitable tools include the Haimer Power Mill endmills with Safe-Lock chuck. Photo courtesy of Haimer.
Benefits of High-Speed Cutting
Safe-Lock is also becoming increasingly popular in other industries and during HSC machining with high-helix endmills, 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 suitable solution because it offers more security than the Weldon system, is easier to install and can be clamped 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.
Related Glossary Terms
Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.
Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.
Flexible-sided device that secures a tool or workpiece. Similar in function to a chuck, but can accommodate only a narrow size range. Typically provides greater gripping force and precision than a chuck. See chuck.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- conventional milling ( up milling)
conventional milling ( up milling)
Cutter rotation is opposite that of the feed at the point of contact. Chips are cut at minimal thickness at the initial engagement of the cutter’s teeth with the workpiece and increase to a maximum thickness at the end of engagement. See climb milling.
- cutting speed
Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).
- depth of cut
depth of cut
Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- metal-removal rate
Rate at which metal is removed from an unfinished part, measured in cubic inches or cubic centimeters per minute.
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling machine ( mill)
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
- numerical control ( NC)
numerical control ( NC)
Any controlled equipment that allows an operator to program its movement by entering a series of coded numbers and symbols. See CNC, computer numerical control; DNC, direct numerical control.
Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.
Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.