Safe-Lock locking type tool holder ensures tool clamping safety

In the search for an optimal tool holder designed for high-performance milling, an American aircraft manufacturer tested the Haimer shrink tool holder with a newly developed Safe-Lock safety locking system (Fig. 1). This chuck is mainly a combined application of the shrinking shank and the locking element.

Milling plays an important role in aircraft manufacturing. In the production of die castings, tools and dies are needed. In addition, forged parts also need secondary processing, and then can be used, such as walking agencies and other parts. The special materials (such as aluminum, titanium, and composite materials) and shapes used in the aviation industry often cause difficulties in processing operations. Another feature of the aerospace manufacturing industry is the milling of large structural parts with a large number of cavities. These types of workpieces will be milled from a single solid part, and up to 90% of the original material will often be cut. All of these processes must achieve the highest quality and highest precision. In addition to the machine tool equipment, the role of the fixture is also very important. The processing of titanium alloy parts is also faced with huge challenges because of the slow processing speeds and the large amount of chips.

Competitive pressures have also prompted aviation manufacturing to focus more on production efficiency. As a result, high-performance milling (HPC), which utilizes the drive power of the equipment to the limit, has been favored by the industry. For a long time, there are special tools available on the market to facilitate such machining operations. These tools can withstand high torques, feed forces and pulling forces.

Friction-connected chucks have limited clamping force

Under this load condition, the danger of the milling cutter coming out of the chuck is increased; therefore, at least one type of tool holding device with high accuracy and accurate tensioning force is required, such as a shrink chuck or a hydraulic expansion chuck. This chuck adopts the mechanism of friction locking, the clamping force is limited to a certain extent, and the clamping force in HPC machining is sometimes insufficient. As an option, the user sometimes chooses to avoid the traditional Weldon tool holder. The tension bolts can act as a locking force. As a result, the torque can be transmitted arbitrarily until the cutter is broken. However, when the user selects the Weldon tool holding device, it is equivalent to returning to home the disadvantages which are well known to everyone: the lack of precision in the roundness and the poor clamping state, because the handle on the chuck requires a little Gap, tools used in HPC applications are expensive and have a short service life. No consideration has been given to other solutions. This is also a challenge faced by the tool holder experts of Haimer. They developed a system called Safe-Lock that combines a shrinking chuck or other precision chuck with a locking element (Figures 1-3). The principle of the system is that the milling cutter is provided with a thread-type groove, and a lock-type clamp is set in the groove. With screw-type keyways, the tool can be fastened at the same time, avoiding over-tightening and falling off. This can also be a ball or a pin. As a result, people combine the advantages of high precision with shrink tension with the advantages of the locking function.

Figure 1 The Safe-Lock system is a locking system for preventing tool disengagement during efficient cutting. The structure of the system shown in the figure is shown in the figure.

Figure 2 Safe-Lock System Combines Shrinkage or Other Chuck with Closing Elements

Figure 3 Power Shrink Chuck shrink chucks come in two models: long (a) and short (b).
It can achieve a very high surface quality and can be used in a variety of difficult cutting applications

Tool length adjustable

This is not enough. Through the threading of the keyway, the length of the tool is adjusted and the clamping process is very simple. People heat the chuck as before, and then introduce the tool by bolt action. The ball or pin enters into the keyway automatically during rotation. The spring supports the clearanceless tool attachment. After a few seconds, the holder cools down, thereby establishing a frictional and latching connection.

The Safe-Lock system has fully demonstrated its practicality after undergoing internal and external reinforcement tests. However, the largest and most impressive intensity test was conducted recently in the production of new aircraft components at a major aircraft manufacturing plant in the United States. When machining titanium, the tool comes out of the chuck of all high-precision tool holders. This also led to serious damage to valuable work pieces. The Weldon gripper was selected for use without the required accuracy, resulting in insufficient tool life. Therefore, the head of the production department is willing to try the new Power Shrink Chuck new shrink chuck with the Safe-Lock system. On a vertical portal milling machine with an HSK-A-100 interface, a Power-Shrink-Safe-Lock shrink chuck was used. The chuck was 120 mm long and provided with a 32 mm drill hole. For roughing and finishing, all hard metal tools with the same coating are used, and the effective cutting length is 83mm. As a test sample, a harsh aircraft part made of titanium 6AL4V material was used. During the test, the roundness of the tool tip was measured on the spindle of the device (total convex length: 171 mm). In the case of the Safe-Lock system with Haimer, the roundness is 0.005mm. When the Weldon gripper from another supplier was used under the same conditions, the roundness value was only between 0.05 and 0.08 mm, ten times worse than the measurement of the Power-Shrink-Safe-Lock chuck.

Tool removal is no longer a problem: Thanks to the Safe-Lock system, there is no movement of the tool on the chuck during the entire machining process. The results of this strength test even exceeded the expectations of the head of the production department: Due to the use of the Safe-Lock chuck, the service life of the tool was more than doubled. There are also significant differences in surface quality. Whether it is roughing or finishing, the use of the Safe-Lock chuck system does not cause vibrations and therefore no waviness - this is exactly the opposite of the Weldon chuck. This difference is very obvious.

Safe-Lock system is not only used to shrink chucks

The principle of the Safe-Lock system is not limited by the Haimer shrink chuck. It can also be integrated into a clamp chuck or a hydraulic expansion chuck. Since Haimer has applied for a patent on this and wants to recommend it to the user as a standard configuration, it is currently cooperating with the suppliers of tool manufacturers and other tool holders. Its experience and ideas should be incorporated into the further optimization of the Safe-Lock system.

Fig. 4 A combination of Weldon and Safe-Lock with milling cutter, left turn and right turn.

Haimer has developed a technology solution that combines the Weldon chuck and the Safe-Lock system to standardize tools for a variety of demanding machining conditions. In order to enable tool manufacturers to achieve greater standardization, Weldon cartridges and Safe-Lock systems can be combined in the future. Two different tool holding and locking solutions for tool manufacturers and their users mean more flexible application of different clamping technologies. By combining Weldon and Safe-Lock keyways on one tool, a reliable combination of a reliable clamping technique and a new type of tool locking technology is achieved.