Tooling, How to choose the correct tool holder for the CNC Machining?

Mosi Li
Mosi Li

Director Project Engineer at 3Q Machining - China top CNC Machining Custom Part Manufacturer

Precision CNC machining center machine tools combined with advanced cutting tools can provide excellent metal cutting productivity. As the key interface between the cutting tool and the machine tool spindle, the tool holder is essential for achieving high productivity. So, how to choose, apply and maintain the most suitable tool holder for production needs?

Workpiece factors affect the choice of tool holder

Factors that affect the selection of tool holders include the machinability of the workpiece material in each job and the configuration of the final part. These factors can determine the size of the tool holder required to reach a specific profile or feature. The handle should be as simple and easy to use as possible to minimize the possibility of operator error.

The basic components of the machine tool play a key role-fast machine tools with linear guides will make full use of tool holders designed for high-speed applications, while machine tools with box grooves provide support for heavy-duty machining. Multi-task machine tools can complete turning and milling/drilling processes at the same time.

Workpiece factors affect the choice of tool holder cnc machining Workpiece factors affect the choice of tool holder cnc machining

The tool holder can also be selected according to the processing strategy. For example, in order to maximize productivity in high-speed cutting (HSC) processes or in high-performance cutting (HPC) applications, the shop will choose different tools. The former involves a shallower depth of cut HHS, and the latter focuses on sufficient power. However, machine tools with limited speed produce higher metal removal rates.

Low repeatable radial runout helps to ensure a constant amount of tool engagement, thereby reducing vibration and maximizing tool life. Balance is very important. High-quality tool holders should achieve precise dynamic balance under G2,5-25000 rpm mass (1 g.mm). The processing workshop can determine the tool holder system that can meet its production needs in a cost-effective manner according to the actual situation or consult the tool supplier.

Each tool holder should meet specific process requirements

Whether it is a simple side-fixed type, jacket type, heat-shrinkable type, mechanical type or hydraulic type, the tool holder should meet the specific process requirements.

Spring collets and interchangeable collets are the most commonly used round tool holder technology. The cost-effective ER type is available in various sizes and provides sufficient clamping force to achieve reliable light milling and drilling operations. The high-precision ER jacketed tool holder has low radial runout (< 5µm at the tip) and a symmetrical design that can be balanced for high-speed processes, while the reinforced type can be used for heavy-duty machining. ER tool holders are easy to change quickly and can be adapted to various tool diameters. .

The thermal expansion tool holder can provide a strong clamping force, has a concentricity of 3 μm at 3xD, and has an excellent dynamic balance quality. The small handle design can well reach the tricky part features.

Each tool holder should meet specific process requirements Each tool holder should meet specific process requirements

The enhanced tool holder can perform medium to heavy milling, but the clamping force depends on the inner diameter tolerance of the tool holder and tool holder. Thermal expansion tools require the purchase of a special heating device, and the heating/cooling process requires more installation time than simply switching the jacket.

The mechanical milling chuck provides strong clamping force and high radial rigidity through multi-row needle roller bearings. This design can realize heavy-duty milling and fast tool change, but the runout may be greater than that of the jacket system. The size of the mechanical chuck is usually larger than other tool holder types, which may limit the tool’s access to certain part features.

tool holder, tooling for cnc machining

Compared with mechanical chucks, hydraulic chucks that use hydraulic pressure to generate clamping force have fewer internal components and are therefore relatively slimmer. The hydraulic chuck has low radial runout and can effectively carry out reaming, drilling and light milling at high spindle speeds, but it is sensitive to large radial loads.

The spindle or tapered end determines the torque transmission capacity and tool centering accuracy

Just as important as how the tool holder fixes the cutting tool is how to install the tool holder on the spindle of the machine tool. Traditional BT, DIN and CAT tool holder tapers are suitable for smaller machine tools, but may be limited in terms of high-speed machining. The model that is in double-sided contact with the tapered surface and end surface of the tool holder can provide higher rigidity and accuracy, especially in the case of large overhangs. Reliable transmission of larger torque requires a larger taper size. For example, HSK-E32 tool holder cannot replace HSK-A125A in heavy-duty machining.

The choice of the taper form of the tool holder usually varies from region to region. In the mid-1990s, 5-axis machine tools became more and more popular, and it was during this period that HSK began to emerge in Germany. CAT tool holders are mainly used in the United States, while in Asia, BT tool holders are very popular, and are often taper/end-face double-contact models.

HSK is often used for 5-axis machining. PSC (Polygonal Clamping System: Capto) and KM connection are mainly used for multi-task machine tools, using ISO standards. Both KM and Capto are modular systems that allow the combination of extension rods or reduced diameter rods to assemble tools of a specific length. As multi-task machine tools become more and more popular, tool holders that can realize turning, milling, drilling and other processing types in a single clamping are becoming more and more popular.

cnc machining, tool holder for cnc

CNC machining centers must pay attention to the importance of tool holders in the machining system, and understand how to correctly match the correct tool holders with specific machine tools, machining strategies and workpieces to increase productivity and reduce costs.

Future technological improvements will no longer be limited to the tool holder itself. The use of software and RFID tags for tool management is an element of data-based manufacturing and is becoming more and more common. Advances in toolholder technology include toolholders equipped with sensors that can monitor the force on the toolholder in real time. The collected data allows the operator to adjust the processing parameters during processing, and can even be automatically adjusted by artificial intelligence (AI) connected to the machine control unit. These technologies and other new technologies will further increase the production contribution value of the tool holder in the machining process

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