Toolholder Evaluation Report: See Who's Balancing Better

MRCM share / 2022-01-17 / Hits(983)

Toolholder Evaluation Report: See Who's Balancing Better
MRCM share: An efficient machining plan must comprehensively consider various characteristics of the tool holder, especially the clamping force and radial runout error accuracy and dynamic balance quality under high-speed operation conditions, which is conducive to reducing the existence of the tool itself. vibration.
Process for Effectively Controlling Tool Runout
There are different types of tool handles, such as spring tool handles, liquid expansion tool handles, heat shrink tool handles, etc. according to the type of clamping. Among them, the heat-shrinkable tool holder works on the principle of thermal expansion and cold contraction. The clamping part of the tool holder is heated in a short time by a thermal induction device, so that the inner diameter of the tool holder is expanded, and then the tool is immediately loaded into the tool holder.
Processing case: Φ32 alloy steel material
Speed: 1000rpm
Feed: 350mm/min
When the tool holder cools and shrinks, the tool clamping surface can be given even pressure, resulting in a high radial clamping force, holding the tool firmly, without any mechanical clamping parts between the tool and the tool holder. Shrink fit holders can solve the extremely important problems of balance, runout accuracy and clamping strength in high-speed finishing
The working process of heat shrinkable tool holder
Heat shrinkable shank heat comes from induction technology heating. As shown in the video, the Shrinkfit tool holder heater has an induction coil that precisely heats the area of ​​the tool inserted in the tool holder.
After inserting the tool, the tool holder needs to be cooled for a period of time, which can be accelerated by the cooling jacket. After the shank has cooled, the shank is clamped by its shrinkage force.
The tool clamped by the principle of thermal expansion and cold contraction almost becomes a one-piece tool with very uniform force, which has many advantages: the accuracy of radial runout error is very high, which can reach the level below 3μm; the transmission torque is large, and the design of the tool holder is relatively high. Relatively small.
Analysis of application scenarios of heat shrinkable tool holders
According to the wall thickness, the length of the clamping tool, the amount of interference, and the heat shrinkable tool holder are divided into the following three types:
1. Standard type.
2. Reinforced type: The wall thickness is increased, and it is used for the clamping of heavy-duty and powerful milling tools in the aerospace industry.
3. Lightweight: lengthened thin wall for deep cavity processing of molds.

Taking the HSK63A heat-shrinkable tool holder as an example, using the finite element software ANSYS, according to the different influencing factors of the clamping force of the heat-shrinkable tool holder and the tool, the finite element models were established respectively, and the influence of structural factors on the clamping force was analyzed. Material physical properties of heat shrink collets and tools.

The correlation between each influencing factor and the clamping force (or contact pressure) is shown in Table 2. Among them, the wall thickness, fit interference and contact length of the heat shrinkable chuck have a positive correlation with the contact pressure.

Increasing the outer wall thickness of the heat-shrinkable chuck, the initial interference and contact length of the heat-shrinkable chuck-tool fit will increase the clamping force; under the same initial interference condition, the inner hole is larger The clamping force of the heat-shrinkable collet is small; as the spindle speed increases, the interference of the heat-shrinkable collet and the tool will decrease, and the clamping force will also decrease accordingly. The heat transfer of cutting causes the temperature of the heat shrink collet to increase, which also reduces the amount of interference, thereby reducing the clamping force of the heat shrink collet on the tool.
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Heat Shrink Holders and Hydraulic/Spring Holders
▌ Spring collet
It is mainly used for the clamping of straight shank tools and tools such as drills, milling cutters and taps. The elastic deformation of the circlip is 1mm, and the clamping range is 0.5~32mm in diameter.

▌ Hydraulic tool holder
The clamping method of the hydraulic tool holder is different from the traditional tool holder system. Only one pressurized bolt is needed for tightening. When the bolt is tightened, a hydraulic oil pressure generated by the sealing block of the piston will be pushed in the tool holder. The pressure is evenly distributed. It is transmitted from the circumferential direction to the steel expansion sleeve, and the expansion wall then clamps the tool.
Hydraulic tool holders can generally control the radial runout error accuracy and repeat positioning accuracy below 3μm. Due to the high-pressure oil pressure in the tool holder, when the tool is clamped, the built-in oil cavity structure and the presence of high-pressure oil increase the structural damping, which can effectively prevent the vibration of the tool and the machine tool spindle.

▌ Heat shrinkable tool holder
According to the above, the heat shrinkable tool holder has a large clamping force and a good dynamic balance, which is suitable for high-speed machining. Compared with the collet chuck and the hydraulic expansion tool holder, the dynamic balance and rigidity are better, and the standardized operation brings a lower cost of use.

▲Tool handle evaluation and comparison
These different toolholder systems have different advantages due to different processing principles, processing designs and methods. For example, a tool holder with high rigidity is not suitable for all processing. A tool holder that is very suitable for high-speed processing may not be able to meet some other processing requirements. Therefore, accurate analysis is the premise of forming a reasonable process plan.

       Zhejiang Meiri Intelligent Equipment Co., Ltd. is a service provider specializing in the development and production of small special tool grinders and precision machines. The company's main products: CNC tool grinder, drill grinder, milling cutter grinder, thread tapping grinder, turning tool grinder, saw blade grinder, universal knife grinder, universal tool grinder, chamfering machine, pneumatic tapping machine , Electric tapping machine, zero point positioning system, precision vise, rotary table, EDM machine and other precision machinery series. Products from research and development, manufacturing, management to sales strictly implement the ISO9001 quality management system, continue to innovate, continuously improve the enterprise management system, improve efficiency, and provide professional, reliable and high-quality products to serve global customers.