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Introduction to the basic elements of spindle selection

Source:NETAuthor:UN Addtime:2022-05-10 Click:
1. Spindle structure form and characteristics
Belt drive spindle; direct spindle; built-in spindle (electric spindle), double contact (with HSK, BBT, NBT toolholder) tapered hole spindle; the same speed spindle, there are many different characteristics, to be reasonably selected, for example: bearing size, specifications and bearing position is different; spindle rigidity has different indicators; spindle front length has different specifications; there are different additional features (spigot type, spindle cooling (e.g., spigot type, medium spray, air curtain protection, with cutting fluid nozzle, loose tool backlash, etc.).
2. The spindle selection factors
Machine tool design is generally to meet the maximum cutting force of the machine tool as the first element, while taking into account the maximum cutting speed, maximum cutting torque, spindle rotation accuracy, machine structure requirements, processing materials, cutting conditions and other factors to be considered when selecting.
If the spindle design calculation is not skilled, you can roughly project the tool tensioning force from the spindle sample to ensure that the spindle can withstand the maximum cutting force, the general tool tensioning force is greater than the spindle to withstand the maximum axial cutting force of about two times.
The highest speed commonly used in processing is not higher than 80% of the maximum speed provided in the sample.
Pull nail type selection: steel ball tensioning device is generally used in the spindle speed below 6000rpm, cutting force is not large can also be selected; high-speed spindle more than 8000rpm, strong cutting to use the four-jaw tensioning device.
Spindle cooling selection: shaft diameter less than 70mm, the maximum speed of 8000rpm (not continuous operation) can not be selected, high-precision machining center machine tools must be selected. The definition of the choice of cooling should be established in the consideration of precision, and try not to establish in the consideration of damage.
In the spray function selection: processing aluminum alloy, titanium alloy, stainless steel materials recommended for machine tools, processing small holes, deep holes in the machine to choose.
Air curtain protection function selection: should generally be used, especially for processing graphite materials, plastic materials, aluminum alloy materials should be used, the choice of the function of the machine tool compressed air must be dry, otherwise it will make the spindle internal rust.
Loose knife buckle function selection: this function can protect the spindle bearing by the impact of the loose knife force to reduce and extend the bearing life.
The same tapered hole specifications of the spindle, the outer diameter of the spindle is often configured with a large steel ball or large ceramic ball bearings, high rigidity, smooth cutting, can withstand large cutting forces, generally in high-powered, powerful cutting machine tools are used.
It is best to let the supplier provide the other parts of the drive and the basic installation size requirements at the same time to achieve complete sets of supply and avoid errors.
Try to use the company's standard specifications of the spindle, the price is relatively low, short delivery time.
3. Notes on selection and use
Belt drive type: belt drive type without gears at high speed vibration and noise problems, can be used at higher speeds, but the shaft is subject to lateral force vibration is larger, in the low-speed belt drive efficiency is almost suitable for low-speed heavy cutting, in the high-speed belt and air friction noise is quite large, in the dmn value of more than 1000000mm / rpm should be changed to other transmission methods.
Built-in type: the most widely used in high-speed cutting processing, light weight is most suitable for high-speed movement, while the number of parts is small, dynamic balance correction and alignment degree is easy, low vibration.
Motor direct type: In order to reduce the vibration caused by lateral force on the mandrel, the motor and spindle are connected by coupling, the speed can be higher than the belt-driven spindle, heavy weight, large volume, but the cost is cheaper than the internal spindle, the speed can be up to 20,000rpm.
Speed: The speed required for high-speed cutting processing is mainly determined by the material of the workpiece, the material of the cutting tool and the diameter of the cutting tool. The speed of BT40 high-speed spindle is below 15,000rpm, and 10,000rpm and 12,000rpm are the most, while the speed of BT50 high-speed spindle is below 12,000rpm and 1,000rpm is the most. The spindle speed is more than 20,000rpm for high speed cutting of light alloy and other materials, and the toolholder specification is HSK-A63, and HSK-A100 is used for larger workpiece processing.
Horsepower: In the goal of improving the processing energy rate, the spindle horse country is enough is also our concern, in the pursuit of high-speed cutting processing high removal rate, high-speed spindle horsepower is much higher than the traditional spindle, but the machine rigidity should also be able to match, otherwise understand the play part of horsepower has machine structure vibration. In the domestic tool machine factory some of the machine directly change high-speed spindle, its main goal is to enhance the cutting speed of processing light alloy or soft material, not the need for high removal rate, can use less horsepower.
Rigidity: Insufficient spindle rigidity will affect the machining accuracy, but rigidity exceeds the functional requirements will cause the spindle bearing life is reduced. dmn value is low, you can use the fixed position pre-pressure, high speed rotation due to temperature rise makes pre-pressure aggravated, you can use the bearing spacer ring cooling, to moderate the pre-pressure increase has a good effect. dmn value is high, you can use the fixed pre-pressure to ensure the pre-pressure value. When the dmn value is low, grease lubrication can be used, the rigidity value must be lower than the use of oil and gas lubrication, to avoid the temperature rise due to excessive pre-pressure to accelerate grease deterioration, and shorten the spindle life.

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