German HOFMANN spindle, HOFMANN model, HOFMANN price

The HOFMANN spindle is a new technology in the field of CNC machine tools that integrates the machine tool spindle with the spindle motor. Together with linear motor technology and high-speed tooling technology, it has ushered high-speed machining into a new era. The electric spindle includes the electric spindle itself and its accessories, such as the electric spindle, high-frequency frequency converter, oil mist lubricator, cooling device, built-in encoder, and tool changer. The rotor of the motor serves directly as the machine tool spindle, and the housing of the spindle unit acts as the motor frame. In conjunction with other components, this achieves the integration of the motor and the machine tool spindle.

HOFMANN spindle structure

The ElectricSpindle consists of a frameless Motor, Spindle, bearings, housing of the spindle unit, drive module and cooling device. The rotor of the Motor is press-fitted to form an integral assembly with the Spindle, which is supported by front and rear bearings. The stator of the Motor is mounted in the housing of the spindle unit via a cooling jacket. Speed variation of the Spindle is controlled by the spindle drive module, while temperature rise within the spindle unit is limited by the cooling device. Speed and angular displacement sensors are installed at the rear end of the Spindle, and the internal taper hole and face at the front end are used for tool mounting. With the rapid development and increasing maturity of electrical drive technologies (such as variable frequency speed control and vector control of motors), the mechanical structure of the main drive system of high-speed CNC machine tools has been greatly simplified, basically eliminating belt and gear transmissions. The machine tool spindle is directly driven by a built-in motor, thereby reducing the length of the main drive chain to zero and achieving "zero transmission" for the machine tool. This drive structure, in which the spindle motor and the machine tool spindle are "combined into one," allows the spindle assembly to be relatively independent from the machine tool's drive system and overall structure; it is also called "ElectricSpindle" (Motor Spindle). Since current ElectricSpindle mainly use AC high-frequency motors, they are also called "High FrequencySpindle". Due to the absence of intermediate transmission links, it is sometimes referred to as "Direct Drive Spindle".

HOFMANN spindle structural composition

A drive shaft consists of a shaft tube, a slip yoke, and universal joints. The slip yoke automatically adjusts for changes in distance between the transmission and the drive axle. The universal joint ensures changes in the angle between the axes of the transmission output shaft and the drive axle input shaft, achieving constant-velocity rotation of the two shafts. The universal joint is a key component on automotive drive shafts. A car is a moving object. In rear-wheel-drive vehicles, the engine, clutch, and transmission are mounted as a unit on the frame, while the drive axle is connected to the frame via elastic suspension. There is a distance between them that requires connection. Uneven road surfaces cause bouncing during vehicle operation. Generally, a universal joint consists of a cross shaft, cross bearings, and a flange yoke. The universal joint is a key component on automotive drive shafts. In front-engine, rear-wheel-drive vehicles, the universal joint drive shaft is installed between the transmission output shaft and the drive axle differential input shaft; in front-engine, front-wheel-drive vehicles, the drive shaft is omitted, and universal joints are installed between the front axle half-shafts (which handle both driving and steering) and the wheels. During vehicle operation, uneven roads cause bouncing, and load changes or differences in assembly positions of the two assemblies cause changes in the angle and distance between the transmission output shaft and the drive axle differential input shaft. Therefore, a device that "adapts to change" is needed to solve this problem, resulting in the universal joint. [In front-engine, rear-wheel-drive (or all-wheel-drive) vehicles, due to suspension deformation during motion, there is often relative motion between the drive axle differential input shaft and the transmission (or transfer case) output shaft. Furthermore, to effectively bypass certain mechanisms or devices (where straight-line power transmission is not possible), a device is required to ensure normal power transmission, leading to the emergence of universal joint drives. Universal joint drives must have the following characteristics: a Ensure reliable power transmission when the relative position of the connected shafts varies within the expected range; b Ensure uniform rotation of the connected shafts. Additional loads, vibrations, and noise caused by the universal joint angle should remain within allowable limits; c High transmission efficiency, long service life, simple structure, easy manufacturing, and easy maintenance. For automobiles, since the output shaft of a single cross universal joint rotates at non-uniform speed relative to the input shaft (due to a certain angle), double universal joints (or multi-universal joints) must be used. The two universal joint yokes connected to the same drive shaft must be arranged in the same plane, and the angles of the two universal joints must be equal. This is very important. The universal joint angle should be minimized during design. Traditional drive shaft slip yokes weld the spline yoke to the flange yoke and the spline shaft to the drive shaft tube. New-type drive shafts change this traditional structure by welding the spline yoke to the drive shaft tube as one unit and making the spline shaft and flange yoke into one unit. Rectangular tooth splines are replaced with large pressure angle involute short-tooth splines, which increases strength and facilitates extrusion forming, meeting the requirements of high-torque conditions. The tooth surfaces of the slip yoke and spline shaft are coated with a layer of nylon material, which not only increases wear resistance and self-lubrication but also reduces damage to the drive shaft from impact loads, improving buffering capacity. This type of drive shaft adds a tubular sealing protective sleeve outside the flange spline shaft. Two polyurethane rubber oil seals are set at the end of the protective sleeve, creating a completely sealed space inside the slip yoke. This protects the sliding spline shaft from external dust and sand, providing both dustproof and rustproof protection. Therefore, applying grease once to the spline shaft and inside the sleeve during assembly fully meets usage requirements, eliminating the need for grease nipple lubrication and reducing maintenance tasks. Bushings are designed to reduce friction and wear during shaft movement. Their basic function is similar to that of bearings, and they are relatively cheaper, but they have higher frictional resistance, so they are only used in certain components. Most bushings are made of copper, but plastic bushings are also available. Bushings are mostly placed between the shaft and the supporting structure, fitting very tightly against the supporting structure, allowing only the shaft to rotate within the bushing. Lubricant is added between the shaft and bushing during assembly to reduce friction generated during rotation.

HOFMANN spindle fault maintenance

Damage, wear, deformation, and loss of dynamic balance in drive shaft components can cause noise and vibration in the vehicle during driving, and in severe cases, lead to damage of related components. When starting or accelerating rapidly, a "clunking" sound may occur, accompanied by a noticeable feeling of looseness in the components. If it is not looseness in the drive axle transmission gears, it is clearly looseness in the drive shaft components. The loose parts are typically the universal joint cross bearings or the steel cup and flange yoke, and the spline shaft and spline yoke of the slip yoke. Generally, the clearance between the cross shaft diameter and the bearing should not exceed 0.13mm, and the meshing clearance between the sliding spline shaft and the spline yoke should not be greater than 0.3mm. If these limits are exceeded, repair or replacement is necessary. If a "humming" sound occurs from the chassis during driving, and the sound increases with speed, this is generally due to wear and looseness of the universal joint cross shaft and bearings, wear of the drive shaft center bearing, damage to the center rubber support or loosening of the hanger, or incorrect positioning of the hanger fixation. 1) Traditional methods: In China, common methods for addressing drive shaft wear include build-up welding, inserting bushings, and knurling. However, when the shaft material is 45 steel (quenched and tempered), using only build-up welding generates welding residual stresses. Under heavy loads or high-speed operation, this may lead to cracks or even fracture at the shaft shoulder. Stress relief annealing is difficult to perform, has a long processing cycle, and incurs high maintenance costs. When the shaft material is HT200, cast iron welding is also unsatisfactory. Some companies with advanced maintenance technologies use electro-brush plating, laser welding, micro-arc welding, or cold welding. These maintenance technologies often require high standards and incur high costs. 2) Latest maintenance methods: The above repair techniques are less common in European, American, Japanese, and Korean enterprises. Developed countries generally adopt polymer composite material technology and nanotechnology. Polymer technology allows for on-site operation, effectively improving maintenance efficiency while reducing maintenance costs and intensity. The most widely applied is the Meijiahua technology system. Compared with traditional technologies, polymer composite materials possess the strength and hardness required of metals, as well as compliance (variable relationship) that metals lack. Through processes such as "mold repair," "component correspondence," and "machining," dimensional fit between the repaired area and mating components can be ensured to the maximum extent. Meanwhile, utilizing the comprehensive advantages of the composite material itself, such as compressive strength, bending resistance, and elongation, it can effectively absorb external impact forces, greatly dissipate and offset the radial impact force of the bearing on the shaft, and avoid the possibility of gaps, thereby preventing secondary wear caused by increased gaps in the equipment.

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