1. Product Application
Ball screw is a high-efficiency structural element that converts rotary motion into linear motion (does not have self-locking function). It has the characteristics of high rigidity, high precision and durability. Ball screws are widely used in various industrial equipment because of their high efficiency and low rolling resistance.
2. The Standard Manufacturing Technology of Ball Screw Thread
The accuracy and quality of ball screw largely depend on the manufacturing technology. In general, the following technologies are mainly used:
? Grinding thread (accuracy grade up to P1)
? Cold rolling thread (accuracy grade up to P5)
3. Ball Screw Shape
In order to achieve maximum transmission efficiency, it is necessary to keep improving on the shape design of ball screw. It is composed of two opposing hemispheres (the so-called "Gothic arch"). This shape provides the ideal load ratio for the ball screw.
4. Product Load (grade), Rigid and Recycling System Life
The Ball Screw's another main parameter is the load capacity, there are two main types of load:
a) static load (Co).
Static load refers to the static load exerted by permanent deformation at the maximum contact stress point between the ball and the raceway surface, which is equivalent to 0.0001 times the ball diameter (Dw).
b) Dynamic load (Ca).
Dynamic load is constant load. Under the condition that the basic rated life is L10 = 1×10^6 RPM, the ball screw can theoretically withstand a constant load. The following formula is used to calculate the basic rated life. When a batch of ball nuts operate at a higher speed under the force of load F, 90% of ball screws do not flake, that is, the reliability rate is 90%, until the first time the material or recycling function is found damaged, the basic rated life.
Rigidity (R) is defined as the ratio of the external force Fa to the nut Δ on the spindle:
R=Fa/Δ (N?μm)
Preloaded Fv is applied to the drive chain to achieve high rigidity, ensuring the elimination of axial clearance, so that the axial force Fa does not create a gap in the drive, Fv needs to meet: Fa/Fv = 2.83. Because preloading can reduce the service life of the transmission, in order to be able to determine the Fa and preloading values, it is necessary to consider the decline time of the ball screw load.
5. Ball Screw Assembly Accuracy
Ball screw needs precise assembly. The parallel clearance between the lead screw and the guide shaft surface needs to be controlled at 0.02mm / 1,000mm, and the verticality between the nut and the vertical axis should be controlled at 0.01mm / 100mm. Nuts can only be axially loaded. For long and narrow lead screws, the lead screw must be designed in such a way that the drive can compensate for shaft displacement due to weight (adding support or modifying the nut design).
6. Nut Assembly and Disassembly
If the customer needs to remove and reinstall the nut from the lead screw, please follow the following steps (KSK will not be responsible for the ball screw damage caused by improper installation and disassembly caused by the customer's own reasons) :
1) In order to avoid the ball falling off when disassembling the nut, the sleeve must be tight to the screw thread surface. Sleeve dimensions refer to the product model table. KSK technicians will assist to confirm the sleeve size.
2) Slowly rotate the nut to move it to the sleeve position.
3) Now the sleeve and nut are removed from the ball screw. Please note that if the sleeve is removed from the nut, the ball will fall out of the nut.
7. Preloading Specifications
According to the required accuracy and rigidity requirements, carefully choose the appropriate nut assembly method. The higher the prepressure, the shorter the life of the ball screw transmission. The standard installation method is as follows:
? Axial clearance mounting nut
? Nut mounting preload corresponding to 3% rated dynamic load (for screws with low precision and load)
? Nut mounting preload corresponding to 5% rated dynamic load (for screws with moderate precision and load)
? Nut mounting preload corresponding to 10% rated dynamic load (for screws with high precision and load)
8. Ball Screw Lubrication
There are two kinds of ball screw lubrication, oil lubrication and grease lubrication. The lubrication method and lubricant are consistent with the lubrication method of roller bearings. The type and dosage of the specific nut lubricant is selected as required. In general, ball screw oil lubrication and roller bearings are lubricated in the same way, for example: at a temperature of 40 degrees, the screw transmission or bearing with 50 mm2/s of the lowest viscosity mineral oil. The amount of oil lubrication depends on the operating conditions. Grease lubrication If grease lubrication is used, lubrication is recommended in accordance with the accuracy standard 2 acc.to DIN51825. The following standards are available:
? KLUBER Isoflex NBU 15
? OPTIMOL OPTITEMP TT1
Grease should be added every 6 to 10 months when the machine is operating normally. Do not mix grease of different materials during machine operation.
9. Ball Screw Sealing Grade Selection
Ball screw sealing grade depends on its working environment, there are three different sealing standards to choose from:
? Polyamide cleaning ring
? Polyamide cleaning ring with felt ring
? Polyamide cleaning ring with felt ring and felt brush
? KSK ball screws are manufactured using the most advanced technology.
? Each screw is subject to multiple quality checks.
? Ensure that each ball screw product passes final inspection.
? Under normal circumstances, KSK's lead time is within six weeks of placing an order.
? Under special circumstances, KSK is able to deliver within five days.
? KSK never delays delivery.
? Once a customer has a question, KSK technicians will be on site to solve the problem.
? Ball screws can be customized according to customer drawings.
? Can be customized to a smaller nut size than the ISO 3408 standard.
? KSK actively assists customers in finding the right size and more cost-effective solutions.
? KSK provides repair and renovation services.
? If the existing ball screw can not be further repaired and refurbished, we will recover it in a short period of time and re-quote the replacement ball screw according to the original ball screw specifications.
1. Precision Ball Screw
Basic technical parameters:
? Diameter range: 12-180 mm
? Length up to 15.5 m
? Accuracy grade: P1-P5
? Minimum strength of screw material: Rm = 800 MPa
? Use efficiency: 94-97%
? Operating temperature from -40 °C to +80 °C (depending on lubrication)
Features:
? Accurate lead screw positioning
? Wide selection of sizes and leads
? Finished product can be pre-pressed according to customer requirements
Application:
? Grinding machine
? Milling machine
? Machining center
? Precision lathe
? Other
2. Basic Ball Screw
Basic ball screw is mainly used in the mechanical field of precision positioning requirements are not high. For example: transport or lifting machinery, wood processing machinery and so on. The lead screw is a cold-rolled thread lead screw.
Basic technical parameters:
? Diameter up to 63 mm
? Accuracy grade: T5, T7
? Minimum strength of screw material Rm = 650 MPa
? Use efficiency: 93-95% ? Operating temperature -20 °C to +60 °C (based on lubrication)
Features:
? High quality and low price
? Design standards, lead screw accuracy, service life and load class are all manufactured according to ISO3408 standard.
Application:
? Transportation machinery
? Wood processing
? Industrial automation
? Other
3. Heavy Duty Ball Screw
After the upgrade of the screw thread, the load and stiffness of the heavy ball screw can reach twice that of the standard ball screw. The operation efficiency of heavy ball screw is low, and it is only used in machinery with low speed and low efficiency. Usually no preload model.
Basic technical parameters:
? Thread diameter range: 40-200 mm
? Minimum strength of screw material Rm = 900 MPa
? Use efficiency: 93-95%
? This type of ball screw needs to use high-load lubricant lubrication
? Dynamic load up to 4,000,000N
Features:
? Long service life, high axial load
applications:
? Injection molding machine
? Voltage machine
? Lifting equipment
? hydraulic cylinder replacement equipment
? Other
4. Special Ball Screw
Telescopic ball screw:
? Mainly used in small size, large lead applications (such as loading and unloading platforms, hexapod robots, etc.).
? The screw is assembled by several ball screws, with ball nuts acting as bearing supports.
? The telescopic ball screw can replace the hydraulic cylinder, and has the characteristics of easy positioning and easy operation.
Linear drive:
? Linear drive can ensure that the machine maintains linear motion within the operating range, it can replace hydraulic cylinder operation. The linear drive can convert the rotating motion into linear motion, and the minimum utilization efficiency of the lead screw can reach 95%.
? Operating speed can be controlled or adjusted autonomously according to demand.
Non-threaded ball screws:
? Non-threaded ball screws are specially designed for transmission equipment control instruments and transportation equipment. These mechanical devices need to convert rotational motion into linear motion, without excessive rigidity and load requirements. This model is simpler and easier to produce and maintain.
Telescopic ball screw:
? Mainly used in applications with small size and large lead (such as loading and unloading platforms, hexapod robots, etc.).
? The screw is assembled by several ball screws, with ball nuts acting as bearing supports.
? The telescopic ball screw can replace the hydraulic cylinder, and has the characteristics of easy positioning and easy operation.
? This shape of thread is used only in spherical nuts, where the power is transmitted through the ball. The unthreaded lead screw uses a hardened grinding spindle for power transmission, in which the prepressed ball rolls. (Nut model and other technical parameters see KSK sample, you can go to the "Data download" column to choose to download)
According to the Czech national standard, KSK selects 42CrMo4 for the production of ball screw spindle, and the production material of screw nut selects 100CrMn6. The hardness of the nut and lead screw thread can reach 58-60 HRC. The minimum strength of the core part and unhardened part of the lead screw is Rm = 800 MPa. After reaching a specific wear limit, KSK will analyze the functional part of the transmission, after which the quality of the final product will be tested for long-term performance durability.
