Trapezoidal-threaded spindles combined with trapezoidal ball nuts to a trapezoidal screw drive.The rolled NEFF-Trapezoidal Threads conform to DIN 103. By rolling the trapezoidal threads we realize a very high firmness and surface quality which lead, together with the trapezoidal ball nuts, to extraordinary good operating characteristics. Additionally, the trapezoidal threads are produced in a higher range of tolerance: you get norm compliant trapezoidal threads with very low backlash.
The trapezoidal travelling nut, produced from red brass by standard, (raw material 2.1090, G-CuSn7ZnPb, RG7), are available either cylindrical or with flange.
We also deliver trapezoidal ball nuts in bearing bronzes with higher solidity, as plastic nuts or as steel nuts.
The trapezoidal screw drive combines a trapezoidal-threaded spindle with a trapezoidal ball nut. The rolled NEFF trapezoidal threads conform to DIN 103. By rolling the trapezoidal threads we realize avery high firmness and surface quality which lead, together with the trapezoidal ball nuts, to extraordinary good operating characteristics. Additionally, the trapezoidal threads are produced in a higher range of tolerance: you get norm compliant trapezoidal threads with very low backlash, high straightness and pitch accuracy. The trapezoidal travelling nut, produced from red brass by standard, are available either cylindrical or with flange. We also deliver trapezoidalball nuts in bearing bronzes with higher solidity, as plastic nuts oras steel nuts.
Ball screws have become indispensable in many industrial environments. They are also called rolling screw drives with balls or rolling elements. Amongst other things, they convert rotational movements into precise linear movements or vice versa and are therefore often used as drive elements for linear movements wherein the screw is usually driven while the nut is connected to the part to be moved.
HOW DO BALL SCREWS WORK?
In a ball screw, the balls inside the nut ensure particularly low-friction movement by transmitting the force evenly between the screw and the nut. These balls move between the screw and the ball nut. In the standard version, the ball screw is not preloaded, thus combining precision with a long service life. The precision can be further increased by preloading the nut on the screw, maximizing precision and travel accuracy. Once the balls reach the end of the nut, they are returned to the other end via a recirculation system. The recirculation ensures smooth movement of the nut even at high load capacities, because the load is distributed over a large number of balls.
These properties make ball screws the perfect candidates for precise linear drive movements. With high repeat accuracy, they ensure precise and fast positioning. Ball screws can also be used in systems with multiple screw drives, where the power transmission and motion conversion of two parallel systems are realised together.
Ball screws are also increasingly used to act as a substitute for hydraulic systems, such as servo-assisted steering, presses, or injection moulding machines.
Thread rolling is a non-cutting cold working process. Threaded spindles manufactured by rolling have clear advantages over spindles manufactured by cuttiing with regard to the homogeneous grain structure and the resulting higher strength. On top of that, the extremely smooth surface texture leads to significantly longer service lives, especially in the case of trapezoidal screws. NEFF manufactures in tolerance class 7e according to DIN 103. Due to the necessary flow radius at the base of the thread, the core diameter of the rolled trapezoidal screws is approx. 0.1 x P smaller than that of spindles manufactured by cutting. Advantages of cold working by thread rolling:
Due to the high forces acting during thread rolling, we supply trapezoidal screws up to Ø 100 in rolled design.
The travel speed for trapeziodal screw drives depends on the pv value of the nut material as well as on the critical rotation speed of the trapezoidal screw drives (see the chapter on calculation of trapezoidal screw drives TGT).
In general the position in which the screw drive is installed can be chosen freely. Please consider that all radial forces that occur need to be absorbed by external guides.
The pitch accuracy (in µm) and the straightness (in mm) of the trapezoidal screws are measured at a thread length of 300 mm. They are dependent on the spindle diameter.
The self-locking depends on the friction coefficient and the pitch angle. There is a distinction between static and dynamic self-locking. In the case of static self-locking, a resting nut stays motionless as long as other influences don´t actuate it. In the case of dynamical self-locking, the trapezoidal screw drive comes to a halt the moment it is no longer powered. If the pitch angle is smaller than the friction angle, the trapezoidal screw drive is self-locking.
The duty cycle (ED) of trapezoidal screw drives affects the pv value of the nut. This means that the lower the duty cycle, the higher is the permissible pv value of the nut material. The duty cycle can be taken from the conversion tables and the appropriate pv value can be found in the chapter on "Calculations for trapezoidal screw drives".
The pv value is the product of the specific thread load (p) and the speed (v). The permissible pv values of individual materials thus result from the multiplication of force (N per mm2 of the thread’s bearing surface) and sliding speed (in m/min) and are primarily influenced by the heat dissipation of the nut and spindle material, the lubrication and the temperature resistance.
Specification pv value: N/mm² x m/min
All NEFF trapezoidal screw drives are designed for continous operations at ambient temperatures from –20°C to 80°C. Temperatures of up to 110°C are also permitted for brief periods. However a basic requirement is a constantly perfect lubrication. For operations at higher or lower temperatures, please contact our sales team.
The load ratings of trapezoidal screw drives are affected by many factors. The most important are:
Due to the numerous influences, it is not possible to calculate the exact service life. At a surface pressure < 5 N/mm2 , a long service life can be assumed.
If there is a risk of dirt accumulation, for example by fine chippings, we recommend additionally installing a bellows or a spiral spring cover. This protects the trapezoidal screw drive from external influences. Trapezoidal screw drives in a corrosion-resistant design can be delivered from stock or on demand.
NEFF´s rolled trapezoidal threads are available from stock in over 70 different sizes. We manufacture our spindles in various materials, also in stainless steel. Continuous process control guarantees consistently high quality. Please contact us for individual spindle specifications.
For movement drives with particularly favourable wear characteristics. EFMs can be mounted using the joints KON, KKA, MAFN and KAR. material: 2.1090 (CuSn7Zn4Pb7; RG7)
Thanks to the material used, the long red bronze nut TGM-LRM is characterised by particularly low wear. The major diameters are generously dimensioned for individual further processing. material: 2.1090 (CuSn7Zn4Pb7; RG7)
Steel nuts are mainly suitable for clamping operations, adjusting movements in manual operation and as fastening nuts. The short steel nut has a large major diameter, which provides space for individual adjustments. material: 1.0718 (11SMnPb30)
Steel nuts are suitable for clamping procedures, adjusting movements in manual operations and as fixing nuts. Material: 1.0718 (11SMnPb30)
Safety nuts are used to protect people and to prevent costly machine damage. It is about a second, load-free nut which is permanently coupled with the actual support nut and a distance X. With increasing wear of the support nut, the distance X to the safety nut decreases accordingly. In the case of direct danger to people, e.g. on lifting platforms, certain regulations must be observed in accordance with EN 280, EN 1493, EN 1570, EN 1756 (formerly VBG 14), among others. This is when the long safety nuts are used. When using long safety nuts, wear monitoring can be carried out by means of an electrical limit switch. material: 2.1090 (CuSn7Zn4Pb7; RG7)
In combination with the rolled trapezoidal screws of high surface quality, the ready-to-install plastic nuts are often an alternative to conventional materials. Particularly low-noise and in many cases lubrication-free, plastic opens up completely new areas of application. The long plastic nuts TGM-LRM have a large major diameter and can be adapted to existing designs by further processing. material: ZEDEX 100 (ZX-100K)
Sales Screw drives
Phone +49 7157 53890-13
Email d.sautter[at]neff-gt.de
NEFF Gewindetriebe GmbH
Karl-Benz-Straße 24
D-71093 Weil im Schönbuch
Fon. 07157 53890-0
info[at]neff-gt.de
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