trapeziodal screw drives (TGT)

TRAPEZOIDAL LEAD SCREW AND TRAPEZOIDAL LEAD SCREW NUT COMBINED TO FORM A TRAPEZOIDAL LEAD SCREW SYSTEM

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.

General technical data (TGT)

Manufacturing process

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:

  • higher strength
  • better surface quality
  • high profile accuracy due to very low tool wear

Due to the high forces acting during thread rolling, we supply trapezoidal screws up to Ø 100 in rolled design.

Speeds

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).

Installation position

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.

Accuracy classes and straightness of spindles

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.

Self-locking

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.

  • self-locking in motion when pitch angle α< 2.4°
  • self-locking from standstill when pitch angle α > 2.4° up to < 4.5°
  •  no self-locking when pitch angle α> 4.5°

Selection criteria for trapeziodal nut material

Characteristics Red bronze 2.1090 (CuSn7Zn4Pb7; RG7)

  • suitable for transmission threads
  • constant lubrication necessary
  • good weather resistance/sea water resistance
  • suitable for high loads
  • good sliding properties
  • high material strength/tensile strength
  • high heat resistance

 

Characteristics Plastic Zedex ZX100K

  • suitable for transmission threads
  • lubricant-free application possible
  • good weather resistance
  • low noise
  • low weight
  • high fatigue strength
  • maintenance-free dry run
  • FDA- and LABS-compliant - FDA - Food and Drug Administration (U.S. authority)
  • KTW certification - Guideline on the hygienic assessment of organic materials in contact with drinking wate

Characteristics Steel 1.0718 (9SMnPb28K)

  • not suitable for transmission threads
  • for adjusting movement while running in manual mode
  • suitable for clamping procedures and useful for fastening nuts

Duty cycle

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".

Pv value

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

Temperatures

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.

Load capacity

The load ratings of trapezoidal screw drives are affected by many factors. The most important are:

  • bearing surface
  • material pairing
  • surface quality
  • pv value
  • duty cycle
  • lubrication
  • temperature

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.

Efficiency

The diagram shows the efficiency of lubricated and non-lubricated trapezoidal screw drives as a function of the pitch angle.

Extreme operating conditions

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.

Axial backlash

pitch p: Max. Axial backlash (in mm)
2 0,13
16x2 0,14
3 0,15
12x3 0,16
4 0,19
5 0,20
24x5 0,21
6 0,24
7 0,25
8 0,28
9 0,30
10 0,30
14 0,36

The table shows the max. axial backlash as a function of the nominal Ø or pitch according to DIN 103 tolerance zone 7e/7H when new.

Trapezgewindespindel (RATS, RPTS)

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.

All information about the trapezoidal threads

Our trapezoidal screw nuts

Ready-to-install Red Bronze Flange Nut (TGM-EFM)

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)

All information about the trapezoidal thread nut

Long Red Brass Nut (TGM-LRM)

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)

All information about the trapezoidal thread nut

Short Steel Nut (TGM-KSM)

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)

All information about the trapezoidal thread nut

Hexagonal Nut (TGM-SKM)

Steel nuts are suitable for clamping procedures, adjusting movements in manual operations and as fixing nuts. Material: 1.0718 (11SMnPb30)

All information about the trapezoidal thread nut

Safety Nut (TGM-SFM)

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)

All information about the trapezoidal thread nut

Long Plastic Nut (TGM-LKM)

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)

All information about the trapezoidal thread nut

Your personal contact

Bild: Dieter Sautter
Dieter Sautter

Sales Screw drives

Phone +49 7157 53890-13
Email d.sautter[at]neff-gt.de