Accuracy and precision in drive technology

1. Why's accuracy so important?

Precision and accuracy are crucial characteristics in lifting drives for several reasons:

1. Positioning accuracy: Screw jacks are often used in applications where precise positioning is required. This can be the case in manufacturing, robotics, automation technology, or other fields. Precision ensures that the system can achieve the desired positions accurately.
2. Repeatability: In many applications, it's important that a screw jack not only positions accurately but does so consistently. Repeatability ensures that the system reaches the same positions during repeated movements.
3. Avoidance of undesired movements: Precisely manufactured screw jacks minimize play and axial play, which helps prevent unwanted movements, vibrations, or oscillations. This is especially important in applications where stability and control are critical.
4. Quality of end products: In manufacturing applications where screw jacks are used, the precision of positioning can affect the quality of the finished products. Precise movements are often crucial to ensure accurate cuts, assemblies, or other processes.

2. What is axial play?

Axial play in a trapezoidal or buttress threaded spindle refers to the axial movement play between the spindle and the nut that occurs when no external force is applied to the spindle. It's the free movement range along the axis of the spindle caused by tolerances, manufacturing inaccuracies, or other influences.

In practical applications, especially in positioning systems, axial play is important because it can affect positioning accuracy. If the axial play is too large, it can lead to unwanted movement and impair positioning precision.

2.1 Trapezoidal / Buttress threaded spindle

Depending on the screw jack size, the axial play typically ranges from 0.1 mm to 0.3 mm. Upon request, versions with reduced axial play (but with a minimum of 0.05 mm) are available.

We also offer a special version with adjustable axial play.

2.2 Ball screw spindle

Depending on the screw jack size, the axial play ranges from 0.03 mm to 0.05 mm.

With a pre-tensioned nut (choice of ball diameter), the axial play is between 0.01 mm and 0.03 mm.

With a pre-tensioned double nut, the axial play is less than 0.01 mm.

3. What is lateral play?

Lateral play in a basic version refers to the side-to-side movement or lateral displacement that can occur between two parts in a mechanical system. It's the side movement along an axis or direction caused by tolerances, manufacturing inaccuracies, or other factors.

In simple terms, lateral play means that parts in a system have some freedom to move or sway sideways when no external force is applied. This play can vary depending on the application and the specific design features.

3.1 Lateral play (y)

Occurs only in the basic version (G).

Depends on the play between the lifting spindle and the guide ring. The longer the spindle, the greater the deviation.

In the retracted state, y ≈ 0.2 - 0.6 mm depending on the size.

4. Tooth profile play in worm gear drives

Tooth profile play in a worm gear drive refers to the axial play or movement between the teeth of the worm and those of the worm wheel.

Tooth profile play arises from tolerances, manufacturing inaccuracies, and material deformations. It is the lateral displacement that occurs between the flanks of the worm and the worm wheel when no external forces are acting on the gear. If the tooth profile play is too large, it can lead to unwanted movement, vibrations, and reduced accuracy. On the other hand, if it is too small, it can result in increased wear and higher friction.

The tooth profile play in the delivered state is 0.1 - 0.3 mm. Over time, the tooth profile play changes due to wear.

5. Pitch accuracy

6. Repeatability

Repeatability measures the ability of a drive system to accurately return to a specific position or movement across multiple consecutive operating cycles. A low error in repeatability means that the system delivers consistent results.

7. Reverse play

Reverse play is the play or free movement space that can exist between the moving parts of a drive system. Reverse play can lead to inaccuracies as it may cause delays in movement or result in inconsistent positioning.

8. Pre-tensioned nuts

In some applications, pre-tensioned nuts are used to minimize reverse play. These nuts are adjusted to apply a constant pre-tension to the drive elements, resulting in improved accuracy.

9. Adjustable play

In some cases, it is possible to adjust or compensate for play or reverse play in a drive system to improve accuracy. This can be achieved by adjusting bearings, spindles, or other components.

10. Product tolerances

The manufacturing tolerances of the individual components of the drive system are also crucial for accuracy. Tighter tolerances generally lead to higher accuracy.

11. Radial play

Radial play refers to the side play or movement in the radial direction that can occur between the components of a drive system. Minimal radial play is important to ensure axial accuracy.