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MODULE 6 OF 8

Linear Drives: Ball Screws, Lead Screws, and Actuators

5 units · approx. 37 minutes total · Step 1 of 8

Getting Started

This module focuses on linear drives: how a ball screw converts rotational motion into linear motion; how its buckling load and critical speed depend on the core diameter, bearing spacing, and bearing type; how a screw jack turns this into a complete stroke unit—and when a linear actuator is the more cost-effective choice instead.

Calculation exercises on drive torque and stroke speed, a hands-on exercise using the spindle stroke configurator, flashcards, and a case study bring the theory to life; a self-test at the end checks your understanding of the material.

Learning Objectives – After completing this module, you will be able to:

  • calculate the drive torque of a ball screw and a screw jack;
  • Calculate the buckling load and critical speed of a spindle for a given bearing arrangement and determine the permissible operating load and speed;
  • Distinguish between ball screws and trapezoidal screws in terms of efficiency and self-locking;
  • distinguish between the four types of linear actuators and match them to an application;
  • Select the appropriate linear actuator and screw jack for a given application.

Learning units

Five short learning units (6–8 minutes) with learning objectives, examples, and knowledge checks—standalone learning content for this module, maintained independently of the website’s guides. Progress is saved locally in this browser.

0 of 5 units

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Calculation Exercise 1: Drive Torque of a Ball Screw

A ball screw transmits an axial force F = 8,000 N with a lead Ph = 10 mm and an efficiency η = 0.85.

Calculate the drive torque M.

For verification: Ball screw calculator (opens in a new tab)

Computer Exercise 2: Spindle Stroke Design

A screw jack has a lead of Ph = 8 mm and a gear ratio of i = 15. The drive speed is n = 900 min⁻¹.

Calculate the stroke speed v.

For verification: Spindle stroke design (opens in a new tab)

Selection Exercise: Determine the Size

The screw jack configurator on the TEA product page for screw jack elements guides you from lifting force to size in just a few steps.

Assignment

Use the configurator to find the size for 25 kN lifting force and 300 mm stroke.

Go to the Spindle Stroke Configurator (opens in a new tab)

Flashcards: Linear Technology Terms

Eight technical terms from the glossary—click on the card (or press Enter or the spacebar) to see the definition.

Flashcards

Tap to see the definition.

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Ball screw
Precision linear motion element with a ball-bearing spindle that converts rotational motion into linear motion—with efficiencies exceeding 90%, it is significantly more efficient than conventional sliding screws. Source: Glossary “Ball screw”
Lead
The lead (also known as pitch) indicates how far the lead screw nut or carriage moves linearly during one complete revolution (360°) of the lead screw —it is the key design parameter for the force, speed, and precision of linear actuators. Source: Glossary “Lead”
Axial play
Axial mechanical clearance of a bearing or guide—the amount by which a component can be displaced in the direction of the shaft axis without requiring a significant force. Source: Glossary “Axial play”
Self-locking
A characteristic of a gearbox or worm gear drive whereby a load acting on the output side cannot cause the gearbox to rotate backward—an essential safety feature in hoisting and actuator systems. Source: Glossary “Self-locking”
Linear Guides
Linear motion guidance systems—available in profiled rail, round rail, or telescopic designs—are used wherever precise, low-backlash linear motion is required. Source: Glossary “Linear Guides”
Dynamic load rating
The dynamic load rating C is the load at which a guide or bearing series achieves a defined nominal service life (typically 100 km of travel). It is the key parameter in the L10 service life calculation: The higher the C value, the longer the service life at a given operating load. Source: Glossary “Dynamic load rating”
L10 service life
The L10 service life is the nominal service life (in kilometers of travel) that at least 90% of all guides in a series achieve without material fatigue. It relates the dynamic load rating C to the equivalent operating load P and is the standard parameter for the service life design of linear guides and rolling bearings. Source: Glossary “L10 service life”
Zero backlash
A state in which there is no measurable mechanical play in a drive element or guide—the fundamental prerequisite for high-precision positioning, minimal reversal errors, and maximum stiffness. Source: Glossary “Zero backlash”

Case study: 2-metric-ton lifting table, 500 mm stroke

A customer in the intralogistics sector is planning a lift table for pallets with a load capacity of up to 2 t and a stroke of 500 mm. To prevent the platform from tilting during lifting, it is raised simultaneously at all four corners. The design engineer has narrowed the options down to two variants: four individual linear actuators, each electronically synchronized via the control system, or four screw jacks, which are mechanically driven by a single motor via drive shafts. He asks TEA which solution is technically more suitable.

Key Questions

  1. Is the lifting force of a single linear actuator (up to approx. 100 kN) sufficient for one-quarter of the 2-t load at one of four lifting points?
  2. According to the learning unit, which of the two systems can be synchronized mechanically, and which can only be synchronized electronically?
  3. Why is this relevant for a four-point-lift table?
View Worked Solution

1. Yes, clearly: With four lifting points, each corner bears only about a quarter of 2 t (approximately 5 kN per corner) in theory—which is well within the capacity of both a linear actuator (up to approx. 100 kN) and a screw jack. So the lifting force alone does not determine the outcome.

2. According to the learning unit, only the screw jack can be mechanically coupled via drive shafts or synchronous belt drives. According to the comparison table, linear actuators can only be synchronized electronically—which is explicitly described there as “more difficult.”

3. A lifting table with four lifting points must rise to exactly the same height; otherwise, the platform will tilt. The guide explicitly identifies mechanical shaft coupling as a robust solution for “synchronized multi-axis lifts,” such as those found in printing presses and automated storage systems. For this application, the screw jack with mechanical synchronization is therefore the recommended choice in the guide—even though the lifting force alone would be sufficient for both systems.

Technical basis exclusively: Linear actuator vs. screw jack (opens in a new tab)

Self-test

10 questions about this module—immediate feedback with explanations and source links. The module is considered complete if you score 7 out of 10 points or higher.

Self-test

10 questions for this module. You see right after each answer whether it was correct.

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Before each answer, you state how confident you feel. This helps distinguish knowledge gaps from uncertainty. It has no effect on the score.

Question 1 of 10

Question 1 of 10

According to the learning unit, what are the three main components of a ball screw?

Explanation

A ball screw consists of the lead screw (with a ground or rolled groove per ISO 3408), the nut with ball recirculation (deflection), which bears the load and continuously returns the balls to the starting point, and the balls rolling between them. A cage that keeps the balls spaced apart is not common in standard nuts.

Source: Ball Screws: Selection and Design →
Question 2 of 10

Which formula calculates the drive torque M of a ball screw based on the axial force F, the pitch Ph, and the efficiency η?

Explanation

M = F · Ph / (2000 · π · η) – the same formula used by the ball screw calculator (F in N, Ph in mm, η as a decimal value).

Source: Ball Screw Calculator →
Question 3 of 10

On what power of the core diameter d_r does the moment of inertia I of a spindle depend?

Explanation

I = π · d_r⁴ / 64 – the moment of inertia increases with the fourth power of the core diameter. This makes the core diameter the most effective lever against buckling and bending resonance.

Source: Ball Screws: Selection and Design →
Question 4 of 10

What is the maximum percentage of the critical speed n_krit that the operating speed of a ball screw should be?

Explanation

n_zul = 0.8 · n_krit – 80% of the critical (bending resonance) speed is considered the permissible operating speed.

Source: Ball Screws: Selection and Design →
Question 5 of 10

What is the typical efficiency range for a trapezoidal screw (DIN 103) in a screw jack?

Explanation

Trapezoidal screws achieve an efficiency of 0.30–0.50 (sliding friction)—significantly less than ball screws with 0.90–0.98; however, they are self-locking at small lead angles.

Source: Properly Sizing Screw Jacks →
Question 6 of 10

What is the difference between a “non-rotating screw” and a “rotating screw” (travelling-nut design) in a screw jack?

Explanation

In the case of a non-rotating screw, the spindle nut acts as a worm gear in the gearbox; the spindle, which is secured against rotation, extends axially. In a rotating screw, the spindle is fixed axially, and a travelling nut moves along it—the installation height remains constant. The rated lifting force depends on the spindle and gearbox size; however, under compressive loads, the spindle’s buckling load may limit the permissible lifting force, which also depends on the design, specifically the free spindle length and the bearing arrangement.

Source: Properly Sizing Screw Jacks →
Question 7 of 10

Which type of linear actuator is suitable for strokes ranging from 500 to 3,000 mm?

Explanation

The open spindle is designed for long strokes (500–3,000mm); the push rod becomes uneconomical at strokes of approximately 500 mm or more, while the telescopic version is designed for extreme compactness with medium strokes.

Source: Linear Actuators: An Overview of Types →
Question 8 of 10

Which statements are correct? (Multiple choice)

Explanation

Screw jacks are mechanically coupled via shafts/belts (A) and are more cost-effective starting at approximately 150 kN (C). In fact, screw jacks achieve the higher lifting forces, not linear actuators (B is incorrect), and ball screws are not self-locking precisely because of their high efficiency (D is incorrect).

Source: Linear Actuator vs. Screw Jack →
Question 9 of 10

A ball screw transmits F = 5,000 N at Ph = 5 mm and η = 0.92. What is the drive torque M in Nm?

Nm
Explanation

M = F · Ph / (2000 · π · η) = 5,000 · 5 / (2000 · π · 0.92) ≈ 4.32 Nm.

Source: Ball Screw Calculator →
Question 10 of 10

A screw jack has n = 1,500 min⁻¹, Ph = 4 mm, and i = 25. What is the stroke speed v in mm/s?

mm/s
Explanation

v = n · Ph / (i · 60) = 1,500 · 4 / (25 · 60) = 4.0 mm/s.

Source: Spindle Stroke Design →

Advanced Topics (optional)

The four key guide articles in this module, in case you’d like to delve deeper. Reading them is not required for the learning units and self-test in this module.

Curriculum v0.1 (Beta) · As of 17.09.2026 · content carefully prepared and reviewed – final sign-off to follow

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