Linear actuators are the self-contained solution up to approx. 100 kN; screw jacks are the more economical choice from 150 kN and strokes over 1 m. Both convert rotary motion into linear motion, yet their fundamentally different designs have clear consequences for cost, envelope size, and maintenance requirements.
Linear Actuator: Compact All-Rounder
In mechanical engineering, the term "linear actuator" typically refers to an electric linear drive in a compact design: motor, spindle assembly, and guide element are housed in an integrated enclosure. This makes the actuator space-saving and ready to use immediately – no complex assembly required.
Which designs exist (push-rod, column, or parallel actuators) and how spindle, toothed-belt, and direct drives differ in detail are covered in depth in our overview article Linear Actuators: Types at a Glance. For the comparison with the screw jack, the shared operating principle is enough here – converting a rotary motion into a linear stroke.
Practical Tip from TEA:
Linear actuators are particularly well suited for applications where space constraints are critical. Think of medical devices, laboratory automation, or compact industrial machines. The pre-calibrated accuracy also saves commissioning time.
Screw Jack: Modular Flexibility
The screw jack is a modular solution made up of individual components. It consists of a separate drive unit (motor + worm gear) and a downstream lifting unit (spindle + guides).
Structure of the Screw Jack
A typical screw jack consists of:
- Drive – electric motor (typically 1–15 kW)
- Worm gear – generates high reduction and torque
- Trapezoidal screw or ball screw – converts torque into lifting force
- Guide rails (LinRol/LinTrek) – stabilize the load during the stroke, especially under high lateral forces
- Load attachment device – can be individually customized
Modularity is the great advantage: you can select motor size, gear ratio, spindle, and guides completely independently. There is an optimal combination for every individual case.
Practical Tip from TEA:
Screw jacks allow the use of synchronization elements (driveshafts, belts) for exact coordination of multiple strokes. This is standard in printing presses, stamping presses, and production systems.
Direct Comparison
| Criterion | Linear Actuator | Screw Jack |
|---|---|---|
| Max. lifting force | Up to approx. 100 kN | 500 kN and higher |
| Stroke length | 100–1000 mm (constrained) | 100–5000 mm (freely selectable) |
| Stroke speed | 5–50 mm/s typical | 10–200 mm/s and higher |
| Positioning accuracy | ±0.5–1 mm standard | ±0.1–0.5 mm (depending on spindle) |
| Synchronization of multiple drives | Difficult, electronic only | Mechanically via shafts/belts possible |
| Design costs | €€ (catalog product) | €€€ (custom assembly) |
| Maintenance effort | Low | Medium to high |
| Scalability | Limited | Very flexible |
Application Scenarios in Practice
When Is the Linear Actuator the Best Choice?
Medical technology: In blood analyzers and dental chair units, space savings are critical. Linear actuators with compact design and precise positioning are ideal.
Laboratory automation: Pipetting robots and sample handlers benefit from the fast commissioning and precisely calibrated kinematics of the linear actuator.
Lightweight assembly: For loads under 50 kN and stroke lengths up to 500 mm, linear actuators are economically unbeatable.
When Is the Screw Jack the Right Solution?
Heavy-duty applications: Hydraulic presses, sheet metal technology, and stamping tools require the high forces and torques that only screw jacks deliver.
Synchronized multi-axis strokes: In printing presses (plate stroke, counter motion) and automated storage systems, multiple spindles must run in exact synchronization. The screw jack offers a robust mechanical solution via driveshafts.
Long and variable strokes: Strokes of 2–6 meters are no problem. Modularity allows adaptation to spatial requirements.
Selection Criteria for Your Application
The following questions help you make the right decision:
- How high is the required lifting force? If it exceeds 100 kN, the screw jack is the first choice.
- Is synchronization of multiple strokes necessary? If yes: screw jack with mechanical coupling.
- What are the space conditions? Tight installation space → linear actuator. Plenty of space → both solutions possible.
- What stroke length is required? > 1 m: screw jack is more economical.
- How critical is commissioning time? Short time required → linear actuator as catalog solution.
- What budget is available? Small budget, low requirements → linear actuator. Large budget, high requirements → screw jack.
Technical Note: Self-Locking & Standards Reference
Whether a screw-driven actuator holds a load without a brake is determined by the lead angle relative to friction: self-locking occurs when tan(lead angle) ≤ μ (μ = static friction coefficient, steel/steel ≈ 0.10–0.15). Trapezoidal screws (DIN 103) typically satisfy this condition and hold the load without a holding brake; ball screws (DIN 69051 / ISO 3408) with η = 0.90–0.98 are not self-locking and require a brake. Achievable positioning accuracy depends on the lead accuracy of the screw (accuracy classes per ISO 3408). All values are indicative — the manufacturer’s specifications are binding.
TEA Recommendation
There is no universal "best" solution. Both systems have their place. Linear actuators are perfect for fast, cost-effective solutions with moderate requirements. Screw jacks enable high-load, synchronizable, long-stroke applications. The decision depends on your specific requirements. Get advice from our application engineering team on sizing – we help you find the economically and technically best solution.
Which Solution Fits Your Application?
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