How to Select an Electric Linear Actuator: An OEM Guide Beyond Force and Stroke
Select an electric linear actuator by verifying its force, loaded speed, stroke, mounting geometry, duty cycle and control compatibility against the equipment’s operating conditions—not by matching catalogue maximums alone.
For OEM engineers and purchasing teams, the useful question is not simply “Which actuator has enough force?” It is “Which complete configuration fits the mechanism, operating sequence and control system?” This guide uses RUNDA specification-sheet examples to show the differences that matter before ordering samples.
Core Steps: Build a Practical Actuator Specification
- Calculate force throughout the movement. Identify pushing and pulling requirements, mounting geometry, friction and changing loads. Equipment weight alone does not establish the actuator force required by a hinged or linked mechanism. Specify stationary holding requirements separately.
- Check the complete mounting envelope. Confirm stroke, retracted and extended mounting lengths, attachment details, motor clearance and cable routing. Inspect clearance throughout the movement, not just at its endpoints.
- Compare loaded speed within the same configuration. Match voltage, load, screw lead and speed from one technical-table row. Do not combine the maximum speed of one variant with the maximum force of another.
- Define the operating sequence. Provide extension time, retraction time, rest periods and peak repetition frequency. The RUNDA sheets compared below state a 10% duty cycle: two minutes operating followed by eighteen minutes resting.
- Confirm the electrical and control interface. Supply existing controller documentation where applicable. Check current requirements, wiring, connector pinout and feedback. For coordinated movement, define the allowable position difference and fault response.
- Validate a sample against written acceptance criteria. Test the intended actuator, controller, power supply, harness and mounting arrangement together. Record loaded travel time, movement behaviour and the operating sequence before approving the production specification.
RUNDA Model Comparison: Why Force Alone Is Not Enough
The following comparison uses the 24 V, 6,000 N maximum-load configuration listed in the technical tables for RD-398B, RD-398C and RD-398H1.
| Specification | RD-398B | RD-398C | RD-398H1 |
|---|---|---|---|
| Supply voltage | 24 V DC | 24 V DC | 24 V DC |
| Listed maximum load | 6,000 N | 6,000 N | 6,000 N |
| Screw lead | 4 mm | 4 mm | 4 mm |
| No-load speed | 7 mm/s | 7 mm/s | 5 mm/s |
| Loaded speed | 4 mm/s | 4 mm/s | 3.5 mm/s |
| Listed self-locking force | 5,000 N | 5,000 N | 6,000 N |
| Duty cycle | 10% | 10% | 10% |
| Stated run–rest sequence | 2 min on / 18 min rest | 2 min on / 18 min rest | 2 min on / 18 min rest |
| Service temperature | 5–40°C | 5–40°C | 5–40°C |
Data basis: the source sheets describe technical-table values as average test data at 25°C. These are reference values, not guaranteed minimum performance limits or independent comparative test results. Confirm the exact ordered configuration, stroke-related load limitations and acceptance criteria before procurement.
Advantages and Trade-offs
| Model | Documented selection advantage | Trade-off or limitation |
|---|---|---|
| RD-398B | The feature list includes thrust configurations up to 8,000 N. | A longer calculated minimum mounting length than RD-398C in the 200 mm stroke example below. |
| RD-398C | A shorter calculated minimum mounting length in that example. | The highest thrust option in the reviewed feature list is 6,000 N. |
| RD-398H1 | A higher listed self-locking force in the compared 24 V, 6,000 N rows. | Listed loaded speed is 3.5 mm/s rather than 4 mm/s. |
These are configuration-specific differences, not a ranking of overall product quality. A higher catalogue force does not automatically make a model the better fit.
Practical Detail 1: The Same Stroke Can Require Different Mounting Lengths
For a 200 mm stroke, the reviewed installation formulas give the following minimum mounting lengths:
| Model | Calculation at S = 200 mm | Calculated minimum length |
|---|---|---|
| RD-398B | S + 175 mm | 375 mm |
| RD-398C | S + 150 mm | 350 mm |
| RD-398H1 | S + 155 mm | 355 mm |
At this stroke, RD-398C has a calculated mounting length 25 mm shorter than RD-398B. This can matter when equipment mounting points are already fixed. It does not establish drop-in compatibility: attachment dimensions, housing clearance, load requirements and electrical connections still need checking.
Practical action: include both required stroke and available retracted mounting distance in the inquiry. For longer strokes, use the applicable safety-distance allowance and confirm the approved installation drawing rather than extrapolating this example.
Practical Detail 2: An 8,000 N Label Does Not Describe Every Load Direction
The RD-398B and RD-398H1 feature lists both include an 8,000 N maximum-thrust option, while the listed maximum tension for that option is 6,000 N. Their 24 V, 8,000 N technical-table rows also differ:
| Specification | RD-398B | RD-398H1 |
|---|---|---|
| Listed self-locking force | 6,000 N | 8,000 N |
| No-load speed | 4.4 mm/s | 4 mm/s |
| Loaded speed | 3 mm/s | 3 mm/s |
Two configurations can therefore share the same listed thrust and loaded speed while differing in stationary holding specifications.
Practical action: document required push force, pull force and stationary holding load separately. Confirm the holding conditions and power-loss behaviour; a self-locking figure alone does not establish a complete safety function.
Common Misconceptions and FAQ
Can I describe these models as continuous-duty actuators?
No. The reviewed sheets specify intermittent operation: 10% duty cycle with two minutes operating followed by eighteen minutes resting.
Can I describe every RD-398B as an 8,000 N actuator?
No. RD-398B has several listed load configurations. Identify the ordered variant and verify the permitted load for its stroke and operating conditions.
Does optional Hall feedback mean synchronization is included?
No. The feedback option must be specified, and coordinated movement must be confirmed with the compatible controller and complete system. The reviewed feature lists identify single Hall feedback and a safety nut as options, not universal requirements or guarantees.
Can these actuators accept side loads?
The reviewed sheets state that lateral loading is not allowed. Address guidance and alignment in the equipment design rather than relying on the actuator to absorb side loads.
Can a matching voltage and connector prove replacement compatibility?
No. Check pinout, signals, current requirements, mounting dimensions, loaded speed, duty cycle and holding behaviour. Validate the replacement in the equipment before production use.
Can I choose a model from these tables alone?
Use them to create a shortlist. Final selection requires the exact configuration, approved dimensions, operating conditions and equipment-level validation.
Technical Sources
RUNDA English product specification sheets for RD-398B, RD-398C and RD-398H1: Features and Options, Technical Parameter, and Product Dimension Drawing sections (PDF pages 2, 3 and 5). The 200 mm mounting comparison is calculated from those drawings. Request the applicable approved specification and drawing for your proposed order.
Request a RUNDA Configuration Review
Send your equipment application, required push and pull forces, stroke, available mounting distance, supply voltage and operating sequence. State stationary holding and coordinated-movement requirements separately. Include an installation drawing and existing controller details where available.
If the project involves a control box or hand control, include those requirements in the same inquiry. If some parameters are unknown, start with the equipment purpose and movement you need.