Selecting the right stroke length means matching the actuator’s travel distance to your application’s motion requirements while accounting for installation space, force needs, speed expectations, and physical constraints like buckling. Get these calculations right and you can avoid costly mistakes and get reliable performance from your system.
What Is Stroke Length and Why Does It Matter?
Stroke length is how far your actuator’s rod travels from fully retracted to fully extended. Need to lift a hatch 18 inches? You need at least an 18 inch stroke. Sounds straightforward enough, but here’s the thing: the stroke you pick also affects how big the actuator is, how much force it can deliver, how fast it moves, and whether you’ll run into mechanical problems like buckling.
Longer strokes mean the actuator is longer even when it’s retracted, and that can be a real headache if you’re trying to fit it into a tight space. You also have to watch out for mechanical issues when you’re pushing heavy loads straight up or running the thing at high speeds.
Key Factors That Influence Stroke Selection
A bunch of different factors work together to determine which stroke length makes sense for what you’re doing. Let’s go through each one so you know what to look for.
Required Range of Motion
First thing you need to do is measure exactly how far your load has to travel. Opening a valve from closed to wide open? That distance is your minimum stroke requirement. Here’s what else you should think about:
- Get precise measurements instead of eyeballing it
- Factor in any angular motion that changes how far things actually move
- Think about whether you want adjustable limit switches if the distance might change
- Consider if you’ll need to reconfigure things down the road
Installation Space and Physical Constraints
Here’s something people forget: a longer stroke means a longer actuator even when it’s pulled all the way in. A 12 inch stroke actuator is going to be way shorter when retracted compared to a 24 inch model. You need room for:
- The whole assembly in both positions, retracted and extended
- Motor housing, gearbox, screw mechanism, and whatever brackets you’re using
- Pivoting brackets if the angle changes while it’s moving
- Enough space to actually install it, maintain it, and swap it out if needed
Working with limited space? You might have to settle for a shorter stroke or get creative with mounting angles. Pivoting brackets can be really useful here because they handle angle changes as the actuator moves, and that can let you get away with a shorter stroke than you’d otherwise need.
Mounting Orientation and Geometry
Mounting the actuator vertically is different from mounting it horizontally. When you mount it straight up and it’s pushing something upward, gravity is fighting against you on the way up. That means you need more force to extend it and less force to bring it back down.
The angle between the actuator and whatever it’s moving matters too. If they’re not lined up perfectly, you’re going to lose some efficiency and you might need a longer stroke to get the same amount of actual movement. That’s why you see pivoting brackets used so often because they’re there to deal with the angle changes that happen when things are moving.
Force and Speed Trade Offs
Electric actuators with longer strokes usually perform differently than shorter ones in the same product line. Here’s the basic relationship you’ll see:
- More force typically means slower movement
- Faster movement means you give up some pushing power
- Longer strokes take more time to finish their travel
- If you need both long stroke and high speed, you might need a beefier model or a completely different type of actuator
This happens because actuators use gears to turn motor speed into force. Want more pushing power? You need higher gear ratios, and those slow things down.
Buckling Force Considerations
Long strokes can create buckling problems, especially when you’re compressing things. The lead screw or ball screw works kind of like a column, and if you push too hard on it, it can buckle and break.
The longer the stroke, the easier it is to buckle. If you’re looking at a stroke over 18 to 24 inches and you’re applying serious compression loads, here’s what you need to do:
- Figure out the critical buckling force for that stroke length
- Compare it to the maximum force you actually need
- Add a safety margin, usually about 25% above what you calculated
- Think about using a shorter stroke or mounting it differently if buckling seems like it’ll be an issue
Critical Speed and Resonance
Really long strokes running at high speeds can cause resonance in the screw mechanism. When that happens, you get vibration, the positioning gets less accurate, and the internal parts wear out faster.
There’s something called critical speed, that’s the speed where resonance starts becoming a problem, and it goes down as strokes get longer. If you need both long travel and high speed, you’re probably better off looking at belt driven systems or linear motors instead of the traditional screw driven ones.
Duty Cycle Impact
Longer strokes mean longer cycle times. If your actuator is moving more and resting less, it’s going to generate more heat. That affects the duty cycle rating, which basically tells you how much of the time the actuator can run without overheating.
Most standard electric actuators have 10 to 25% duty cycles where they can run for that chunk of time in any given period. You can get premium models that handle higher duty cycles, and some can even run continuously. If you’re going to be cycling through a long stroke frequently, you’ll want to account for that when you’re picking out an actuator.
Step by Step Stroke Selection Process
Now that you know what factors matter, here’s how to actually work through picking the right stroke.
1. Measure Your Required Travel Distance
Get precise measurements of how far your load needs to move. Don’t guess on this one because you need to grab a tape measure or ruler and measure the full range from where it starts to where it ends up.
2. Add Safety Margins
Build in a little buffer for where the limit switches sit and to keep the actuator from slamming into the ends. A 5 to 10% margin gives you room to make adjustments and keeps you from stressing the end stops. The limit switches, either internal or external, will automatically stop the actuator at those endpoints.
3. Check Your Available Space
Measure where the actuator’s going to mount in both its retracted and extended positions. Don’t forget that the motor housing, mounting brackets, and any pivoting hardware all add to how much length you’re dealing with. The stroke length you need directly affects how big the actuator is when it’s fully retracted.
4. Calculate Required Force and Speed
Figure out how much force you need to move your load and how fast it needs to get there. Check the manufacturer’s specs to make sure that actuators with the stroke length you want can actually deliver enough force at a speed that works for you.
TheAOX L Series linear electric actuators offer force ranges from 3000N to 30000N with different stroke options, plus intelligent control features that help optimize how they perform across various stroke lengths.
5. Verify Duty Cycle Compatibility
Calculate how often the actuator is going to cycle through its full stroke. If you’re running it frequently, make sure the duty cycle rating can handle your usage pattern without overheating. Longer strokes or frequent movement affects the duty cycle, and that ties directly into heat management and how long the components last.
6. Consider Drive Mechanism Type
Different drive mechanisms work better depending on how long the stroke is:
- Ball screw actuators give you high efficiency and precision across a pretty wide range of strokes, so they work well when you need high force and good accuracy
- Lead screw models are fine for lighter loads and less frequent use, but they have practical limits on stroke length because of efficiency issues and potential resonance problems
- Belt driven systems are great for really long travel and high speed work where you don’t need super precise positioning
For travel distances over 2 meters, rack and pinion systems or linear motors might be more cost effective and give you better consistent performance than traditional screw based actuators.
Using Manufacturer Resources
Most manufacturers have selection tools and calculators that make the stroke selection process easier. You can plug in your motion requirements, force, and speed parameters, and these tools will filter down to products that match what you need.
Technical datasheets usually show stroke length options right alongside force ratings, speed specs, and duty cycle info. A lot of manufacturers also have online calculators that’ll run the math for force, speed, and potential problems like buckling to help you narrow things down.
If you’re dealing with a demanding application or an unusual mounting setup, reach out to the manufacturer’s technical support. They can help you work through the trade offs and confirm that the stroke length you picked is going to work with everything else you need.
Common Stroke Selection Mistakes to Avoid
Even people who’ve done this before can miss important details when they’re selecting stroke length. Watch out for these common mistakes:
- Getting the travel distance wrong or just estimating instead of measuring properly
- Forgetting about how long the actuator is when it’s retracted, especially in tight spaces
- Ignoring how force and speed trade off against each other because this gets more pronounced with longer strokes
- Missing buckling risks when you’re doing vertical compression with long strokes
- Underestimating how much duty cycle you actually need for frequent operation
- Not thinking about how mounting angle interacts with effective stroke length
Final Considerations
Stroke selection doesn’t exist in a vacuum because it interacts with force, speed, duty cycle, and how you’re mounting the thing. If you can’t find a single actuator that hits all your requirements at the stroke length you want, you might need to rethink your design or look at different types of actuators altogether.
Aoxiang has over 30 years of manufacturing experience and can help you figure out the optimal stroke length for what you’re working on. The AOX L and AOX Q L Series cover force ranges from 3000N to 40000N with customizable stroke options, intelligent control modes, and IP67 or IP68 protection ratings.If you need help working through the calculations or you’re dealing with a challenging application that needs a customized solution, our team can give you detailed guidance tailored to your specific requirements. Contact us today.y has protected critical infrastructure for decades because it works independently of power supplies. When you need absolute certainty about valve positioning during emergencies, this proven technology delivers consistent results that you can verify through mechanical position indicators even during complete power loss.
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