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FT Series

Electric Linear Actuator

Industrial - Exlar

  • Designed for trouble-free operation in any environment
  • Compatible with a wide range of motors
  • Sealed housing options for severe environments. 
  • Multiple models and sizes with planetary roller screw. 
More Details

Overview

FT Series

Quick Data
Model
Frame Sizes in (mm)Stroke (in)Max Continuous Force lbf (kN)Max Speed in/s (mm/s)
FT353.5 (90)6, 12, 18, 24, 36, 485,000 (22.2)59.3 (1506)
FT454.7 (120)6, 12, 18, 24, 36, 4810,000 (44.5)23 (584)
FT605.9 (150)12, 24, 36, 4820,000 (89.0)39 (991)
FT807.9 (200)12, 24, 36, 4840,000 (177.9)34.4 (874)

Hydraulics are being replaced by robust roller screw actuators, which offer enhanced power and performance. 

The FT Series actuators from Exlar® use a planetary roller screw mounted inside an extruded aluminum housing. These electric linear actuators are compatible with a wide range of standard motors. Motor mounting and gearing configurations are available to meet the requirements of a wide variety of applications. The standard product is offered in four frame sizes with standard stroke lengths up to 36 inches (914 mm) and a load rating up to 40,000 lbf (177 kN).

Engineered Performance

As with all Exlar roller screw actuators, the FT Series delivers high load capacity, high speed, and exceptionally long life compared to acme and ball screw solutions. At equivalent sizes, under moderate to heavy loads, you can expect the FT Series to deliver up to 15 times the working life of other solutions. Greater power, exceptional durability and a much smaller footprint make the FT series a superior electric alternative to hydraulics.

Other Advantages

  • Versatile design can be used for a range of applications. 
  • Multiple frame sizes and an array of options to address almost any requirement
  • Engineered solution accelerates integration and minimizes downtime

Related Industries

Quick Data
Models:FT35, FT45, FT60, FT80
Frame Sizes:3.5, 4.8, 6.0, 8.0 in (89, 122, 152, 203 mm)
Stroke Lengths:6, 12, 18, 24, 36, 48 in (152, 305, 457, 610, 914, 1219 mm)
Linear Speed:up to 60 in/s (1524 mm/s)
Maximum Force:up to 40,000 lbf (178 kN)
Standards/Ratings:IP65S

AA = FT Frame Size
35 = 3.5 inch (90 mm)
45 = 4.7 inch (120 mm)
60 = 5.9 inch (150 mm)
80 = 7.9 inch (200 mm)

BB = Stroke Length
06 =   6 inch (152 mm)  FT35, FT45
12 = 12 inch (305 mm)  FT35, 45, 60, 80
18 = 18 inch (457 mm)  FT35, 45
24 = 24 inch (610 mm)  FT35, 45, 60, 80
36 = 36 inch (914 mm)  FT35, 45, 60, 80
48 = 48 inch (1219 mm)  FT35, 45, 60, 80

CC = Screw Lead
05 = 0.2 inch,  FT35, 45
06 = 0.2a3 inch,  FT60, 80
10 = 0.39 inch,  FT35, 45
12 = 0.47 inch,  FT60, 80
20 = 0.79 inch,  FT35
30 = 1.18 inch,  FT60, 80

D = Mounting Style1
N = None
F = Front flange, English
Z = Front flange, Metric,  FT45
R = Rear flange, English4, 5
C = Rear clevis, English4, 5
G = Rear clevis, Metric4, 5
Y = Rear eye, English4 FT45
W = Rear eye, Metric4 FT45
L = Side lugs
S = Side mount, English  FT35, 60, 80
J = Side mount, Metric  FT35, 60, 80
T = Side trunnion mount, English5, 6 FT35, 60, 80
Q = Side trunnion mount, Metric5, 6 FT35, 60, 80
2 = Rear trunnion mount, English,  FT45
P = Rear trunnion mount, Metric,  FT45
E = Extended tie rods, English
M = Extended tie rods, Metric

E = Motor Mounting Configurations3
N = None
I =  Inline direct drive (includes Exlar standard coupling)
P = Parallel, 1:1 belt reduction
Q = Parallel, 2:1 belt reduction

F = Rod End
M = Male, US standard thread
A = Male, metric thread
F = Female, US standard thread
B = Female, metric thread

GGG = Motor Mount Provisions3,4
See catalog for details

MM = Mechanical Options2
XT = High capacity roller screw

Limit Switches 
See catalog for details






NOTES:
1. Mounting face size, shaft length and other details of particular motors may require special adapters or provisions for mounting. Always discuss your motor selection with your local sales representative.
2. For extended temperature operation consult factory for model number.
3. MAX Std. motor size: FT35: 5.6 inch/165 mm, FT45: 7.1 inch/215 mm, FT60: 7.9 inch/215 mm, FT80: 8.5 inch/300 mm. For oversized motors, contact your local sales representative.
4. Not available with inline motor mount, contact your local sales representative.
5. Application details must be approved for use with an FT80.
6. IP65 environmental sealing option not available.

* Some options are not available with every configuration. For options or specials not listed above contact your local representative.


L1, L2, L3 = Adjustable External Travel Switch(es)
External travel switches indicate travel to the controller and are adjustable for either the home or end position.


XT = High Capacity Roller Screw
Note: The XT designation is used o specify several different special travel options. When ordering, it is important to describe, in detail, the specific XT option(s) that you need

Product Specifications

FT35 Performance SpecificationsOpen arrow

FT35 Mechanical Specifications

    HIGH CAPACITY STANDARD CAPACITY
    5 10 20 5 10 20
Screw Lead in 0.197 0.394 0.787 0.197 0.394 0.787
  mm 5 10 20 5 10 20
Maximum Force^1 lbf 5000 5000 5000 5000 5000 5000
  kN 22.2 22.2 22.2 22.2 22.2 22.2
Estimated L_10 Life at Maximum Force in x 10^6 15.4 24.6 56.7 8.88 14.15 32.05
  km 392 626 1440 225.6 359.4 814.2
C_a (Dynamic Load Rating) lbf 21400 19850 20800 17800 16500 17200
  kN 95.2 88.3 92.5 79.2 73.4 76.5
Maximum Input Torque lbf-in 196 392 783 196 392 783
  Nm 22.1 44.3 88.5 22.1 44.3 88.5
Max Rated RPM @ Input Shaft RPM 4500 4500 4500 4500 4500 4500
Maximum Linear Speed @ RPM Maximum Rated in/sec 14.7 29.5 59.3 14.7 29.5 59.3
  mm/sec 373 750 1500 373 750 1500



FT35 Inertias

  5 MM LEAD 10 MM LEAD 20 MM LEAD  
NMT Unit - J (0) 0.0004087 0.0004121 0.0004259 kg-m² (at input shaft) kg-m²/inch of stroke
NMT Unit - J (Stroke) 0.0000159 0.0000162 0.0000171 kg-m² (at input shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (0) 0.0005127 0.0005161 0.0005299 kg-m² (at motor shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (Stroke) 0.0000159 0.0000162 0.0000171 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (0) 0.0011042 0.0011855 0.001448 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (Stroke) 0.0000159 0.0000162 0.0000171 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (0) 0.0014029 0.0014038 0.0015345 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (Stroke) 0.0000040 0.0000040 0.0000043 kg-m² (at motor shaft) kg-m²/inch of stroke
         
Standard Inline Coupling Inertia 0.000104 kg-m² (0.000920 lbf-in s²)



FT35 Weights

BASE ACTUATOR WEIGHT LB KG
6 Inch Stroke Length 30 14
12 Inch Stroke Length 35 16
18 Inch Stroke Length 40 18
24 Inch Stroke Length 45 21
36 Inch Stroke Length 55 25
48 Inch Stroke Length 65 30
Adder for Inline (excluding motor) 8 3.6
Adder for Parallel Drive (excluding motor) 16 7.3
Adder for Front Flange 5.4 2.5
Adder for Rear Flange 7.4 3.4
Adder for Rear Clevis 3 1.4
Adder for Rear Eye NA NA
Adder for Front/Rear Angle Mounts NA NA
Adder for Two Trunnions 19.5 8.9
Adder for Two Foot Mounts 3.3 1.5
FT45 Performance SpecificationsOpen arrow

FT45 Performance Specifications

    HIGH CAPACITY STANDARD CAPACITY
    5 10 5 10
Screw Lead in 0.197 0.394 0.197 0.394
  mm 5 10 5 10
Maximum Force* lbf 10000 10000 10000 10000
  kN 44.5 44.5 44.5 44.5
Estimated L_10 Life at Maximum Force in x 10^6 9.81 19.14 5.67 11.06
  km 249.2 486.3 144 280.9
C_a (Dynamic Load Rating) lbf 36800 36500 30650 30400
  kN 163.7 162.4 136.3 135.2
Maximum Input Torque lbf-in 392 783 392 783
  Nm 44.1 88.2 44.1 88.2
Max Rated RPM @ Input Shaft RPM 3500 3500 3500 3500
Maximum Linear Speed @ Maximum Rated RPM in/sec 11.5 23 11.5 23
  mm/sec 292 583 292 583

*Maximum allowable actuator-generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For high force, short stroke applications, consult factory.



FT45 Inertias

  5 MM LEAD 10 MM LEAD  
NMT Unit - J (0) 0.002463 0.002474 kg-m² (at input shaft) kg-m²/inch of stroke
NMT Unit - J (Stroke) 0.000045 0.000046 kg-m² (at input shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (0) 0.002571 0.002581 kg-m² (at motor shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (Stroke) 0.000045 0.000046 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (0) 0.006911 0.006921 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (Stroke) 0.000045 0.000046 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (0) 0.003466 0.003469 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (Stroke) 0.000011 0.000011 kg-m² (at motor shaft) kg-m²/inch of stroke
       
Standard Inline Coupling Inertia 0.00010743 kg-m² (0.000951 lbf-in s²)

*Pulleys for parallel mount match actuator max performance ratings. Pulley inertias reflected at motor including typical pulleys, belt and standard bushings. Because of differences in belt and pulley selection due to particular motor choices, please contact your local sales representative if these values are critical to your application.



FT45 Weights

BASE ACTUATOR WEIGHT LB KG
6 Inch Stroke Length 57 26
12 Inch Stroke Length 68 31
18 Inch Stroke Length 79 36
24 Inch Stroke Length 90 41
36 Inch Stroke Length 112 51
48 Inch Stroke Length 135 61
Adder for Inline (excluding motor) 7.1 3.2
Adder for Parallel Drive (excluding motor) 42.5 19.3
Adder for Front Flange 6.1 2.8
Adder for Rear Flange 17.4 7.9
Adder for Rear Clevis 18.9 8.6
Adder for Rear Eye 19.8 9
Adder for Front/Rear Angle Mounts NA NA
Adder for Two Trunnions 17.2 7.8
Adder for Two Foot Mounts 10.4 4.7
FT60 Performance SpecificationsOpen arrow

FT60 Mechanical Specifications

    HIGH CAPACITY STANDARD CAPACITY
    6 12 30 6 12 30
Screw Lead in 0.236 0.472 1.181 0.236 0.472 1.181
  mm 6 12 30 6 12 30
Maximum Force ^1 lbf 20000 20000 20000 20000 20000 20000
  kN 89 89 89 89 89 89
Estimated L_10 Life at Maximum Force in x 10^6 5.7 7.3 38.6 4.1 5.2 10.7
  km 145.8 184.7 981.1 104.8 133.1 271.9
C_a (Dynamic Load Rating) lbf 57933 49750 63958 51900 44600 41700
  kN 257.7 221.3 284.5 230.9 198.4 185.5
Maximum Input Torque lbf-in 940 1880 4699 940 1880 4699
  Nm 106 212 531 106 212 531
Max Rated RPM @ Input Shaft RPM 2000 2000 2000 2000 2000 2000
Maximum Linear Speed @ Maximum Rated RPM in/sec 7.9 15.8 39 7.9 15.8 39
  mm/sec 201 401 1000 201 401 1000

1 -Maximum allowable actuator-generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For high force, short stroke applications, consult factory.



FT60 Inertias

  6 MM LEAD 12 MM LEAD 30 MM LEAD  
NMT Unit - J (0) 0.0078464 0.0078709 0.0080424 kg-m² (at input shaft) kg-m²/inch of stroke
NMT Unit - J (Stroke) 0.0002539 0.0002547 0.00026 kg-m² (at input shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (0) 0.0081764 0.0082009 0.0083724 kg-m² (at motor shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (Stroke) 0.0002539 0.0002547 0.00026 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (0) 0.0129357 0.0146113 0.0312682 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (Stroke) 0.0002539 0.0002547 0.00026 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (0) 0.0049158 0.0057202 0.0214777 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (Stroke) 0.0000635 0.0000637 0.0000650 kg-m² (at motor shaft) kg-m²/inch of stroke
         
Standard Inline Coupling Inertia 0.000330 kg-m² (0.002921 lbf-in s²)

*Pulleys for parallel mount match actuator max performance ratings. Pulley inertias reflected at motor including typical pulleys, belt and standard bushings. Because of differences in belt and pulley selection due to particular motor choices, please contact your local sales representative if these values are critical to your application.



FT60 Weights

BASE ACTUATOR WEIGHT LB KG
12 inch Stroke Length 100 45
24 inch Stroke Length 130 59
36 Inch Stroke Length 160 72
48 Inch Stroke Length 190 86
Adder for Inline (excluding motor) 20.4 9.3
Adder for Parallel Drive (excluding motor) 39.1 17.7
Adder for Front Flange 13.4 6.1
Adder for Rear Flange 15.9 7.2
Adder for Rear Clevis 11.1 5
Adder for Rear Eye NA NA
Adder for Front/Rear Angle Mounts NA NA
Adder for Two Trunnions 44.3 20.1
Adder for Two Foot Mounts 10.4 4.7
FT80 Performance SpecificationsOpen arrow

FT80 Mechanical Specifications

    HIGH CAPACITY STANDARD CAPACITY
    6 12 30 6 12 30
Screw Lead in 0.236 0.472 1.181 0.236 0.472 1.181
  mm 6 12 30 6 12 30
Maximum Force^1 lbf 40000 40000 40000 40000 40000 40000
  kN 177.9 177.9 177.9 177.9 177.9 177.9
Estimated L_10 Life at Maximum Force in x 10^6 3.1 4.4 16.3 1.94 2.55 5
  km 78.7 111.4 414.3 49.3 64.9 127
C_a (Dynamic Load Rating) lbf 94330 84079 95971 80700 70200 64700
  kN 419.6 374 426.9 359 312.2 287.8
Maximum Input Torque lbf-in 1880 3760 9399 1880 3760 9399
  Nm 212 425 1062 212 425 1062
Max Rated RPM @ Input Shaft RPM 1750 1750 1750 1750 1750 1750
Maximum Linear Speed @ Maximum Rated RPM in/sec 6.9 13.8 34.4 6.9 13.8 34.4
  mm/sec 175 351 875 175 351 875

1- Maximum allowable actuator-generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For high force, short stroke applications, consult factory.



FT80 Inertias

  6 MM LEAD 12 MM LEAD 30 MM LEAD  
NMT Unit - J (0) 0.0302504 0.0303275 0.0308673 kg-m² (at input shaft) kg-m²/inch of stroke
NMT Unit - J (Stroke) 0.0008022 0.0008035 0.0008124 kg-m² (at input shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (0) 0.0314604 0.0315375 0.0320773 kg-m² (at motor shaft) kg-m²/inch of stroke
Inline w/ Coupler - J (Stroke) 0.0008022 0.0008035 0.0008124 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (0) 0.0721056 0.0535533 0.1342578 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 1:1 - J (Stroke) 0.0008022 0.0008035 0.0008124 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (0) 0.0198765 0.027049 0.0753395 kg-m² (at motor shaft) kg-m²/inch of stroke
Parallel 2:1 - J (Stroke) 0.0002006 0.0002009 0.0002031 kg-m² (at motor shaft) kg-m²/inch of stroke
         
Standard Inline Coupling Inertia 0.0001210 kg-m² (0.010709 lbf-in s²)

*Pulleys for parallel mount match actuator max performance ratings. Pulley inertias reflected at motor including typical pulleys, belt and standard bushings. Because of differences in belt and pulley selection due to particular motor choices, please contact your local sales representative if these values are critical to your application.



FT80 Weights

BASE ACTUATOR WEIGHT LB KG
12 Inch Stroke Length 190 86
24 Inch Stroke Length 265 120
36 Inch Stroke Length 340 153
48 Inch Stroke Length 415 187
Adder for Inline (excluding motor) 54.9 24.9
Adder for Parallel Drive (excluding motor) 79.1 35.9
Adder for Front Flange 28.5 17.5
Adder for Rear Flange NA NA
Adder for Rear Clevis NA NA
Adder for Rear Eye NA NA
Adder for Front/Rear Angle Mounts NA NA
Adder for Two Trunnions NA NA
Adder for Two Foot Mounts 34.8 15.8

Product Literature

Catalogs, Brochures, and Success Stories

Industrial - Exlar, Brochures/Catalogs
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Industrial - Exlar, Success Stories
Exlar’s roller screw actuator technology was chosen over less capable linear motion solutions.
Industrial - Exlar, Success Stories
The Exlar actuation solution nearly doubled the production rate from 20 cpm to 37 cpm. It also provides significantly better consistency of the finished product.
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Actuator Technical Data

Manuals and Technical Tips

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Videos

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Exlar® actuators from Curtiss-Wright are an industry leader in electric actuation. Our research, pride, and creativity shine in this short video as we highlight our top product lines.
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Ever wonder about the benefits of changing your system from hydraulic cylinders to electric actuation. We have the information you need.
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Designed and manufactured by Mannetron. Featuring Exlar FT60 Series Actuators.
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How can we help?

Can you please provide a cost comparison between a ball screw and a roller screw actuator?Arrow
Cost comparison of a roller screw to a ball screw is really a difficult subject, mainly because we have to take into account the differences in the pieces that we are comparing. A roller screw is typically going to be competitive to a ball screw in regards to price because we can oftentimes use a roller screw that is smaller in size compared to its “equivalent” ball screw. This is because of the significant life advantage roller screws have. Therefore, if you are using a smaller frame size roller screw and comparing that to a larger size ball screw, with similar life expectancies, your pricing is going to be very similar. Now depending on what your needs are, if you are looking for something with much greater life, we’re not necessarily comparing an equal product. So you may have to buy two ball screws in comparison to one roller screw. If you look at that from a value standpoint, you may pay more for a similar frame size roller screw but you may have to buy two ball screws in the same period of time that you would have to buy that one roller screw.
How do you calculate the maximum duty cycle allowed vs the amount on current/force applied?Arrow

Below is the maximum-allowable duty cycle for your application given the percentage of input current over the continuous current rating:

For example: If your actuator has a continuous current rating of 10 A and a continuous force rating of 1000 lbf, this means it will take about 10 A to produce 1000 lbf of force, or 5 A to produce 500 lbf of force, and so on. What if you need to push more than 1000 lbf? In most cases, you would look at a stronger stator or a larger actuator. What if it’s only for a few seconds? Could you over-work the current actuator? Well the answer is yes, and calculating by how much isn’t too difficult.

Let’s say you need to push 1500 lbf. This would be equivalent to 1.5x the continuous current rating of 10 A. If you look below, the graph recommends no more than a 22% duty cycle in this case. This means you can run the actuator 22% of the time at 15 A without overheating. The other 78% of the time, it needs to be off/cooling.

How long can you run at peak current?

Not a simple question, nor a simple answer. In reality, so many things affect this (how the system is built and how well the actuator is able to dissipate heat, are there additional heat sinks, particles in the air, degree of vacuum, new starting temp each time? (i.e. doesn’t always start from cold, etc.). Therefore, accurate times and temperature are quite difficult to estimate.

For example: At peak current (2x Continuous), the allowable duty cycle is 4%. That doesn’t mean you can run for 4 hours straight as long as you have 96 hours of off time in between however. From experience, a good rule of thumb we’ve estimated is 30s to a minute of peak current run time. Try to keep it under that, and then of course allow it to cool for the other 96% of the time.

How does a roller screw compare to a hydraulic actuator of equal size and rate force?Arrow
That is going to depend on the application, but with equivalent specifications and characteristics, a roller screw actuator will typically be very similar in size to (sometimes slightly larger than) a comparable hydraulic cylinder. Hydraulics are always going to have their place in the market once you get beyond 100,000 lbs. of force, but anywhere an electromechanical roller screw actuator fits the bill, size will be very similar.
How long until my specific actuator/application needs to be serviced/re-greased?Arrow

We are asked about re-lubrication intervals a lot. The reality is that there is no generic interval to re-lube actuators. It depends on so many things and every application and situation is different, it is nearly impossible to accurately calculate a re-lube interval per application. So instead, we have a rough guideline table (shown below) to give users an idea on when to start checking for old contaminated grease that needs to be replaced. However, since ambient temperature, heat dissipation, speed variation, particles in the air, etc. can vary so much from application to application, this is only a guideline. The actuator should be checked more frequently around the period this table suggests and once it is noticed that the grease is ready to be replaced (Dirty, contaminated / very dark, filled with particles / debris) – a re-lube interval can be determined.

Remember, grease needs to be cleaned out and replaced – don’t just insert more. (Except for FTX’s, those can handle 5-6 greasings before they need to be cleaned out)

RMS ROTATIONAL SPEED (RPM) RECOMMENDED GREASE RENEWAL PERIOD (HOURS)
250 10,000
500 10,000
1000 8000
1500 7000
2000 5800
2500 5000
3000 4000
What are the primary benefits of using an electric actuator system over hydraulics?Arrow
Electric actuators offer high speed and force, are flexible and easily programmable for a variety of load conditions, have high accuracy and repeatability, are efficient, simple to install, require little maintenance, and are environmentally friendly.

By not using a hydraulic system, the user can eliminate oil leaks, reduce pollution, and improve worker safety. Electric actuators are also a non-toxic solution, especially in the food industry
What is the accuracy of the actuator?Arrow

A very common question for us. For the actuator itself, that is easy. There is a mechanical lead accuracy of the screw, which is usually 0.001 in/ft, a typical specification for precision positioning screws of any type. This means that at any point over the cumulative length of the screw, the lead will vary by a maximum of 0.001 inches per foot of screw length. This is not the same as mechanical repeatability. The mechanical repeatability is a tolerance on how close to the same linear position the screw will return, if approaching from the same direction, and driven exactly the same number of turns. This value is approximately 0.0004 inches.

The electronic positioning resolution is a function of the feedback device and the servo amplifier. Let’s assume that we have Exlar’s standard encoder on a GSX30 with 0.2 inches per revolution lead on the roller screw. Exlar’s standard encoder has 2048 lines and 8192 electronic pulses per revolution that it outputs to the servo drive. So in a perfect world, the positioning resolution would be (0.2 in/rev)/ (8192 pulses/rev) or 0.0000244 inches. Anyone who has used servo drives knows that you can’t position to one encoder pulse. Let’s use 10 encoder pulses as a reasonable best positioning capability. This gives us a positioning resolution of 0.000244 inches.

More things to consider: When addressing repeatability and accuracy, several things must also be taken into account. One of these is the stiffness of the system. Stiffness is how much the system will stretch or compress under compressive or tensile forces. If the combination of the stiffness of the actuator and the stiffness of the mechanical system, including all couplings, mounting surface, etc. allows for more compression or stretch than the required positioning resolution of the system, obtaining acceptable positioning results will be nearly impossible. Another consideration is thermal expansion and contraction. Consider a GS actuator attached to a tool that is doing a precision grinding process. Assuming that the tool is steel and 12 inches long, a 5 degree rise in temperature will cause the tool to expand by 0.0006 inches. If the system is programmed to make 0.0002 inch moves, this expansion could cause serious positioning problems. The same applies to the components of the actuator itself. The actuator rod can change in temperature from a cold start up to running temperature. This change may need to be accounted for in very precise positioning applications.

What is the maintenance schedule life for a typical roller screw?Arrow
The maintenance schedule for any geared mechanical device, whether ball screw, roller screw, or gearhead, is going to be based on the amount of heat that is generated in the application, the amount of degradation of the grease, the type of grease being used, and the duty cycle. We provide some guidelines for our customers as starting points, but we recommend that for all new installations the lubrication be periodically inspected for presence and degradation as the best method for determining the right maintenance schedule for a given application. Having said that, we’ve seen repairs of units that have been in use for 15 years and when we’ve asked about grease renewal, they didn’t even realize that the unit could be serviced in the field. So we’ve had situations like that where they’ve gone for long periods of time with effectively no maintenance or no grease renewal. There are other applications that require grease renewal in very short intervals just due to the nature of the application.
What keeps the output shaft from rotating?Arrow
On a conventional roller screw design package, there typically is an anti-rotation groove designed into the housing, and a tab designed into the nut that rides in the housing groove as the actuator extends and retracts. In regards to the inverted roller screw design, part of the installation or the application requirement is going to be having that shaft solidly mounted a machine coupling or tooling on the machine otherwise providing some sort of external anti-rotation device on that output shaft. There are other ways of using splines and different types of non-circular output shafts that can allow for different types of spline nuts that will provide anti-rotation, but typically you’re going to see that mounted on the machine.
How do I estimate life of the actuator?Arrow
The L10 expected life of a roller screw linear actuator is expressed as the linear travel distance that 90% of properly maintained roller screws manufactured are expected to meet or exceed. This calculation should be used for estimation purposes only.

The underlying formula that defines this value is: Travel life in millions of inches, where:
Ca= Dynamic load rating (lbf)
Fcml= Cubic mean applied load (lbf)
ℓ = Roller screw lead (inches)

For additional details on calculating estimated service life, please refer www.cw-actuation.com.

L10=(Ca)3 x ℓ Fcm

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