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K Series

Electric Linear Actuator

Industrial - Exlar

Benefits:
  • Easily retrofit into existing equipment. 
  • Increased motion control compared to fluid actuation. 
  • Lower total cost of ownership. 
  • Easy integration with 3rd party motors. 

Features:
  • Long, robust actuator life due to Exlar roller screw technology. 
  • Sealed to IP65S for harsh industrial environments. 
  • Stroke lengths up to 48” (1200 mm). 
  • Minimal maintenance. 
  • Flexible mounting option. 
More Details

Overview

K Series

Quick Data
ModelFrame Size mm (in)Stroke mm (in)Max Continuous Force kN (lbf)Max Speed mm/s (in/s)
KX6060 (2.36)
150 (6), 300 (12), 600 (24), 900 (36)
6 (1,350)
833 (32.8 )
KX7575 (2.95)
150 (6), 300 (12), 600 (24), 900 (36)
11.1 (2,500)666 (26.2)
KX9090 (3.54)
150 (6), 300 (12), 600 (24), 900 (36)
15.6 (3,500)500 (19.7)

ROLLER SCREW ACTUATORS: PERFORMANCE & SERVICE

Roller screw actuators have several advantages over hydraulic or pneumatic actuators for many applications, especially those involving heavy loads and fast cycles. Other benefits include a small system footprint, long functional life, and low maintenance requirements. And because roller screw systems don’t require high-pressure fluid, they reduce noise levels and are not subject to potentially hazardous fluid leaks.


Big Performance and Small Form Factor

These robust electric actuators provide an ideal replacement for pneumatic cylinders and feature comparable dimensions with a similar form factor. Better performance, greater flexibility, and longer life culminate to make the K Series a smart choice for many applications. The high-performance planetary roller screw in the KX class offers performance that is far superior to competing actuator technologies. These actuators are ideal for Exlar automation, mobile equipment, process control and many other demanding applications.


Other Advantages

  • Flexible design suitable for numerous applications and configurations
  • Universal mounting options compatible with DC, stepper, and servo motors
  • Preconfigured parallel and inline motor mounts available for most motors
  • Multiple models for maximum flexibility
  • Anodized aluminum housing with sealed body options for harsh environments
  • Specialized material and coating options
  • Built for long life and low maintenance


Applications

The high-performance planetary roller screw in the KX class offers performance that is far superior to competing actuator technologies. As a result, these actuators are ideal for a range of demanding applications, including:

  • Industrial automation
  • Mobile equipment
  • Process control

Related Industries

                 


                  


Quick Data
Models:KX60, KX75, KX90 (high capacity roller screw actuators)
KM60, KM75, KM90 (standard capacity roller screw actuators) legacy product
Frame Sizes:2.4, 3, 3.5 in (60, 75, 90 mm)
Stroke Lengths:6 in (150 mm), 12 in (300 mm), 24 in (600 mm), 36 in (900 mm)
Linear Speed:up to 32.8 in/s (833 mm/s)
Maximum Force:up to 3,500 lbf (15 kN)

AA= Actuator Frame Size
60 = 60 mm (2.375 inch)
75 = 75 mm (2.95 inch)
90 = 90 mm (3.54 inch)

BBBB = Stroke Length (mm)
0150 = 150 mm (5.9 inch)
0300 = 300 mm (11.8 inch)
0600 = 600 mm (23.6 inch)
0900 = 900 mm (35.4 inch)

CC = Lead (linear motion per screw revolution)
05 = 5 mm (0.2 inch)
10 = 10 mm (0.4 inch)

D = Mounting Options
N = None, Base Unit
C = Rear Clevis
F = Front Flange
G = Metric Rear Clevis
T = Side Trunnion
Q = Metric Side Trunnion

E = Rod Options
M = Male, US Standard thread
A = Male Metric thread
F = Female US Standard thread
B = Female Metric thread

FFF = Input Drive Provisions
NMT = Drive shaft only, no motor mount
ISC = Inline, includes shaft coupling

Keyed Motor Shaft Options
P10 = Parallel, 1:1 belt reduction
P20 = Parallel, 2:1 belt reduction

Smooth Motor Shaft Options
S10 = Parallel, 1:1 belt reduction
S20 = Parallel, 2:1 belt reduction

GGG = Motor Mount Provisions1
See catalog for details

MM = Mechanical Options2 
PB = Protective bellows for extending rod

Limit Switches
L1 = One N.O., PNP
L2 = Two N.C., PNP
L3 = One N.O. PNP & two N.C., PNP
L4 = One N.O., NPN
L5 = Two N.C., NPN
L6 = One N.O., NPN & two N.C., NPN


NOTES:
1. For oversized motors, contact your local sales representative.
2. For extended temperature operation consult factory for model number.

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

Product Specifications

K60 Performance SpecificationsOpen arrow

K60 Mechanical Specifications

Models   KX KM - Legacy Product
Screw Lead in 0.1969 0.3937 0.1969 0.3937
  mm 5 10 5 10
Maximum Force^2 lbf 1350 675 1350 675
  kN 6 3 6 3
Life at Maximum Force in x 10^6 1.6 18.2 0.4 4.5
  km 41.7 461.4 10.4 115.3
C_a (Dynamic Load Rating) lbf 2738 2421 1725 1525
  kN 12.2 10.8 7.7 6.8
Maximum Input Torque^1 lbf-in 53 53 53 53
  Nm 6 6 6 6
Max Rated RPM @ Input Shaft RPM 5000 5000 5000 5000
Maximum Linear Speed @ Maximum Rated RPM in/sec 16.4 32.8 16.4 32.8
  mm/sec 417 833 417 833

1 - Input torque should be limited such that Max Force is not exceeded. For a parallel belt ratio, the input torque ratings must be divided by the belt ratio for allowable motor torque. The output force ratings remain the same.
2 - Maximum allowable actuator–generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For maximum allowable externally-applied axial forces, consult factory. For high force, short stroke applications, consult factory.

 


K60 Intertias

  kg-m^-2 (lbf-in-sec^-2) kg-m^-2 (lbf-in-sec^-2)
  5 mm Lead Add per 25 mm, 5 mm Lead
Base Unit - Input Drive Shaft Only 1.480 x 10^-5 (1.31 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
Inline Unit - w/Motor Coupling 2.702 x 10^-5 (2.39 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
  10 mm Lead Add per 25 mm, 10 mm Lead
Base Unit - Input Drive Shaft Only 1.616 x 10^-5 (1.43 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-5)
Inline Unit - w/Motor Coupling 2.837 x 10^-5 (2.51 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-5)
Parallel Drive Inertias (P10 Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (66 mm) 4.339 x 10^-5 (3.84 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
1:1 Reduction Parallel Belt Drive (86 mm) 7.378 x 10^-5 (6.53 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
1:1 Reduction Parallel Belt Drive (96 mm) 8.564 x 10^-5 (7.58 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
2:1 Reduction Parallel Belt Drive (96 mm) 7.095 x 10^-5 (6.28 x 10^-4) 2.555 x 10^-7 (2.261 x 1^-6)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (66 mm) 4.474 x 10^-5 (3.96 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-5)
1:1 Reduction Parallel Belt Drive (86 mm) 7.514 x 10^-5 (6.65 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-5)
1:1 Reduction Parallel Belt Drive (96 mm) 8.704 x 10^-5 (7.70 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-5)
2:1 Reduction Parallel Belt Drive (96 mm) 1.966 x 10^-5 (1.74 x 10^-4) 2.931 x 10^-7 (2.595 x 10^-6)
Parallel Drive Inertias (Smooth Motor Shaft Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (66 mm) 6.015 x 10^-5 (5.32 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
1:1 Reduction Parallel Belt Drive (86 mm) 1.103 x 10^-4 (9.76 x 10^-4) 1.022 x 10^-6 (9.045 x 10^-6)
1:1 Reduction Parallel Belt Drive (96 mm) 2.176 x 10^-4 (1.93 x 10^-3) 1.022 x 10^-6 (9.045 x 10^-6)
2:1 Reduction Parallel Belt Drive (96 mm) 8.768 x 10^-5 (7.76 x 10^-4) 2.555 x 10^-7 (2.261 x 10^-6)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (66 mm) 6.150 x 10^-5 (5.44 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-6)
1:1 Reduction Parallel Belt Drive (86 mm) 1.117 x 10^-4 (9.88 x 10^-4) 1.173 x 10^-6 (1.038 x 10^-6)
1:1 Reduction Parallel Belt Drive (96 mm) 2.190 x 10^-4 (1.94 x 10^-3) 1.173 x 10^-6 (1.038 x 10^-6)
2:1 Reduction Parallel Belt Drive (96 mm) 8.802 x 10^-5 (7.79 x 10^-4) 2.931 x 10^-7 (2.595 x 10^-6)
 


K60 Weights

  lb kg
Base Actuator Weight (Zero Stroke) 3.7 1.7
Actuator Weight Adder (Per mm of Stroke) 0.017 0.008
Adder for Inline (excluding motor) 0.93 0.42
Adder for Parallel Drive (excluding motor) 1.6 0.73
Adder for Front Flange 0.93 0.42
Adder for Rear Clevis 0.98 0.44
Adder for Two Trunnions 0.72 0.33

 

K60 Data CurvesOpen arrow
K60-Critical-Speed-(1).jpg
Actuator Rated Speed (speed at which we have tested and rated the actuator)
* With longer stroke length actuators, the rated speed of the actuator is determined by the critical speed



K60-Maximum-Radial-(1).jpg



K60-Rated-Force-(1).jpg
K75 Performance SpecificationsOpen arrow

K75 Mechanical Specifications

 
Models   KX KM - Legacy Product
Screw Lead in 0.1969 0.3937 0.1969 0.3937
  mm 5 10 5 10
Maximum Force^2 lbf 2500 1250 2500 1250
  kN 11.1 5.6 11.1 5.6
Life at Maximum Force in x 10^6 2.4 22.6 0.6 5.6
  km 60.7 573.3 15.2 143.5
C_a (Dynamic Load Rating) lbf 5746 4820 3620 3036
  kN 25.6 21.4 16.1 13.5
Maximum Input Torque^1 lbf-in 98 98 98 98
  Nm 11 11 11 11
Max Rated RPM @ Input Shaft RPM 4000 4000 4000 4000
Maximum Linear Speed @ Maximum Rated RPM in/sec 13.1 26.2 13.1 26.2
  mm/sec 333 666 333 666
1 - Input torque should be limited such that Max Force is not exceeded. For a parallel belt ratio, the input torque ratings must be divided by the belt ratio for allowable motor torque. The output force ratings remain the same.
2 - Maximum allowable actuator–generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For maximum allowable externally-applied axial forces, consult factory. For high force, short stroke applications, consult factory.

 


K75 Inertias

  kg-m^-2 (lbf-in-sec^-2) kg-m^-2 (lbf-in-sec^-2)
  5 mm Lead Add per 25 mm, 5 mm Lead
Base Unit - Input Drive Shaft Only 9.26 x 10^-5 (8.20 x 10^-4) 3.13 x 10^-6 (2.77 x 10^-5)
Inline Unit - w/Motor Coupling 1.25 x 10^-4 (1.11 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
  10 mm Lead Add per 25 mm, 10 mm Lead
Base Unit - Input Drive Shaft Only 9.48 x 10^-5 (8.39 x 10^-4) 3.32 x 10^-6 (2.94 x 10^-5)
Inline Unit - w/Motor Coupling 1.44 x 10^-4 (1.28 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
Parallel Drive Inertias (P10 Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (86 mm) 2.29 x 10^-4 (2.03 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
1:1 Reduction Parallel Belt Drive (96 mm) 3.19 x 10^-4 (2.82 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 5.96 x 10^-4 (5.28 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 2.82 x 10^-4 (2.50 x 10^-3) 7.83 x 10^-7 (6.93 x 10^-6)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (86 mm) 2.31 x 10^-4 (2.05 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
1:1 Reduction Parallel Belt Drive (96 mm) 3.21 x 10^-4 (2.84 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 5.98 x 10^-4 (5.30 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 2.83 x 10^-4 (2.51 x 10^-3) 8.30 x 10^-7 (7.36 x 10^-6)
Parallel Drive Inertias (Smooth Motor Shaft Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (86 mm) 2.84 x 10^-4 (2.51 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
1:1 Reduction Parallel Belt Drive (96 mm) 4.25 x 10^-4 (3.76 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 7.33 x 10^-4 (6.48 x 10^-3) 3.13 x 10^-6 (2.77 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 3.32 x 10^-4 (2.94 x 10^-3) 7.83 x 10^-7 (6.93 x 10^-6)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (86 mm) 2.86 x 10^-4 (2.53 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
1:1 Reduction Parallel Belt Drive (96 mm) 4.27 x 10^-4 (3.78 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 7.35 x 10^-4 (6.50 x 10^-3) 3.32 x 10^-6 (2.94 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 3.33 x 10^-4 (2.94 x 10^-3) 8.30 x 10^-7 (7.35 x 10^-6)
 


K75 Weights

  lb kg
Base Actuator Weight (Zero Stroke) 6.75 3.06
Actuator Weight Adder (Per mm of Stroke) 0.0235 0.0107
Adder for Inline (excluding motor) 2.46 1.12
Adder for Parallel Drive (excluding motor) 4.06 1.84
Adder for Front Flange 1.91 0.87
Adder for Rear Clevis 1.85 0.84
Adder for Two Trunnions 1.56 0.71
K75 Data CurvesOpen arrow
K75-Critical-Speed-(1).jpg
Actuator Rated Speed (speed at which we have tested and rated the actuator)
* With longer stroke length actuators, the rated speed of the actuator is determined by the critical speed




K75-Maximum-Radial-(1).jpg




K75-Rated-Force-(1).jpg
K90 Performance SpecificationsOpen arrow

K90 Mechanical Specifications

Models   KX KM - Legacy Product
Screw Lead in 0.1969 0.3937 0.1969 0.3937
  mm 5 10 5 10
Maximum Force^2 lbf 3500 1750 3500 1750
  kN 15.6 7.8 15.6 7.8
Life at Maximum Force in x 10^6 7.1 90.4 1.8 22.6
  km 179.6 2295 44.9 573.8
C_a (Dynamic Load Rating) lbf 11548 10715 7275 6750
  kN 51.4 47.7 32.4 30
Maximum Input Torque^1 lbf-in 137 137 137 137
  Nm 16 16 16 16
Max Rated RPM @ Input Shaft RPM 3000 3000 3000 3000
Maximum Linear Speed @ Maximum Rated RPM in/sec 9.8 19.7 9.8 19.7
  mm/sec 250 500 250 500
1 - Input torque should be limited such that Max Force is not exceeded. For a parallel belt ratio, the input torque ratings must be divided by the belt ratio for allowable motor torque. The output force ratings remain the same.
2 - Maximum allowable actuator–generated force that can be applied routinely. Exceeding this force may result in permanent damage to the actuator. For maximum allowable externally-applied axial forces, consult factory. For high force, short stroke applications, consult factory.



K90 Inertias

kg-m^-2 (lbf-in-sec^-2) kg-m^-2 (lbf-in-sec^-2)
  5 mm Lead Add per 25 mm, 5 mm Lead
Base Unit - Input Drive Shaft Only 2.97 x 10^-4 (2.63 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
Inline Unit - w/Motor Coupling 3.84 x 10^-4 (3.40 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
  10 mm Lead Add per 25 mm, 10 mm Lead
Base Unit - Input Drive Shaft Only 3.00 x 10^-4 (2.66 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
Inline Unit - w/Motor Coupling 3.87 x 10^-4 (3.43 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
Parallel Drive Inertias (P10 Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (96 mm) 5.12 x 10^-4 (4.53 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 7.98 x 10^-4 (7.07 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 3.41 x 10^-4 (3.02 x 10^-3) 2.77 x 10^-6 (2.45 x 10^-5)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (96 mm) 5.15 x 10^-4 (4.56 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
1:1 Reduction Parallel Belt Drive (130 mm) 8.02 x 10^-4 (7.10 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
2:1 Reduction Parallel Belt Drive (130 mm) 3.42 x 10^-4 (3.03 x 10^-3) 2.82 x 10^-6 (2.50 x 10^-5)
Parallel Drive Inertias (Smooth Motor Shaft Option)
  5 mm Lead Add per 25 mm, 5 mm Lead
1:1 Reduction Parallel Belt Drive (96 mm) 6.18 x 10^-4 (5.47 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
1:1 Reduction Parallel Belt Drive (130 mm) 9.35 x 10^-4 (8.27 x 10^-3) 1.11 x 10^-5 (9.80 x 10^-5)
2:1 Reduction Parallel Belt Drive (130 mm) 3.91 x 10^-4 (3.46 x 10^-3) 2.77 x 10^-6 (2.45 x 10^-5)
  10 mm Lead Add per 25 mm, 10 mm Lead
1:1 Reduction Parallel Belt Drive (96 mm) 6.21 x 10^-4 (5.50 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
1:1 Reduction Parallel Belt Drive (130 mm) 9.38 x 10^-4 (8.30 x 10^-3) 1.13 x 10^-5 (1.00 x 10^-4)
2:1 Reduction Parallel Belt Drive (130 mm) 3.92 x 10^-4 (3.47 x 10^-3) 2.82 x 10^-6 (2.50 x 10^-5)
 


K90 Weights

  lb kg
Base Actuator Weight (Zero Stroke) 11.96 5.42
Actuator Weight Adder (Per mm of Stroke) 0.0366 0.016
Adder for Inline (excluding motor) 3.35 1.51
Adder for Parallel Drive (excluding motor) 5.8 2.62
Adder for Front Flange 3.4 1.54
Adder for Rear Clevis 3.21 1.45
Adder for Two Trunnions 1.768 0.8

 
K90 Data CurvesOpen arrow
K90-Critical-Speed-(1).jpg
Actuator Rated Speed (speed at which we have tested and rated the actuator)
* With longer stroke length actuators, the rated speed of the actuator is determined by the critical speed



K90-Maxium-Radial-(1).jpg



K90-Rated-Force-(1).jpg

Product Literature

Catalogs and Brochures

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Actuator Technical Data

Manuals and Technical Tips

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Videos

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Learn how we build our actuators
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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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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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