Converting Hydraulic Cylinder Systems to High-Force Electric Actuators

Improve process control, increase efficiency, eliminate leaks, & many other advantages by adopting electric actuator systems

     

Learn how high-force electric actuators provide better performance and lower total cost of ownership than hydraulic cylinder systems

Hydraulic cylinders, known for their high force at an affordable cost, have been widely used in factory automation equipment and other special automation equipment for decades. Hydraulics are rugged, relatively simple to deploy and provide a low cost per unit of force. What is sometimes not as well known is that electric rod actuators (cylinders) also have very large force capacities and offer improved system flexibility, precision and reliability. These advancements in electric rod actuators have created an ongoing debate over which technology, hydraulic cylinders or electric actuators, offers the best overall solution. Download Tolomatic’s paper on the pros & cons of Electric Actuator vs. Hydraulic cylinder systems.
 

Total Cost of Ownership

Besides improvements in motion control, there are other factors that contribute to the overall total cost of ownership.  In many cases, if all these factors are considered over a reasonable life of the equipment, the electric actuator system will have a lower total cost of ownership.  These factors include:

  • System components – Hydraulic systems require more components to purchase and maintain.

  • Footprint – Although hydraulic cylinders are compact, the overall footprint of an electric actuator system is typically much smaller when factoring in the footprint of the hydraulic power unit, allowing for a more compact and efficient machine design.

  • Life – The life of electric actuators can be estimated with a L10 calculation & dynamic load rating while the life of hydraulic cylinders is extremely hard to predict. Download "Calculating Total Cost of Ownership" Infographic. Electric actuators allow users to better calculate and select an actuator that meets their system life requirements.

  • Efficiency – Electric actuator system efficiency is typically in the 75-80% range while hydraulic systems typically realize around 40-55% efficiency.

  • Utility costs – Due to efficiency, hydraulic actuators can consume 2-3 times the amount of electric utility each and every year. Download "Electric vs. Servo-hydraulic vs. Hydraulic Actuators" Infographic

  • Maintenance -  Electric actuators require very little maintenance, hydraulic systems rely on seal integrity through the system for proper performance.  Due to wear, temperature, and other factors, seal integrity will diminish and performance along with it.

  • Temperature – With high / low temperature grease, electric actuator can operate in temperature extremes minimal effect on performance.

  • Leaks and environmental concerns – Only a matter of time before hydraulic systems will leak.  Leaks can be safety hazards as well as contribute to many environmental concerns.

  • Data collection – Servo systems used with electric actuators provide position, velocity, and force/torque data at all times to the control system and better monitor processes.

  • Other factors – Noise, shock loads, side loads

Determining the work being done by the hydraulic cylinder to appropriately size the electric actuator

Once the decision has been made to convert from hydraulic cylinder systems to electric actuators, the biggest and most costly mistake that machine designers make is to make an oversimplified force calculation of pressure (remove extra space)  multiplied by the area of bore size.

Force = Area x Pressure

Since hydraulics are high pressure systems (typically 2000+ psi or 140+ bar), theoretically they can achieve very high forces, but in practice are typically not deployed near their peak force capabilities.  Additionally, the jobs that hydraulic cylinders perform usually do not require full force over the full stroke. In most cases, the force profile will change over the length of the stroke.  For example, a pressing application may only have high forces for a very small portion of the stroke and be virtually unloaded during the approach and retract portions.  Because of these reasons, it is important to take a little time to make some pressure measurements at the cylinder or valve in order to better determine true applications forces.  It is quite a simple procedure and Tolomatic has created an easy to follow guide on how to make pressure measurements in a hydraulic cylinder system.

Along with force, electric actuators must also know the speed and duty cycle of the application in order to properly size the application.  Watch the video (above) on how to convert hydraulic cylinders to an electric actuator alternative.  Again, it is a simple process to determine with readily available tools such as a phone and a ruler.  Take a video of the motion cycle with time stamps and measure the distances.  Combine this with the pressure measurements to estimate force, and you have everything you need to size an electric actuator alternative.

Creating an electric actuator system

Once the proper measurements have been taken and the actuator can be sized.  To make it easy, Tolomatic has an online sizing software tool to input the motion and force details to select the proper electric actuator for the job.  Decisions will need to be made on gearing (ratio), motor size (torque vs. speed), type of power screw (ball or roller screw) and also considering the environment (temperature, contaminants, etc..) that the actuator will be deployed in.

 

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Tolomatic offers the most capable product line of industrial strength electric actuators 

Tolomatic’s expansive and ever expanding Electric Actuator product line ranges in forces up to 50,000 lbf, ingress protection (IP) options, flexible screw technology (roller or ball screw) options, stainless steel / hygienic options, and compact integrated servo actuator options. With Tolomatic’s very popular Your Motor Here program, just about any 3rd party servo motor can be mounted to one of our actuators.  Check out a quick video overview of our very capable product lines for hydraulic cylinder replacement.


RSX Extreme Force Electric Rod Actuators

Roller screw driven

Forces up to 30,000 lbf  (133.5 kN)

Flexible motor mounts


RSA-HT Heavy Duty Electric Rod Actuators

Add any servo motor

Forces up to 13,039 lbf (58 kN)

Economical ball screw options


ServoWeld® Resistance Spot Welding Actuators

Multiple designs for various weld guns

20+ million welds

Superior welds & force repeatability


IMA Integrated Servo Motor Actuators

Integrated servo motor design

Forces up to 6,875 (30.6 kN)

Compatible with many servo drives


IMA Food Grade Linear Actuators

Food Grade white epoxy coating

Forces up to 6,875 lbs (30.6 kN)

IP67 rating


ERD Hygienic Electric Actuators

IP69k, clean-in-place

Forces up to 7,868 lbf (35 kN)

USDA and 3A hygienic design approved