Using Servo Drives to Enhance Safety and Productivity

How can you use servo drives to improve BOTH safety AND productivity?

Are you interested in developing more productive machines? It’s important to keep productivity in mind when you weigh all the safety considerations for a system. The team at Horizon Solutions likes to use the phrase: “Safety doesn’t have to come at the expense of productivity”. We believe that safety improves efficiency and ultimately saves you money. Today, we’re going to talk about how servo drives will BOTH keep your team safe AND improve your productivity.

Interacting safely with machines.

No, this post is not about robots with a corrupt AI. This post is about developing more productive industrial machinery that can continue working while you maintain it. Rather than totally stop or lock out a machine for operations & maintenance, you and your team can limit the speed/direction/position of the machinery for safer interaction.

Servo DrivesSynchronization: safety and motion working together.

Industrial control systems bring together drives, motors, light curtains, switches, sensors, and more. This represents a lot of unique and connected devices. You want your moving parts (motion) to be safe and reliable. What is controlled motion? Why do you need safe motion? To get a better understanding, let’s look at a quick Top 10 list of applications. This list is not definitive or exhaustive, rather – it shows ten common instances that you might find very relatable:

  1. Moving heavy payloads. This might include sleds or tables that have a lot of intrinsic momentum. p = mv so if it’s really heavy you’ll have high momentum, or if you have high velocity, or if your system has very little internal resistance (i.e. friction) you’ll face high momentum. These result in very literal pinch points. Ouch!
  2. Hazardous cutters. These are sometimes also known as Fly-knife Cutters. In a very informal term, we could call this: spinning whirring blades. Picture a machine that cuts cardboard. Or a machine that slices fabric. Or even something cutting paper. These parts that spin in a rotary direction to produce a cut often move laterally as a part of that process, and it is a very dangerous combination.
  3. Mixers. In the food and beverage industry we often see ribbon mixers, blenders, and other similar equipment used for dry ingredients. These might be vertical or horizontal and the amount of possible human interaction varies greatly. Most systems are similar in that if there is possible operator interaction you want the moving parts that are controlled by a servo drive to stop quickly. Safety first.
  4. Brake presses. Many of the common tools used to press or stamp sheet metal are cam driven. Have you heard of 10-ton or even 30-ton presses? They’re a very quick and efficient piece of machinery, but given the enormous forces in play – a safe shop will have controlled safety measures to engineer out as much of the hazard as they can.
  5. Rollers. Equipment that is designed to roll is usually going to push down with forces great enough to cause injury to human limbs.
  6. Assembly machines. These can be quite varied, and include gluing, ultrasonic welding, inserting, twisting, and others. Often automated and not intended for on the fly maintenance.
  7. Packaging machinery. Stacking finished product, sealing individual boxes, sealing master boxes.
  8. Material handling. Conveyors, pickers, pullers.
  9. Converting. Print, web, webbing. Winders and unwinders.
  10. Manufacturing. Almost any other physically long process lines. Food, beverages, bottling, canning, glass, and more.

Machine Safety Functionality.

Are you interested in machine safety? When you talk with a Horizon Solutions Specialist, our team considers servo drives a “motion” technology. Our team also includes dedicated machine safety experts as well as Drives Specialists who can assist with AC and DC drive systems. When it comes to servo drives for Motion let’s look at a real-life example: Kinetix 5700. This family is considered a “Safe Monitoring Servo” and it offers some great functionality when it comes to machine safety.

  • Safe Torque Off & Safe Stop
  • Controlled Stopping
  • Safe Limited Speed
  • Safe Limited Position
  • Advanced Safety Encoder
  • Safe Drive Instructions

We’ll spend just a bit of time delving into each of those pieces of functionality, what they mean, and how they all come together to keep your people and your finished product safe.

servo drives

Pictured: an array of Kinetix 5500 servo drives in a control panel

Safe Torque Off + Safe Stop + Controlled Stopping

The standard (dare we say “old”) way: STO – Safe Torque Off – means power is cut to the motor. The productive way: SS1 – Safe Stop 1 is a smarter way to bring the machine to a safe state. To better understand, let’s consider this car analogy:

STO
Driving down the highway, eliminate fuel supply.

SS0 Uncontrolled Stopping
Driving down the highway, turn off engine (STO); vehicle continues to move – coasting to a stop

SS1 Controlled Stopping
Driving down the highway, uses braking to bring you to a stop, then turn off engine (STO).


STO: Power that can cause rotation (or linear movement in the case of a linear motor) is removed from the motor. The drive will not provide energy to the motor, which will not be able to generate torque (or force in the case of a linear motor).

SS1, Controlled Stopping: Initiates and monitors the motor deceleration rate within set limits to stop the motor and initiates the STO function when the motor is at zero speed.


Kinetix5700 servo drives application Using Servo Drives to Enhance Safety and ProductivitySo, what does this all mean? It means you can now slow the machine down, real nice, at whatever requirements you need. You’re not just slamming down and screeching the brakes. Nobody knows your machinery and processes better than you. It’s just a matter of a few calculations to determine the safe stop time and the best way to slow down your system. Do you need help with these calculations? Contact a Horizon Solutions Motion Specialist today to learn more.

Safe Limited Speed + Safe Limited Position

For Safe Limited Speed and Safe Limited Position, the safety set points can be changed on the fly. This means that when a machine is changed over to run another widget, the safe speed setting for example, can change with the new widget. Also, safety zones can be changed. This functionality drives productivity as your team can produce more widgets, quicker, and with less hassle. Depending on your system, you can even build the ability to run multiple safety functions on the same axis of motion simultaneously. This flexibility will further improve productivity. The combination of Kinetix 5700 servo drives and GuardLogix controllers can offer a solution to meet SIL2/PLd and SIL3/PLe requirements. This gives you the ability to “right size” your safety solutions and not pay for anything you don’t need.

Advanced Safety Encoder + Machine Safety Software (Safe Drive Instructions)

When you start using Kinetix 5700 servo drives, to ensure safe operation. one of the options available is to use dual encoders to safely know the position of your devices. We are talking at great length about servo drives, but have not yet mentioned why, specifically, they’re a better option when compared to traditional DC or AC motors. There are two big reasons:

  1. Control. Intrinsic motor feedback can detect unwanted motion and/or ensure the accuracy of the commanded motion.
  2. Improved performance. Higher speeds and easier programming.

Intrinsic motor feedback example: Kinetix VPL Low-inertia Servo Motors have a SIL2 Pl(d) Safety Rated Encoder option which allows for redundant checking of speed and position.

Motion systems require some intelligent work up front, and assuming that all of those calculations are correct – you want to make the actual implementation as straightforward as possible. Our real-life example, the Kinetix 5700 family, is completely programmable. Safe Drive instructions let you achieve complete system configuration with one software package, Studio 5000® Logix designer v31. Discrete, motion, drive safety, and HMI development in one standard package.

Want to learn even more about servo drives?

We covered a lot of technical details in this post. Horizon Solutions will be hosting a series of six events in May/June of 2018. These Smart Manufacturing Expo events are a great opportunity to talk face to face with the experts. You can look, touch, and demo servo drives as well as many of the safety devices that can be integrated with them. These events are certainly a good fit for anyone that helps specify new machine safety systems or that has been tasked to improve existing equipment. There is no charge for this event, continental breakfast and lunch are included, pre-registration is required, seating is limited. Reserve your seat today.

Share this with your colleagues and network ...

About the author

Chris Williams
Chris Williams

Chris is an Automation Specialist with for Horizon Solutions, focusing on motion control and motion applications. He has experience with a wide variety of automation technologies. Chris is a graduate of the Rochester Institute of Technology and resides in Rochester, NY. He enjoys hiking and biking throughout the city. Both at home and at work, Chris is often a leader for identifying new technologies and opportunities to use them in real world applications.