Why Are There Different Servo Drive Form Factors?

Servo drives with different form factors

Servo drives of various form factors

We say it all the time: Servo drives come in all shapes and sizes. Oftentimes, a key part of deciding which servo drive to use for your application is deciding which form factor to use. Which raises the question...

What exactly is a form factor?

Form factor is a term used to define the structure, size, and other physical aspects of electronics. In the realm of motion control, form factors are one of the most common ways servo drives are categorized.

But why?

Why are there so many different servo drive form factors? With the technology that's been around for decades, you might think that it would be pretty uniform by now.

But different form factors are often better suited for different applications. Besides power capabilities, the choice of servo drive styles for engineers can often come down to factors such as space constraints, accessibility, exposure to the elements, and even personal preference.

Let's explore the different types of servo drive form factors and where it might be best to use a certain one.

Panel Mount

Panel Mount Servo Drive

A digital panel mount servo drive, featuring a cover, bracket baseplate, and external connectors.

Panel Mount servo drives are the traditional servo drive form factor. They've been around for several decades. They're pretty simple in appearance; it's a box with connectors on it. The circuit board is attached to a metallic base plate with a plastic or metal cover surrounding most of the rest.

The baseplate typically has an L-shaped cross-section, so it covers two sides of the servo drive. The baseplate serves multiple purposes.

  • Mounts the servo drive to the application, either on its back or on its spine
  • Provides sturdiness and maintains the drive's shape
  • Acts as a heat sink for the electronics

Panel mount servo drives mounted

Panel mount servo drives mounted

The simple panel mount design lends itself to being very scalable, coming in sizes as small as a pocket dictionary to… a regular dictionary. Because of this, the most powerful, high voltage servo drives tend to be of the panel mount form factor.

Larger panel mount servo drives can be equipped with cooling fins and even fans for thermal management. So it shouldn't be surprised that the most powerful ADVANCED Motion Controls servo drives available are panel mount servo drives.

The name says it all; panel mount servo drives are usually simply mounted to the electrical panel in an application. While the electrical panel can be just that (a panel) it usually refers to a cabinet with electrical equipment.

So while they can be used just about anywhere, they are ideally suited for installations that use electrical panels such as factories and machinery.

See our full selection of panel mount servo drives here.

PCB Mount

PCB mount servo drives

Several examples of PCB mount servo drives.

Also known as an embedded style drive, the PCB mount servo drive was a design pioneered by ADVANCED Motion Controls in the late 80's.

PCB mount drives forego wire connections and connect directly to another printed circuit board solely using pins, offering tight integration.

Unlike panel mount servo drives, PCB mount servo drives have an open structure. There's no protective cover, so the printed circuit board is largely exposed. Some PCB mount servo drives, however, do feature a baseplate that acts as a heat sink.

The pin-based connection of PCB mount servo drives lends itself best to compact servo drive designs. For many years, the PCB mount form factor has been associated with lower power servo drives because of their small size. However, innovations in power density have allowed PCB mount servo drives to compete with larger panel mount servo drives that came before, as evident in ADVANCED Motion Controls' FlexPro drive family.

PCB mount servo drives inside robot

4 PCB mount servo drives installed in a robot, mounted directly to a main pcb and taking up very little space.

Because of their compact form, PCB mount drives are typically found nested within robotic applications. In fixed robotics, PCB mount servo drives can fit within arm joints just behind the servo motors, and their light weight makes them well suited for multi-link arms. In mobile robots, small drives means less weight to carry which means less power used.

If an engineer doesn't want to design a mating PCB connection for a PCB mount servo drive, ADVANCED Motion Controls also offers mounting cards for AxCent and DigiFlex Performance servo drives. Mounting cards convert the pin outputs into connectors, allowing for a wired connection. These make the PCB mount servo drive very similar to our next form factor…

See our full selection of PCB mount servo drives here.

Machine Embedded

2 machine embedded servo drives with built-in mounting cards

Machine embedded servo drives featuring connectors and flying leads.

Our machine embedded drives combine the compactness and open structure of PCB mount servo drives with the connection style of panel mount servo drives.

Essentially, it's a PCB mount servo drive with a built-in mounting card.

The machine embedded servo drive is fairly new at ADVANCED Motion Controls, our first ones appearing in the FlexPro drive family. It offers machine and robot designers more flexibility in their designs, especially those that want to use the compactness of FlexPro servo drives but to do not want to spin a mating PCB.

As the name implies, machine embedded servo drives are well suited for machine applications where space might be limited. They're also great for mobile applications out in the field where small size is necessary but maintenance and replacement need to be done on the fly.

See our machine embedded servo drives here.

Vehicle Mount

a plastic enclosed servo drive

A fully covered vehicle mount servo drive.

Vehicle mount servo drives are heavy duty amplifiers with rugged exteriors and high current outputs.

Vehicle mount servo drives have a hard ip65-rated plastic shell enclosing the drive with a thick baseplate, keeping the internal electronics well protected. The supply power and motor connections are achieved through 5 screw terminals, while all the communication is done through a sealable connector.

As the name implies, vehicle mount servo drives are meant to drive the movement of large electric vehicles, outputting high current to provide the necessary traction. The extra thick baseplate serves as a great heat sink to help manage the high current output.

Outdoor all terain mobile robot with 6 wheels

Vehicle mount servo drives are tough and well-suited for all terain mobile robots.

The drives' durable architecture also protects the electronics from dust, debris, splashes, and impacts that the vehicle might encounter. This kind or protection is essential for search and rescue robots or other all-terrain vehicles that will be exposed to the elements.

Because electric vehicles are battery operated, it's important to have a wide supply voltage range. As electric vehicles work throughout the day, the batteries become depleted and their voltage output capacity is reduced. A wide voltage range allows the drives to remain enabled and provide traction even as the batteries are depleted during the work cycle.

See our vehicle mount servo drives here.

Custom Form Factors

Modifications and Customs

Some examples of custom servo drives with unusual form factors.

When developing a custom servo drive with ADVANCED Motion Controls, customers aren't restricted to any specific form factor; they can choose whatever best fits their application. Sometimes we even get a request to take the power and network capabilities of one of our standard servo drive models and simply incorporate it into a different form factor.

While most custom servo drives fall into the category of one of the previously listed form factors, some break the mold entirely. Custom servo drives can deviate far from the typical rectangular structure.

Their baseplates can become part of the frame of the machine or robot they're in. They can have multiple servo axes in one unit. They might be mounted and connected to the application through non-standard means.

Offering various form factors to our customers gives them some nice standard options for their applications, but customs open a completely new world of possibilities for servo drive sizes, shapes, coverings and mounting styles.

See our full range of custom capabilities.

Final Thoughts

The rules for selecting a servo drive form factorThe rules for selecting a servo drive form factor aren't all absolute.

Sometimes the mounting style of the servo drive or how big it is simply won't affect the application.

There are small PCB mount servo drives that can match the performance of certain larger panel mount servo drives. Sometimes a vehicle mount servo drive is the best choice for an application that's completely static.

Other times, choosing a servo drive with the right form factor will make the difference between a successful application and a lackluster one.

A vehicle mount servo drive might help endure the elements better than a traditional panel mount servo drive. A PCB mount servo drive or a machine embedded drive will fit much more easily into a robot arm than a panel mount or vehicle mount drive. And a panel mount servo drive might make maintenance on a machine much easier than a tightly-fitted PCB mount servo drive. It all depends on the needs of the application at hand.

To see what other properties you should consider when selecting a servo drive, see 5 Rules of Thumb When Selecting a Servo Drive. And if you're not sure what servo drive form factor is best for you, you can always ask us.


- by Jackson McKay, Marketing Engineer

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