Choosing between chassis-mount and PCB-mount motion controls

Motion controllers come in many shapes and sizes to fit unique and specific application needs. From small embedded controllers that can be integrated into a servo motor along with a drive and feedback, to large stand-alone controllers attached to machines, there’s a controller to match every application need.

The type of controller can usually dictate its mounting method as well. When referring to different controller mounting options, it’s common to use the term form factor. It basically describes the physical structure of the controller such as the size and mounting features. Here, there are two common mounting methods:

The chassis mount form factor has been common for quite a while. It’s a simple construction, with the circuit board containing the controller mounted to a metallic base plate which is mounted to the box and then to the machine.

Sizes vary and can be as small as an index card to shoebox size or larger. The larger units can handle higher voltages and currents, thus more power, for applications with higher power demands.

In contrast, PCB mount motion controls lack a metallic or plastic cover which houses the controls, like the chassis mount controls above. Instead, a PCB mounted controller is just the controller connected to a PC board via pins or a wired connection. Smaller than chassis-mount designs, PCB mount controllers are suitable for more compact applications where space is at a premium.

Closely related to PCB mounted controllers are embedded controllers. They reduce the space required by plugging directly into a PC board and eliminate the need for any extra housing or connectors.

Reduced space requirements open up more room for other components if needed, or can just lead to a smaller machine footprint in general. For example, many robotic systems use PCB mounted controllers. In mobile robotic applications, a compact PCB-mounted controller can easily fit inside the body of the robot. In these applications with space constraints, PCB-mount controllers are ideally suited for the job. But not only mobile robotics applications; in a robotic arm on a factory floor, for instance, PCB mount controllers can fit inside arm joints or other small spaces.

So, which form factor to choose? The rule of thumb here is that different applications and uses call for different form factors more ideally suited for that specific application.

Some of the common factors determining which style to choose include the already mentioned space requirements, but also whether or not easy access to the controller is required in daily operation. Plus, there are considerations for environmental factors, such as washdown or temperature or other factors.

 Other considerations — is the controller to be mounted inside of an electronic cabinet housing the controller and other components such as power supplies, IO modules and connections? Or can it be mounted directly to the machine it is controlling? This would mean it must be designed to withstand the environmental and mechanical impacts of being directly mounted to a machine such as vibration or any high impact forces, any EMI interference, or oil, dust, and debris.