If you build machines, you probably work with actuators and positioning stages every day. But do you truly get the best performance or lowest cost of ownership from these motion devices? The answer may not be what you expect.

All too often, engineers think of stages or actuators as just another item on the bill of materials. As long as the motion device nominally meets the desired positioning, force, payload, speed and cost requirements, it’s good to go.

With simple motion requirements, this approach to stage or actuator selection may yield acceptable results. However, machines with complex mechanical motion requirements will benefit from an embedded motion design strategy. Rather than a collection of electromechanical components, which may or may not work well together, embedded motion systems function as true plug-and-play machine subsystems.

Embedded motion systems are engineered to fit within a predefined physical space on a machine and tie into the machine’s motion control system, ready to accept commands from a top-level computer interface, control card or PLC. At their simplest, embedded motion systems may consist of little more than a stage or actuator that has been connectorized to make the drop-in installation easier. At their most complex, these motion subsystems extend from pinout to payload. They encompass not only the motion device itself but also everything it carries.

Compared to a component-by-component approach to machine movement, embedded motion offers some compelling advantages:

Mechanical Performance

Even when they use the same stage or actuator, embedded motion systems will typically outperform component-built motion systems. The reason why comes down to application and assembly expertise. A good embedded motion vendor will have years of experience solving difficult positioning problems and a collection of proven motion building blocks that can be customized for the task at hand. They will have an intimate understanding of how the stage dynamics, the motion control architecture and the operating environment will affect positioning requirements.

As for assembly, many machine builders lack the skilled technicians, specialized fixtures, laser interferometers and other metrology systems needed to align the most precise multi-axis stages—which often have axis-to-axis alignment tolerances measured in microns.

Controls Expertise

Embedded motion systems may or may not ship with motion controls, depending on the customer requirements. But a control strategy should always be part of the embedded motion equation. A good embedded motion vendor will have an extensive knowledge of how different motion control platforms and their kinematic capabilities will interact with the mechanical motion systems. This knowledge can allow us to push the envelope on what’s possible in terms of dynamic capabilities, such as acceptable inertia mismatch ratios.

Reliability

When commissioning a new motion system, some of the most common problems occur because individual, seemingly minor components fail to work properly—or fail to work properly with one another. For instance, a single faulty connector or the wrong wire can leave even the best motion stage motionless. Embedded motion systems avoid this type of failure because they are assembled and tested as a system before integration on the production machine. With motion systems composed of individual components, small failures and incompatibilities can go undetected until the production machine comes together.

Cost Reduction

Embedded motion systems typically cost 25 to 50% less than their component-based counterparts. In part, this savings comes from the ability to reduce parts count—for instance, by designing in brackets, connectors and other components. The cost reduction can skyrocket well above 50% when you factor in all the hidden cost components associated with building and installing a motion system. These include costs related to design engineering, inventory, time-to-market and more.

Many types of applications can reap the benefits of embedded motion. We have implemented this approach on dozens of semiconductor, wet bench, laser cutting, packaging and lab automation machines.

The Hidden Costs Of Motion Systems

Component-built motion systems have a number of hidden costs that can be eliminated by the embedded motion approach, including:

1. Time-To-Market Costs. Embedded motion systems, which inherently support concurrent engineering, can shave weeks or even months off the development time of a complex machine.
2. Program, Production and Materials Management Costs. Embedded motion systems ship as a single bill-of-materials item, eliminating hundreds of parts to be ordered, inventoried and assembled.
3. Production Costs. Precision motion systems require skilled assembly technicians and specialized production equipment that can be difficult to cost justify at less than full utilization.
4. Warranty and Failure Costs. A good embedded motion vendor will warranty their systems against failure and stand behind their work, which reduces the OEM’s risk.

This nontraditional CNC machine has all the hallmarks of an ideal embedded motion application. It required:

1. Both controls and mechanical expertise. Marrying the mechanical system with the controls and amplifiers that support the complex kinematics for polar motion required a systems approach and months of testing. We also had to develop a suite of alignment techniques and tools to build this new CNC system.

2. Compact design, easy integration. Space was at a premium on this desktop-sized CNC machine. servo module Rotary’s design, which features a large unobstructed through hole, allowed us to use the available space efficiently. The 100-mm through holes made it easy to bring the air supply right to the spindle, embed a material indexer on the workpiece side and make all the required power connections.

3. Cost containment. One interesting aspect of this embedded motion system is that it is no more complex than it needs to be. The main functional requirement involved surface finish, not positioning accuracy. The positioning needs are actually quite modest, at least by our standards. So we were able to forego direct reading encoders and run the entire system in open-loop mode. That saved our customer thousands of dollars per machine.

Getting Started With Embedded Motion

The jump from component-by-component motion systems to embedded motion systems may seem like a leap of faith. You will, after all, be outsourcing the motion control to a vendor.

If you pick the right vendor, though, the outsourcing will pay off with improved performance and reliability. Costs will fall too as motion subsystems arrive at your plant fully-tested, warrantied and ready to drop into your machine.