A frameless motor is the active torque and speed producing part of a conventional motor, but without the shaft, bearings, housing or endbells. The frameless motor consists of only two parts: the rotor and stator. The rotor is usually the inner part, consisting of a rotating steel donut assembly with permanent magnets, that mounts directly onto your machine shaft. The stator is the outer part, with steel laminations and copper windings around the teeth to create the electromagnetic forces that mounts compactly within the body of your machine housing.
Why should I use frameless motors?
Frameless motors are generally designed into advanced machines that would benefit from one or more of the following:
Increased machine performance
No mechanical compliance (no backlash, no lost motion)
Higher system bandwidth
Improved machine efficiency
A more compact form factor
Smaller machine footprint
Highest torque per volume
Fewer mechanical parts
No components subject to wear or maintenance
How do I size a frameless motor for my machine application?
Frameless motors are sized the same way that you might size a conventional, housed servo motor. The machine application is evaluated for the motion requirements for both torque and speed. A machine designed with a frameless motor will generally have higher efficiency due to the lack of gearing, belts and pulleys, or coupling elements in the mechanical drive train. This efficiency often simplifies frameless motor sizing. Knowing the actual machine or part duty cycle timing generally gets you the RMS torque and speed as well as the peak conditions needed to select a motor. There are online motion sizing tools available to help you properly calculate your motor sizing requirements.
There is also a frameless motor performance curve tool that allows machine designers to understand actual motor and drive performance, even at different bus voltages, available drive current, and ambient temperature limitations. This tool helps you optimize the choice of frameless motor winding based on actual machine requirements rather than choosing from a limited set of windings based on standard input bus voltage.
Which applications are best suited for frameless motors?
Frameless motors are broadly used across virtually all machine markets: robotics, medical, machine tool, packaging, printing, converting and general automation. Basically, anywhere the benefits of improved machine performance, compact form and reduced maintenance are valued.
How easy is it to install a frameless motor?
Most people assume that the installation of a frameless motor is a complex and daunting task. A quick review of this “how-to” installation video will help to dispel those concerns. Typically, frameless motor components can be installed in a basic machine housing design using slip-fit tolerancing and readily available industrial adhesives. The use of frameless motor part sets often leads to improved manufacturability and reduced machine setup times through the elimination of couplings, gearing and belt adjustments. Also, system tuning and commissioning time is reduced due to increased repeatability of the system mechanics.
Kollmorgen provides frameless motor solutions in 17 standard frame sizes (60 mm to 850 mm diameter, with torque up to 13,000 Nm), each with multiple stack lengths and winding options. These standard designs can provide your machine with an ideal-fit frameless motor solution optimized for your application.
Tom S. Wood, a 35+ year veteran in high-performance motion, has integrated motion control solutions as a machine designer, manufacturer’s representative, High-Tech distributor, and as a Kollmorgen Motion Control Product Specialist. He has extensive experience designing next-generation motion systems for the aerospace and defense industry as well as for robotics applications that improve everything from workplace safety to patient mobility. Tom enjoys helping engineers understand how to enhance their projects through frameless technology that delivers high performance in a compact form.
There really isn't anything to fear when utilizing high performance frameless servo motors in your machine design. Many engineers get concerned about "air gaps" and "concentricity" when discussing frameless servo motors - but there is little to be afraid of! In applications where an embedded motor design makes sense, the application shaft that the frameless motor will be mounted on will already be machined to tolerances well within the range required for robust servo driven performance.
Frameless, or “servo motor kits”, open up numerous possibilities in designing motion elements for your machine related to performance. A frameless motor consists of rotor and stator components which are built into a machine assembly to transmit torque to a load. Many applications which take advantage of a frameless motor are direct driven, which eliminates bandwidth robbing compliance. Effectively, this means you have eliminated torsional losses and any wind-up or spring losses.
The KBM series offers high performance, long life, simple installation in a motor kit that can be embedded directly in your mechanical design. A huge selection of standard motors and cost-effective modifications ensure a perfect fit.