In the past three years, the robotics industry has become increasingly popular, and attention to the robotics industrial chain has also been rising steadily.

In the robotics industry chain, joint motors are attracting considerable attention—and they have a special term: frameless torque motors!

What is a frameless torque motor?

Does it have any cutting-edge technology?

If you’ve never worked on motors before, you’ll probably get completely brainwashed by a series of articles on frameless torque motors and start thinking that they’re incredibly sophisticated and high-end. But once you’ve actually done motor design yourself, you’ll realize a simple truth:

In the motor industry, frameless torque motors—whether in terms of electromagnetic design, structural design, or even manufacturing processes—are hardly considered high-end. To put it bluntly—

Frameless torque motors are considered low-end products in the motor industry!!

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First, don't be fooled by its name!

Frameless →

What does “frameless” mean?

It just doesn't come with a casing!

That’s right—without a frame, it’s called frameless!

Why don’t we just call it “without a housing”? Because this motor is actually housed inside the robot’s joint—so the joint itself serves as its housing! It’s not some magical, frameless wonder; this deliberately mysterious terminology really leaves me baffled! If we’re going to be that literal, then the electric-drive system motors in new-energy vehicles should also be called “frameless,” since they’re fixed right inside the housing!

Torque motor →

The torque motor itself is a pseudo-concept—why is that?

Start directly from the definition of a torque motor:

→ Low-speed, high-torque (achievable with all permanent-magnet synchronous motors)

→ Wide constant-torque operating range (all motors can achieve this as long as the winding parameters are properly matched with voltage and current)

→ Long stall time (this has nothing to do with the type of motor; whether the stall time is long or not is related to the motor’s thermal management!)

After seeing all this, do you still think the term “torque motor” is anything special? It’s just a way of referring to a particular type of motor performance—nothing special at all!

Motor process →

Let’s first take a look at what the so-called frameless torque motor really is before discussing motor manufacturing processes!

A frameless torque motor is essentially a brushless DC motor!

I’ve seen some promotional materials claiming that frameless torque motors have a “large gap ratio.” What exactly is a “large gap ratio”? Simply put, it means the stator’s inner diameter and the rotor’s inner diameter are both larger. Why are they made larger? Because the space and structure of robotic joints dictate that frameless torque motors must be designed this way!

→Therefore, a frameless torque motor is essentially a brushless DC motor with a relatively small footprint!

*Everyone is probably familiar with brushless DC motors, right?

Compared to the electric drive system motors used in new-energy vehicles, brushless DC motors are significantly easier to design and manufacture from both electromagnetic and process perspectives!

Stator concentrated winding →

For concentrated-winding motors that are manufactured without segmenting, only manual or machine wire insertion can be used. The copper fill factor for the slots in these motors typically ranges from 30% to 40%. The winding equipment for such motors is highly mature and presents virtually no technical challenges.

*Rotor →

To enhance the torque density of brushless DC motor rotors, a surface-mounted structure is often employed. This surface-mounted structure typically uses tile-shaped or bread-shaped magnets. As for this manufacturing process, there’s really not much to say—it’s genuinely quite simple.

If there’s any real difficulty, it’s the fixation of the rotor magnets—but since the robot joint motors don’t operate at very high speeds, the requirements for fixing them aren’t that stringent.

All the technical features of the frameless torque motor have now been fully demonstrated. So, if anyone ever claims that frameless torque motors are incredibly high-end and sophisticated, don’t believe a word of it!

So, are robot motors really not that difficult at all?

No!

The hollow-cup motor at the finger joints is extremely challenging!

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*Its greatest challenge lies in the stator windings; however, over the past two years, breakthroughs have been made in the winding technology for hollow-cup motors, further accelerating the production, manufacturing, and widespread adoption of hollow-cup motors!*

Author’s Note: The WeChat public account and the article “Five Phenomena Are All Empty” have been introduced. If you have any objections, please contact our company to have them removed.

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