Features and typical applications, explained
See how our compact, high-torque hollow-shaft direct drive motors help achieve space savings and higher precision
What is a Direct Drive Motor (DD Motor)?
A direct drive motor (DD motor) drives the load directly without a gearbox, belt, or pulley.
Because the drivetrain is simple, you eliminate backlash and wear, and you can achieve quiet operation, long service life, and highly repeatable positioning.
DD motors also deliver high torque at low speed, which is why they are widely used in industrial robots, inspection and metrology systems, semiconductor equipment, medical devices, and other precision automation.
Microtech Laboratory’s μDD Motor combines compact size, high torque, and a high-resolution integrated encoder, helping machine builders reduce footprint and weight while improving positioning performance.
What is Gearless Drive?
Gearless drive means the motor rotates the load directly without any reduction gears.
With no gear wear and no backlash, you get smooth motion and precise positioning.
Fewer mechanical parts also supports a lighter, more compact machine design, quieter operation, and reduced maintenance.
These benefits make gearless direct drive ideal for precision motion systems and robotics.
What is Backdrivability?
Backdrivability is the ability for the output shaft to rotate smoothly when an external force is applied.
In geared systems, friction and reduction mechanisms often resist motion, making it harder to achieve compliant, natural behavior.
Backdrivable direct drive systems respond cleanly to external forces, which is beneficial for force interaction, haptic feedback, and safer collaboration with people.
How Micro Direct Drive Motor Helps
High positioning repeatability
With no gearbox, there is no backlash. This supports stable, repeatable positioning for precision axes.
Smaller, lighter machine design
Eliminating belts and reducers reduces parts count and helps shrink the overall mechanism.
Quiet and smooth motion
Fewer mechanical interfaces means less friction noise and smoother rotation at low speed.
Lower maintenance burden
With fewer wear components, maintenance intervals and downtime can be reduced.
Better human interaction and safety
High backdrivability can be beneficial for collaborative systems and force interaction.
Cleaner cable and tubing routing
Hollow-shaft designs allow cables, air tubes, or optics to pass through the motor, simplifying integration.
Why Choose a Gearless System
Lower noise
No gear mesh noise improves the working environment and makes abnormal sounds easier to detect.
Higher precision
Backlash-free transmission improves the accuracy and repeatability of the drive axis.
Compact footprint
Fewer parts can reduce the overall mechanism size and free up valuable space.
Better acceleration performance
With fewer mechanical losses and less compliance, available torque can be used efficiently for acceleration and deceleration.
Backdrivability
A beneficial characteristic for master-slave control and haptic/force-feedback systems.
The μDD Motor (Micro Direct Drive Motor) is Microtech Laboratory’s original compact direct drive servo motor developed for high-precision motion in tight spaces.
Because it uses a gearless direct drive architecture, it avoids backlash and wear and delivers smooth, highly repeatable motion.
The design provides strong torque at low speed, and the high-resolution encoder is integrated into the motor, enabling accurate position feedback for precision control.
With a hollow-shaft structure, cables, air tubes, and optics can pass through the motor, simplifying mechanical layout and improving design freedom for compact machines.
μDD Motors help solve integration constraints that are difficult to address with conventional gear-driven actuators and support next-generation motion control for semiconductor equipment, inspection systems, robotics, and more.
2. Less engineering effort: configurable options and simpler integration
3. No gears or belts: low particle generation, improved backdrivability
Case studies and Customizations
Case Studies
Wafer flip mechanism
Gearless direct drive eliminates backlash and reduces vibration, helping flip delicate wafers smoothly and reliably.
The compact structure also supports a lighter mechanism and space savings, improving stability and throughput in semiconductor handling.
Customization example
Tapped hollow shaft (μDD Motor)
We added an M5 × 0.8 tap inside the hollow shaft of the MDH-30 series.
This allows direct mounting of a rotary joint for clean air-tube routing through the axis.
Often adopted in back-end processes. Hollow-shaft integration and customization help solve tight packaging constraints.
Download the brochure
Life science
Precise rotary motion in limited space. Adopted in compact testing and automation instruments.
Optics and photonics
Ideal for coaxial laser attenuators and high-precision pan-tilt gimbal axes where a hollow-shaft motor helps with clean routing.
Robotics
Compact high torque supports smaller robots. Large hollow bores also simplify cable routing through joints.
Universities and research
Backdrivability is valued for control schemes involving haptic feedback and force interaction.
μDD Motor Compared to Typical Drive Systems
Item
Stepper motor
AC servo motor
Direct drive motor
μDD Motor
Repeatability
Good
Good
Excellent
Excellent
Absolute accuracy
–
Good
Good
Excellent
Heat generation
Fair
Fair
Good
Excellent
Stiffness
Fair
Good
Excellent
Excellent
Hollow shaft
Good
Good
Excellent
Excellent
Size
Excellent
Good
Fair
Excellent
Torque (gearless)
Good
Good
Excellent
Excellent
Best speed range
Mid to high
Mid to high
Low to mid
Low to mid
Low-speed speed ripple
Poor
Fair
Excellent
Excellent
Backdrivability
Poor
Fair
Excellent
Excellent
Typical configuration
Gear or belt
Gear or belt
Direct drive
Direct drive
Cost
Low
Mid
High
High
Best-fit examples
High-speed rotation
General positioning
Precision rotation (larger)
Precision rotation (compact)
Note: This is a general reference. Actual performance depends on your load, stiffness, tuning, and thermal conditions.
Reliable support and production solutions
● Selection support
When you contact us, a dedicated engineer will support your motor and driver selection.
Please reach out via this form.
● After-sales support
Our products are managed under a strict quality assurance system after passing extensive validation tests.
In the unlikely event of initial defects, we will replace the unit at no charge.
After-sales support includes repair services and root-cause analysis for abnormal behavior.
• Tuning support
・Auto-tuning function
Setup steps and measured performance are available here (released in 2024).
・Manual tuning for further optimization
Tuning recipes and procedures are available here (user registration required).
Paid tuning support by MTL engineers: contact us.
・You can also use a third-party servo driver.
Compatible driver brands are listed here.
FAQ
These are the questions we see most often when engineers switch from geared or belt-driven rotary axes to direct drive.
If you share your duty cycle and load profile, we can confirm sizing and integration quickly.
Q
What type of motor is the μDD Motor?
A
μDD Motor is a compact direct drive servo motor with an integrated high-resolution encoder. The motor is a three-phase permanent magnet design intended for smooth position, velocity, and torque control.
Q
What information should we prepare so you can select the right model quickly?
ASend any of the items below. Even partial data is okay, we can estimate the rest.
Load mass and geometry (or CAD), plus the rotation radius that dominates inertia
Speed profile: target rpm, accel and decel time, move time, settle time
External torque: friction, cable drag, vacuum seal drag, or process torque
Accuracy targets: repeatability, settle window, and required smoothness at low speed
Environment: vacuum, cleanroom, temperature limits, available heat sinking
Mechanical constraints: OD limit, allowable height, required through-bore size
Practical tip: if your issue is low-speed ripple or settling, a short video of the behavior helps.
Q
How do we size torque for a direct drive rotary axis?
A
Direct drive sizing is usually based on your torque profile over time:
acceleration torque (inertia × angular acceleration) plus steady torque (friction and process load).
Peak torque: needed during accel and decel events
Continuous torque: average torque tied to heating, duty cycle, and mounting
Q
Why does inertia ratio matter so much, and what happens if it is too high?
A
Inertia ratio strongly affects control stability and settling. If the reflected load inertia is far larger than the motor rotor inertia,
the servo may require more careful tuning and can show overshoot, hunting, or low-speed ripple depending on stiffness and feedback resolution.
Practical actions if you see issues:
Reduce inertia where it matters most (lighter payload, smaller rotation radius, shorter arm)
Review tuning and filters (auto-tune first, then refine for settle and smoothness)
Select a motor with more torque and thermal capacity when duty cycle is demanding
Q
We have low-speed vibration or speed ripple on a rotary axis. Can direct drive help?
A
Often, yes. Geared and belt systems can add compliance, friction, and backlash effects that show up as ripple at low speed.
A direct drive axis simplifies the drivetrain and can improve low-speed smoothness, especially for inspection rotation, alignment, and indexing.
Confirm mechanical stiffness first (mounting, bearing preload, coupling)
Then tune for the real goal: smooth low speed or fast settling, not just fast acceleration
Check cable routing and cable force, it can create periodic torque disturbance
Q
Can we route cables, air tubes, or optical paths through the hollow shaft?
A
Yes. This is a common reason to choose a hollow-shaft direct drive motor.
It helps reduce interference, simplifies assembly, and keeps the axis clean.
Plan for bend radius and strain relief at both ends of the axis
Separate signal and power routing where possible to reduce noise risk
For air routing, confirm tube abrasion risk and rotary joint mounting method
Q
Do we need an external bearing, or can the motor support the load directly?
A
It depends on your load path. Many direct drive integrations use a dedicated bearing set to handle radial and axial loads,
while the motor provides torque and feedback.
If your axis sees significant radial or thrust load, design the bearing system first
Runout and wobble are usually dominated by bearings, not the motor
Send your load direction and bearing layout, we can review integration risk early
Q
What happens when power is off, will the axis hold position?
A
Direct drive systems are generally backdrivable, so holding behavior depends on your mechanism.
If you need position holding during power-off, plan a brake or mechanical lock, or design a safe resting position.
Safety note: for vertical or gravity-affected mechanisms, always define a fail-safe strategy.
Q
How do we manage heat in a compact direct drive axis?
A
Heat is mainly driven by duty cycle and continuous torque. Mechanical mounting matters because the motor body often serves as the heat path.
Use a rigid metal mount that can act as a heat sink
Avoid insulating spacers unless required
Confirm continuous torque based on your real cycle, not only peak events
Q
Can μDD Motors replace an existing motor plus gearbox actuator?
A
In many cases, yes, if required torque, speed, and footprint allow it.
A direct drive approach removes backlash sources and reduces wear parts, but it shifts more responsibility to sizing, stiffness, and tuning.
If you send your current motor, gear ratio, output torque, speed range, and axis dimensions, we can propose a compact direct drive option.
Q
What servo drive and controller can we use?
A
We offer MTL driver options and also support third-party servo drives depending on the encoder interface and control requirements.
Please refer to our compatibility list and contact us if you are unsure.
Q
What are the typical design checks when switching to direct drive?
A
Here is a practical checklist we recommend during concept design:
Torque: peak and continuous based on duty cycle
Inertia: reflected load inertia and stiffness of the structure
Feedback: encoder resolution and interface, and cable noise risk
Mechanical: bearing layout, runout targets, and assembly tolerance
Thermal: heat path, ambient temperature, and allowable temperature rise
Routing: through-bore plan for cables, tubes, or optics
About Microtech Laboratory
Microtech Laboratory Co., Ltd. has been a specialist manufacturer of compact, high-precision rotary encoders and direct drive motors since its establishment in 1981.
Headquartered in Sagamihara, Kanagawa, we supply products to a wide range of industries including precision instruments, robotics, and semiconductor manufacturing equipment.
Our strength is proprietary engineering that delivers high performance in compact form factors. The μDD Motor integrates a high-resolution encoder and uses a gearless direct drive design to support precision control with low noise. With hollow-shaft options and flexible customization (even from one unit), we help machine builders solve integration constraints and accelerate development.
Company name
Microtech Laboratory Co., Ltd.
Established
February 1, 1981
Capital
JPY 45.5 million
President & CEO
Yusuke Nomura
Business
Design, manufacturing, and sales of rotary encoders “Micro Encoder” and direct drive motors “μDD Motor”
Fiscal year end
July 31
Head office
8-1-46 Kamitsuruma-honcho, Minami-ku, Sagamihara, Kanagawa 252-0318, Japan
