Why the Archimedes Drive is the only True Zero Backlash Speed Reducer,
and others are not.
‘Instant gear changes’ in an automatic car transmission, ‘unlimited data’ with limits in telecom, and ‘chemical-free’ claims where everything involves chemicals. In the precision-driven world of mechanical engineering, we encounter our own version of this contradiction: Zero Backlash.
The quest to eliminate backlash—a common flaw in drive systems—remains a pivotal challenge. Backlash, the undesirable play between mating gear teeth, not only undermines the accuracy of mechanical drives but also contributes to increased wear, noise, and decreased reliability over time. Despite many manufacturers claiming to have conquered this issue with “zero backlash” drives, the reality falls short. Traditional drive technologies such as Strain Wave Gears, Precision Planetary, and Cycloidal drives, despite their advancements, still inherently suffer from some degree of backlash, which can worsen as the gears wear.
Engineers working on servo applications generally consider “zero backlashes” to be between 0.5-5 arcmin. Not really ‘zero’ if you ask me. This is not great news if you need an application where precision and controllability are of utmost priority.
What is Backlash?
Definition Backlash, often referred to as “play” or “slop,” is the gap between mating gear teeth that occurs when the direction of load or motion is reversed. Backlash should not be confused with ‘lost motion’. This gap is not merely a design flaw; it’s an inherent aspect of many geared systems. Gears must have a certain amount of space between teeth to allow for lubrication, thermal expansion, and manufacturing imperfections. However, in practical applications, this space can lead to decreased precision, reliability, vibrations and control.
Why Backlash is Unavoidable in Geared Drive Systems
In traditional geared systems, achieving perfect tooth-to-tooth contact without any space is, to put it mildly, impractical. Factors such as material wear, temperature changes, and load variations alter the dimensions and alignment of gears during operation. These changes necessitate a minimal gap to prevent gear teeth from jamming, ensuring the system can operate under varying conditions. As gears wear over time, this backlash increases, further degrading system performance.
Problems Caused by Backlash
Precision Loss: In precision applications such as CNC machines or robotics, even a small amount of backlash can result in significant errors in output. For example, a robotic arm that places components on a circuit board might misalign parts, leading to manufacturing defects.
- Wear and Tear: Backlash causes gears to impact each other with every change in direction, leading to accelerated wear. This is similar to how a car’s transmission suffers more wear when it frequently shifts gears under high load.
- Noise: The repeated impact of gear teeth as they come in and out of contact can produce significant high-pitched noise. Which is undesirable in environments requiring quiet operation, such as in medical equipment or precision laboratory instruments.
- Vibrations: Backlash can also cause vibrations in systems, particularly affecting arms and end-effectors. This is problematic in fields like surgical robotics, fine assembly tasks or welding, where stability and smoothness are critical. The vibrations can degrade the performance of the system, leading to less accurate or reliable results.
Eliminating backlash is crucial for improving the reliability, efficiency, and accuracy of mechanical systems. While some traditional methods involve complex arrangements or high-precision manufacturing techniques, these solutions often cannot completely eliminate the problem and tend to increase the cost and complexity of the systems
Why the Archimedes Drive can claim true zero backlashes over its entire operating time
The Archimedes Drive represents a significant departure from conventional drive technologies through its innovative design and operating principles, which enable it to achieve true zero backlash over its entire operating life. Here’s how:
Using traction instead of gear teeth to transmit torque
The core of the Archimedes Drive is based on a patented Flexroller-based mechanism, rather than traditional gear teeth. This design eliminates the typical point of contact — and hence the potential for play — between gears. Instead, the drive uses a tightly interlocked yet smoothly interfacing roller system that maintains constant contact without any gaps throughout its life, under all circumstances.
Operating Principles
Contact Mechanics: The Archimedes Drive operates on the principle of surface contact rather than point or line contact. The rollers in the drive distribute forces across a larger surface area, which significantly reduces wear and maintains precision.
Tension-Based Transmission: Instead of relying on the meshing of gears, the Archimedes Drive uses a tensioning mechanism that ensures the rollers are always in optimal contact with the drive’s housing. This system adjusts dynamically to operational stresses, which prevents any slack from developing over time.
Material and Fabrication: The drive utilizes high-grade materials and precision fabrication techniques that ensure minimal wear. The materials chosen are capable of maintaining their shape and properties under a wide range of operational conditions, which supports the drive’s longevity and consistent performance.
Overcoming Traditional Limitations
- No Wear-Induced Backlash: Unlike gear-driven systems, where wear and tear on teeth can lead to increasing backlash, the Archimedes Drive’s roller mechanism and tension-based operation inherently avoid these issues. As there are no teeth to wear down, the mechanism does not suffer from the typical degradation that plagues traditional drives.
- Adaptability to Load Changes: The drive’s design allows it to adapt to changes in load without affecting the backlash. This adaptability is crucial in high-precision industries where even minute deviations can lead to significant errors.
- Consistent Performance: The consistent surface contact and absence of traditional gear teeth mean that the drive’s performance doesn’t degrade over time. This consistency is a key advantage in applications requiring long-term reliability and precision.
Conclusion
The Archimedes Drive’s unique roller mechanism and tension-based transmission system provide a robust solution to the problem of backlash. By eliminating traditional gear teeth and employing advanced materials and manufacturing techniques, only the Archimedes Drive offers a true zero-backlash experience throughout its lifespan, setting it apart from other technologies in the field.
