PRE-LOAD PINION

Backlash is one of the key influencing factors when it comes to the precision and performance of rack-and-pinion drives. Par- ticularly during changes in direction, it can lead to delays, inaccuracies, and irregular motion behavior. This not only impairs positioning and repeatability accuracy, but also places increased demands on drive sizing and control technology. Against the backdrop of growing requirements for dynamics, precision, and efficiency, the reliable control of backlash is becoming increasingly important in modern mechanical engineering.

This whitepaper examines ATLANTA’s pre-load pinion technology as an innovative solution that enables a paradigm shift in drive technology. By integrating a precisely adjustable preloading unit into a compact, single component, backlash is reduced directly at the point of contact.

Controlling backlash in rack-and-pinion drive systems represents a key design challenge in mechanical engineering. Traditionally, designers have faced a fundamental trade-off: either mechanical dual-drive concepts are used, which require increased instal- lation space and introduce elastic compliance, or electronic twin-drive systems are implemented, which come with significantly higher hardware and software complexity. ATLANTA solve the problem through the ingenious solution of Pre-load Pinion.

The concept of “advanced simplicity” makes it possible to achieve high feed forces in the range of 20 to 30 kN using just one ser- vo drive unit. Compared to conventional two-axis solutions, the pre-load pinion shaft concept offers clear advantages in terms of integration, cost efficiency, and commissioning.

Dual-Drive mechanical pre-load (1 drive – 1 motor – 2 gearboxes)
In mechanical dual-drive concepts, the drive torque is distributed via a kinematic chain to two pinions. Typically, this involves the use of two planetary gearboxes and two right-angle gearboxes, which are interconnected by a torsion shaft or an elastic coupling.

From a design perspective, this approach results in several inherent system disadvantages:

• Increased installation space requirements:
  Integrating two complete reduction gear trains per axis leads to a significantly higher space requirement on the machine slide. This
  limits design flexibility, complicates compact machine layouts, and increases the moving masses.
• Limited torsional stiffness (wind-up effect):
  Additional connecting elements such as shafts and couplings introduce elastic compliance into the force transmission path. This reduces the effective torsional stiffness of the overall system and negatively affects dynamics, control behaviour, and positioning accuracy.
• High assembly and adjustment effort:
  Precisely matching the phase position of both pinions relative to the rack requires tight tolerances and accurate alignment of the entire kinematic system. This increases assembly effort and extends the commissioning time of the machine.
• Increased probability of failure:
  The large number of components, particularly bearing points, seals, and additional gear meshes, raises system complexity and,
  consequently, the statistical likelihood of wear and failures.

Twin-Drive electronic pre-load (2 drives – 2 motors – 2 gearboxes)

In electronic twin-drive systems, two independently controlled drive units act on the same rack. The required pre-loading torque is generated within the control system by deliberately superimposing opposing torques (torque bias).

From a design and system engineering perspective, this approach presents the following challenges:

• High system complexity (over-engineering):
  The architecture requires a complete duplication of all core drive components, including motors, gearboxes, power electronics,
  and sensors. This results in significantly higher investment costs as well as increased integration effort.
• Demanding synchronization and parameterization:
  Stable system operation depends heavily on precise tuning of the two drive controllers. In particular, interactions and potential resonance effects between the coupled drives must be deliberately suppressed. This requires advanced control engineering ex- pertise, increases design effort, and significantly complicates commissioning.
• Increased demands on diagnostics and service:
  Fault analysis becomes more complex, as two independent drive trains must be examined and evaluated. Interactions between the
  systems make clear root-cause identification more difficult and can lead to extended machine downtime during service interventions.

Building on the proven principle of split gears, long established in precision engineering and watchmaking, ATLANTA has consist- ently further developed and implemented this concept for industrial drive technology applications.

The focus lies on the functional integration of the pre-loading mechanism directly into the pinion itself, resulting in a compact yet high performance solution for eliminating backlash.

Design Advantages of the Integrated Approach:

• Integrated mechanics:
  il pignone di precarico è costituito da due corone dentate indipendenti, ottimizzate per un preciso ingranamento in tandem con la cremagliera. Il precarico viene generato interamente all’interno dell’assieme, senza la necessità di ulteriori componenti esterni.
• Precise adjustment:
  The pre-load pinion consists of two independently designed gear rings, optimized for precise tandem engagement with the rack. Pre-loading is generated entirely within the assembly, without the need for additional external components.
• Double flank engagement:
  An integrated adjustment unit allows fine, reproducible setting of the angular offset between the two gear rings. This enables
  targeted and controlled elimination of backlash.
• High torsional stiffness:
  Eliminating elastic transmission elements in the force path significantly increases overall system stiffness. This improves dynamic performance, enhances control quality, and enables higher system bandwidths.
• Simplified system architecture:
  Implementation with just one drive unit reduces design complexity, saves installation space, and minimizes moving masses
  compared to dual or twin drive solutions./li>
• Reduced commissioning effort:
  Since the pre-load is generated purely mechanically, complex control strategies or additional software parameterization are not required. This simplifies commissioning and increases process reliability.

The ATLANTA Pre-load pinion offers an optimal combination of performance, stiffness, and cost efficiency. By integrating the pre-load mechanism into a compact assembly, a standard axis can be transformed into a high precision, zero backlash axis with a moderate additional cost of only around 10.4%.

In contrast, mechanical dual drive and electronic twin drive solutions require significantly greater effort, resulting in cost increa- ses of 68% to 100%. The ATLANTA Pre-load pinion therefore represents an efficient solution that provides design engineers with precise positioning while simultaneously reducing integration and commissioning times.