What does « fine pitch gear machining » mean and what is achievable today with traditional machining?

(24.07.2019)
How would you handle production of gears with modules starting at 1 down to 0.01, or DP from 25 up to 2'500? Many applications use gears within this range and key point are surface condition and precision in the geometry, all this with a productivity focus? Many 3rd party suppliers and original dealers can provide with live tools for hobbing operations, allowing virtually any swiss machine to become a gear production device. For ultra-precise geometries, dedicated machines will be preferred. But for both options, cutting tool is the key component of this chain and you need to have quality tools to produce quality parts!

Today’s situation

Gearboxes are widely used in applications that require a desired output speed (RPM), a control of the rotation direction, and to translate torque or power from one input shaft to another. Technological advances and evolution of gears have made it possible to develop more efficient and powerful gearboxes manufactured at lower costs. Toothed gear systems have evolved from fixed axis gear systems to new and improved gears including helical, cycloid, spur, worm and planetary gear systems. 

Figure 1 - Faulhaber – planetary gearhead for micromotors

Figure 2 - HNP Mikrosysteme - Components of micro annular gear pumps

Following trends influence gearbox designs in making advances in gear’s design, should they be internal or external:

  • miniaturization of the production concept
  • Portable medical instrumentation
  • Remote surgery devices
  • Weight savings in transportation due to electrification of cars
  • General robotization
  • precision dosing of concentrated drugs or liquids

Experience to take advantage of

The complexity and required quality level from products coming from the watch industry should be a way for setting new standards in the industry. Gear trains found in the mechanical movements of Swiss watches are probably the smallest and more precise gear systems. Of course, the balance between over quality and price competitivity needs to be set between cutting tool’s manufacturer and user. This said, there still is the room for improving a lot all the gear trains to make them more efficient.

Figure 3 – The Naked Watchmaker - Deconstruction Breguet Classique Chronographe 5287

New production possibilities

Gear hobs with module of 0.01 or DP 2500 are not an exception in the watch industry. But Swiss know-how not only makes it possible to source cutting tools for very fine pitch. It also takes a step forward in the actual production of small parts in terms of precision, quality and repeatability!

A brief outlook into the future:

3D printing thanks to laser sintering for instance seems to be a way to achieve quality parts for some applications. However, if you need micro precision, repeatability and high-volume production, chip making solutions like hobbing or power skiving are far more efficient. Furthermore, these techniques can be applied on existing machining centers, avoiding the need to invest in new equipment.

Figure 4 – 3dprinting.com – Selective Laser Sintering (SLS)


Author

Hervé Baour, Dipl. Ing. FH, International Business Development Manager

Tel.: +41 32 474 0410
Mobile: +41 78 646 9418
Mail: hblbsach
Louis Bélet SA, Les Gasses 11, 2943 Vendlincourt, Switzerland
www.lbsa.ch