Frequently Asked Questions
Couplings
u-Flex helical couplings are one-piece shaft couplings made from homogeneous materials. Their basic shape is a cylindrical body with a helical groove—also known as a spiral—machined into it. This screw-like or DNA-shaped design creates a precise flex zone, resulting in elasticity that can be calculated with exact precision. The advantage of a helical coupling being made from a single piece is that multiple functions and individual parts are combined into a single, space-saving unit. Helical couplings have no additional moving parts and are therefore wear-free. This guarantees high dynamic stability as well as vibration-free, smooth-running bearing loads—even with large displacements.
For connecting the input shafts, standard couplings offer a choice of either clamping hubs or stud bolts. For custom-made products, u-Flex GmbH offers the following connection types:
Alternating set screws or clamping connections*
Pins, bolts, studs
Key
Flange
Threaded stud, threaded bore
Tapered bore
Single- or double-flanged bore
Spline
*The frictional fit generated here is sufficient to transmit the required torque; an additional key is not necessary. However, upon request or in special cases, we also supply a clamping connection with a key.
For specific designs, the connections can be chosen freely. The material specifications can also be chosen freely. The only requirement is that the material must be machinable.
u-Flex helical couplings can be used in a wide variety of applications—namely, wherever movement needs to be managed and controlled. Whether in valve technology, medicine, aviation, aerospace, or mechanical engineering, u-Flex products stand out for their precision and durability.
As long as the couplings are used within the specified torque range, they are torsionally rigid.
Angular misalignment occurs relatively frequently. In a helical coupling, this is achieved by the inner ribs closing and the outer ribs expanding. If there is sufficient space between the helical grooves, u-Flex allows for misalignments of up to 20°.
Yes. To compensate for radial misalignment, a coupling system must meet high technical requirements. If the misalignment is not compensated for, the resulting transverse forces will damage the bearing seats. The helical principle offers an optimal solution—the maximum permissible values in the standard catalog range are ± 0.8 mm. Custom applications also allow for higher values.
Yes, a helical coupling from u-Flex can do that, too. In this case, the drive shafts are not in the same plane, so a helical coupling can compensate for this three-dimensional displacement. Prerequisite: a relatively long helical element.
Thanks to their low moments of inertia, helical couplings can operate over a wide speed range, in reversing operation, and at very high cycle rates. Our standard helical couplings are designed for speeds up to 10,000 min⁻¹, although speeds of up to 50,000 min⁻¹ have already been achieved. Please contact our engineering department regarding your specific needs and application. We will be happy to advise you on what is feasible.
In addition to materials (aluminum and stainless steel), a distinction is also made between couplings with through-holes and couplings with blind holes or non-through holes.
Precision Springs
Thanks to CNC manufacturing, maximum customization is possible in terms of dimensions, spring rate, and geometry. All machinable materials can be used to manufacture springs, so a wide range of materials is available. In addition to conventional materials, lightweight aluminum springs, electrically insulating plastic springs, or even high-strength titanium springs can be produced—the choice of material is therefore virtually unlimited.
They are machined from a single, homogeneous piece of material. Such springs can be subjected to compressive, tensile, and torsional forces as well as bending stresses—and allow for an optimally coordinated combination of different spring rates. In multi-coil springs, the compression or tension is also distributed across multiple points, which enables an even, parallel force distribution relative to the central axis. Thus, the more coils a spring has, the more precisely the parallelism is maintained during compression or extension.
This exceptional spring design enables highly precise and consistent spring rates of up to ±0.1 with a repeatability of up to 1%. The spring is manufactured from solid material, such as a bar or tube, into which a helical groove is cut. This machining process is far superior to coiling a spring, as it generates no internal stress—only the natural stress of the material. This gives the spring a linear spring characteristic with high repeatability and fatigue strength.
In situations where coiled springs fail, whether due to service life, design, material properties, or precision.
Springs manufactured using machining processes have connections that are reduced to the bare essentials and reinforced where necessary. Unsupported moments are prevented, for example, by using double pins, cross slots, grooves, mounting flanges, etc. Such integrated connections increase the service life of springs, and the installation space can also be optimized. This often makes it possible to reduce both production and assembly costs at the same time.
The spring rate of a conventional coiled spring falls within a tolerance range of +/- 10%, while machine-manufactured springs fall within a range of only +/- 5%. Upon customer request, we can also manufacture precision springs with a tolerance of +/- 1%. A major advantage: Machining processes do not generate internal stresses that must first be relieved before the force can be applied.
The integration of additional features (e.g., bores, threads, flanges, or grooves) optimizes the installation space and greatly simplifies assemblies, which significantly reduces assembly time. Integrated connections (e.g., flanged ends, grooves, threaded holes/pins, etc.) further increase the spring’s stability.
Multi-coil springs can be used to manufacture components that can simultaneously absorb compressive, tensile, and torsional forces. In multi-coil springs, the compressive or tensile force is distributed evenly across multiple points, resulting in a balanced, parallel force distribution. Additional spring guidance is not necessary, as multi-coil springs do not allow for unwanted lateral buckling.
By optimizing the coil geometry at the start and end sections. The coil tail is thickened, thereby increasing the spring’s strength in the critical area. The finite element method (FEM) can provide precise predictions regarding strength and service life.