Frequently asked questions
Couplings
u-Flex spiral couplings are shaft couplings made from a single piece of homogeneous material. Their basic shape is a cylindrical body with a helical groove, also known as a spiral, incorporated into it. This screw-like or DNA-shaped structure allows for a precise flex zone, resulting in exactly calculable elasticity. The advantage of a spiral coupling consisting of a single piece is that several functions and individual parts are combined into a single, space-saving unit. Spiral couplings have no additional moving parts and are therefore wear-free. This guarantees high dynamic stability and vibration-free, smooth-running bearing loads – even with large displacements.
Standard couplings offer a choice of clamping hubs or stud bolts for connecting the drive shafts. For custom-made products, u-Flex GmbH offers the following connection types:
Alternating adjusting screw or clamping connection*
Pins, bolts, studs
Key
Flange
Threaded pin, threaded bore
Conical bore
Single or double flattened bore
Spline gearing
*The fastening friction generated here is sufficient to transmit the required torque; an additional key is not necessary. However, on request or in special cases, we also supply a clamping connection with a key.
For specific designs, the connections can be freely selected. The material specifications can also be freely selected. The only requirement is that the material must be machinable.
u-Flex spiral couplings can be used in a wide range of applications, namely wherever movement needs to be controlled and regulated. Whether in valve technology, medicine, aviation, aerospace, or mechanical engineering, u-Flex products impress with their precision and durability.
As long as the couplings are used within the specified torque range, they are torsionally rigid.
Angular displacement occurs relatively frequently. In spiral couplings, this is achieved by the inner ribs closing and the outer ribs expanding. With sufficient space between the spiral groove, u-Flex allows for displacements of up to 20°.
Yes. In order to compensate for radial displacement, a coupling system must meet high technical requirements. If the displacement is not compensated, the resulting transverse forces will damage the bearings. The spiral principle offers an optimal solution—the maximum permissible values in the standard catalog range are ± 0.8 mm. Customized applications also allow for higher values.
Yes, a spiral coupling from u-Flex can do that too. In this case, the drive shafts do not share a common plane, so a spiral coupling can also compensate for this three-dimensional displacement. Prerequisite: a relatively long spiral.
Thanks to low moments of inertia, spiral couplings can operate across a wide speed range, in reverse operation, and at very high cycle rates. Our standard spiral couplings are designed for speeds of up to 10,000 rpm, but speeds of 50,000 rpm have also been achieved. Please contact our technical department with your requirements and specific application. We will be happy to provide you with information on what is possible.
In addition to materials (aluminum and stainless steel), a distinction is also made between couplings with a through bore and couplings with blind holes or non-through bores.
Precision Springs
Thanks to CNC manufacturing, maximum customization is possible in terms of dimensions, spring rate, and geometry. All machinable materials can be used for the production of springs, so a wide range of materials is available. In addition to conventional materials, lightweight aluminum springs, electrically insulating plastic springs, and even high-strength titanium springs can be manufactured—the choice of materials is therefore almost unlimited.
They are manufactured from a single piece of material using a cutting process. These 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 values. In multi-coil springs, the pressure or tension is also distributed across several points, which enables an even parallel distribution of force to the center axis. The more coils a spring has, the more precisely the parallelism is implemented during compression or expansion.
This outstanding spring shape enables very precise and consistent spring rates of up to ± 0.1 with a repeatability of up to 1%. It is manufactured from solid material, e.g., from a rod or tube, into which a helical groove is cut. This machining process is much better than winding a spring because it does not create any internal stress, only the natural material stress. This gives the spring a linear spring characteristic with high repeatability and fatigue strength.
Where coiled springs fail, whether due to service life, design, material properties, or accuracy.
Machined springs have connections that are reduced to the bare essentials and reinforced where necessary. Unsupported moments are prevented, for example, by the use of double pins, cross slots, grooves, mounting flanges, etc. Such integrated connections increase the service life of springs and also optimize the installation space. This often reduces production and assembly costs at the same time.
The spring rate of a conventional wound spring lies within a tolerance range of +/- 10%, while machine-manufactured springs lie within a range of only +/- 5%. On 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 overcome before force can be applied.
The integration of additional functions (e.g., bore, thread, flange, or groove) optimizes the installation space and greatly simplifies assemblies, which significantly reduces the amount of work required for installation. Integrated connections (e.g., flange ends, grooves, threaded holes/taps, etc.) further increase the stability of the spring.
Multi-coil springs can be used to manufacture components that can absorb compressive, tensile, and torsional forces simultaneously. With multi-coil springs, the compressive or tensile force is distributed evenly across several points, resulting in a balanced, parallel distribution of force. Additional guidance of the spring is not necessary, as multi-coil springs do not suffer from unwanted lateral buckling.
By optimizing the coil geometry at the start and end areas. The coil outlet is thickened, which increases the strength of the spring in the critical area. The finite element method (FEM) can provide precise information about strength and service life.