Gears: Continuous quality control, research and development

This method is especially suitable for small-batch production with its large number of variants and is considered one of the universal processes. Engineering of many parameters such as the module, the helix angle and the contact pattern can be influenced during the design phase. The name given to this gearing variant is derived from the longitudinal teeth pattern in the form of an elongated epicycloid.

The gearing is rolled continuously and exhibits a constant tooth depth across the entire tooth width. The cutter head is designed with two parts and is driven by a special coupling to enable eccentric adjustment of the outer cutter head relative to the inner cutter head. This adjustment capability allows longitudinal variability of the contact zone, i.e. the contact pattern. After hardening, the parts are finished using lapping, hard peeling with CBN blades (HPG-S) or a grinding process (semi-completing).

This gear type is produced using a conical tool, which is often referred to as a ‘Christmas tree cutter’ (Fig. 12.2) due to its distinctive shape. The milling method is continuous. A special feature of this bevel gearing is that the longitudinal teeth are designed in an involute form. The tooth depth and thickness remain constant throughout the tooth. Lapping is the only feasible method of finishing once hardening is complete, which makes the selection of low-warpage heat treatment particularly important.

We manufacture the palloid gearing on a high-quality, latest-generation CNC machine from Klingelnberg. Many of our customers use this highly resilient form of gearing in the area of motor sport. Constant tooth thickness, good root rounding and the special longitudinal shape of the teeth make palloid gearing highly insensitive to misalignment under load, which is why it was once used as the gold standard in many high-performance and high-torque sports cars.

The HPG-S method enables downstream processing of oversized, rough-machined gears produced using the cyclo-palloid method. This involves roller peeling of the gears using special CBN blades. The benefit of this method is that rough and fine processing take place using the same machine. The achievable qualities come very close to grinding. However, the high forces required to cut the gears mean that some restrictions will apply to the accuracy of reproduction, e.g. the precise fit, and that process control is extremely complex due to incalculable wear on the sensitive tool blades.

Unlike in grinding processes, some corrections can only be made using special blades. We use this method for customers who do not permit grinding due to certified processes that have been in place for many years. There is little demand for this method because of the rising demands that are placed on accuracy. Grinding is always possible as a rule. We would be delighted to offer this option.

Our bevel gear sets can also be manufactured with axis offset. Single-piece batches are also easy to manage using our modern machinery. The achievable accuracy is comparable to other gear sets. Many properties, such as high gear ratios in one stage or special mounting circumstances in vehicles, are only possible using this procedure.

The offset between the axis and the pinion means that the pinion head can be larger, thus increasing the load-bearing capacity of the gearing. In practice, however, it is necessary to check the design of the individual parameters very precisely to ensure that the overall system remains balanced with regard to efficiency, increased performance and smooth running. We would be delighted to assist and advise you during the design phase.

Zerol gearing can replace a straight-cut gear in many cases. This test is generally recommended for larger runs. Grinding is possible in this case, unlike planed gear sets that can only be lapped after hardening.

In Zerol gearing, the crown wheel and the pinion have an average spiral angle of 0° to 10°. This tooth design is often selected to replace a straight-cut gear set without recalibrating or modifying the bearings. Spiral-toothed gear sets can be ground and therefore enable higher quality levels.

Straight-cut gears are often used in planetary gears or for drive forms that do not require a specially reinforced axial bearing due to the absence of an axial force component during operation. Splined shaft profiles are an exception in this regard and are used exclusively as a driving gear. Broadly speaking, the transmittable torque of spur gears is a little lower compared to helical gears, as the proportion of teeth that mesh simultaneously is lower.

Apart from a few exceptions, helical toothed spur gears are used as running gears. The magnitude of the helix angle depends on numerous factors, and the axial force component must be considered when designing the bearing arrangement. Unlike in straight-cut gears and depending on the design, several teeth may mesh at the same time, which increases the transferable torque.

Modified flanks are possible, both in terms of the tooth width and its depth. In some cases this may depend on the tool machine used in the production process. Load flanks and thrust flanks can be designed with separate topographies.

The teeth are arranged symmetrically in double helical gearing. The helix angle is often designed in a range of between 20 and 30°. The axial forces in the bearing are virtually neutralised by this tooth configuration. This type of gearing is mainly used in fast turbo gears.

The flank lines converge at the apex point. By measuring directly on the grinding machine, we can produce purposeful modifications and ensure highly precise determination of the apex point. A run-out for the tool must be taken into account for machining in all cases.

This spur gear variant, often referred to as a conical gear, is used to adjust the backlash in gears. During production, the profile shift is continuously changed over the tooth width. Even small angles in a range of approx. 12° between the input and output shafts can be realised.

We offer internal gearing as running gears and splines according to DIN 5480, DIN 5481 and DIN 5482. Depending on your requirements, we can draw on various machining processes, ranging from broaching and gear shaping to wire erosion and profile grinding.

A precision gearwheel only works in combination with a shaft-hub connection that satisfies this accuracy requirement. But this aspect is often neglected in reality. We ensure precise coordination of the production steps on your behalf to ensure that the components are tailored exactly to your requirements. Reduced play, increased concentricity, an easy sliding fit or special covers for fitted components are our bread and butter.

Worm gears are mainly used for high transmission ratios, low speeds and high torques. The sliding motion is very high in this type of gearing.

Specific properties such as effectiveness or any self-inhibition must be taken into account during design in order to enjoy the benefits of this type of gearing. The materials used in the worm and the worm gear must be coordinated carefully. In addition to the worm gears in our gear range, we also manufacture workpieces to suit customer specifications. We would gladly design the engineering parameters on your behalf.

A gear rack is an important machine element when rotary movements are translated into linear movements (and vice versa). Racks are basically spur gears with involute toothing, but possess an infinitely large base circle. This is why the involute in gear racks becomes a trapezoid profile. The profile is also used as a reference for spur gears. We produce gear racks in milled and flank-ground versions, based on your wishes.

In addition to their non-circular toothing on an elliptical pitch circle diameter, the elliptical or non-circular gears have an eccentrically positioned bore. Watching the two gearwheels roll against each other is an unusual and amusing sight. It is one of the exceptional cases when things do not run ‘smoothly’.

In addition to the grinding fits and bores, our high-precision machinery allows us to produce polygonal profiles as well as various other individual shapes.

Even helical toothed hub connections or stainless steel segments with cyclo-palloid gearing and very high transmission ratios are no problem for us. Just contact us. We will find the right solution for your application.

We would be delighted to collaborate on developing your custom solution. You can rely on us coming up with a steady stream of new variants when handling individual components and toothing systems.

We have been able to grind spiral bevel gears on stateof-the-art G-series machines from Klingelnberg since 2008. These machines enable the production of different types of bevel gear teeth thanks to the CNC-controlled axes and their many degrees of freedom. This process is vendor-independent, and rough machining can take place for special applications by deep grinding the solid material.

In a longitudinal direction, the teeth are arc-shaped in all grinding processes, as they are always division processes. In response to increasing demands for transmission without angular misalignment and low-noise design, over 90% of all gear sets at Tandler are processed by grinding.

This grinding process is suitable for gears with rough machining according to the cyclo-palloid method. As the name suggests, each flank is machined in a separate work cycle based on the partial hobbing method.

While the parallel tooth depth is preserved, the longitudinal shape of the teeth as an elongated epicycloid is transformed into an arc. Many topographical modifications are possible during the separate machining of each flank. This gearing form can easily be corrected during the production process. It also enables excellent and highly reproducible qualities.

Hob grinding is a highly productive method. The grinding wheel is designed in the form of a grinding worm and the dressed profile in the wheel shows straight flanks. A continuous rolling process produces the shape of the tooth flanks. Theoretically at least, almost any number of teeth can be produced by one grinding wheel in modular operation, merely by changing the machine settings. A special dressing tool with a diamond contact surface is often needed for profile modifications. When dealing with smaller series, this can be managed using a special roller in a linear dressing process.

Each tooth space is machined individually in profile grinding. Unlike hob grinding, this is a discontinuous process. As the tooth shape also changes depending on the number of teeth, it is necessary to attach a diamond roller to the grinding wheel for each tooth variant. High-precision, CNC-controlled dressing of the grinding wheel permits numerous profile modifications in relation to the tooth depth. Simultaneous machining of both flanks in a dual-flank grinding process is not possible for some corrections, as this method requires a synchronous combination of many individual axis movements. In this case, the two flanks in a tooth space are machined separately using a single-flank grinding process.

Among our particular services is the ability to machine workpieces with a length of 2000 mm. We are able to grind the entire tooth surface. Compatible grinding wheels can have a diameter of up to 40 mm. Feel free to send us your profile data in DXF format.

We fit an attachment head to our profile grinding machine in order to accommodate special accuracy requirements when grinding internal gearing. In this process, we use dressable grinding wheels and are hence able to respond rather rapidly to special requests. An integrated measuring device on the machine ensures that the gearing is centred accurately during production and is subject to in-process controls. It is necessary in some cases to accommodate manufacturing restrictions due to the frequently limited space. This applies in particular to helical gears and run-outs. We would gladly advise you in this regard during the engineering phase.

Spectral analysis is used to determine the material composition, for instance of sample parts. This means we can identify the chemical composition of metals quickly and reliably and prepare a corresponding test report on request.

Hardness testing is among the most important steps in quality assurance. It enables an assessment of material properties such as strength, toughness and wear resistance. We can test hardness according to the Brinell, Rockwell and Vickers scales.

Industrial production measuring technology demands the fast, simple and nevertheless highly accurate measurement of workpieces. The roughness of ground surfaces is a crucial aspect in this process. We use our Mitutoyo mobile surface roughness measuring device to determine contact surfaces and fits. Our precision measuring centres are also available for gears. These gear measuring machines can determine tooth roughness during the manufacturing process.

Suitable for series runs and final inspections, our highly accurate and continuously calibrated 3D coordinate measuring machine Wenzel LH65 can measure a wide variety of components in the axis sizes x = 650 mm, y = 1000 mm, z = 500 mm. The machine can be operated in the 1/1000 range in our climate-controlled measuring room.

The arm-based mobile measuring solution Faro PowerGage allows us to capture coordinate points in a spatial relationship, for example for theoretical dimensions such as the angular dimensions of bevel gears and many other components. Thanks to its simple handling and fast operability, the Faro arm is ideal for conducting in-process controls during production.

The best available measuring techniques and an optimised machine and software strategy are vital to accommodate the strict accuracy requirements and the constantly evolving complexity of our components. Our Klingelnberg precision measuring centres from the P-series can currently handle a significant proportion of our measurements and are integral elements in our closed-loop manufacturing process. These measuring centres can replace up to six different, conventional measuring devices, work automatically and often without the need for retooling.

Among other things, these machines perform tasks such as general coordinate measurements, shape and positional measurements, roughness measurements and contour measurements. Our measuring centres are used to compare gear geometry against the calculated target data. We are able to accommodate an outer diameter of up to 1000 mm in this process. In a target/ actual comparison, we check the current status, e.g. the topography, concentricity, geometry and quality against the target data. This enables us to make quick corrections during production operations.

We are able to assess your sample parts or existing but unknown gearing configurations to create a gearwheel sample for the production of a new part. This only works if the gearing is present. We are happy to prepare a tooth flank log for your components. Please understand that this service is subject to a charge.

The rolling behaviour of a bevel gear set says a lot about the quality of the gearing. Conventional single flank rolling testing, which is performed at low speed and load according to DIN 3960, is an excellent method of assessing the production quality. The test is carried out with specified installation dimensions, tooth clearance and axis angle according to the standards DIN 3965, ISO 1328 and AGMA 17485. The test assembly is created based on the same specifications that are used for the mounted part and hence ensures trouble-free operation.

Subject to a charge, we would also be delighted to prepare a log of the single flank rolling test containing all the data relating to your gear set.

We use the term ‘balancing’ to describe imbalance reduction in our gears. Given that imbalance affects virtually all rotating bodies and can cause vibration, noise or elevated wear, customised mass distribution is necessary in order to restore equilibrium to highly stressed parts.

We run a Schenck typeVE3/cab920 at our company to keep delivery times short as well. This device enables us to balance workpieces with a diameter of Ø 600 mm and a mounted height of 320 mm in both a static and dynamic range.

Magnetic particle testing is another important resource in our quality assurance process. This method of non-destructive surface testing detects crack defects near to and on the surfaces of ferromagnetic materials. It draws on the principles of magnetism. The first step is to magnetise the material. Defects in the material produce small stray fields on the surface, and the magnetic particles collect on them. Our test agent possesses fluorescent properties that we visualise using ultraviolet light to enable better assessment of the cracks.

Barkhausen noise analysis is based on the magnetoelastic or micromagnetic method. The method involves inductive measurement of a noise-like signal generated when a hardened component is magnetised. It is among the non-destructive methods to test grinding burn and heat treatment defects. We perform our measurements using the Stresstech Roll-Scan 300, a device which has enriched our quality control and optimised our grinding process.