Methodical investigation of distortion biasing parameters during case hardening of spur wheels

Gear distortion is influenced by several effects which might originate in various steps of the entire production chain. To understand the distortion mechanisms including interactions between different influencing parameters, a system approach for the whole production process is required. As distortion is not constrained to the toothing but also effects the gear's base body, an extended measuring strategy (compared to the standard) has been devised. Based on this strategy, an areal evaluation has been developed and new quality parameters describing the deviations of the whole gear and of each tooth have been defined. In contrast to the standard evaluation, the new quality parameters consider the relationship between different measured lines. This offers the possibility to determine the influences of the base body deviations on the toothing distortion and to separate them from the intrinsic toothing deviation. This paper describes the developed strategies and methods and compares them with the standard inspection process.Keywords: gear / distortion / areal evaluation / measurement strategy / cmm / Der Verzug von Zylinderrädern wird durch verschiedene Effekte beeinflusst, die in unterschiedlichen Teilen der Fertigungskette auftreten können. Um die Verzugsmechanismen inklusive der Wechselwirkungen zwischen den einzelnen Einflussgrößen vollständig zu verstehen, ist ein Systemansatz für den gesamten Fertigungsprozess erforderlich. Da der Verzug nicht nur auf die Verzahnung beschränkt ist, sondern am gesamten Zylinderradkörper auftreten kann, ist (verglichen mit dem Standard) eine aufwändige Messstrategie für Zylinderräder entworfen worden. Basierend auf dieser Strategie konnte eine flächenhafte Auswertung inklusive neuer Qualitätspara-metern entwickelt werden, welche sowohl die Formabweichungen des gesamten Zylinderrades als auch die der einzelnen Zähne beschreiben. Die Auswertung berücksichtigt im Gegensatz zum Standard-Verfahren die Beziehungen zwischen den einzelnen gemessenen Linien. Damit ergibt sich die Möglichkeit, die Einflüsse der Grundkörperverformungen auf den Verzahnungsverzug zu bestimmen und sie von denen der Verzahnung zu separieren. Der Artikel beschreibt die entwikkelten Strategien und Methoden und vergleicht sie mit dem standardisierten Mess-und Auswerteprozess.

“…Steinbacher and Kohlhoff present corresponding results and their interpretation, obtained for different experimental designs and carried out within the SFB 570 [12,13].…”

Section: Evaluation Examplementioning

confidence: 89%

“…This parameter correlates with the total pitch deviation, if its average is subtracted and the sign is adapted, Figure 5. But, especially this average or offset value implies additional information (i. e. an estimation of the mean tooth thickness deviation at the pitch circle), which turned out to be useful for the distortion analysis [12]. …”

Section: Definitionmentioning

confidence: 99%

Areal parameters for the characterisation of gear distortions

Stöbener

Freyberg

Fuhrmann

et al. 2012

Hardening distortions of serial produced crown wheels

Olofsson

Jönsson

2017

The hardening distortions of serial produced crown wheels are studied with respect to gear runout, inner diameter and back‐face tilt. The data analysed originates from a production data base from ordinary production as well as from directed experiments carried out in production, resulting in a large set of data. Strong influences are found for steel plants, position of material in ingots and stacking levels on hardening trays. It could be concluded that rectangular strands have a detrimental effect on gear runout, which, however, can be strongly decreased by disabling the magnetic stirring during casting. Furthermore, the inner diameter after quenching is influenced by the stacking level on the hardening tray when free‐hardening or when using a segmented central expander during press quenching. This influence is attributed to variations in hardening temperature. When press quenching using a fixed mandrel, the effect of stacking level disappears. Moreover, it is found that the back‐face tilt strongly depends on the position in the ingot as well as on the stacking level on the hardening tray.

Identifying process parameters influencing gear runout

Olofsson

Köhn

Jönsson

2018

The hardening distortions with respect to base body, clutch teeth and helical gears are investigated for a serial‐produced main shaft gear of a 20NiCrMoS6‐4 steel. The influences of casting geometry, annealing heat treatment and stress relief annealing of blanks, as well as vertical and horizontal loading arrangements during case hardening, are studied. The concentricity, roundness and runout of clutch teeth and helical gears are measured in the soft machined, hardened and hard‐machined conditions. The Brinell hardness is measured on blanks obtained from different manufacturing routes showing differences in hardness and scatter. Stress relief annealing lowers the hardness and the scatter for all groups, but has no significant effect on distortions. The case depth, core hardness and surface hardness are measured after hardening. The study shows that the surface hardness correlates with the oil flow measured in the quench tank. The effect of casting geometry is stronger for the clutch teeth compared to the helical gears. For the clutch‐teeth roundness and runout, significantly lower values are found for square geometry compared to rectangular. It is also seen that the major part of the runout comes from roundness errors which are mainly induced by the hardening. Horizontal loading reduces roundness errors and runout but produces conical base‐bodies with worse backplane flatness.