All modifications applied on mating gears are interacting, so the decision of which modification to add or to change is difficult. Unfortunately, the interpretation of LTCA results is not easy. Now the use of LTCA to check and improve the efficiency of modifications is growing fast.
Helical gear design using kisssoft software#
Today’s market request for lighter, cheaper, and stronger gearboxes together with the availability of easy-to-use LTCA software changed things considerably in many gearbox design offices. In modern system software, such as KISSsys where the complete transmission chain with gears, shafts, and bearings is modeled, all data for an LTCA is available, and the calculation is performed without further input.
Therefore, the input for a stand-alone program is complicated and time-consuming. For an LTCA calculation, all gear data together with the geometry and load condition of the shafts is needed. In the last years, it has become easier to use LTCA software. Thus, modifications were designed based on simple rules without checking if the rule used was appropriate for a specific case. Furthermore, such software was not available or too complicated to use for most gearbox designers. LTCA is a complex semi-FEM calculation procedure that needs a lot of calculation time.
Helical gear design using kisssoft verification#
One problem is that the verification of the effect of modifications can only be made with an LTCA. Nevertheless, designing modifications is not easy. The choice of the best macro geometry is primordial before starting the layout of modifications.įlank line and profile modifications have been in use in the gear industry for a long time. Therefore, it is extremely important to keep in mind that a bad choice of macro geometry (module, helix angle, profile shift, etc.) can never be compensated with a nice micro geometry. The layout of the modifications is the last step in the gear design process. To find the optimum profile and flank line modifications for a given gear pair a three-step procedure can be implemented to perform a targeted sizing. When performing a targeted sizing of the micro geometry, a step-by-step approach should be used, first specifying the flank line modification and then the profile modification. Today, much more time is needed to optimize the micro geometry than the macro geometry when designing a toothing. It is easy for the design engineer to lose sight of the bigger picture and fail to find the optimum solution because the calculation method for proving the effects achieved by micro geometry and the contact analysis under load (Loaded Tooth Contact Analysis, LTCA) is complex and time-consuming and interpreting the results is challenging. Certainly, it is not possible to achieve all types of optimization simultaneously, and some actions will worsen some features while improving others. To do so, it is first necessary to select the primary objective for which optimization has to be achieved: noise, service life, scuffing, micropitting, or efficiency. The last phase in sizing a gear pair is to specify the flank line and profile modifications, also known as the micro geometry.