3-d mathematical modeling of geared mechanical systems.
ph: +1 949 378-0941
hypoid gears: 3d CAD models and software.
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Hypoid gear program works in Excel. Save as 3d igs tooth surface directly from Excel. Download hypoid 35/7 set sample in igs. Notice correctly modeled geometry of the undercut on the root of the tooth. The sample has localized tooth contact 40% from the tip and 40% from the Toe. The program generates a good running gear set from very few entries. The program suggests other design data to get a good gear set. It is easier to design a new set using the suggestions.
Reverse engineering and design of hypoid gears in 3d for 5-axis CNC machining or for traditional Gleason/Klingelnberg manufacturing. Machine summary, TCA, FEA. Profile and lead crowning are added to the tooth surfaces. Tooth contact pattern is checked in 3d on our TCA software.
Computer generated 3d pinion tooth surface has all the detailed geometry including the undercut on the pinion root toe.
The software accurately generates the undercut: a transitions surface on the root by simulation of the generating rolling motion as the pinion tooth was cut by a tool identical to the gear tooth with increased addendum to provide correct radial clearance. This method delivers less undercut compare to the undercut that generated by the imaginary crown wheel (face cutter) on Gleason or Klingelnberg gear generating machine. Undercut is common on hypoid and spiral bevel pinion with low (<11) number of teeth. Correct calculation of the undercut is critical for stress calculation and for preventing interference in the tooth root:
Less undercut results in more of tooth thickness on the critical area of the tooth that delivers higher bending strength for more operating torque and better endurance. Cutting correct undercut surface (without other improvements) may increase operating torque for up to 30% and endurance up 100% or more compare to hypoid and spiral bevel gears from Gleason or Klingelnberg machining. The higher benefit is achieved on lower ratio spiral bevel gear set that are more common in helicopter transmissions and turbofan engine accessory drives. The basic explanation to understand the phenomena is in the difference of the local pressure angle between the generating imaginary crown wheel (Gleason/Klingelnberg face cutter) and the local pressure angle on the crown gear. This software is using the real crown gear tooth to generate the undercut while Gleason/Klingelnberg machines using the imaginary crown gear (face cutter). The blade angle (pressure angle) on the imaginary crown wheel is always less compare to the pressure angle on the real crown wheel. Lower pressure angle tool generates more undercut - reduction of the tooth thickness and unnecessary reduction of the root fillet radius.
When hypoid gear teeth are cut on a CNC machine it becomes possible to add design improvements to increase torque capacity.
Cylindrical surface is added to the pinion root toe to account for a flat on the gear face.
A flat is added to the gear heel root to account for the OD of the pinion.
These additional design elements serve the purpose to maximize the contact area on the available tooth surface. It provides better and more cost effective result compare to Gleason ease-off in CAGE. Based on our experience, the first time, ease-off tooth topology has been developed by Boris Zakoldaev at MIL Helicopter in 1986 on helical gears and resulted in several patents. Gleason current CAGE software offers ease-off topography by modification of the gear tooth surface geometry. Based on what we see from our customers in 50 countries CNC machining method provides better result to maximize the width of the immediate contact line along the tooth pass compare to the ease-off from Gleason CAGE.
Unlike Gleason CAGE ease-off and previously used by Zakoldaev we use modification of the gear blank and tooth root for more effective use of the gear tooth area.
This picture shows several immediate contact lines forming combined contact pattern. The contact pattern is usually elliptical shape, while the perimeter of gear tooth surface is more or less a trapezoid. Ideally, the perimeter of the gear tooth needs to be the same elliptical shape (but larger in size to account for misalignment) as the contact pattern for maximum use of the tooth area to transmit the load. But in particle, simple straight cuts as we have shown are good enough and easy to machine on a CNC.
See more accurate 3d CAD models of hypoid gear sets at:
This program allows to model mating pinions for the ring gears known as FORMATE (per Gleason). FORMATE gear tooth geometry is easy to cut - not generating needed. Can be cut on 2-axis = rotary table holding the gear + spindle with a fly cutter. The pinion needs to be cut on 5-axis, but the pinion has low number of teeth and it can be cut on a smaller CNC machine.
Tooth contact is checked at different misalignments of the shafts in 3d on our other software.
ph: +1 949 378-0941