Cutting of spiral bevel gear on PC.
Here is an explanation how to use standard CAD software for gear tooth surface simulation. The author uses this method for debugging VB programs. It is still unknown how for example Gleason or Oerlikon were able to check the accuracy of their geometrical calculation without having an alternative calculation methods. They could cut and measure real gears but it can not be absolutely accurate.
The following step by step technique was used to make the models.
1. Create a solid gear blank
2. Create a solid gear-cutting tool.
3. Align the blank and the cutting tool.
4. Run AutoLISP routine.
(defun G()
(setq al nil)
(setq al (getreal " cutter/gear ratio <0.4>:"))
(if (= al nil) (setq al 0.4))
;;;step of gear rotation
(setq dfi nil)
(setq dfi (getreal "\n Step of the gear rotation <1 degrees>:"))
(if (= dfi nil) (setq dfi 1.0))
(setq dfi (/ (* pi dfi) 180))
(setq gear (entsel "\n Select gear."))
(setq axis (entsel "\n Select axis of the gear."))
(setq sb (entsel "\n Select cutter."))
;;;step of cutter rotation
(setq dt (* dfi al))
(setq x 0.0)
(getreal "stop")
(setq i 0)
(while (< x pi)
(setq i (+ i 1))
(command "copy" sb "" (list 0 0) (list 0 0))
(command "subtract" gear "" (entlast) "")
;;; rotate the cutter
(command "rotate" sb "" (list 0 0) (list (cos dt) (sin dt)))
;;; rotate the gear
(command "ucs" "ob" axis)
(command "ucs" "y" 90)
(command "rotate" gear "" (list 0.0 0.0) (list (cos dfi) (sin dfi)))
(command "ucs" "w")
(setq x (+ x dfi))
)
)
The cutting begins after starting the LISP program. The solid cutter moves around the gear blank and subtracts pieces out of it like on real cutting machines. The final CAD gear tooth surface has real faces from the cuts. The accuracy depends on the increment of cutting. As more cuts as more accurate the final surface.
CAD gear tooth cutting can be used:
- Creating a 3D tooth models for Final Element Analyzes
- Simulate the contact pattern and transmission error.
Contact Stepan Lunin: stepanlunin@stepanlunin.com