POSTED ON 4/28/2022 – Recently, a customer challenged Mazak to develop a programming and machining solution for producing a variety of Double Enveloping Worm Threads. The customer not only wanted the solution to be user-friendly and provide the ability to adjust the thread geometry based on inspection data (such as a roll test with a Master Worm Gear) but to also allow for the use of common off-the-shelf cutters.
Worm drives are designed in sets – namely, the worm and the worm gear or wheel. The thread geometry on these are parts is complex. However, when the mating worm gear geometry is a known, it is possible to calculate the thread toolpath trajectory. While it’s common for many shops these days to cut gears on Multi-Tasking machines such as our INTEGREX i-450ST, fulfilling the customer’s request for tailored software to aid in programming proved a bit challenging to overcome.
There are several benefits to gear machining on a Multi-Tasking machine. Doing so is cost-effective when it comes to producing a wide variety of gear types, and the machines allow for complete part processing from raw stock to finished part on a single platform. For gear machining, a Multi-Tasking machine offers the ability finish turn datums (i.e., bearing diameters) and gear teeth in the same setup, which gives more control between the gear pitch diameter and the mounting geometry. Additionally, Multi-Tasking machines simplify workholding and reduce tooling because they compress the machining cycle from multiple machines down to a single machine.
There are two process options to machine the Double Enveloping Worm Thread on the Multi-Tasking machine – turning and milling. Turning is a process option that depending on whether or not the machine’s longitude axis (in this case the Z-axis) can travel at the required speed. Much like chasing threads on a lathe, the Z-axis travel speed is based on the part rpm and the thread pitch. For multi-start threads, the Z-axis speed requirement increases even further.