@Garwood
Let me write a few thoughts about turning a hobbing machine into a CNC hobbing machine.
1. Making a CNC machine from a non-CNC machine is a very, very thankless task. It seems to me that this only makes sense for some rare, unique and / or very expensive machines.
BUT! This applies mainly to conventional lathes or milling machines. The hobbing machine is very different: the processes are slow, interpolation as such is practically non-existent.
2. New gear machines are expensive. Very expensive. According to my information, the cost of the new Liebherr, which can machine gears in various ways, is approaching a million dollars. So the modernization of the gear-cutting machine, in principle, can be relevant.
3. You need to think about why you need to turn your machine into a "CNC" at all. Or in CNC. Making parts faster? Get rid of a lot of manual operations so that the machine works by itself? To give the machine the ability to make cool and complex parts that it cannot do now? Cut costs?
4. Even to build a very cool gear hobbing machine that can change mills itself, a full-fledged CNC system is not at all necessary - a good PLC is enough.
I have dealt with several hobbing retrofit projects. At a minimum, as a result, the time for equipment changeover has been reduced - it is no longer necessary to install 8-10 gear wheels. As a maximum, the owners received a more accurate machine.
I have never seen a project where someone would make a machine "like the new Liebherr". One team was developing mechanization for tilting the milling caliper, but they did not seem to have reached the implementation. No one even thought about the direct drive of the rotation of the table, as well as the direct drive of the rotation of the mill.
That is, usually people leave the rotation of the main spindle from a conventional asynchronous motor, and the table rotation drive - using a worm gear.
You can install some kind of controlled motor to rotate the worm of the worm gearbox of the table drive. And you can install the same motor to turn the vertical movement screw of the milling carriage.
As a result, you will already have a machine that does not require the installation of gears. You can cut any number of teeth, any angle of inclination of the teeth - restrictions are only on the geometry of the tool.
I will say what else I saw in the implemented modernization projects.
-Encoder on the table for precise rotation of the part. Let's say you can calibrate the error once, enter it into the correction table and not install the encoder.
- A linear encoder to control the movement of the milling caliper and another linear encoder to control the radial movement of the table, this was in the same project. Let's say it might be cheaper to put a ball screw in place of a conventional trapezoidal lead screw and ditch the linear scales. The result, together with precise control of the table rotation, is a very precise match of the tooth angle to the drawing.
- Mechanization of movement of the spindle with the mill along its axis, for uniform wear of the mill. Movement does not occur during cutting.
- Encoder on the milling spindle for machining worm wheels with a single cutter. For this, in the pre-CNC era, "tangential calipers" were needed.