A stick blade-type face hobbing system used for completing operations. In the face hobbing process, the cutting action causes the blades to cut on both the pressure angle side and the top portion of the clearance side. Because of the negative rake on the clearance side of a conventional blade, excessive tool wear is produced.
The TRI-AC® System solves this problem with a patented rake angle modification on the front face of the blade. This modification produces a positive hook of front rake on the top portion of the clearance side, thus eliminating the need for a bottom cutting blade.
The continuous indexing method requires a second rotational coupling (electronic gear box) between the cutter head rotation and the workpiece rotation. For this reason the method is also called a three-axes process. This is where the name TRI-AC is derived.
Each blade group of a TRI-AC cutterhead has only two blades, one outer blade and one inner blade. While one blade group passes through a slot, the work gear rotates in the counter direction of the cutter. This relative motion produces an epicycloidal function along the face width of the work gear. After the blade group leaves the slot, the next blade group enters the next slot. The ratio between the cutter head and the gear must be the number of the teeth of the work divided by the number of starts (Blade groups) of the cutter head. In the generation process the roll motion is used as cutting feed. This roll is very slow compared with the face milling process.
Since face hobbing cuts tooth after tooth immediately in about the same roll position, the roll motion can be slower (by the number of teeth of the work gear) and still have about the same cutting time as face milling. Of course the Gleason face hobbing is based on a uniform tooth depth. This simplifies the design calculation dramatically.