Cylinder head porting on a turn/mill machine

CNC milling is the machining that an automotive cylinder head is likely to require. Turning is not a capability you would look for in a machine tool meant to run such a part.

Indeed, when Mazak (Florence, Kentucky) first started to work on a better machining process for the benefit of a maker of high-performance heads, the machine tool company's first attempt involved a five-axis machining center. But Robin Cave, national applications engineer for Mazak, says that a more capable and efficient process has now been developed for an Integrex machine.

"Integrex" is the company's brand name for a family of CNC turn/mill machines. The term is traditionally associated with multitasking lathes.

However, the machine tool proving effective at cylinder head porting is no lathe, says Mr. Cave. It's an "e"-series Integrex, and this distinction is significant. Earlier machines in the family have the slanting structure of a lathe, with the wedge-shaped work zone causing Y-axis travel to get progressively more limited toward the bottom of the machine. The e-series design gives the machine's milling spindle the freedom to move like a machining center can move, with a box-shaped work zone permitting the same full field of travel at the machine's top or bottom. The unit is still a turn/mill machine, but while the traditional Integrex might be thought of as a lathe effective for milling, the e-series version is essentially a machining center effective for turning.

The machine permits full five-axis milling. While B-axis motion comes from the tilting of the e-series machine's spindle head, C-axis motion comes from the rotation of the horizontal spindle used for turning. The maker of cylinder heads does no turning on this machine, but instead uses this turning spindle exclusively in the five-axis mode. This direct-driven rotation does not involve a worm gear, unlike a previous process in which the company used indexers on vertical machining centersThe milling cutter is a long-reach lollipop tool capable of cutting from various engagement angles along the inside of a complex channel. Mazak is working with cutting tool supplier Kennametal (Latrobe, Pennsylvania) to develop a diamond-coated version of this tool. The higher spindle speeds on the newer machine (relative to the previous process) will make it possible to use this tool productively. Comparison testing between coated and uncoated tooling in this application shows a clear improvement in finish. With a coated tool incorporated into the process, says Mr. Cave, it may be possible to perform this porting solely through CNC machining, without a subsequent need for finishing by hand