Published 7/27/2011

Top Shops 2011: Air Flow Research

One of our 2011 Top Shops, this manufacturer of high-performance cylinder heads has a long history of applying five-axis machining to create complex internal features.

Top Shops

Derek Korn

Executive Editor, Modern Machine Shop

AFR is a third-generation, family-run business. It started in 1970 providing hand porting services for cylinder heads used by top NHRA and NASCAR teams across the country. Household NASCAR names such as Richard Petty, AJ Foyt, Carl Yarbrough, Darrel Waltrip and Junior Johnson were winning with AFR. Plus, top NHRA Pro Stock drag racing teams including Bill Jenkins, Bob Glidden, Warren Johnson and others looked to AFR for increased performance.

After more than 20 years of partnering with professional race teams, AFR began to move in a different direction, taking the knowledge gained from the partnerships and developing affordable aftermarket cylinder heads for the general public. For the first time, weekend warriors and car enthusiasts were able to obtain five-axis, fully CNC-ported heads at a reasonable price.

In the video above, AFR Plant Manager Chris Paul gives a brief overview of the various reverse engineering, machining and five-axis porting operations involved in completing high-performance AFR cylinder heads.

Applying Five-Axis Machining

AFR was one of the first aftermarket cylinder head manufacturers to adopt NC technology for cylinder head machining. It progressed to three-axis CNC equipment in the 1980s, and developed a five-axis machining process in the early 1990s to mill head intake and exhaust ports. Initially, the company added fourth- and fifth-axis rotary tables to an existing Fadal machine. However, it later worked with Haas Automation to refine the machine tool builder’s five-axis HS-1 machine. AFR now has 12 such CNC machines performing five-axis porting 24/7.

Cylinder head production begins with castings provided by one of the company’s three foundries. First-op machining is performed on each casting primarily to establish datum points for subsequent operations on a dual-pallet Mori Seiki HMC. Five pairs of castings are installed on the faces of each of two tombstones used on the HMC. The HMC machines each head’s intake, exhaust and deck surfaces in addition to features such as valve guides, valve seats, spring pads and bolt holes. Once these operations are completed, the heads are taken to one of the company’s five-axis machines for intake and exhaust port machining.

AFR benefits from five-axis port machining in two primary ways. First, each machined port is precisely the same, meaning they all have identical flow characteristics. This consistency is impossible to achieve when ports are machined by hand as they were at AFR years ago. Second, five-axis machining creates ports faster than hand porting. Porting a pair of competition-style heads by hand can take as long as one week. Conversely, the cycle time for five-axis port machining of heads ranges from 3 to 6 hours, depending on the type of head.