High Speed Machining Shaves Ounces for the Racers’ Edge

The Challenge

VAC Motorsports was looking to increase production speed and part capacity which maintaining their reputation for accuracy and quality. They are also concerned with making parts that improve handling and performance, while at the same time, decreasing the weight of stock BMWs (and maximizing structural integrity).

• Mastercam was used to increase production speed and part capacity at VAC Motorsports. They had to make the parts as light as possible while maintaining full structural integrity.
• Mastercam kept VAC Motorsports competitive in a market that demands competitive excellence from their customers.
• Tony Salloum (owner) is now able to design and machine their flywheels completely in-house (they used to out source it).
• Mastercam’s associativity allows VAC to make changes to their geometry and the toolpaths are automatically updated.
• Mastercam’s high speed machining is used to maximize speed in less complex portions of a cut, while automatically reducing feed speed for corners and curves. High speed machining gives high removal rates which speeds up production and maintains VAC’s reputation for accuracy and quality.

VAC Motorsports was established in 1984 as Verna's Auto Clinic, operating as a three-man shop specializing in bodywork. By 1987 VAC had added BMW automotive repairs to their services. It wasn't long before they hit their stride with consumer BMW work and decided they needed more of a challenge. This is when VAC Motorsports entered the racing ranks.

In 1992, VAC’s racing endeavors began overseas in FIA-sanctioned rallies. They built a 1988 VW Golf GTI 16V Group A Rally Car that entered competition in 1994. After two years of hard work, VAC won the 1996 FIA F2 Group A Championship in the Middle East. In 1997, VAC expanded again by acquiring a long-time neighbor, Milano Engine and Machine, helping to make VAC a truly “One Stop Race Shop.” The growth increased their competitiveness in both the sales and racing arenas. Today, the VAC machine shop features the latest in equipment, including an RMC Boring Mill, a Serdi Valve Machine and a Haas VF-2 CNC Mill.

By the numbers… not!
“We design and build everything from performance racing engine components, to drive trains, custom roll cages, and interior seat brackets,” says Mr. Salloum. “In 2000, we bought a Haas VF-2 30x16 gear driven high-torque vertical machining center to increase production speed and part capacity. When I tried using doing CAD design and NC programming for the VF-2, I was lost. By December I was so frustrated that I called our HASS dealer and learned enough to realize that I needed Mastercam (by CNC Software, Inc., Tolland, CT) to keep me competitive in a market that demands competitive excellence from my customers.

“After a three-day Mastercam course, I was on my way to cutting parts,” Mr. Salloum continues. “Every part of the drive train that turns at engine speed is reduced to minimum mass but kept at maximum structural integrity. BMW flywheels were the first targets of opportunity to put my new skills to work in a racing mode. The flywheels run at about 8,000 RPM under racing conditions, so we had to continually recheck structural integrity as we hunted down ways to reduce the mass of the flywheels. Low flywheel mass means faster acceleration, and more importantly, faster deceleration when drivers let up on the accelerator.”

Every ounce counts
VAC initially outsourced flywheel cutting to a local machine shop, but with Mastercam under his belt, Mr. Salloum now designs and machines the flywheels completely in-house. His goal is to achieve a smaller moment of inertia, and to make the parts as light as possible while maintaining full structural integrity. The redesigned flywheel, combined with Tilton Engineering’s specialized clutch assembly, weighs in at less than 12 pounds. Some BWM OEM flywheel/clutch combinations run up to 50 pounds. In a business where every pound-foot of torque matters, a saving of up to 38 pounds at 8,000 RPM can be a winning factor.

VAC’s CAD/CAM choice gives this specialty machining company the same kind of edge. One custom flywheel customer isolated a performance problem to having mismatched the flywheel to his drive train. “We decided the flywheel needed to be beefed up by .125” in the x and y dimensions in some places,” Mr. Salloum recalls. Though they could have changed the geometry and Mastercam’s associativity would have automatically updated the toolpaths, “we wanted to redesign it from scratch to compensate in other design elements for the added weight and to reduce potential stress risers.”

Speeding up success
“We stuck with the center dimensions of the original flywheel, working the major radii outward in concentric circles to the O.D.,” Mr. Salloum reports. He generally tries to do similar geometry in increasing steps toward final dimensions. A constant high cutting speed – with appropriate plunge and retract rates - was perfect for the pocketing and contour toolpaths which hogged out the rough circles of the flywheel geometry.

This concentric approach to toolpathing is the most efficient cutting order for Mr. Salloum, and the eight bolt holes for crankshaft attachment followed that pattern. Next within the toolpath group, Mr. Salloum quickly spot-drilled, peck-drilled to depth, chamfered, and tapped the 12 threaded holes for attachment of the clutch friction disc, based on geometry from Tilton Engineering, the clutch designers.

Among the final toolpaths for the flywheel face (the clutch side) are a number of chamfering operations. Chamfering, according to Mr. Salloum, removes all sharp edges, including those around the threaded holes, and helps pilot the screws into the holes without cross threading. “If the chamfer diameter is too large, I just back up in Mastercam’s Operations Manager and easily change the depth of the drill to achieve the correct chamfer size, and Mastercam automatically updates,” Mr. Salloum says.

Master touches
“Since I know every hole starts with a spot drill,” Mr. Salloum continues, “I do all the spot drills and chamfers, then I switch tools and drill all the through-holes, and tap the required holes. We then move to the eight pressure plate holes, which are drilled and tapped. The final four holes approaching the O.D. on the backside accept bolts, the heads of which help hold the flywheel flush with the .010” press-fit circumferential ring gear.

The first step in machining the backside was to pocket .200” deep, moving outward to the ring gear mounting flange, which is the thickest part of the flywheel. Mr. Salloum next used another of Mastercam’s convenient features. Instead of drawing each of the eight pockets that cut the voids between the flywheel “spokes,” he created just one, then quickly rotated the toolpath to create the other seven pockets.

In programming the pocketing operations themselves, Mr. Salloum also rotated the single set of pocket parameters around the origin eight times. As further radius and stock removal work continued, Mr. Salloum took full advantage of the ability of Mastercam’s high speed machining to maximize for speed in less complex portions of a cut, while automatically reducing feed speed for corners and curves.

After performing all operations on the face, Mr. Salloum flipped the flywheel, using four of the pressure plate holes as fixturing points for all backside operations. He created similar toolpath groups to rough and finish the backside of the flywheel.

Mr. Salloum says “Using ISCAR indexable end mills and Mastercam’s High Speed Machining gave us high material removal rates, speeding up production and maintaining our reputation for accuracy and quality.” For this fast-paced producer in an even faster-paced aftermarket racing environment, that’s what is needed to stay a winning lap ahead of the competition.

MACDAC is a Veteran Owned Small Business

27 Quality Avenue - Upper Level, Somers, CT 06071, USA
Phone: (860) 749-5544 || FAX: (860) 749-5373