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When Ray and John Connelly's father, Leroy, founded Connelly Machine Works fifty years ago, he probably never envisioned using water to machine parts. Today, the Connellys have discovered how to reduce the time and cost of traditional machining using an abrasive waterjet.

Connelly Machine Works is a family-owned and operated shop based in Santa Ana, California. They employ 20 people at their 10,000 square foot facility and offer an array of machining, welding and grinding services to the aerospace and other commercial industries. Equipment used at Connelly includes CNC and conventional mills, lathes, saws, welding and grinding machines.

Connelly's senior management concluded earlier this year that the shop needed to streamline its traditional machining process. Previously, parts were cut to near net with a saw and machined to finished tolerance on a CNC mill. This often required multiple passes, or wire EDM. "Time was a big disadvantage to this approach," said Ray Connelly. "It tied up our milling machines and EDM was too expensive and slow."

Intent on purchasing a wire EDM, the Connellys attended a trade show in Los Angeles. However, instead of the intended wire EDM, the Connellys purchased the Bengal abrasivejet machining center manufactured by Flow International Corp., in Kent, Washington.

They were pleased to discover that the Bengal would net and near net parts to ±0.006-inch accuracy from virtually any flat material up to four inches thick. Compact in size, the fully-integrated machining center is equipped with the Windows-based FlowMaster PC controller, the Paser 3 abrasive waterjet, an X-Y motion system, a 40,000 lb per square inch (psi) pump and a 39 inch by 19.6 inch worktable.

Connelly machines stainless and carbon steel, Inconel, titanium and brass with its abrasivejet machine. "When we saw what the Bengal could do, how fast it could cut and how easy it was to operate, we were convinced it was machined for us," said John Connelly.

"We now hog parts out in one pass with the Bengal and machine them to finish tolerance in a single pass with our CNC mills," said Ray Connelly. "And, we can use the same program on both the Bengal and the CNC mill. All we do is change the offsets."

The shop also utilizes the Bengal for other applications. "The machine is very good for prototyping and short run production. The simplicity of the software makes it an excellent machine for prototyping."

This ease of operation was a major factor in Connelly's decision to purchase the Bengal. The FlowMaster controller is pre-programmed with cutting parameters for a variety of materials, dramatically simplifying abrasive waterjet machining. To produce parts from a DXF or CAD file, users select material type and thickness and click on icons to execute waterjet commands. The controller determines optimum cutting parameters for the application. No special knowledge of abrasivejet machining or CNC programming is necessary.

"My daughter just started working at the shop," said Ray Connelly. "She has no programming experience, though she is familiar with PCs. She was able to program the Bengal, including complex parts within one week."

FlowMaster includes a CAD/CAM package and drawing functions. An optional scanner makes it possible to scan a drawing into FlowMaster where users can convert it to a DXF file in minutes. All components of the Bengal are controlled through FlowMaster.

Abrasivejet machining offers several key benefits to machine and job shops. A cold-cutting process, abrasivejet machining leaves a finished edge free of a heat-affected zone (HAZ). Consequently, abrasivejet machining reduces or eliminates secondary operations. Cutting without heat also protects against metallurgical changes, leaving the material structure of the part intact. "We previously consumed a lot of tooling trying to penetrate edges hardened by HAZ," said Ray Connelly. "An edge machined with abrasive waterjet is very easy on inserts and bits."

Abrasivejet is also said to improve material utilization, cutting from the edge or middle of a plate along specified lines in any direction. Minimal kerf (0.030 to 0.060 inch) width of the abrasivejet adds to the material savings. "The Bengal consumes much less material than saw cutting," said Ray Connelly. "We nest the parts pretty tight and definitely get more parts from a piece of material."

Set up for the abrasivejet takes less than five minutes. Tooling consists of an orifice and mixing tube, both lasting in excess of 120 hours. No tooling alignment is necessary and fixturing is minimal. "Set up time is very low," said John Connelly. "Our fixturing is very simple, one or two clamps or sometimes none at all."

Easy maintenance and uptime are other advantages. "Our machine has been running ten hours a day, six days a week. We run every minute of the day we're open. Maintenance is not a problem," said Ray Connelly. Operating cost amounts to approximately $19 per hour, excluding labor.