May 2007 Edition

CAD/CAM

Software Turns a 100-Year-Old Idea into Reality

Keeping things simple doesn’t mean keeping them stupid, for a one-man shop, a CAD/CAM package allowed fast prototyping

Rapid prototyping is critical for inventors. Waiting three weeks to have a wireframe drawing turned into metal, and then finding errors and having to repeat the process was wasting Chris Gamble’s time. He turned to a 3D solid CAD/CAM package and his own vertical machining center to change his ideas into reality.

 “Designing in solids makes sense for me,” Gamble said. “I found it tough to visualize a product in wireframe, but I can see it in a solid.”

What drove Gamble into setting up his own shop was an ef for t to bring an engine patented more than a hundred years ago into reality. Although patented, a working version was never developed since the materials and machining necessary to create the engine didn’t exist.

“I knew it would work,” Gamble said. “This engine weighs just under 200 lbs, but puts out more than 300 hp.” Crucial to the engine’s development were a scotch yoke and modern ceramic materials. A scotch yoke converts linear motion to radial motion. A metal scotch yoke needs lubrication. But, Gamble realized a ceramic version would need no lubrication. Ceramics also have the benefit of hardness and operating at extreme temperatures.

From 3D to Reality

After designing the engine with a 3D modeler, Gamble bought a stereolithography machine and made the first mockup. The yoke works by twisting the crankshaft. The advantage of the engine is that each piston has two combustion chambers.

He constructed a operating prototype, but found the process he used was inefficient. Subcontractors made parts based on solid drawings, but the parts weren’t always right, not surprising in a trail-and-error invention mode.

Gamble would make changes, but it could take weeks to get a part machined. When it came back, a design revision might be needed and the part had to be sent back to the machine shop again with another couple of weeks’ delays.

“After two or three cycles, I realized I would never finish it unless something changed,” Gamble said.

 Gamble bought a vertical machining center, as well as a CAM system based on wireframe models. Manually programming the VMC took a long time, so he added a programming system. The programming system based on wireframe geometry was a step backwards for Gamble since he was used to designing in solids. He found wireframe work frustrating and time-consuming.

Easier Visualization

“Designing in wireframe is tough,” Gamble said. “You can’t see where a part ends and another begins. Programmers use wireframe because they have years of experience, but they would program a lot faster and make better products using solids. Probably make less errors, too.”

Searching for a method that would let him work in solids, he found CAMWorks from TekSoft, Inc., Scottsdale, AZ, a system designed to operate inside the SolidWorks environment.

“With less than a day’s training, I was producing parts,” Gamble said. Because CAMWorks operated from inside Solid- Works, he didn’t need to create an IGES fi le, transfer it into the CAM program, and then clean up the geometry to generate a tool path.

“It saved a lot of time since I didn’t have to convert, transfer, and clean up fi les” he said. “When I make a change, the software automatically updates the model because it’s fully associative.” All the parts for the engine – aluminum, steel, and ceramic – were programmed and cut by Gamble on his VMC.

“If I had relied on contractors, it would have taken three years to get a completed engine,” he said. He created one himself in about a year in his off hours.

“I spent about $100,000 on materials and labor building the engine. By doing the work myself, I saved at least $80,000 and CAMWorks was only a fraction of that.”

The integration between SolidWorks and CAMWorks allows programming machining processes without leaving the SolidWorks session. The same familiar command trees and functions are used to generate the tool path. Working off the same geometry file ensures that the machined part is exactly the same as modeled.

Quick Change Artist

Allen Hock, H&M Machine, Greendale, WI, also purchased a Weiler lathe from the Weller Machinery dealership.

“With CAMWorks I can make changes faster and see exactly what it will look like when I’m done,” Gamble said. “Using a wireframe, I can’t tell what I’ll get. With SolidWorks, I can design a small part on my computer in a matter of minutes, then click on the CAMWorks menus, create a tool path, run the post, run the simulation, send it to the machine, and in as little as 30 minutes have a completed part. Then I can plug it in and make sure it actually fits.”

Gamble was hindered when he started because of his lack of machining experience, such as knowing feed and speed rates. He crashed the machine a few times when trying to cut steel at speeds more suited for aluminum.

Since he was a novice, he came to rely on the knowledge based machining capabilities of CAMWorks. It automatically captured vital machining data, including feeds and speeds, as he programmed his models, allowing continual process improvement and repeatability throughout all his part programs.

“CAMWorks made it so easy to program tool paths, I couldn’t believe it,” Gamble said. “Once the geometry is completed, I click a button to launch the CAMWorks menus. “If I need to drill a hole, I click on the point where I want the hole and another click opens a dialog box. I enter the diameter and depth, and then preview it to see where the hole begins and ends. Since I can program rigid tapping, I don’t have to drill the hole and then setup for tapping, which would take forever.”

 “Now I’m cutting cams,” he said. “The CAMWorks reseller, Cimtronics, offered personalized support and guided me through the entire process. We had to rewrite the post to handle the simultaneous fourth axis.

“Cutting cams on a VMC requires cutting a flat, then following a curve to the other side and cutting another fl at. Some of the machinists that came to check out what I was doing thought they were cut on a lathe. They weren’t; they came off my VMC.”

Later this year, Gamble plans to show his prototype engine at a trade show in Las Vegas.

TekSoft, Inc.

Visit www.rsleads.com/705mn-206 for more information

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