Cutting it fine

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Tight production schedules and the drive for quality create an ever-present challenge for tool and die makers.

Comparison points show the numerical deviation at a few different locations

When rework threatens production schedules, the pressure gets intense and failure is not an option. To guarantee success, tool and die makers need skill, experience, technology and all the data they can acquire.

For B & J Specialty, a tool and die maker in Wawaka, Indiana, this data comes from its newly purchased 3D scanning tools.

Using Rapidform software and a GOM ATOS II white light scanner, B & J captured the information needed to avoid a costly delay on a hot stamping die.

According to Dave Chrisman, B & J’s process engineer, “3D scanning prevented a $20,000 mistake. But what is more important is that it helped us avoid a four week delay that could have jeopardised an OEM’s production schedule.” B & J’s customer, a supplier to automotive OEMs, discovered that B-pillar stampings were not conforming to design specifications.

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Using a Coordinate Measuring Machine (CMM) to pick up 20 key dimensions, the customer determined that the stamping die needed significant changes. With no time to waste, it turned to B & J for rework of the offshored die, and it provided details on the machining that needed to be done.

But the customer ’s solution was incorrect. “To verify the CMM report, we decided to spend a day scanning the B-pillar and generating a 3D colour map in Rapidform,” states Chrisman. “The client was glad we did because what seemed to be the obvious solution would have made the problem worse.”

The Rapidform colour map confirmed that the sweeping arc along the rise of the part was too flat, but it also gave Chrisman more information than a CMM could provide. With only a few dimensions from the CMM, the client had concluded that the die was high in the centre of the arc.

What the colour map showed was that steel needed to be removed from the ends of the arc, not the middle. “3D scanning let us see what was really going on with the part. Without it, we would have reworked the die only to discover that the stampings still weren’t correct,” says Chrisman.

Knowing what they had to do, B & J then scanned the stamping die and made colour maps with Rapidform XOV. Chrisman notes that inspection with a CMM was out of the question, “Considering disassembly of the die and the amount of detail to inspect, we would have wasted two weeks if we used a CMM.

This is time that we did not have.” The colour maps were included with the work instructions for the NC department. “It is common for dies to have handwork, so you can’t be sure that it matches the CAD data. We needed to know what we had before creating tool paths,” says Chrisman.

The colour maps of the die presented a visual reference that helped the NC department design efficient tool paths. “It keeps us from machining air, which wastes time, or breaking carbide tools with cuts that are too deep,” explains Chrisman. “A heavy cut on hardened tool steel with a Rockwell of 56 to 58 can destroy a carbide tool in a matter of seconds.”

The final role for Rapidform was documentation of the changes to the tool. The reworked die was scanned, and Chrisman used Rapidform XOR to build a parametric model that was directly imported into the client’s CAD system. “The 3D CAD data provides a baseline for wear inspection, rework and redesign,” he explains. “Without it, changes and repair can be a nightmare.”

“Rapidform software was a crucial tool from beginning to end. We found the problem, fixed it and documented the changes,” concludes Chrisman. “I don’t know how we ever did without it.” With this success, and many others, 3D scanning is now a routine part of B & J Specialty’s tool and die process.
B&J Specialty
Rapidform software saves the day for tool and die maker B&J Specialty
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Cutting it fine

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Automotive manufacturers are using increasing quantities of aluminium forgings for their suspension systems in order to reduce weight and increase mileage.

In 2005, Kobe Aluminum Automotive Products (KAAP) started production in Kentucky to help meet this demand. It now manufactures around 280,000 components each month. The company’s customers
include some of North America’s major automotive companies.

PowerMill simulations show the surface finish that will be achieved in the final die

KAAP’s greatest programming challenges are closed forging dies. These dies are used to produce parts with geometry ranging from simple to complex shapes, such as a half metre long link that starts
off shaped somewhat like a baseball bat, tapering down over its length to meet a larger diameter end. The end itself has a number of different radii that blend into each other.

“We were able to program these parts with the CNC software that we used in the past even though it was not very intuitive,” recalls Victor Steele, tool shop manager for KAAP. “Roughing operations
were relatively slow because the tools spent much of their time cutting air.” The most efficient way to rough out a forging die is to start with a large tool and use it to cut as much of the cavity as possible.
Then, you switch to the next size smaller tool and again cut as much of the cavity as possible.

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Final machined closed forging die

The problem with KAAP’s previous software was that each successive cutter traced the complete path of the part profile even when there was nothing for it to cut, either because the section had already
been finished or because the cutter was too large.

Kobe Steel’s Japanese operations had successfully programmed this type of die with PowerMill and recommended that KAAP try the Delcam software. “One of Kobe Steel’s programmers from Japan
visited us and showed us how to use PowerMill,” said David Taylor, engineer for KAAP. “Despite his limited English he was able to teach us how to use the program without a great deal of difficulty. We liked the way the user interface is laid out.”

Later, KAAP programmers had two days of on-site instruction provided by the local Delcam reseller, Design and Software.

“As we got to know the software in more detail, we were impressed with the large number of powerful machining strategies that it offers to help optimise cycle time and accuracy of machining operations,”
Mr. Taylor added.

“The big difference with PowerMill is that you can generate a stock model of the material left from the previous tool,” explained Mr. Taylor. “The software compares the material that is left on the workpiece with the geometry of the next tool and determines the areas of the part that it is capable of cutting. PowerMill then produces a toolpath that rapidly traverses directly to the areas that can be cut by the tool while skipping areas where there is nothing it can cut.”

“These rest machining capabilities save us a considerable amount of time, reducing cycle time by 40% to 45%,” Mr. Taylor explains.

“It now takes about 24 hours to machine a complete die or about two hours to machine a die repair.”

KAAP has also benefitted from PowerMill’s simulation capabilities. The software provides fully integrated simulation and collision detection, to ensure the CNC program is both safe and efficient, and also to predict axis reversals and surface quality.

“PowerMill has helped us substantially improve the efficiency of our machine shop operations,” Mr Steele concludes. “We have been able to substantially reduce the time required to machine dies and greatly reduced handfinishing times. The software is also much easier to use which saves time in training additional programmers.”

www.delcam.com/powermill

Delcam Powermill simulations
PowerMill cuts KAAP’s drilling time down to size


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