Kim Laudrum
1,217 words
1 November 2002
Canadian Machinery and Metalworking
ISSN: 0008-4379; Volume 97; Issue 9
English
Copyright 2002 Gale Group Inc. All rights reserved. COPYRIGHT 2002 Maclean Hunter Canadian Publishing Ltd.

"Visitors come from all over the world to see this process because they have heard about it. When you tell people that you are hydroforming 518,000 car frames and cutting 268 holes with a laser, they all go 'Wow!' because no one else in the world has done that prior to us. It makes this a good place to be for people like me who find this technology interesting."

The process Gareth Davies is referring to is the four-line hydroforming and laser-cutting system Budd Canada installed in the spring of 2001 at its Kitchener, Ont. plant. Budd, the stamping and framing group of Thyssen Krupp Automotive, uses these lines to produce one hydroformed frame every 32 seconds. These are delivered to client General Motors for their sports utility vehicles, including the Trailblazer, the Envoy and the Bravada.

Davies is the hydroforming manager at the plant, a pretty happy camper these days, now that the lines are running smoothly. But it took some time to get there--eighteen months, actually. And, of course, they needed some help, which they received from Toronto-based Rumble Automation Inc.

Rumble specializes in the manufacture of custom-designed robotic systems. They work with clients, like Budd, Dana Corp. or Magna, to provide services ranging from design, engineering, fabricating and assembly to machine start-up, installation and post installation services.

The 360 series of frames ordered from GM required Budd to use a known, but relatively unused process for high volume parts: hydroforming. This process could produce a frame that was lighter, yet more stable than conventional manufacturing methods. Hydroformed rails are formed from 3.2-mm, 1018-steel tubes, rather than made of two stamped C-shaped sections welded together to produce a rectangular shape. Because hydroforming strain-hardens the steel, the rails are less likely to become distorted -- a problem with the welded rails.

GM also wanted Budd to consider hydroforming both front and rear rails -- something no one in the industry had done on such a large scale before.

There are now four hydroforming lines with in-process laser cutting at Budd. Each line is dedicated to one of the four rails required for the SUV (front left hand, front right hand, rear left hand, rear right hand). Each line has three laser cells. Each laser cell has four laser-cutting robots, processing two rails at a time. In total there are 48 laser cutting robots.

The hydroforming presses are from Schuler; the lasers are Nd:Yag lasers from Trumpf; and the robots are Fanuc.

HOW MANY HOLES DOES IT TAKE?

Initially, the GM order included about 20 holes per rail, Davies recalls.

"We ended up with 268 holes in the frame," he laughs.

"The holes are there for crash initiation. A lot of the holes take clips so GM can bolt things to the frame, some of them are access holes, some are there for what they call road-wash, to allow rain water to escape from the frame," Davies explains.

Initially, Budd's intention was to pierce the holes in the hydroforming die. But it soon became apparent that process could be problematic. With a new model, design changes are inevitable. These require quick turnaround. Given the stiff competition in today's SUV market--particularly from Ford's Explorer--GM wanted to push the pedal to the metal.

FINDING A BETTER PROCESS

In-line laser cutting the holes after the hydroforming press was an alternative worth investigation.

"I wouldn't say it is more cost-effective to cut the holes with a laser. However, engineering changes become very easy. If the customer wants to add more holes, and if you are doing it in a die, it becomes very difficult and time consuming," said Davies.

"Now, for example, I have a customer coming in on Tuesday because they have requested that some holes be added, and it's very simple for us to do that. It's just a matter of programming the robot with a laser on the end to add holes and away we go," he said.

Davies has high praise for the support the company has received from Rumble Automotive, the company contracted to design, build, and integrate the laser cells.

Two of those key players, Dennis Nadeau, Rumble's sales manager, and Randy Paura, the company's laser division manager, saw the project through from conception to production. Rumble continues to provide assistance with such things as programming changes to any of the 48 laser-cutting robots.

THE CHALLENGES

Paura explains some of the challenges the project presented.

* The lubricant used in the hydroforming process affected the cutting process.

"The fluid partially vaporizes or atomizes from the focused laser beam and does create contamination problems for the optics arrangement," notes Paura. "There is a 'cover slide' or protective lens on the laser that is a consumable, and as such, it does see greater wear than in other operations where hydroform lubrication is not present.

"This problem was minimized by optimizing the cutting parameters (pierce process, laser power, assist gas pressure, cut speed and focal position), Paura explained.

* The focal position of the laser beam relative to the part was one of the most crucial aspects of the project. "Initial factory settings were not the 'most correct' for this project," Paura explains diplomatically.

"Rumble invested in diagnostic equipment that allowed us to precisely measure and calibrate the laser equipment for the appropriate focal position with respect to the part surface. Once the optimal focal position was accomplished, we were able to increase cut speed, cut quality and more importantly, provide process tolerance," he said.

* Fume extraction for laser material processing is opening a new realm for the filtration companies.

"The fine particulate generated, along with the hydroform fluid can be problematic by clogging filter systems," Paura points out.

A two stage filter system was employed, with the last filter providing HEPA class protection (with activated carbon). Controlled air flow through the laser cell is also crucial to ensure the particulates are drawn out efficiently rather than accumulating within the cell.

"Like every thermal manufacturing process--such as MIG welding--cleaning the equipment is still part of the preventative maintenance requirements for uptime," he notes.

* A considerable amount of software programming is required to provide, not only the necessary cutting operations, but also monitoring and control of the laser power source and cutting head. Automatic error recovery solutions were incorporated into these routines.

Rumble worked with Budd to develop, not only robust robot code for the laser cutting operations, but also PLC system monitoring features that enabled Budd to gather necessary system performance data. This data was then used as feedback for focusing attention on those areas that furthered the system ownership process.

In today's competitive auto parts industry, finding ways to keep up with your customer's demands can give you the edge. The in-process hydroforming and laser-cutting line does that for Budd.

Total number of pages for this article: 3 FULL TEXT Maclean Hunter Canadian Publishing Ltd.