The right-size 5-axis machine, with the right capabilities

It sounds like a variation on the fairy tale Goldilocks and the Three Bears. One size was too big, another too expensive, but the machining solution that Norris Precision Manufacturing Inc. found was “just right.”

“No one else in the market offered the machine that we purchased from GROB,” explains Joe Norris Jr., the company’s executive vice president. “To get a trunnion, 5-axis machining center with horizontal capabilities, it’s usually 500mm and 50 taper. It’s a much bigger machine than we required.”

Due to limited floor space at Norris’ Clearwater, Florida, shop and the need only for a 400mm work envelope, requirements were very specific.

Norris Precision Manufacturing specializes in aerospace and precision hardware, including fuel controls, hydraulics housings, titanium valve bodies, and electronic chassis enclosures in aluminum, titanium, stainless steel, and magnesium. Its bread-and-butter pieces are geometrically complex machined castings and forgings with multiple, varied ports and threaded openings. The company did this work on 4-axis machines, but the owners wanted 5-axis because they needed more capacity and wanted to reduce costs. Rather than buying additional 4-axis horizontal machining centers and stacking a fifth axis on them, the owners decided to buy simultaneous 5-axis machines.
 

The move to 5-axis

Norris says his father, Joe Norris Sr., who founded the company in 1978, did some research and found the GROB G350 modular machining center fit his needs. Father and son took a trip to GROB’s Bluffton, Ohio, facility to see the machines first-hand. They learned GROB supplied machining centers to automotive companies.

“If the automotive industry is that big on GROB, obviously they’re doing something right,” Norris says.

Norris Precision Manufacturing bought two G350 machines, one as a standalone center, the other with a Schuler LoadMaster Compact pallet changer. The machines’ combined footprint is less than one of the company’s existing horizontal machining centers and its dedicated pallet system.

The principal part made on the GROB machines is a fuel controller housing for an auxiliary power unit used on most Boeing 737s and Airbus A320s. Norris Precision Manufacturing, the sole source of the aluminum housing and sub-assembly, makes 24 of them per week. Norris expects his customer to ramp up demand to 32 per week – another reason for getting simultaneous 5-axis machines.

The parts took eight operations on the previous machine; with the GROB, only two operations are needed.

“We picked up about 30% productivity by going with GROB, and saved about an hour per piece,” Norris says.

He also likes the horizontal application and the ability to invert the table to let chips fall away. “There are a lot of 5-axis vertical machines, but everything cut falls back down into the workpiece.”
 

Many tools, toolholders

Despite its small footprint, the TM 171 tool magazine Norris specified for his GROB G350s can hold 207 tools. The large number is for better speed and repeatability.

“Boring heads, thread hobs – it’s better if they stay in the machine,” Norris asserts. “We often dedicate holders as well. Holders never get broken down, so it’s an easy switch.”

The same goes for fixtures for parts the company has made hundreds or even thousands of times.

Norris saw the potential in a pallet loader, knew parts would run faster because they’re going to be handled less, and more can be processed in a given time. Although only one G350 has a Schuler pallet system now, Norris has the machines positioned so he can extended the pallet system to both.

“A pallet system is the way to go because things stay set up. It’s easy to pull a pallet out and put one in,” Norris adds. “We use the same offsets. We put it back the same way we did it before. If there’s no setup time, it’s a one-piece flow – we can do one or 100 at the same price.”

All of the tooling stays in the machine, so maintaining good quality is not too difficult, according to Norris. “We can keep tolerances of 0.00050" ±0.00025" on diameters all day long, and can hold 0.00020" on aluminum,” he states.

A smooth transition

Although the small-footprint GROB machines seemed the right fit for Norris Precision, there was concern the machine operators would have difficulty adjusting to the new controller, a Siemens Sinumerik 840D sl. It wasn’t a problem.

“Most everyone likes new technology,” Norris says. He picked two machinists and gave them time to learn. “It’s a brand new piece of equipment, and we have to learn it together,” he told them. The pair went to GROB’s Bluffton factory for training a few weeks prior to the first machine’s delivery.

“We knew the Siemens control was more powerful, so we’re glad that we went with that choice,” says Norris. “We did some 5-axis work on the standalone GROB just to get our feet wet, then moved to the palletized G350, where we’re now running three products.”
 

No time for downtime

Norris is proud of his company’s 100% on-time, 100% quality reputation, and appreciates that if service is ever needed on his G350s, GROB’s Ohio facility can supply replacement parts quickly.

“They’re going to have a part most of the time,” Norris says. With the machine shop’s intensive parts production schedules, this knowledge is reassuring, because he’s had bad experiences waiting on parts for other manufacturers’ machines he’s owned in the past. “I can’t afford downtime,” Norris states.
 

Core competency

Norris notes that almost all of the parts the company makes will fit in standard-sized blue totes, and the parts’ small dimensions were a principal motivation for buying the smaller GROB machines.

“We have the option for a 600mm work envelope if we need something bigger,” Norris says. “But we try to stay within our core competency of size – not too big, not too small – just right.”

Watch a video of Norris Precision Manufacturing’s GROB G350 machining a fuel control casting at https://goo.gl/iD4ESi.

GROB Systems Inc.
www.grobgroup.com

Norris Precision Manufacturing Inc.
www.norrisprecision.com

About the author: Eric Brothers is senior editor with Aerospace Manufacturing and Design magazine. He can be reached at 216.393.0228 or ebrothers@gie.net.