Aerospace Job Shop Draws a Virtual Line in the Sand

Northstar Aerospace insists that all CNC manufacturing projects be delivered
with Parasolid® CAD models.

2009

(DULUTH, MN – MARCH 2009) Early in 2008, Northstar Aerospace, primarily a production aerospace shop at the time, was given an opportunity to do a huge prototyping project for one of its good aircraft customers. The project would involve making nearly 300 complex, irregularly shaped parts and delivering them in a matter of months. Northstar would be able to make money on the project, but only if it could do the work quickly and avoid making scrap.

This opportunity came as an epiphany. It was the sort of project that could establish the company as an agile, diversified manufacturer capable of handling projects of any size. They couldn’t afford to take a pass on it, especially in an economy that was already slowing. Taking it on, however, meant that the company would have to dramatically alter its approach to engineering and manufacturing.

The pivotal move would be to upgrade its CAD (Computer-Aided Manufacturing) capabilities with software that would allow Northstar to automate CNC programming to the greatest extent possible, establish a viable manufacturing strategy for parts in a virtual environment rather than on-machine, and resolve potential problems before the part was set up for manufacturing.

The company evaluated several CAM software alternatives and decided on Mastercam® X2 Mill Level 3 with Solids (from CNC Software, Inc., Tolland CT). Don Winberg, Director of Manufacturing for Northstar, explained that Mastercam with its Solids add-in package fit in very well at Northstar because their parts can be so irregular. They can import the solid model directly from whatever CAD program the customer is using and generate the toolpaths automatically. On the other hand, in the places where tight control is needed, the programmer can go in randomly and edit the toolpath down to a single point, if necessary.

Tsunami of Parts
The company's main programmer, Michael Peterson, had six years experience using an earlier version of Mastercam, so he had no problem making the transition from the software Northstar had been using. However, with all the parts that would be coming his way with short lead times, there was no way he was going to be able to do all the programming for this project himself.

He said, "The idea was to have our customer receive parts as fast as possible, but everything had to be right. By importing the solid model we could be sure we would not miss anything, and the part would replicate the CAD model every time."

To handle the tsunami of parts coming its way, Northstar bought a second Mastercam seat and trained several others to bring in CAD models and automatically generate initial toolpaths. Peterson put in final touches and validated programs before sending then to the CNC machines. He said a number of Mastercam features were instrumental in expediting the programming, minimizing machining time, and assuring that there were no programming errors that would result in scrap.

High Speed Roughing: If the parts had been production work, Peterson would have had to spend a lot of time fine tuning the program to optimize machining cycles. There was no time for this. He said, “You could play with tooling and take bigger stepovers or bigger depth cuts, and maybe go a little faster.” However, he did manage to shave a lot of time from machining by using Mastercam’s High Speed Roughing feature. “This saves a lot of time,” he continued “because you don’t have to figure out how much stepover you need or multipass rough or finish pass or different depths. It will just rough the whole part in and you can start programming your finishing paths.”

Work Coordinates: One big timesaver Peterson discovered quickly was Mastercam’s WCS (Work Coordinate System), which allows the user to orient the part model in the programming environment only once, rather than each time a new view of the part or a different tool plane is required. He said, “We can program everything from the same zero. When it gets to the CNC machines, we create macro programs that recognize when work offsets are at different orientations. We can machine everything picking up only one number at the machine.”

Fast Tooling and Fixturing: Northstar uses Mastercam as a CAD program to design any tooling or fixturing that might be required. This design can be fast because work-holding devices frequently rely on the mirror images of surfaces for which toolpaths have already been created. In the end, all of the parts’ tooling and the tombstone itself have been created. They can be assembled within Mastercam, and the CNC program can be proven on-screen in a virtual manufacturing environment.

Backplot and Verify: Before they cut a chip, Peterson has established within Mastercam what he calls a “complete theory of and process for how the part will be manufactured.” But will it work? Almost always, the answer is yes, but Northstar does not have to cut a bad part to find out. Two tools in the Mastercam software, - Backplot and Verify - provide the answers. Backplot shows a computer-animated representation of all the tooling moves to make sure tool and tool holder will avoid crashing into the part or the fixturing. Verify provides a color-coded representation of the part showing when too much or too little material has been removed. With these software tools, Northstar has no fear of making a disastrous move on the machine or making a bad part.

Don Windberg said that the prototyping project turned out to be a profitable one even though it has not, at present, resulted in follow-on production work. Because the company was counting on the project’s profitability from the outset, Northstar burned its boats on the beach by purchasing only enough of the expensive alloy material to make each part.

Lines in the Sand

Two years ago, work came into Northstar primarily in the form of drawings, which Northstar had to recreate in CAD and then transfer to CAM for manual programming. Before changing over to Mastercam in 2008, about 45% of the programming was semi-automated using imported surface models and some solids.
Today, about 90% of the CNC programs are generated automatically using Solids and the company is taking a hard line by insisting that customers provide solid models instead of drawings. This can dramatically reduce lead times by shaving hours or even days of programming labor. It also shifts the responsibility for feature and dimensional issues squarely to the customers. They will get back exactly what has been represented in the CAD model.

Northstar Aerospace defines itself as a shop specializing in close-tolerance machine parts relying on CNC milling, turning, and mill/turn equipment, rather than an aerospace manufacturer. “We are still always going to be aerospace,” he continued. “That’s our core competence. We will keep it there. But we also want to keep moving forward. Being aerospace, we have a whole set of standards like ISO 9001:2000 and AS9100: 2004 REV B certifications that can open doors to new markets and keep us ahead of our non-aerospace competitors.”

Northstar has some clear ideas about where it will be heading in the future. The shop intends to continue building on its newly enhanced computer-aided manufacturing capabilities. It has a software Maintenance license so that it can upgrade to the latest versions as they become available. Peterson himself is an avid reader and participant in online forums so that he is continually learning from his peers across the world.

Peterson is taking advantage of the knowledge he is acquiring to push much of the company’s manufacturing onto the Haas horizontal CNCs with tombstones because they allow for efficient multi-sided machining, typically with a single setup. Five-axis and Swiss turning systems may be used to further improve productivity in the future. Some of these developments will result in a need for additional CAM programming talent. When this happens, Northstar hopes to take advantage of nearby Lake Superior College, which offers courses and training in Mastercam and other manufacturing disciplines.

Winberg said, “The big thing we have learned from this and similar projects is that we can use Mastercam to shorten our lead times and drive out engineering costs. So everything we do can be profitable, no matter what the volume. This has allowed us to compete for and win projects that call for shorter runs than we have been used to. Not all of the new work is related to aerospace manufacturing. For example, we are making medical device parts. Being able to diversify our customer base has allowed us to keep our people and equipment busier and our project volume on an upward trajectory.”