Hamilton Sundstrand Gets the Job Done with Solid Imaging

At Hamilton Sundstrand Space Systems International in Windsor Locks, Connecticut, two-dimensional drawings don’t make the grade any more. Even 3-D computer graphics don’t quite cut it. When engineers at Hamilton Sundstrand want to show something to customers that include NASA and the U.S. Navy -- or to any of their suppliers -- they build a three-dimensional model of the part or subsystem using solid imaging equipment from 3D Systems.

Hamilton’s use of solid imaging has not only improved its ability to communicate ideas,
but has enabled the company to perform vigorous product testing, save money and improve quality--all within a reduced product development cycle. Recently, Hamilton Sundstrand built a wearable mockup of a new spacesuit concept for Mars, validating the company’s new design for NASA.

The Mars space suit design is an extension of Hamilton Sundstrand’s primary business, producing life-support equipment for spacecraft and submarines. "We make equipment that helps keep the atmosphere on Navy submarines fresh," says Robert Davis, manufacturing engineer. "We also make hardware that flies on the Space Shuttle, revitalizes the atmosphere inside the cabin, and performs thermal management during its many flight phases. We are currently supplying life-support equipment for the space station, and we are the prime contractor for the EMU (Extravehicular Mobility Unit) space suit that is used whenever astronauts go outside the shuttle."

Designing and building such equipment is totally unlike any other manufacturing operation. Clark Dean, senior principal engineer at Hamilton Sundstrand, explains: "Not many copies of space hardware parts are built. However, parts must be very precise, and able to be machined to the exact dimensions. Every single dimension and specification on a print must be met. If not, the part is rejected. We spend a lot of money on every part we build, so high quality is vital."

Davis says solid-imaging technology -- specifically the stereolithography process developed over a decade ago by 3D Systems’ founder Chuck Hull -- also helps cut the design approval process from years to months. The SLA“ system literally builds a physical prototype – layer by ultra-thin layer – using a liquid epoxy plastic that is hardened by a laser to precise CAD-generated specifications. In many cases, three-dimensional parts are fabricated full size. If a part is too large for the machine, a scale model can be made, or a large part can be made from several smaller parts which are then fit together. Parts made from this epoxy plastic are exact, strong and durable, and can often be painted or finished. In some cases, the result is a model that is indistinguishable from a real part.

"The ability to sift through several possible solutions to a problem saves us hundreds of thousands of dollars per year."
                                                         Clark Dean, Hamilton Sundstrand

Iterating and Innovating
"NASA representatives and astronauts visited us to examine our design for a high-speed fan," Davis said. "We fabricated two functional models using stereolithography. When the astronauts walked in, expecting to just review a design, they saw two models that looked like real parts. Then we turned the fans on, and they ran at their actual operating speed of 15,000 rpm – in the model. The astronauts were very impressed. We have also manufactured smaller stereolithography fans that have run at even higher speeds, which allowed us to do performance and acoustic testing."

"The ability to physically test a system using a part made with stereolithography is very important," adds Dean. "For the fan, we could generate airflow and acoustic information using the model, change the number of blades, vary the design and produce another 3-D model for testing at very low cost. This ability to sift through several possible solutions to a problem saves us hundreds of thousands of dollars per year."

"We impressed NASA again with the Mars suit," said Davis. "Using our SLA system, we were able to produce a wearable ‘hard upper torso’— essentially a torso without limbs and head. We invented a new geometry that absolutely had to have a 3-D working-model to prove that the design would work. We built a full-size model from four sections that we glued together. We put standard arms, legs, and a helmet bubble on it, attached an air supply, put one of our engineers inside and had him walk around in a closed-loop life support system."

Davis continues, "It took two iterations to get the upper torso part right and then we showed it to NASA. They were absolutely amazed. We had produced this suit in only a matter of months, not years. Without solid imaging technology, it simply could not have been done in the time allotted."

"Perhaps even more important than all the time and cost savings, it vividly demonstrated to NASA the value of having Hamilton Sundstrand as a prime contractor for spacesuits," says Dean. "It showed them that we have good ideas and the engineering talent to build innovative solutions. That kind of customer satisfaction is priceless."

Payback on Their Investment
Hamilton Sundstrand has found that solid imaging technology can eliminate a great deal of confusion in machining complicated parts and actually saves a significant amount of money.

"We wanted to build a large frame for a system that flies on the space shuttle. The price to machine the frame was very high. The quotes from three separate suppliers were based on a stack of 2-D prints," says Dean. "We made a model of the frame using our equipment from 3D Systems, took that model to the suppliers, showed them what it was really going to look like and asked them to re-bid. Each supplier dropped its bid to about two-thirds of their previous quote. As a result, we were able to save enough money on the three purchased frames to pay for more than half the cost of our SLA machine."

Experiences like this caused several of the divisions of United Technologies, including Hamilton Sundstrand and sister division Pratt & Whitney, to form a consortium nine years ago to buy solid imaging equipment and consolidate it in East Hartford, Conn. "The consortium grew, and several SLA machines were purchased from 3D Systems. Since the consortium was formed, we’ve utilized solid imaging technology on every program I’ve been involved in," says Dean. "We used the consortium’s equipment so much that we decided to buy an SLA system for our own use."

From Model to Metal
"Because we make so few copies of parts, traditionally we machine them from a solid block of metal," says Dean. "This avoids the high cost and long lead time of hard tooling for investment castings. Stereolithography has fundamentally changed our design process. It allows me, as a designer, to use investment castings for low-volume production runs. I can produce a 3D model of a part and then examine it to determine where I can add metal or take away metal in a casting, optimizing the design for maximum strength and lowest weight."

Dean can make little changes, add a flange or a bracket, run a second iteration through the CAD system, produce a model on the SLA system and send it to the metal casting process when he’s satisfied with the design. "We produce a stereolithography master pattern and then we take it to one of our casting suppliers who pours metal. Within just a short time after I get an idea for a part, I can see it in metal."

He adds, "Once we decide exactly what we want, we can make a production run of 15 to 20 parts, which is a lot for a spacecraft component. The only tooling investment we have is in the 3-D casting database. This saves us about six months of time and many thousands of dollars in tooling costs for each part. If changes are required, I don’t have to scrap any hard tooling."