When a company has to do almost everything in the production of its products, quality assurance assumes a predominant role in day-to-day operations. This is especially true at Schweizer Aircraft Corp., an Elmira, New York-based producer of small helicopters and unmanned aircraft or “drones.”

Schweizer must be doing a lot of things right, however. After almost 65 years in business it is still family owned and family managed. One key to this success has been careful diversification from gliders to powered aircraft, then helicopters, drones and parts production for military aircraft OEMs.

Manufacturing is, of course, a core strength. And Schweizer backs up its production people with computer-aided design (CAD), computer-aided manufacturing (CAM) and computer numerical control (CNC) routing plus stretch forming, rubber press forming, drop-hammer forming, aluminum heat treating, and welding (both TIG and resistance or “spot”).

“Fundamentally, portable inspection techniques are part of what allows us to do so well in so many different manufacturing processes,” said Rick Kent, production manager at Schweizer. “We are able to quickly determine whether a component or tool is dimensionally accurate or whether a fixture is properly aligned. And, if not, how it can best be corrected. On large components and fixtures, there often is no other reliable and cost-effective way to measure critical dimensions.”

Schweizer’s extensive quality assurance capabilities include:

• Three coordinate measuring machines (CMMs), two 3-axis CNC Brown & Sharpes and an older Bendix Sheffield Cordax system. The biggest has a work envelope of 63 x 31 x 27 inches.

• A “dock station” for large fixtures consisting of optical gauging equipment (fixed and portable) plus levels and transit systems, also called theodolites.

These systems and instruments have one of two things in common: Either they are not portable or they are not very easy to get repeatable results from. For dimensional measurement tasks requiring both portability and straightforward repeatability, Schweizer relies on a3000i portable CMM with PowerINSPECT software.*

The arm has six key roles at Schweizer:

• Measuring stretch-forming and rubber molding tools that are too large for the three conventional CMMs and verifying them against downloaded CAD data.

• Measuring large assembly fixtures that exceed the 63 x 31 x 27 inch CMM limitation.

• Tool checking in lofting, when large numbers of 3D coordinate points (“point clouds”) are taken from form blocks and airfoil surfaces and checked against the lofts, i.e., the master drawings.

• Aligning or realigning fixtures from conventional X-Y-Z coordinate systems of production machinery and the factory floor to the aircraft-based orientation of waterline, station line and buttocks line.

• Troubleshooting, especially in measuring large components and even entire aircraft when fit-up problems occur during assembly.

• Reverse engineering of old tooling as a quick and uncomplicated alternative to redesigning the tools in CAD.

Until 1999 when it bought the portable CMM, tooling blocks for stretch-forming and rubber-forming presented some of Schweizer’s biggest measurement challenges. “Like a lot of the parts we check with the arm, tooling blocks are too big for even the largest [conventional] CMM,” Kent explained. “While the stationary CMM might be more precise, the 3000i will measure to a thousandth of an inch. However, the operator has to have a light touch and some finesse. For almost everything we do with it, one one-hundredth is good enough.”

These tooling blocks are also where reverse engineering is needed. Aircraft have long service lives; it is not uncommon for a helicopter to be older than its pilot. This means parts including the stretch-formed or rubber-molded aluminum skin panels must be produced long after the aircraft has gone out of production.
“For those older blocks, we do a lot of reverse engineering with the 3000i, PowerInspect and point clouds,” Kent said. “It may not be as precise as a complete redesign in CAD but, again, it’s close enough and we don’t have to change everything else such as plugs and tooling restrictors in the forming system. That would be way too costly just to accommodate a tool that will only make a few pieces a year.”

Reverse engineering in this way also helps Schweizer avoid “having to ‘guess-timate’ block dimensions for forming,” Kent added. “The arm has eliminated almost all the old cut-and-try approach to dimensional tolerances in those form blocks.

“We start with downloaded CAD files sixty to seventy percent of the time and we use CAD files more and more all the time, primarily AutoCAD 2000 and some Pro/Engineer,” Kent said. “It was primarily for this capability that we chose the 3000i."

For measuring and checking some large fixtures, the 3000i is “taking work away” from the dock station. This is a pair of Keuffel & Esser optically based Brunson transit systems and levels on perpendicular rails. Its sole purpose in life is to align large jigs and fixtures. Reflective buttons are attached to key bosses in the fixture for the aligning process.

This is the so-called three-sphere alignment method unique to the aircraft industry. Three-sphere alignment uses station lines from the nose of the aircraft rearward, buttocks lines from the center of the aircraft outward, and waterlines measuring from the ground up. These are the reference coordinates for the aircraft and they are established before a line goes into production.

A key PowerINSPECT capability comes into play with three-sphere alignments. That is the ability to map and reference planes from one set of coordinates to another, i.e., from X in a machine or on the factory floor to aircraft station line, Y to aircraft buttocks line and Z to water line.

“What’s most important about the 3000i and PowerINSPECT is the flexibility it gives us in measuring things quickly and in whatever ways wethink will give us the best data..."

“Sometimes we have to measure the dimensions inside a helicopter body, side to side,” he said, “and it’s a very cramped space. You could get wound around the arm in there.”

If it were not for another key characteristic of the arm, infinite rotation in all but the base joint, the operator would have to stop, back out, break the setup, unwind the arm, and waste a lot of time. (Arms lacking infinite rotation typically lose their reference points when the operator has to break the setup; those arms must be re-zeroed in before the operator can get back to work.

Schweizer has not kept any financial statistics on its portable CMM. Kent is convinced, however, that the arm long ago paid for itself “even if it gets used only two or three times a month. We did not buy it on return on investment (ROI) basis,” he added. “We had to have what it can do for us in checking parts, troubleshooting and installing fixtures.

“What’s most important about the 3000i and PowerINSPECT is the flexibility it gives us in measuring things quickly and in whatever ways we think will give us the best data,” Kent said. “Tool blocks are a good example. We could take them into the CMM room and verify their dimensions on the Brown & Sharpe machines. But the CMM operators don’t see those kinds of jobs very often so they have a lot of reorienting to do. All that takes time. It is much faster to measure tooling on the factory floor, right where it is used, especially if reference planes must be established first.”

Time to measure has been slashed in many tasks. When troubleshooting fit-up of skin components on an aircraft, “bringing in transits, setting them up and leveling them took hours,” Kent said. “We can get the same kinds of measurements, such as a plane to a station line, in just a few minutes with the portable arm. And it’s a lot more accurate than a tape measure,” he added.

This is especially vital in troubleshooting, Kent concluded. “Now we don’t have to guess or try to recalibrate and fix things that might not have been a problem. In the aircraft, some things were just too difficult to measure so we would live with it as long as it was structurally okay. That was a very time consuming way to approach what might turn out to be a very simple problem to fix.”