One of the toughest challenges faced by a leading manufacturer of composite motorsports components is drilling and tapping holes that need to be closely aligned with embedded metal bushings. The complex, freeform shape of the components makes them difficult to accurately align in fixtures, and even a slight misalignment causes cutting tools to crash into bushings, usually breaking tools and requiring three-to-four hours of manual effort to extract them from the part.
Aerodine Composites Corp. overcame this problem by using Delcam’s PowerInspect software to generate numerical control (NC) code that drives a touch probe in the spindle of a CNC router to determine the position of the part in the fixture and recalculate the machining datum prior to cutting the part. The machining process has nearly eliminated tool breakage, reducing the time required to produce each part by about 90%.
Aerodine Composites’ team of repairmen and composite technicians work together to produce highly specialized alterations of existing composite structures and to repair damaged components to original equipment specifications. The company’s experience as a premier supplier of structural assemblies, research and development parts, ancillary support components, and structural repair schemes to the high-performance motorsport industry has enabled the company to build a vast catalog of damage scenarios, repair techniques, and manufacturing methods to ensure that safety is not compromised.
One of Aerodine’s recurring projects is producing about 50 front wing assemblies per year for an Indy car racer. The parts consist of carbon fibers and various metallic components such as bushings, bonded together by epoxy resin. The value of each assembly is about $15,000, and individual components range from $1,000 to $1,500. Many holes need to be drilled through the composite material in perfect alignment with the bushings, and then the bushings need to be threaded. Aerodine employees had produced these parts on manual machine tools, but operators had difficulty aligning the machine spindle with bushings buried in the composite material. Bushings or taps frequently broke off when the tool crashed into the bushing. Part machining time was only 15 minutes, but it took the operators three-to-four hours to manually extract the broken drills and taps. Repairs cost about $150 per hour, including both labor and machine time.
Looking to improve on this operation, Aerodine engineers studied CNCs to produce these and similar parts. Aerodine purchased its first CNC machine, a DMS router with 5ft x 10ft x 4ft travel, and was immediately successful in producing parts with flat surfaces that allowed them to be accurately positioned in a fixture. But every surface in the front wing assemblies is curved, as are other parts produced by Aerodine, so they are much more difficult to accurately align. Machine operators did the best they could, but the inevitable misalignments caused drill bits and taps to continue to crash into the bushings embedded in the composites.
Kyle Castor, patternmaking manager for Aerodine, says engineers were already using Delcam PowerMill to produce CNC programs, so he spoke to Design and Software International, the local systems integrator that recommended and provided PowerMill.
“The reseller recommended Delcam’s PowerInspect part aligner as a tool to help us accurately locate the part prior to machining,” Castor says.
He now opens a CAD model of the part in PowerInspect and uses a mouse to select a series of points that can be used to accurately locate the model in 3D space. PowerInspect then generates a CNC program that runs on the machine tool with a touch probe in the spindle. Each time a new part is loaded onto the fixture, the machine tool control runs the CNC program generated by PowerInspect which determines the actual position of the locator points, compares the results with the CAD model, and performs a best-fit analysis to determine the actual position of the part in the fixture.
“Finally, PowerInspect updates the CNC program to incorporate the actual position of the part,” Castor says. “This approach eliminates the collisions that wasted so much time in the past.”
As Aerodine adopted the PowerInspect location technique, it also switched from using drills and taps for machining the holes to using end mills and threads mills. The new tools increase machining cycle time but reduce the delamination of the composite parts, improving quality. Eliminating the need to accurately position the part in the fixture also saves time. And nearly every part is produced in the specified cycle time of 20 minutes, a reduction of about 90% from the average time required to produce parts in the past.
On another project, a customer asked Aerodine to change three existing patterns used to lay up composite parts. The patterns are about 3f x 2ft x 8ft and weigh more than 900 lb. They consist entirely of curved surfaces without any flat surfaces that can be used to locate them in the fixture. The customer provided a CAD model of an existing pattern that showed the changes they wanted to make, comprising about 30% of the surface of the pattern. The challenge was that the pattern needed to be precisely aligned with the CNC program so that the cuts blended smoothly into the existing curves.
“I estimate that it would have taken about a week using manual methods to position the part in the fixture accurately enough to smoothly blend the needed machining operations into the pattern,” Castor says. “We ran the risk of damaging the part if we made a mistake.”
Using PowerInspect to select points on the CAD model of the pattern to determine its location in 3D space allowed engineers to incorporate position data into the CNC program.
“The result was that we were able to get the patterns located and aligned in only an hour,” Castor says. “This approach made it possible to repurpose the existing patterns at a fraction of the cost that would have been required without this software. We also use PowerInspect to inspect parts and fixtures with complex curves that are very difficult to accurately inspect using conventional measurement methods.
“PowerInspect has dramatically improved our ability to locate and align parts with complex curved surfaces,” Castor concludes. “The result is that we have been able to substantially reduce the time required for part alignment while delivering increasingly accurate products to our customers.”
Aerodine Composites Corp.
Delcam, an Autodesk Co.
IMTS 2016 Booth #E-3222