Machining Composites: Errors Cost More Because They Are Harder to Fix
Andrew Wheeler posted on July 19, 2017 | 2946 views

In the world of CNC machining, one could argue that making cuts to composite workpieces requires the most complete validation possible of the part program prior to its execution. The reason being: if an error is made during the trimming of a composite workpiece, the ability to repair it is diminished by the amount of tedious and methodical work needed to prepare it for machining in the first place, along with the workpiece’s complicated material structure.

Composites differ from other commonly machined materials (like metals) because their structure is assembled with a larger degree of materials that react unpredictably when cut. CNC machining can be thought of as “breaking” block materials down instead of cutting them into sections.

The more attuned and predictive the part program is to the material properties of a given composite, the better the actual result will be compared to the desired post-machining outcome. Given the amount of reactive variables there are in composite materials such as fiber and resin types, it is advantageous topossess software that can accurately verify and simulate the effects of each cut or “break,” as well as the matrix hardness, part construction (solid laminate versus sandwich) and heat sensitivity of composites.

Remember that in the supply chain, composites fundamentally differ in the sense that they are manmade materials, not mined materials(such as metals). Metals are easier for CNC machines to “break” or cut because of the natural geometry of their crystalline structures. Metals also have more natural stress and fracture lines, which cause them to naturally break in more uniform pieces at the hands of machine tools or waterjets, as opposed to composite materials.

Therefore, the importance of software that accurately verifies the part program and performs simulations of the way a CNC machine will make cuts becomes crucial when machining composite materials. Since the risk of delamination and breakage is harder to predict with composite materials, machinists must carefully account for many more variables than if they were cutting metals.

Allowing machinists to input the specific combination of material variables into VERICUT’s Composite Simulation improves users’ ability to detect collisions and verify specific actions like course stagger, reducing the probability of costly errors. (Image courtesy of CGTech).
Allowing machinists to input the specific combination of material variables into VERICUT’s Composite Simulation improves users’ ability to detect collisions and verify specific actions like course stagger, reducing the probability of costly errors. (Image courtesy of CGTech).

There is an upcoming Composite Applications conference during the Composites and Advanced Materials Expo (CAMX) in Orlando, Florida where CGTech (the company that created VERICUT software) will exhibit both VERICUT Composite Simulation (VCS) software and VERICUT Composite Programming (VCP) software.

This will give attendees a chance to see how a CAD model of a composite part becomes ready for production, and visitors will have a firsthand view of the steps needed to transform a CAD model into an actual composite part. They will also be able to observe how VERICUT is used for verification and simulation with Automated Fiber Placement (AFP) and Automated Tape Laying (ATL) machines.

Customers at CAMX won’t have a shortage of interesting exhibits to explore. Some of the topics include the prolific use of ultrasonic knives, robots, lasers, and probing to highlight the adoption of independent NC programming software for AFP and ATL machines, including the 16-tow Electroimpact AFP machine being utilized by NASA's Langley Research Center.


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