The Lowdown on Layups

Why automated composite manufacturing is the clear path towards better quality and greater throughput

Manual layup of composite material is slow, painstaking work. A layup expert must apply the right pressure to the workpiece, assure even coverage and consistent layer thickness, and be certain to vary the material direction sufficiently that structural integrity is assured. Those who master such an activity are true artisans, and without them the composite industry would not exist.

Yet there are times when manual layups either don’t make sense or are downright impossible. Large aircraft structures, high-volume automotive and consumer components, energy and military applications are just a few of the areas where humans struggle with production and quality demands, no matter how skilled they are. Further, many of the products for these industries require extensive traceability and in-process build monitoring, and consistency impossible to achieve without automated processes.

Difficult decisions
But how can a robot or CNC machine replicate the complex motions of a human hand, one driven by an experienced human brain? True, automated machinery can bend, weld, form, and cut virtually any material with ease, but are they able to cost-effectively replace their flesh and blood counterparts in any but the most difficult components? And what about situations where a “personal touch” is needed to get into a tight corner, or make a judgement call on a complex geometry? With the cost of some automated systems upwards of a million dollars (and oftentimes a great deal more), it might be easiest to set aside these difficult questions and just go with what you know.

Andrew Purvis, project manager for automated fiber placement at Electroimpact Inc., a factory automation and tooling solutions provider in Mukilteo, Wash., says that might be a mistake, noting that Automated Fiber Placement (AFP) and Automated Tape Laying (ATL) processes have improved mightily over recent years, and if you haven’t taken a look lately, now might be a good time to reevaluate.

“Certain aspects of AFP and ATL aren’t just a little bit more productive than they were a few years ago, they’re easily five times more productive,” he says. “Thanks to what we’ve learned while working with companies such as Boeing on their 777X wing skins, for example, and the advanced layups heads that we’ve developed as a result, there are definitely things we can do now what were previously not possible or cost-effective. In terms of material deposition rates, quality control, and even on the raw material side, the technology as a whole has really advanced.”

Making the case
Still, for those managers faced with putting their reputations (and possibly their jobs) on the line over a hugely expensive, complex, and still relatively novel manufacturing method, it’s a tough call. Aerospace companies with fuselage and layup tools larger than a suburban house have little choice but to embrace such technology, but for manufacturers of smaller, simpler composite components that are easily managed using conventional layup techniques…not so much. Lot and part size, tolerances and inspection requirements, manufacturing difficulty, and especially budget—all must be evaluated before an automation discussion can even take place.

When implemented correctly, however, the ROI on such an investment becomes clear. Purvis lays down the following reasons why, when, and for whom the decision to automate makes sense:

  • Deposition floor to floor rates of 65 to 120 kg. per hour (176 to 265 lb.) are achieved on wing skin type parts. That is several times greater than what was possible a few years ago. Also, layup consistency is far better than what can be expected from a human worker. And if an area needs tweaking, that adjustment can be programmed into the system and repeated on every part thereafter, or even applied to similar features on other parts.
  • Use of unidirectional slit tow material can lead to a lighter higher performance part, with lower per part material costs when compared to a cost of a equivalent kit of plain weave hand layup material.
  • Machines don’t care about irritating fumes or the possibility of cancer. Manual processing of composite materials presents health risks due to repetitive motion, exposure to chemicals and lack of ergonomics. Some materials such as PEEK (polyether ether ketone) carbon fiber require the use of a laser or flash lamp for material consolidation, potentially causing eye damage if the proper safety precautions aren’t taken. Worse, the risk to human workers is only going to increase as composite material use becomes more prevalent, making automated equipment the safest choice.

  • Some automated machines are equipped with modular process heads that can be automatically changed midstream. This provides the ability to lay down different materials and even different material forms in the same job, or switch to an ultrasonic cutting head to trim the completed layup, create windows, or cut out nested preforms, and so on. This type of modular system allows for future flexibility in terms of laying up different parts.
  • It is now possible to have real-time inspection and analysis systems monitor layup quality as the part is being built. If there is a problem like a misplaced tow in a critical area or an incorrect overlap, an operator can be alerted to intervene. Laser projectors are now integrated into the machine control and highlight the exact location on the part that needs attention. This makes repairs of the affected area much easier and less costly than after the fact. Also, in-process build data is continuously collected so that a historical record of the build process can be maintained for traceability.
  • Automated machinery makes material placement, overlap, toe twists, layer thickness, and other process variables more controllable than with manual layups. This allows for precise tuning of the layup technique and programming method. Thus insuring adherence to AFP or ATL process specifications for a range of commercial or military aerospace programs.

    Purvis admits that manual layups aren’t going away anytime soon. Low volume and prototype parts will continue to be produced using traditional methods, as will smaller, suitcase-sized and smaller parts, or those with simple geometries and less stringent quality requirements. But for the increasing number of production or mission-critical parts, he encourages people who may have evaluated AFP and ATL technology in the past to take a second look.

    Loading the shopping cart
    Okay, great. But where do you start? After all, this isn’t like picking out a new car at the auto mall. For starters, once you’ve determined the size and type of machinery needed (or whether you need a machine at all), Purvis says it’s important to evaluate the various options. Aside from the in-process inspection and modular process heads just mentioned, any new system should have a robust programming system, one that integrates well with the machine and is hopefully machine manufacturer neutral.

    This is one reason why Electroimpact partnered with California-based software provider CGTech. Rather than develop their own CAM functionality, Electroimpact management decided it would focus on the company’s core strengths—machine and process development—and leave the rest to someone who specializes in programming and simulating of automated composite layup machinery.

    “Why would we try to reinvent the wheel when there was already a system available that does everything our customers needs?” Purvis says. “That, and it doesn’t take a genius to know that machine independent programming tools are the way to go, regardless of the type of manufacturing you do.”

    Get with the program
    CGTech composites product manager Andre Colvin agrees. He says the company has offered programming and simulation software supporting a wide array of AFP and ATL machines for more than a decade, and is the most successful machine-independent solution available. The VERICUT Composite Programming system (VCP) also supports ultrasonic knife cutting, probing, and laser inspection, and is compatible with virtually all of the CAD providers in this arena.

    “We’ve configured nearly every type of composite-laying robot and gantry machine out there,” he says. “That being said, it’s far from a cookie cutter solution. Almost every single system made has its own special quirks or some sort of special features that were added for the customer and their unique situation. Also, the technology is evolving so quickly that you might buy a robot today and three months later the technology has changed again. Every project and every implementation is a little bit different, and there’s usually some time and effort needed to get everything behaving as expected. That’s why it’s important to partner with a company that thoroughly understands the industry, and can support both the hardware and the software.”

    Another thing that’s important is accurate simulation. A virtual simulation can tell you a variety of mishaps before they happen, such as if the backside of your layup head will interfere with the workpiece as it rounds a corner, that you are going to exceed the machine’s X-axis travel halfway through the build, or that the ultrasonic knife is going to crash into a fixture during the trimming process.

    Simulation goes well beyond crash protection. The programming software VCP also allows for various checks to ensure the part is conforming to customer specifications by offering a variety of different analysis tools. And because the simulation software VCS reads the actual G-code used by the machine control, the programmer can feel confident running their part programs on the equipment in real life.

    The big wrap up
    “If I had just bought a five-million-dollar machine, I’d want to protect it,” Colvin says. “But to me, the biggest benefit of an automated system—and VCP is a big part of that solution—is that it eliminates the variability of manual layups, where the engineer is left powerless. Instead of leaving it up to one technician versus another technician to try eyeballing how much material he or she is laying down, and then rotate the strip to the exact angle that they think is correct, these systems can control with great accuracy how much material is being applied, where and in what direction, how much stress there is in a given area, and do so day after day, job after job. Scrap is reduced, the parts are better and more consistent, and throughput is predictable. Like Andrew said earlier, ATL and AFP machines aren’t for everyone, but if you’re looking to grow your business, you should definitely take a look.”