CAM for Composites: Today and Tomorrow
Composites makers who take advantage of new and emerging CAM software capabilities will surge ahead.
By Gary Hargreaves
Vice President--Business Development
By Karlo Apro
Product Marketing--Technical Manager
The breathtaking acceleration of composites manufacturing in aerospace and defense as well as other markets makes it a daunting task for manufacturers to stay current with newly commercialized or emerging CAM software technology. What makes this task particularly difficult is that CAM software has been evolving at a frenetic pace that is more or less equivalent to that of composites manufacturing. If it has been a year or more since a composites manufacturer has taken a look into how CAM software might be employed to improve manufacturing consistency and productivity while reducing costs, he may be missing out on some important developments.
During the past decade, the superior strength-to-weight ratio, corrosion resistance and insulating properties of composites has created an increasingly high demand on these constructions. That makes it necessary to drive manufacturing processes away from those with high levels of labor content to ones that are increasingly reliant on automation and computer aided manufacturing. Today, the most frequent application of CAM technology occurs in the following areas:
- Trimming of the finished parts (molded parts, tape layup parts, etc.)
- Drilling and fastening
- Milling of molds (for either forming or tape layup)
- Milling of jigs for trimming
- Spraying (fiber chop spray, resin spray, etc.)
These operations are performed on a variety of manufacturing equipment including mills, lathes and robots along with specialized systems for material layup (an emerging application area for CAM software and equipment). Here are some of the most recent CAM software developments that impact composites manufacturing with these systems—starting with trimming.
Composite parts cannot be manufactured by laying materials up to the edge of the component because fibers protruding from the material would make for rough edges that are unacceptable in terms of both fit and finish. As a result, efficient external edge trimming is an essential manufacturing step. Internal trimming is also required to cut openings for doors, windows, and subcomponents such as landing gear and sensor mounts. A great deal of time can be lost unless fixtures and processes used for trimming can be made as efficient as possible because the aerodynamic nature of many composite free-form structures makes them best trimmed using five-axis equipment.
Integration with CAD: Efficient trimming operations begin not by creating five-axis toolpaths but by using the CAD model to develop a holding solution that will allow the cutting tool to reach all of the areas designated for trimming. These jigs are created in an iterative process that alternates between creating holding fixture solutions and then simulating tool and machine movements to ensure both secure holding and optimal reach of the tool so that trimming can be performed in one or two setups.
When manufacturing process developers find themselves switching frequently between the CAD and CAM environments to perform successive simulations and design modifications, then it can be very useful to have a software solution in which CAD and CAM can be instantaneously accessed from the same operating environment. For example, Mastercam for SolidWorks (from CNC Software) resides as a menu within the SolidWorks CAD environment. Users can access nearly all of the product’s five-axis CAM functionality without ever leaving the CAD system. Changes instituted in one mode are automatically recorded in the other because both are working from the same model. This approach can streamline development of fixtures as well as create molds that are used in composites molding and layup processes.
Oscillate Five-Axis Toolpath: One of the biggest impediments to date in creating efficient five-axis trimming toolpaths has been the problem of tool wear. Composite structures can be very hard and abrasive. What’s more, trimming requires the tool to travel continuously along a narrow edge, not only wearing the tool, but also creating a groove in it. A new five-axis toolpath developed specifically for edge trimming continually oscillates the tool as it moves along the edge. This action spreads wear over a long section of the flute so that the tool wears gradually and the problem of grooving is eliminated. With this approach offsets are far more accurate and tools can last up to 10 times longer.
Safe Transitions: To ensure that the tool can make a rapid move without crashing into the part, it is possible to set a safety zone that allows the tool to retract to the shortest safe distance before moving to the next location for engagement. Safety zones, however, do not prevent all potential crashes during these transitions. A crash is especially likely to happen when “rapiding” the tool creates a dogleg (an L-shaped move that occurs when the X and Y axes are traveling at the same speed but over different distances). In this case one axis will arrive at the required distance before the other and the tool will be travelling off-course until it corrects at the end of the move. A new Safe Link option presents an alternative to this loose transitioning, allowing the user to specify a controlled move that travels almost as quickly as a rapid move, but in a straight line.
Trimming Air Cuts: Toolpaths frequently assume that shapes will be cut from a block of material. When that block is not there at the outset, as in the case of a forging or a part that only needs to be trimmed, there is a significant amount of cutting action that happens in empty space before the tool actually enters the part. If the software has a “trim-to-stock” option, the user can use the CAD model to create a stock model in CAM so that the cutter will adhere to it and eliminate most of the air cutting.
Better Tool Management: Good CAM software gives users the capability to manage all of the tools that might be used for various projects. Tool management capabilities may incorporate the ability to:
- Incorporate many tool databases supplied by tool manufacturers
- Update databases as tool specifications change
- Virtually construct assemblies incorporating specific tools, holders and “stick out” dimensions
- Create libraries for specific applications, machines or groups of machines
While this functionality is important, there is no reason it should tie up a CAM seat. To this end, the most recent version of Mastercam (X7) makes its Tool Manager available as a stand-alone module that can be used independently from a CAM seat (right at the tool crib, for example).
More Processing, Less Waiting: Where we work, nearly everyone has two monitors on their desk. That’s because, for the past several years, the standard CAM software we use routinely to explore customer applications and solve manufacturing problems is multithreaded. While the software is generating a very complex toolpath, it can also be performing a simulation, or be used to write another CAD program. Multithreading means that people no longer have to wait for their computer to complete complex tasks before they can move on to something else they need to do using the software.
The Importance of Proactivity
Engineers and manufacturing supervisors rarely have time to accomplish everything they would like to get done. That is why it is so easy to put off taking a little time to review, understand, and implement some of the new capabilities that arrive in the latest version of their CAM software. We understand there are many other demands on manufacturers for their attention, and we are no longer surprised when manufacturers of all types approach us with requests to provide them with capabilities that are already present in their software package and have been for a long while. Time ticked by when they could potentially have been saving time and money. It only takes a fraction of those savings to stay abreast of the latest developments in CAM.
The trade press is currently full of predictions for explosive growth of composites applications in the coming decade. Composites manufacturers who invest some time to understand and take advantage of emerging CAM capabilities will surge ahead on the opportunity that is predicted for them. Make your company one of the successful ones. ✈
This article was first published in the 2013 edition of the Aerospace and Defense Manufacturing Yearbook.