Overview of AFP and ATL
Today’s automated composite layup machinery and software has many similarities with the state of the CNC metal-cutting industry of the 1950’s and 60’s. The technology is difficult to adopt for all but the largest manufacturers because of the high infrastructure costs. The process technology is complex and only understood by few. Software is generally provided by machine manufactures, with different software required for each machine brand, resulting in limited software implementation and advances.
In the same way cutting speed in “centimeters per minute” is boasted by manufactures of high-speed CNC milling machines, manufactures of Automated Fiber Placement (AFP) and Automated Tape-Laying (ATL) machines promote composite material application rates of “kilograms per hour,” while often ignoring other significant process complexities that must be addressed in order to lay-up parts quickly. The parallels don’t end there however; just as Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) software must continually evolve with new machining techniques, the software for programming AFP machines must also evolve to handle advances in technology. Software that narrowly supports one brand, vintage, or model of AFP machine, quickly becomes inapplicable and obsolete.
The most obvious difference between AFP and ATL is the width of material placed on the form. This directly affects the parts producible with each process as well as the manufacturing edge of part. For AFP, which usually deals with material 1/8" to 1" wide, each tow is cut perpendicular to the length of the tow. ATL features much wider material, usually at least 3" but sometimes up to 12" wide. Another distinguishing feature of ATL is that the cut end of the material can be shaped to the placement boundary, which can reduce scrap and reduce time for downstream processes like composites trimming.
The most widely used material for ACM is preimpregnated carbon fiber ("pre-preg"), which, after it is placed on the layup form by the NC machine, undergoes a curing process in an autoclave. For pre-preg, the layup process is aided by slightly heating up the material to tack it into place until it can be completely cured with much higher heat and pressure. Usually, an infrared heater is used to slightly heat up the material like this, which you can see in the picture above.