The article examines the development of Automated Tape Laying (ATL) as a manufacturing process for layering material, known as prepreg tape, onto a mold surface in a specific direction to build up layers. The process is similar to additive manufacturing, or the reverse of machining, as material is added rather than removed. The development of these systems has a long history, starting with the use of carbon fiber in aerospace manufacturing in the 1960s. The article discusses the various developmental stages of ATL and explains why they function in their current form and why they may not be in high demand.
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Historical Developments of Automated Tape Laying: 1960-1980
In 1966, carbon fibers became commercially available, which led to early efforts to automate prepreg layup to improve productivity and quality
Automated tape laying (ATL) systems were developed in the late 1960s and were in use by the mid-1970s
In the 1970s, aerospace manufacturers and research institutions developed early ATL systems
In the 1970s, ATL layup speeds of 10-20 m/min were reported, with improved material utilization and reduced layup errors.
Materials were wasted 50-100% at the time of the 1980 manual layup, with a productivity estimate of 1 kg/h
For certain components, ATL was able to reduce material waste and layup time by 65% compared to manual layup
Automated Tape Laying Development from the 1980s to 1990s: Challenges and Advances
In the early 1980s, ATL technology was changed to a generic process and layup speeds were increased to 60 m/min with new systems
ATL machines at that time were mostly Flat Tape Laminating Machines (FTLM), which could only apply tape to flat tools
Robot arms were used for layup applications but had speeds limited to 60 m/min and required high accuracy for offline programming
Many ATL systems became high-rail gantries that were stiff and heavy, with difficulties in delivering tape with defined compaction pressures and regular debulking cycles
By the end of the 1980s, increased layup capability led to issues with ply alignment due to uneven layup pressure and tape tension on the head
To prevent transverse movement of the ply and improve alignment, systems were developed with controlled tension and layup pressure
In 1995, the approach was extended to multiple layup elements operating independently from the layup head
The aim of using layup pressure control became mainly focused on reducing debulking operations,
Material outline and changing tack levels remained unresolved, and actual layup speeds remained unchanged at 10-20 m/min
Commercial aircraft adoption was slow during this period due to the high cost of ATL systems (estimated at $3.5M for basic systems) and high productivity requirements.
The end of the 1980s showed no significant improvement in productivity for an automated layup over manual forming, but automation was still desirable as it improved reliability, consistency, and reduced material waste
Automated Tape Laying development from the 1990s till today
Tape heating was introduced in the 1990s to improve laminate layup and control tack
The first thermoplastic layup used tape heating in 1991, and a hot-air heater was added to the ATL to enable tape attachment to complex contours
To keep plies aligned during layup on complex geometries, the layup roller diameter was decreased to 50 mm in order to improve dexterity.
There was no relationship between layup pressure and the number of plies during thermoset tape layup, while ply orientation and roller diameter were weakly related, although tack was not included in the study.
In order to lay up and consolidate thermoplastic materials directly, laser-assisted heating of thermoplastic tape was proposed, but AFP was adopted instead.
Today, ATL layups are in very limited usage in aerospace and renewable energy industries owing to their high initial capital expenditures, limited geometric complexity capabilities, and higher material wastage rates than AFPs.
ATL (Automated Tape Layering) Process for Prepreg Layup in Aerospace Manufacturing
Automated Tape Laying (ATL) is a manufacturing process in which a continuous sheet of material, known as prepreg tape, is added to a mold surface in a specific direction to build up layers in different directions, resulting in a layup. The process can be thought of as a form of additive manufacturing, or inverse machining, as the material is added rather than removed through machining.
Prepreg tape is used in ATL, typically 75, 150, or 300 mm wide, and supplied on a cardboard core similar to prepreg used for a manual layup
ATL systems are mounted on horizontal gantries or vertical columns and are CNC systems that follow predefined paths accurately and reproducibly to eliminate layup errors
The tape is adhered to the mold or previous layers without any air voids using a flexible silicone roller or segmented laying shoes.
The layup speed is typically 0.83-1 m/s, with compaction of 445 N for 75 mm wide thermoset tape or 1000 N for 300 mm wide thermoset tape, and pressure of 0.1 MPa for thermoset material or 1.4-3.6 MPa for the thermoplastic material.
In order to improve alignment, and enable layup into curved geometries, tension is imparted on the plies and ply backing between the material supply and layup point.
Material can be heated during layup to control temperature, either in front of the layup head or on the layup system as it is passing through the ATL head
At the end of a ply course, the tape is cut using rotating or ultrasonic blades, and the remaining length is delivered to finish the ply course
The process is repeated until the ply is finished, or stopped by the program, user intervention, or an automated fault detection system.
In conclusion, the development of Automated Tape Laying (ATL) has evolved significantly since its inception in the 1960s. From its early beginnings as a process specifically developed for carbon fiber and aerospace manufacturing, the technology has undergone numerous changes and advances. In the 1980s and 1990s, challenges such as high layup speeds, difficulties in delivering tape with defined compaction pressures, and limited heating capabilities were addressed through the development of new systems and technologies. In the years since, ATL has been further refined and diversified, with a focus on increasing productivity and addressing specific layup issues. Despite the significant progress made in the field, ATL Today, they see very limited usage in aerospace and renewable energy industries owing to their high initial capital expenditures, limited geometric complexity capabilities, and higher material wastage rates than AFPs.
Addcomposites is the provider of the Automated Fiber Placement (AFP) ecosystem - including the Fiber Placement System (AFP-XS), 3D Simulation and Programming Software (AddPath), and Robotic Cells (AddCell). With the leasing program for the AFP system (AFPnext), composites manufacturers can work with thermosets, thermoplastics, dry fiber placement, or in combination with 3D Printers on a monthly basis.