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How to Upgrade your AFP System with Filament Winding Capability?

Updated: Jan 20

Introduction

This article discusses the similarities and differences between automated fiber placement (AFP) and filament winding technology and introduces AddPath software as a solution for converting an existing AFP system into a filament winding system. The article explains that both AFP and filament winding use multiple narrow tows instead of a wide tape, and that tension control is important in both technologies. However, filament winding has the ability to be programmed for winding, which has not traditionally been possible with AFP systems. The AddPath software allows for the conversion of an AFP system into a filament winding system, enabling the use of the system in a more flexible and efficient way.


Jump to the right section

  1. Introduction

  2. AFP Process Description

  3. Filament Winding Process

  4. Limitations of Filament winding

  5. AFP Systems: Enhanced Filament Winding Systems with Increased Control

  6. Enhanced AFP Systems: The Advantages of Using Them as Filament Winding Systems

  7. Converting Your AFP System into a Filament Winding System: A Step-by-Step Guide

  8. Summing Up: How to Enhance Your AFP System with Filament Winding Capabilities


Introduction

AFP Process Description

In an automated fiber placement process, an AFP head is attached at the end of an industrial robotic arm that is simulated and programmed using digital twin software like AddPath. As the AFP process is running, the head moves and places multiple strips of composite material tapes, or tows onto a tool surface. It is crucially important for the tape/tows to adhere with minimal defects. To ensure adhesion between incoming tows and substrate the fiber placement head utilizes heating and compaction. Tow tension plays a key role in ensuring the accurate placement of the tow. Each row of tows forms a course. Put together in a surface slice the course forms a ply, and all plies stacked together in a precise sequence form a laminate.



Filament Winding Process

Helical Filament Winding Application [1]
Helical Filament Winding Application [1]

Continuous fiber tows are fed through a fiber delivery system to the filament winding machine, where they are wound onto a mandrel in a predetermined, repeating geometric pattern. The tow location is guided by a fiber delivery head, which is attached to a movable carriage on the filament winding machine. The relative angle of the tow to the mandrel axis, called the winding angle, can be tailored to provide strength and stiffness in the desired directions. When sufficient layers of tow have been applied, the resulting laminate is cured on the mandrel. The overall size and shape of the finished part are determined by the mandrel shape and thickness of the laminate.


Video 1. SM+ Filament Winder Commissioning Video (Source: Engineering Technology Corporation)


The winding angles will determine the mechanical properties of the composite part, such as strength, stiffness, and weight. The density of the laminate is the result of the tension of the tows during winding. The composite parts made through these methods generally have good strength-to-weight properties.


Limitations of Filament winding

The FW process has several disadvantages, including:

  • Issues with fiber sliding and fiber bridging, which can result in uneven thickness and strength in the finished product and make the fibers easy to break away from the mold

  • Limited freedom in fiber placement direction due to geodesic or quasi-geodesic trajectories

  • Difficulty implementing fiber placement on concave surfaces due to the influence of winding tension and the requirement for positive Gaussian curvature on the mold surface

  • Difficulty evenly covering the mold surface with continuous fiber, which can affect the mechanical properties of the final product

Modern automated Fiber Placement (AFP) addresses these issues through four successive procedures: mold design, placement path planning, post-processing, and motion simulation. More on this in our blog section.

AFP Systems: Evolved Filament Winding Systems with Increased Control

AFP and filament winding technology share a common history. When AFP was first developed, it borrowed elements from both ATL and filament winding. Both technologies use multiple narrow tapes or tows, but AFP systems also offer precise tension control over each individual element. This allows for greater control during the manufacturing process. In this sense, AFP systems can be thought of as fine-tuned filament winding systems.


Recent advances in robotics and a decrease in the cost of accessing AFP systems have made them more accessible to manufacturers. This has made it possible for manufacturers to choose an AFP system over a filament winding system.


Enhanced AFP Systems: The Advantages of Using Them as Filament Winding Systems

Filament winding is a widely used composite manufacturing automation approach in the industry. Its advantages include the use of easily accessible raw materials (such as dry strands and two-part resins) and a well-established base of knowledge and experience in the market. These factors make filament winding an attractive choice for applications that are cost-sensitive and do not require high performance.

Enhanced AFP systems, when used as filament winding systems, offer several benefits, including:

  • Production of dry tape wound products that can be infused and cured later

  • Production of thermoset or tow-preg wound products for autoclave curing

  • Production of thermoplastic wound products using in-situ or post-cure approaches

  • Production of UV-curable tow-preg wound products that are ready for industrial use


Depending on the geometry, an enhanced AFP system can be used as either a tape winder or a filament winder. In the case of a tape winder, compaction is applied to the mandrel and the fiber trajectory is steering-controlled. In the case of a filament winder, tension is controlled away from the mandrel and the fiber trajectory is friction coefficient controlled.


Converting Your AFP System into a Filament Winding System: A Step-by-Step Guide

Converting an AFP system into a filament winding system is a straightforward process. There are two key aspects to consider: tension control and planning.


Tension control

To use an AFP system as a filament winding system, the user must have digital control over the AFP tensioner. This is standard on AFP-XS systems and can be enabled with an over-the-air firmware update. This allows the program to specify and control tension parameters during the filament winding process.


Planning

Most AFP planning software does not have filament winding functionality. AddPath is open-access software that can be downloaded for this purpose. It includes all the standard AFP planning options, as well as a module for fiber placement on open tube shapes. The AddWinding module in AddPath enables filament winding features such as differ