An example of a situation where a specific wind angle is required is discussed below. Consider a cylinder with domed or cone ends (or some other shape of reducing diameter). The user wishes to generate ±30 degree winding on the cylinder but is not concerned about the end opening diameters at the cone end. Referring to the previous section on starting the fibre path the user can use the CURSOR option to approximately fix the path start location on the cylindrical section of the mandrel near the cone end. The start angle can then be specified using the ANGLE option. In this case, as we wish to pass over the cone end first we specify and angle of 150o, (180-30=150, refer to figure). The fibre can then be advanced one segment at a time menu using the ACTION option. Setting STEP to a larger number (5 or 10 for example) will speed things up.
As the fibre advances down the cone the winding angle displayed will be seen to change and eventually the fibre will turn around. Thus the first hoop point has been fixed. This position will later be the start or tie on position on the winding machine! The fibre angle will then increase and then due to geodesic theory when the path is back on the cylinder the wind angle will be 30 degrees. There may be a small angle change e.g. 0.1 degrees, due to the fact that numerical methods are used. Larger changes may be seen if the mandrel is poorly defined (very few sections and/or few elements per revolution - see the sections on mandrel meshing).
The fibre will now advance (with ACTION) along the cylindrical section of the mandrel and will turn around on the dome end. Once the fibre has turned around the second hoop point has been defined and the path is complete. The fibre should always be advanced at least three segments past the point where it is seen to turn, as this allows the software to accurately locate the turning point at a later stage. If this is not done an error will be given during payout path generation.
The path can now be saved and the user can exit and proceed to the payout path generation.