Overview of Mandrel & Envelope Creation

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For rotationally symmetric shapes the first stage in generating winding programs is to create a mandrel file defining the shape to be wound. At the same time the user can create a mandrel envelope. This is described in the section entitled Editing of Mandrel and Envelope X,R Data. The mandrel and envelope data are saved in a text file with the .mnd file name extension

A mandrel definition consists of X,R data co-ordinates defining the surface. The user needs to define sufficient points to have a reasonable representation of the curvature of the mandrel profile. There are a few points to note:

• Fine detail such as small internal (concave) blend radii are not required and indeed can prove counter productive.
• It is usual to divide the mandrel such that (for example) long cylindrical sections are split into lengths of not more than about 10 diameters.
• Consider where the X=0 position is for the mandrel, this is the datum position for the mandrel. The mandrel must be located with reference to the winding machine datum. This is discussed further in post-processing under the heading XDAT- Carriage Axis Datum.
• The positive X-axis direction of the mandrel must be in the same direction as the positive direction of the machine carriage axis.
• A mandrel envelope is a clearance surface around the mandrel on which the fibre-dispensing head will move. It is defined in the same way as the mandrel shape. When creating an envelope the user should consider several things:
• It gives better control to have the dispensing head close to the mandrel at all times.
• If clearances are too small test winding will be worrying! Also, on some machines there may be small positional errors as the winding speed is increased so beware.
• The programmed position is for the centre of the dispensing eye or roller. If this has a large width this must be reflected in the envelope or a crash may occur on the corners at the mandrel ends when moving in.
• It is best not to have too many points or a more complex envelope than is necessary.

Cadfil will automatically create a default envelope if the user does not create one. This may not be always be ideal it is best to check.

Mandrel and envelope data can be created by importing a DXF file created in a CAD system such as AutoCAD this is described in the following section.