Spar Winding (Prismatic non-round sections)

The SPAR winding software is found on the QuickCAD main menu (if optionally supplied). This allows the winding of non-round sections of constant or near constant section. The section should not have concave portions, as these cannot be wound successfully.

The program a created by the user specifying data parameters on a single windows dialog entry form, there are three main options:

Low angle winding where the winding paths pass over the mandrel end, this is generally required for wind angles less than about 40 degrees (0 degrees being axial). The software automatically generates the mandrel geometry. Click this link to see the low angle parameters.

High angle winding typically 40-90 degrees is where the end are not over-wound and there is a turning length at each end of the mandrel. Generally if the wind angle is less than 40 degrees the turning length (which may be scrap material) tend to become impracticably long. Note that for hoop winding it is quicker and simpler (and the programs are smaller) to use the Cadfil pipe winding option using the equivalent mandrel radius (spar perimeter/2PI) and ensuring the radial clearance is greater than the maximum radius of the section.

Transition (joining) paths generate a single path program to be created to go from programs of different wind angle and/or start position.

This data entry form includes an entry for the name of the DXF file containing the mandrel section geometry. Rules for creating this geometry are given in the next section.

SPAR Mandrel Generation

The mandrel is generated from a cross section created in a external CAD program such as AutoCAD. The section is supplied in the form of a DXF file. To allow Cadfil to successfully use the DXF file some rules MUST be followed.

The

a) The Mandrel data is defined by a 2D profile in the X,Y plane using lines and circular arcs

b) The axis of the mandrel should be the World Z-axis (i.e. through point 0,0) the mandrel is assumed to rotate about this axis.

c) The Lines and arcs for the mandrel must be joined to form a closed polyline or lwpolyline (use the AutoCAD Pedit or PE command).

d) This polyline must be on a layer called SEC and this layer should contain only one polyline but can contain other data.

e) A clearance envelope for creating the payout path can also be created in the DXF file. The rules for creating the envelope are exactly the same as for the mandrel cross section except that the polyline for the envelope must be on a layer called SNV. In some versions of AutoCAD it is possible to offset a polyline using the OFFSET command. Thus having created a polyline for the mandrel section the envelope can be created with an all round constant clearance by offsetting it outwards, and then moving the new polyline to the SNV layer.

Cadfil has been tested on AutoCAD R12, R13, R14 & 2000 DXF files.

SPAR Winding Dialog and Parameters

There are five button options:

CANCEL to quit doing nothing

HELP to jump into this help file

READ PARAMS to read a set of data parameters created at an earlier time and that were saved to a .PAR data file.

WRITE PARAMS to write the current data parameters on the screen to a .PAR data file.

BROWSE DXF FIILES to select from existing DXF files and add the DXF name to the winding data parameters.

CALCULATE to save the existing winding parameters on the screen and if possible calculate the winding pattern using them, some useful information messages are given to the Cadfil text window, read them!

The numeric parameters are as follows, for further information see below and a diagram for parameters.

Note that dependant on the spar option selected some of the paramneters will be ‘greyed’ that is the user cannot select of enter data. This is because those options are not used and are retained for compatability with different softwar3e options or for future options.

Mandrel X Start and Mandrel X finish. These define the length (X start –X finish) of the winding program and where it is positioned relative to the mandrel origin (the x=0 position). The position of mandrel origin in the machine will depend on the machine datums and the XDAT parameter described elsewhere in this help file.

Minimum Arc length around the section, is the typical spacing of data points along the path on the mandrel surface. For reasonably accurate winding about 8 points per rotation (for higher angles) is more than adequate, however when the user looks at the Cadfil graphics the path will appear not to be smooth. If good graphics are required use a small spacing. Please note that calculate time will be large and the data files and winding programs will be large if the spacing is small.

End Plane X position 1 & 2. These values are used for low angles winding to limit the travel of the mandrel carriage at the mandrel ends and to determine the smallest radial position the cross feed axis can move in to at the mandrel ends. Position one is at the X- end of the mandrel and position 2 is at the X+ end. If these items are grayed they are not required for the winding option chosen. WARNING the machine can move inwards and could clash with the mandrel if the planes are not positioned outside the extremes of the constant spar section.

End hold radius. For low angle winding the payout head moves in to this radial position on the end planes during the end winding and hold this position during the dwell rotation. This value must be greater than the mandrel shaft radius or else there will be a crash.

Bandwidth is the actual width of the fibre band to be used. This is used to calculate the number of carriage circuits required for a layer and is also used for the graphics of the banding structure.

End turning length is the length (at both ends of the mandrel) than can be used to turn the fibre. The fibre starts at hoop and progresses down to the required winding angle. If the software can achieve the required wind angle in a shorter distance it will do so and the length of winding at the required angle will be correspondingly longer. If the length is less than that actually required a warning is given and the wind-angle that is achieved will not be the specified wind angle, the wind angle that is achieved is reported to the Cadfil text window.

Friction coefficient is used to determine how quickly the fibre turns, a high value makes it turn faster and visa-versa. A value of about 0.2 is good for most purposes. If winding with pins on the mandrel near the ends use a very high value to turn the path quickly just outside the row of pins. Please not, Cadfil cannot defy the laws of physics, wishing for a high friction value to turn a path quickly will not make the impossible possible.

Wind angles, is the value in degrees that the user requires in the central portion of the wind path i.e. the total length excluding and turning zones. The Low angle option does not have a turning zone as the fibre turns on the mandrel ends thus the wind angle is fully upto the mandrel end.

DXF file name is the name of the DXF files to use, use the browse button to aid selection and please read the notes on the DXF format required.

Payout clearance and mode. There are two modes available at present, constant fibre length i.e. the distance between the point the fibre touches the mandrel surface e and the fibre dispensing point remains constant, and a constant radial position (except in the end zones where end plane positions are specified). The mode is selected by clicking the appropriate radio buttons. Note that for constant fibre length, because the section is non-round the cross feed will move in and out as the section rotates. This leads to slightly slower winding and more wear and tear on the winding machine, it does however give better control when this is needed.

Additional dwell End1 (and End2). At the ends of the winding (for turning on the mandrel) there will be some dwell to achieve a structured band pattern. For the purposes of reliable tie down of the fibres at the ends it may be necessary to specify some additional dwell. This value is the DISTANCE of addition dwell around the section. End 1 is the X- end and end2 is the X+ end.

Mandrel Direction check box. If ticked (default) the program is generated such that the mandrel rotates in the positive direction.

Payout Clearance drop-down box. This currently has three options for creating the payout path. There are:

A constant radius (no cross feed will be used except on the end planes), the radius is the value from the payout clearance box. Because the crossfeed is not used there is potential to wind faster with this option but control not ber as good as with the DXF option.

A constant fibre length, this being the distance from the fibre on the mandrel to the payout head, i.e. the free fibre length. The value is taken from the payout clearance box. This method is not recommended for low angle winding as the length must be long to give clearance and if a short length is used the payout head may be very close to the mandrel surface.

Envelope from the DXF file (which must having been previously defined. See the pervious section for details of the DXF option. This option gives the potential for the best machine control.