# Calculation of program start position

If the reference point data given in the machine data file (.SM) is correct and if the XDAT and payout extension values (POELEN) specified by the user are also correct, then the automatic start point will be correct.

If any of the above data is incorrect, the command for the motion to move to the program start position is useless. The possibility of the payout arm crashing with the mandrel exists if the program is used to move to the start position as intended.

This section shows how the start point is calculated from the data supplied to the program. It is intended as an aid so that the user can check if he wishes to.

For the Linear axes (carriage, cross-feed and Vertical):

SP_AX_4 = OFFSET-AX-4 + (POS-AX-4 + XDAT) *\$GEARING-AX-4*\$AX-STATUS-4

SP_AX_5 = OFFSET-AX-5 + (POS-AX-5 + POELEN) *\$GEARING-AX-5*\$AX-STATUS-5

SP_AX_6 = OFFSET-AX-6 + (POS-AX-6) *\$GEARING-AX-6*\$AX-STATUS-6

For the Rotary axes (Mandrel, eye-roll, eye-yaw):

SP_AX_1 = OFFSET-AX-1 + (POS-AX-1) *\$GEARING-AX-1*\$AX-STATUS-1

SP_AX_2 = OFFSET-AX-2 + (POS-AX-2) *\$GEARING-AX-2*\$AX-STATUS-2

SP_AX_3 = OFFSET-AX-3 + (POS-AX-3) *\$GEARING-AX-3*\$AX-STATUS-3

Where:

SP_AX_n is the computed absolute start position off the winding machine for axis n.

OFFSET-AX-n is the machine constant from the reference (home) position of the machine to the spindle datum for axis n.( See OFFSETS )

GEARING-AX-n is the relation between mandrel units and machine units (see post-processor configuration)

AX-STATUS-n takes the value -1,0 or 1 depandant on the postive direction of axis the machine with respect to sign convention used in CADFIL for axis n (zero indicates the axis does not exist on the winding machine).

XDAT and POELEN are values that are usually requested each time a file is post-processed. If the Payout eye (the fibre dispensing tool) is never changed on the machine then the offsets can be set up so the POELEN is always zero.

XDAT is to position the mandrel in the machine. It is from the spindle datum to the mandrel datum (origin) It is in mandrel units.

POELEN is the length of the payout eye (roller/ comb/ etc), it is in the mandrel units.

POS-AX-n is the start position of the fibre track relative to the mandrel origin, in the mandrel axis system and units for axis n.

In addition to the linear axes (carriage, cross-feed, vertical), there may also be some eye-roll or eye-yaw motions. These assume an origin for the motions. The zero position for these rotational axes is a function of both the machine and payout eye orientation in the machine. Some machines have a zero position, whilst on others the zero position must be set when the machine is started up.

Cadfil has an internal zero position assumed for the 'eye-roll' axis (axis-2). This is as follows; imagine the cross-feed axis is horizontal; the fibre is being dispensed from a roller; and the axis of the roller is vertical. The zero position is with the fibre coming of the positive carriage motion side of the roller i.e. the side of the roller that is in the carriage axis positive direction. In this case for normal winding (which starts at hoop) in moving to the start position the eye-roll axis will rotate either + or - 90 degrees dependant on the direction of mandrel rotation. As a consequence the majority of winding machines have a \$OFFSET-AX-2 value of +90 or -90 (or the equlvaent in the machines units)

The eye-Yaw axis (axis-3) zero position is assumed to be in the straight 'ahead' position, that is with the payout arm normal to the winding axis this Cadfil Zero can be modified to suit the winding-machine setting \$OFFSET-AX-3 in the .SM file.

Depending on the machine the user may have to 'jog' the machine axes into the correct positions and then 'zero' the axes.

Next Section

Updated: 20 October 2020