Tweco 20mm Cutmaster - Manual (Page 40)

CUTMASTER 20mm
OPERATION 4T-8 Manual 0-5078
Standoff Distance
Straight Arc
Trailing Arc
Leading Arc
Direction of Torch Travel
A-02586
Mechanized Torch Operation
For optimum smooth surface quality, the travel
speed should be adjusted so that only the leading
edge of the arc column produces the cut. If the travel
speed is too slow, a rough cut will be produced as
the arc moves from side to side in search of metal
for transfer.
Travel speed also affects the bevel angle of a cut.
When cutting in a circle or around a corner, slowing
down the travel speed will result in a squarer cut.
The power source output should be reduced also.
Refer to the appropriate Control Module Operating
Manual for any Corner Slowdown adjustments that
may be required.
Piercing With Machine Torch
To pierce with a machine torch, the arc should be
started with the torch positioned as high as possible
above the plate while allowing the arc to transfer
and pierce. This standoff helps avoid having molten
metal blow back onto the front end of the torch.
When operating with a cutting machine, a pierce or
dwell time is required. Torch travel should not be
enabled until the arc penetrates the bottom of the
plate. As motion begins, torch standoff should be
reduced to the recommended 1/8 - 1/4 inch (3-6
mm) distance for optimum speed and cut quality.
Clean spatter and scale from the shield cup and the
tip as soon as possible. Spraying or dipping the
shield cup in anti - spatter compound will minimize
the amount of scale which adheres to it.