Tweco 30 O2 Auto-Cut - Manuel (Page 78)

Manual No. 0-4818 Auto-Cut 300
2
4-10 OPERATION
Direction of Cut
The plasma gas stream swirls as it leaves the torch to maintain a smooth column of gas. This swirl effect results
in one side of a cut being more square than the other. Viewed along the direction of travel, the right side of the
cut is more square than the left.
Right Side
Cut Angle
Left Side
Cut Angle
A-00512
Scrap
Clockwise
Counter-
Clockwise
Art # A-04182
Workpiece
Scrap
Swirl Effect on Side Characteristics Of Cut
To make a square - edged cut along an inside diameter of a circle, the torch should move counterclockwise
around the circle. To keep the square edge along an outside diameter cut, the torch should travel in a clockwise
direction.
Underwater Cutting
Cutting on a water table either underwater or with the water touching the plate or with a water muffler system
is not recommended. If a water table is used the water level must be a minimum of 4 inches from the bottom of
the plate. Failure to follow this recommendation could result in poor cut quality and short consumable parts
life.
Ohmic Height Sensing
Ohmic Height Sensing is not recommended with water shield (‘water mist secondary’). Water on the plate
interferes electrically with the ohmic height sensing system.
4.05 Gas Selection
A. Plasma Gases
1. Air Plasma
• Most often used on ferrous or carbon base materials for good quality at faster cutting speeds.
• Air plasma is normally used with air shield.
• Only clean, dry air is recommended for use as plasma gas. Any oil or moisture in the air supply will substan-
tially reduce torch parts life.
• Provides satisfactory results on nonferrous materials.
2. Argon/Hydrogen (H35) Plasma
• Recommended for use on 3/4 in (19 mm) and thicker stainless steel. Recommended for 1/2 inch (12 mm) and
thicker nonferrous materials. Ar/H
2
is not normally used for thinner nonferrous materials because less
expensive gases can achieve similar cut quality.
• Poor cut quality on ferrous materials.
• Provides faster cutting speeds and high cut quality on thicker materials to offset the higher cost.
• A 65% argon / 35% hydrogen mixture should be used.