Module 2: Material Science & Cut Parameters Assessment Quiz

Module: U5M2 - Material Science & Cut Parameters Duration: 25 minutes Passing Score: 70% Format: Multiple choice and scenario-based

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Which property of a metal most affects the required amperage for plasma cutting?

Thickness and thermal conductivity

Color and surface finish

Magnetic properties

Hardness and tensile strength

Submit

Explanation: Thicker metals require more amperage to fully penetrate. Metals with high thermal conductivity (like aluminum and copper) conduct heat away from the cut zone faster, requiring higher amperage or slower speeds to maintain a quality cut.

What is "kerf" in plasma cutting?

The width of material removed by the plasma arc during cutting

The heat-affected zone adjacent to the cut

The angle of the cut edge relative to vertical

The distance between the torch and the workpiece

Submit

Explanation: Kerf is the slot width created by the plasma arc. It varies with amperage, speed, and nozzle orifice size — typically 0.05"–0.12" for makerspace plasma cutters. Kerf must be accounted for in part layout to maintain dimensional accuracy.

When cutting aluminum with a plasma cutter, which gas is preferred for the best cut quality?

Nitrogen (N₂) or nitrogen/hydrogen mix

Pure oxygen

Carbon dioxide

Acetylene

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Explanation: Nitrogen produces the cleanest cuts on aluminum. Oxygen reacts with aluminum to form aluminum oxide on the cut face, which is extremely hard and difficult to clean. Air (which contains oxygen) works but produces more dross than nitrogen.

What is the "heat-affected zone" (HAZ) in plasma cutting?

The area of base metal adjacent to the cut where the microstructure has been altered by heat

The area directly under the plasma arc

The zone where the workpiece clamp contacts the metal

The protective area around the nozzle

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Explanation: The HAZ extends from the cut edge into the base metal. In this zone, the metal was heated enough to change its grain structure (but not melted). The HAZ can be harder and more brittle than the base metal, which matters for welding or bending near the cut edge. Typical HAZ width: 0.02"–0.10".

A student increases cutting speed significantly on ¼" mild steel. What is the most likely result?

Incomplete cuts with heavy dross on the bottom and excessive drag lines

A cleaner, wider cut with no dross

The plasma arc will extinguish automatically

The metal will melt into a puddle

Submit

Explanation: Cutting too fast means the plasma arc does not have enough time to fully penetrate the material. The result is an incomplete cut (the arc may not go through) with heavy, hard-to-remove dross on the bottom edge and steep drag lines angled back from the direction of travel.

Why should galvanized steel be cut with extra caution?

The zinc coating produces toxic zinc oxide fumes that cause metal fume fever

The zinc coating is electrically insulating and prevents arc transfer

Galvanized steel is too hard for plasma cutting

The zinc coating makes the steel flammable

Submit

Explanation: Galvanized steel has a zinc coating that vaporizes at 1,665°F — well below plasma arc temperatures. Zinc oxide fumes cause "metal fume fever" (flu-like symptoms 4-12 hours after exposure: chills, fever, muscle aches, nausea). A P100 respirator with organic vapor cartridge and maximum ventilation are required.

What determines the correct nozzle orifice size for a plasma cutting operation?

The amperage setting — higher amperage requires a larger nozzle orifice

The type of metal being cut

The thickness of the base metal only

The operator's personal preference

Submit

Explanation: Each nozzle is rated for a specific amperage range. The orifice diameter must match the amp setting — too small and the nozzle overheats and wears rapidly; too large and the arc is unfocused, producing a wide, rough cut. Always use the manufacturer's recommended nozzle for the selected amperage.

What is "pierce delay" and why is it important?

A brief pause after the arc starts to allow the plasma to fully penetrate the material before travel begins

The time it takes for the pilot arc to transfer to the workpiece

The cooling period between consecutive cuts

The delay before the compressor reaches operating pressure

Submit

Explanation: Pierce delay gives the plasma arc time to melt through the full thickness of the material at the starting point. Without adequate pierce delay, the torch begins moving before the cut is through, resulting in an incomplete starting edge. Pierce delay increases with material thickness — from 0s for thin gauge to 2+ seconds for ½" plate.

What is "bevel angle" in plasma cutting, and which direction does it typically lean?

The slight angle of the cut edge from vertical, typically 1°–5°, with the good side on the right of the direction of travel

The angle at which the torch is tilted during cutting

The angle of the drag lines on the cut face

The angle of the workpiece on the cutting table

Submit

Explanation: Plasma cuts are not perfectly perpendicular — the arc constriction creates a slight bevel, typically 1°–5°. Due to the swirl direction of the gas, the right side of the cut (in the direction of travel) has a squarer edge. Parts should be programmed so the good side of the kerf faces the finished part (typically clockwise for outside profiles, counter-clockwise for holes).

A student notices their ¼" mild steel cut has very little dross on the bottom but the top edge has excessive rounding and a wide kerf. What is the most likely cause?

Cutting speed is too slow — excessive heat input is melting too much material

The nozzle orifice is too small

The air pressure is too high

The workpiece ground clamp is loose

Submit

Explanation: Cutting too slowly allows excessive heat to build up, widening the kerf, rounding the top edge excessively, and creating a large HAZ. While dross may be minimal (the slow speed gives the gas time to clear molten metal), the part dimensions suffer and the edge quality is poor.

Which of the following metals should NEVER be plasma cut in a standard makerspace environment?

Beryllium copper — produces extremely toxic beryllium fumes

Mild steel — too common for makerspace use

Aluminum 6061 — too soft for plasma cutting

Stainless 304 — too expensive for student use

Submit

Explanation: Beryllium copper alloys produce beryllium fumes when heated — beryllium is an OSHA-regulated carcinogen with an extremely low permissible exposure limit (0.2 μg/m³). Cutting beryllium-containing alloys requires specialized industrial ventilation and monitoring equipment far beyond makerspace capabilities. Other restricted materials include cadmium-plated metals and certain lead-containing alloys.

What role does air pressure play in plasma cut quality?

Proper pressure ensures a focused arc and effective molten metal removal; too low causes poor cuts, too high damages consumables

Air pressure only affects the speed of cutting, not quality

Higher pressure always produces better cuts

Air pressure is only relevant for piercing, not continuous cutting

Submit

Explanation: Gas pressure affects arc constriction (focus), cooling of the nozzle, and ejection of molten metal from the kerf. Too low: arc wanders, poor penetration, heavy dross. Too high: arc blown out, rapid consumable wear, double arcing. Typical operating pressure: 60-75 PSI for air plasma cutters.

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Last Updated: 2026-03-19