Introduction

Achieving optimum cut quality may require adjusting your plasma process parameters. There are numerous parameters that affect cut quality, including torch type, gas type, material, and condition of the material.  This discussion only focuses on the common items that a cutting machine operator may need to adjust in order to maximize cut quality.

Many of the variables that affect cut quality are interdependent. Changing one variable affects the others. Determining a solution may be difficult. The following guide offers possible solutions to undesirable cutting results. To begin, select the most prominent condition:

Recommended cutting parameters will usually give optimal cut quality. Occasionally, conditions may vary and slight adjustments will be required. If so:

• Make small incremental adjustments when making corrections.

• Adjust arc voltage in one volt increments, up or down as required. Adjust cutting speed 5% or less as required, until conditions improve.

 

Cut Angle

Negative Cut Angle

Top dimension is greater than the bottom.

• Misaligned torch

• Bent or warped material

• Worn or damaged consumables

• Standoff too low (arc voltage)

• Cutting speed too slow

 

Positive Cut Angle

Top dimension is less than the bottom dimension.

• Misaligned torch

• Bent or warped material

• Worn or damaged consumables

• High standoff high (arc voltage)

• Cutting speed fast

• Current too high or too low for the nozzle

• Wrong sheild gas flow.

Cut Flatness

Top And Bottom Rounded

Condition usually occurs when material is 0.25" thick (6,4mm) or less.  Current may be too high for given material thickness.

 

Top Edge Undercut

Standoff (arc voltage) is too low.

 

Surface Finish

 

 

Process Induced Roughness

Cut face is consistently rough and may be confined to one axis.

• Incorrect shield gas mixture (See process data) 
• Worn or damaged consumables 
• Too high O2 flow

 

Machine Induced Roughness

Can be difficult to distinguish from process induced roughness and is often confined to one axis.

• Roughness is inconsistent. 
• Dirty rails, wheels and/or drive rack/pinion. (Refer to maintenance section in machine owner's manual). 
• Carriage wheel adjustment

Dross

Dross is a by-product of the cutting process. It is the undesirable material that remains attached to the part. In most cases, dross can be reduced or eliminated with proper torch and cutting parameter setup. Refer to Process Data.

 

High Speed Dross

 

Material weld or rollover on bottom surface along kerf. Difficult to remove. May require grinding or chipping. Easily identified with "S" shaped lag lines.

• Standoff high (arc voltage) 
• Cutting speed too fast

 

Slow Speed Dross

 

 

Forms as globules on bottom along kerf. Removes easily.  Usually indicates cutting speed is too slow.

Top Dross

 

 

Appears as splatter on top of material. Usually removes easily.

• Cutting speed fast 
• Standoff high (arc voltage).

 

Intermittent Dross

Appears on top or bottom along kerf.  Non-continuous.  Can appear as any kind of dross.  Possible worn consumables

 

Other Factors Affecting Dross:

• Material temperature 
• Heavy mill scale or rust 
• High carbon alloys

Dimensional Accuracy

Generally, using the slowest possible speed (within approved levels) will optimize part accuracy. Most material thickness can be cut at several different amperages. To maximize edge quality and part dimensional accuracy, select the lowest possible amperage to allow slower cutting speed.

ESAB Solution

ESAB's m3 plasma system fully automates the plasma cutting process, making it easy to set up all of the process variables discussed above.  

ESAB CNC Plasma Cutters

The following machines can be equpped with plasma cutting torches: