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CUT QUALITY TIPS & TRICKS
Achieving the best possible cut quality is always the goal, understanding what factors contribute and being able to identify and correct the problems is the skill you need to master. For specific information on consumables check the consumables tips and tricks page.
What factors contribute to cut quality?
Air Quality -
Torch Height -
Cut Direction -
Torch Square -
Proper cutting speed -
Out of Square -
Lets Talk Bevel -
This problem may be caused by a worn nozzle, high torch standoff (arc voltage), inadequate amperage, or excessive speed. All of these variables cause the arc to lag which causes more energy to contact the top of the kerf than the bottom. As a result, the kerf is wide at the top and narrow at the bottom. Improper cut direction around the part may also cause excessive positive bevel angle. A part with excessive positive bevel all around it may also have a hard bead of high-
This problem can be caused by low torch standoff (arc voltage), excessive amperage, or low speed. These parameters cause the arc to remove more material at the bottom of the plate. Usually a consistent negative bevel around the part is accompanied by low speed dross.
Positive cut surface -
This problem usually indicates that the nozzle has failed, the torch is out of square or the electrode and nozzle are misaligned. These variables cause the arc to deviate from a straight path through the material. Often one side of a square part will have a positive bevel and the opposing side a negative. The cross section of the part looks like a parallelogram rather than a rectangle. Sometimes the cut surface may not be flat, but rather concave on one side and convex on the other.
These are all signs of severely worn or misaligned parts.
High speed dross -
Check the nozzle first for signs of wear (gouging, oversize or elliptical orifice)
Decrease the cutting speed in 5 ipm increments
Decrease the standoff in 1/16 increments or 5 volts increments
Increase the amperage (but do not exceed 95% of the nozzle orifice rating)
Low speed dross -
Increase the cut speed in 5 ipm increments
Increase the standoff in 1/16 increments or 5 volt increments
Decrease the amperage in 10 amp increments
If none of these measures improve the cut, consider a smaller nozzle size
Top spatter dross -
Check the nozzle for signs of wear
Decrease the cutting speed in 5 ipm increments
Decrease the standoff in 1/16 increments or 5 volt increments
Other factors that can affect dross accumulation -
To achieve cuts with the least amount of dross you can do a series of straight line cuts at different speeds and select the speed that gives you the best results for your material. Even when conditions are perfect its still normal to end up with dross in the corners and in detail work because the torch will be forced to slow down and thus be out of the dross free window.
Pierce high and cut low: The rule of thumb is to pierce at 1.5-
Use a creeping pierce: If your CNC is capable, use a creeping pierce. This feature slowly moves the torch during the pierce operation causing the "rooster tail of molten material to miss the front end of the torch. (Think of the shot glass with the water streaming into one side rather than the middle).
Don't eyeball the pierce height: Use the initial height sensing if it is available. Manual piercing is usually not recommended. Even experienced operators don't have a perfectly calibrated eye.
Don't pierce beyond system limits: Pierce rating is typically 1/2 the cut rating
Avoid piercing: Whenever possible use chain cutting or edge starting (for example off the edge of a punched hole) to reduce the number of pierces.
Cut height -
Proper cut height is critical due to the shape of the plasma arc. The arc is an hour glass type shape and if your height is not correct you will end up with excessive bevel. Either top bevel or bottom bevel.
High Speed Dross
Low Speed Dross
Information photos and video courtesy Hypertherm Inc.
The 10 most common plasma cutting mistakes
A combination of fast cut speeds and low operating cost make plasma cutting one of the most productive metal cutting processes around. But there's an "if." You need to have a good operator and you need to keep your plasma system and table (if you're using a table-
Another thing that really helps system performance and consumable life: avoiding common plasma cutting mistakes. Here's our list of the top 10 things to avoid.
1. Using consumables until they "blow"
2. Changing consumables too often
3. Using the wrong parameters & parts for the job
4. Assembling the torch incorrectly
5. Neglecting routine maintenance
6. Not checking gas and coolant flow
7. Piercing too low
8. Cutting too fast or too slow
9."Stretching" the arc
10. Crashing the torch
|WHAT IS PLASMA|
|G CODE DEFINED|
|WHAT DO I NEED TO GET STARTED|
|WHAT CAN I DO WITH A CNC PLASMA MACHINE|
|HYPERTHERM PLASMA CUTTERS|
|WATER VS DOWNDRAFT|
|STEPPERS VS SERVOS|
|WESTCOTT PLASMA TABLES|
|PLASMA TABLE SHOPPING GUIDE|
|DESIGN SOFTWARE CAD/ART|
|PRO SERIES TABLE TUTORIALS|
|COREL DRAW TUTORIALS|
|HYPERTHERM POWERMAX TUTORIALS|
|PRICING YOUR WORK|
|MARKETING YOUR PLASMA BUSINESS|
|WHERE TO BUY SUPPLIES & CONSUMABLES|
|NAMING & ORGANIZING FILES|
|TURNING YOUR HOBBY INTO A BUSINESS|