Improve cut quality with these CNC steel and metal cutting tips
Positive cut angle
More material was removed from the top of the cut surface than from the bottom.
Negative cut angle
More material was removed from the bottom of the cut surface than from the top.
Top edge rounding
Slight rounding along the top edge of the cut surface.
Small, linear bead of molten material that attaches and hardens along the bottom edge of the cut (“S” shaped laglines present; dross ...
A bubbly or globular accumulation of molten material that attaches and hardens along the bottom edge of the cut (vertical laglines may be ...
Light spatter of molten material that collects on the top edges of the cut (typically inconsequential, most common with air plasma).
The following plasma cutter tips offer several solutions to help improve cut quality on metal plate. These tips are designed to work when cutting metal on a CNC table. Whether the job calls for CNC steel cutting, aluminum cutting, or some other type of metal, it is important to try and work through the suggestions provided – as often there are many different factors to consider:
- Type of machine (e.g. X-Y table, punch press, motorized track, robot)
- Plasma cutting system (e.g. air plasma system, oxygen plasma, high definition class plasma)
- Motion control device (e.g. capability of the CNC machine and torch height control)
- Process variables (e.g. cutting speed, cut height, choice of consumables)
- External variables (e.g. material variability, gas purity, operator experience)
It is important to consider all of these factors when attempting to improve the appearance of a cut.
Step 1: Is the plasma arc cutting in the appropriate direction?
When CNC steel cutting, the squarest cut angles are always to the right side, with respect to the forward motion of the torch.
- Check direction of the cut
- Adjust the cutting direction, if needed
The plasma arc typically spins clockwise with standard consumables.
- Torch travels clockwise
- Good side of the cut is to the right side of the torch, as it travels forward
Internal feature (hole):
- Torch travels counter-clockwise
- Good side of the cut is to the right side of the torch, as it travels forward.
Plate with internal hole
Step 2: Was the correct process selected for the material and thickness being cut?
Refer to the cut charts in the Operation section of the Hypertherm Instruction Manual.
Be sure to follow the specifications in the cut charts:
- Select the appropriate process for:
- Metal type
- Metal thickness
- Desired cut quality
- Productivity goals
- Select correct plasma and shield gas if using a dual-gas plasma cutting system
- Select correct parameters for:
- Gas pressures (or flow rates)
- Torch-to-work distance and arc voltage
- Cutting speed
- Confirm the correct consumables (tips) are being used and verify the part numbers
Note: Generally, lower amperage processes offer better angularity and surface finish; however, cutting speeds will be slower and dross levels will be higher.
Step 3: Are the consumables worn?
- Inspect consumables for wear
- Replace worn consumables
- Always replace the nozzle and electrode at the same time
- Avoid over-lubricating o-rings
Note: Use genuine Hypertherm consumables to ensure maximum cutting performance.
Step 4: Is the torch square to the workpiece?
- Level the workpiece
- Square the torch to the workpiece (both from the front and side of the torch)
Note: Check to see if material is bent or warped; in extreme cases this limitation cannot be corrected.
Step 5: Is the torch-to-work distance set at the proper height?
- Adjust torch-to-work distance to the correct setting
- If using arc voltage control, adjust voltage
Note: As consumable parts wear, arc voltage settings need continual adjustment to maintain torch-to-work distance.
Step 6: Is the cutting speed set too fast or too slow?
- Adjust cutting speed, as needed
Note: Cutting speed may also impact your dross levels.
Step 7: Are there problems with the gas delivery system?
- Identify and repair any leaks or restrictions
- Use properly sized regulators and gas lines
- Use pure, high-quality gas
- If manual purge required, such as with the MAX200, confirm purging cycle was completed
- Consult the gas distributor
Step 8: Is there torch vibration?
- Make sure that the torch is secure to the table gantry
- Consult OEM; table may require maintenance
Step 9: Does the table need to be tuned?
- Check and ensure that the table is cutting at specified speed
- Consult OEM; table speed may need tuning