Common CNC Plasma Table Problems [Signs and Solutions]

As a CNC plasma table operator, you should maintain composure when faced with some of the more common CNC plasma table problems. First, you need to analyze the causes and the symptoms of the issues and then devise solutions for troubleshooting.

But don’t worry; in this article, we have included everything. Read on as we discuss these issues and what may cause them.

6 of the Most Common CNC Plasma Table Problems

1. Low air pressure
2. High air pressure
3. Inadequate mounting of wearing components
4. Low AC voltage input
5. Poor grounding
6. Torch grip speed and verticality

Low air pressure

Suppose the operating air pressure for the plasma cutter is significantly lower than the air pressure specified in the instructions. In that case, it weakens the plasma arc’s ejection speed, and the input air flow is below the specified value of the CNC plasma table.

A high-energy, high-speed plasma arc cannot form at the time. As a result, the caliber of the incision is poor, it is not penetrated, and it accumulates.

Insufficient air intake from the air compressor is the main cause of low air pressure. The oil contaminates the solenoid valve, the air path is not smooth, and the pressure regulation of the cutter’s air-regulating valve is too low.

High air pressure

One of the most common CNC plasma table problems is when the input air pressure is too high. The excessive airflow that results after the plasma arc forms will blow away the concentrated arc column. Then, spread the arc column’s energy, and reduce the plasma arc’s cutting power.

The cause for this can be incorrect input air. It can be an excessive air filter pressure-reducing valve. Or it can be the valve’s failure.

Source: shutterstock.com / Photo Contributor: Zoran Zeremski

Inadequate mounting of wearing components

It is necessary to install consumables like the threaded electrode nozzle into position properly. An uneven nozzle cut will destroy the wearing parts if it is incorrectly placed. This is when it’s not tightening the screw thread or the eddy current ring.

Low AC voltage input

You should check whether the power grid linked to the plasma table has enough carrying capacity before use. Also, you need to check the power cord’s parameters to see if they adhere to the standards.

Install the plasma cutting table far from major electrical equipment. It should be away from areas where there is often electrical interference.

Poor grounding

Before cutting, grounding is a crucial step in the process. In the absence of a particular grounding tool, insulate the workpiece’s surface. Prolonged usage of a ground wire will result in poor grounding practice.

Check out our guide on how to ground a CNC table.

Torch grip speed and verticality

Depending on the materials, the cutting speed should either be fast or slow. Nonetheless, the cutting size should remain fixed. A cutting surface that is too quick or too slow will have slag on the top and lower edges.

The plasma arc is also sprayed, resulting in the cutting surface having a slope and not holding the cutting torch vertically.

4 of the Most Common CNC Plasma Cutting Problems

• Excessive dross
• Cut angularity
• Material warpage
• Cut-edge metallurgy

Excessive dross

Dross is the resolidified metal that sticks to the top and bottom edges of the material being cut. Dross is a pretty common issue with many causes and solutions. It is also referred to as slag or a burr.

Dross can happen in three different forms:

• Thick frothy buildup on the bottom due to low-speed cuts.
• A tiny hard bead of uncut material due to high-speed speed.
• A minor surface coating due to top spatter.

Many process factors are necessary for dross production, including torch travel speed, standoff distance, amperage, voltage, and consumable quality.

Material factors like grade, chemical composition, surface quality, and flatness can affect it. Even temperature fluctuations in the material affect the cut.

While forming dross, you should consider the cutting speed, amperage, and standoff distance.

Low-speed cuts

Low-speed cutting is the most prominent reason for bottom dross. Inexperienced operators slow down the process when faced with a cut quality issue. In reality, they ought to speed it up.

Low-speed dross often manifests at a certain speed on a given material thickness. You can erase the dross as you accelerate to greater speeds.

Nevertheless, excessive acceleration can result in high-speed dross. The sweet spot between the low and high-speed dross is known as the dross-free zone (DFZ). The cut quality improves with DFZ width.

High-speed cuts

The arc starts to lag back in the kerf when the cutting speed is too high. This will leave a small, hard bead of uncut material or rollover dross down the plate’s bottom. Since it is more rigid, you will need much machining to remove this high-speed dross.

The arc becomes unstable and starts swinging up and down in the kerf at very high speeds. This produces a rooster tail of sparks and melting matter. The arc may not burn through the metal or extinguish at these speeds.

High standoff or low amperage can also result in high-speed dross for a given material thickness and cutting speed. This is because they both reduce the plasma jet’s energy.

Surface coating spatter

The top spatter is an accumulation of resolidified metal that sprays along the cut piece’s top. This is easy to remove. The usual culprits include a worn nozzle, a fast cutting speed, or a high standoff.

It occurs by the plasma jet’s swirling movement. It throws molten material out in front of the kerf at a particular angle rather than down through it.

Cut angularity

Edge angularity is expressed as a positive or negative angle from the plate’s surface relative to 90 degrees. The plasma cutters always have some edge angularity. Due to this, a small positive edge angle is preferable. In contrast, the undercut is a term for negative angles.

Designing the torch and consumables with as little angularity as possible is challenging. Plasma process technicians put a lot of effort into maintaining a constant angularity.

Plasma system manufacturers suggest optimal cut rates. The cuts should be at the lowest you can cut without producing low-speed dross. Since cutting slower generally reduces edge angularity.

The best angularity is in the lowest power level recommended in your material thickness cut charts. Slow down even further if you want better angularity. However, this can cause a broader kerf and more dross if you do.

Source: shutterstock.com / Photo Contributor: Zoran Zeremski

How to achieve the optimal cut angularity?

You should match the power output and consumables to the thickness of the material. Less edge angularity will result from lower power and speed.

You need to double-check the consumables are in good shape before operating the plasma cutter. If your edge angle fluctuates all around a cut, the first thing to check is a damaged nozzle or shield orifice.

Since the nozzle orifice creates the arc, you can anticipate that if there is a nick or crater, it will change the shape of the arc and the cut. Incorrect piercing is the main killer of nozzle orifices.

After the piercing, make and use the proper cut height throughout. A standard plasma cutter should be within roughly 0.010 in. A high-quality one needs to keep within 0.005 in of the suggested cut height. Verify that the height control maintains a steady height without diving.

The key to optimal cut angularity is utilizing good consumables in good condition. Additionally, a good plasma system and adhering to the manufacturer’s suggested cutting criteria.

Material warpage

Use the recommended power and speed settings to prevent material warpage during plasma cutting. The material absorbs less heat at higher speeds. This generally results in less heat-induced material warpage. 

Some further ideas we recommend:

• Use consumables at their fastest possible speed and the lowest power level.
• Use your CAM program to design cut paths on very thin materials that reduce the amount of heat input. This is due to allowing areas to cool before cutting neighboring pieces.
• Some materials that have been cold-rolled contain kinetic stresses within their grain structure. Even without cutting, this kind of stress frequently gets released.
• Keep water in contact with the material to reduce dross when using a water table. Remember that contact with water can change the edge’s smoothness. In some situations, even the edge hardness (hydrogen embrittlement) of many materials.

Cut-edge metallurgy

All plasma-cut materials have metallurgical impacts on their edges. You can reduce these effects by concocting the proper gas mixtures and process power levels.

The localized high temperature of the cutting process frequently affects edge metallurgy. Atmospheric gasses nearby also have an impact.

Yet, we advise contacting your CNC table manufacturer. Double-check if your equipment can handle a particular gas combination. Using the wrong gas mixtures can indeed hurt people and destroy equipment.

Conclusion

Some of the common CNC plasma table problems have easy solutions. But it’s important to recognize these issues early on and practice safety. It will also save you time and resources knowing the issues that could arise and prevent them from happening.