Plasma Cutting Power Requirements by Metal Thickness

January 03, 2024 · Leave a comment · Red-D-Arc
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Plasma Cutting Power Requirements by Metal Thickness

You should always consider the most typical use scenarios when evaluating plasma cutter rentals. It’s vital to examine your metal-cutting needs to get the most out of your plasma cutting equipment, whether you buy it or rent it. 

Plasma cutter power sources, consumables, output power, and cutting speeds vary depending on the cut material and its thickness. So, let’s see how to choose your plasma cutting system without falling short on vital specs and capabilities.

Plasma Cutting Considerations for Thin Metal Sheets

Plasma cutting thin metal sheets creates unique problems like warping and melting. HVAC, auto body shops, custom interior design, and large-scale fabrication are just some applications where fine precision is required when cutting thin metals. 

Thin Metal Sheets And Their Characteristics

Sheet metal thickness classification depends on the material type. But, most materials like stainless steel, mild steel, and aluminum are considered sheet metal if thinner than 7 gauge (8 gauge for stainless steel). 

Plasma arc cutting thin metal sheets can lead to warping and a wide melting cut line if the cutting speed is too low. Moving the torch quickly across the cut line won’t let the heat propagate deep into the material, which reduces the warping. Thankfully, one of the plasma cutting advantages is its immense heat, which allows exceptionally high travel speeds and prevents warping.

Thin metal sheets can flex and slide due to low rigidness and weight. This is especially true when working with polished stainless steel or aluminum. Mild steel has a mill scale on its surface, which may provide slightly better traction over its surface. So, it’s important to properly secure metal sheets when cutting manually or using a CNC plasma cutting table setup. 

Selecting The Appropriate Plasma Cutter For Thin Metals

Choosing a suitable cutter and plasma system components for thin metals primarily depends on the duty cycle, cut precision, and production rate you wish to achieve. 

If you plan to cut thin metal sheets occasionally, even the handheld plasma cutters, like the Hypertherm Viper 30 XP, will get the job done. However, the Viper 30XP has a 35% duty cycle (20% with 120V input), so you can only cut for 3.5 minutes (2 minutes on 120V) before the plasma cutter needs to rest for the remainder of the 10-minute interval. 

Large-scale fabrication or employing a plasma cutter on a CNC table for HVAC or similar applications requires a durable machine that can withstand high uptime. So, even if you don’t need high amperage output for sheet metal, the unit must be designed to endure a constant workload. 

Hypertherm Viper 65 can output 46A at 100% duty cycle, which is more than enough for cutting sheet metal. Or, you can opt for the Hypertherm Viper 45, which outputs 32A at 100% duty cycle, if you know you won’t cut thicker than sheet metal with high uptime. But, the Viper 65 has a cutting speed of 145 IPM when cutting 1/4-inch mild steel, while the Viper 45 is rated at 60 IPM for the same thickness. So, consider the production speed since low speed could become the bottleneck of your business. 

Techniques For Achieving Clean And Precise Cuts On Thin Metal Sheets

To achieve precise and clean cuts on thin sheet metal, you must set the appropriate amperage output for cut thickness and use suitable plasma cutting consumables. For example, the Hypertherm Viper 45 should be set to 45A output when cutting stainless steel above 1.5mm thick and to 30A to cut 0.8mm and below. You can see all the settings in the user manual of your plasma cutter. It’s also important to use appropriate pierce time delay if you don’t start the cut from the sheet edge.

Hypertherm’s FineCut consumables can help you achieve cut quality similar to laser and waterjet when cutting sheet metal. FineCut consumables produce a narrow kerf and a stiff arc, making them ideal for cutting thin metal at 40A or below. 

You can also cut multiple sheets simultaneously by stacking them together. But, their cumulative thickness can limit the cutting speed and cut quality, and you may experience a larger kerf at the bottom layer. 

Common Challenges And Safety Precautions For Plasma Cutting Thin Metals

Thin sheets of metal are a safety hazard due to their razor-sharp edges and pointy corners. It’s vital to wear heavy-duty gloves when handling sheet metal to avoid lacerations and deep cuts. Safety glasses, reinforced boots, and appropriate worker apparel will prevent sharp debris from injuring the workers. It’s all too easy to accidentally step on a cut-off piece of sheet metal. So, wearing regular sneakers when dealing with sheet metal could quickly turn into a hospital trip. 

Plasma cut sheets of metal can be extremely hot, even if the plasma cutting process doesn’t induce much heat into the material. So, exercise caution and never handle recently cut parts with bare hands to prevent burns.

Plasma Cutting Techniques for Medium-Thickness Metals

Arguably, plasma cutting medium-thickness metals is the easiest and most suitable plasma cutting application. Medium-thickness plates or pipes aren’t thin enough to experience significant warping or thick enough for the plasma cutter to struggle. 

Understanding Medium-Thickness Metals And Their Properties

Medium-thickness metal plates typically fall in the range between 1/4-inch (6.35 mm) and 1-inch (25.4 mm). These plates are far more rigid than sheet metal, making them easier to set up and clamp since there is no risk of warping. In addition, thicker plates can’t easily slide over each other or the work surface area, thanks to their weight. 

You are unlikely to cause any warpage on materials thicker than 6 mm when using a plasma cutter. But, it’s crucial to maintain a relatively high travel speed to prevent a wide heat affected zone (HAZ), especially when cutting stainless steel. It’s easy to ensure a high travel speed when cutting sheet metal. But, cutting thicker materials at high travel speed requires additional power.

Choosing The Right Plasma Cutter For Medium-Thickness Metals

Choosing a plasma cutter for cutting materials up to 1-inch thick comes down to finding a machine that outputs the necessary power with the duty cycle and cutting speeds that suit your production needs. In addition, you should choose quality machines designed to withstand relatively high amperage outputs and provide a high-quality cut finish, like Hypertherm plasma cutters. 

The Hypertherm Powermax 85 SYNC has a maximum cutting speed of 200 IPM when cutting 1/4-inch steel and 21 IPM for 1-inch steel. But the Powermax 85 SYNC duty cycle is rated at 60% at its maximum amperage output of 85A. 

If your production demands high uptime from the power source, consider the Hypertherm Powermax 105 SYNC. It can output up to 94A at 100% duty cycle, depending on the power input (1-phase or 3-phase, and voltage input), with a maximum output of 105A at 80% duty cycle. The Powermax 105 SYNC has a maximum cutting speed of 220 IPM for 1/4-inch, and 30 IPM for 1-inch steel.

Addressing Common Issues And Troubleshooting Tips

Make sure you are using adequate amperage output and consumables for the cut thickness. You will find this data in the machine’s instruction manual. It’s best to use about 95% of the maximum amperage the consumables can handle to prolong their lifespan. 

Cutting too slowly will widen the kerf, produce significant dross at the cut edge, and likely cause sensitive materials like austenitic stainless steel to lose corrosion resistance or mechanical properties. So, it’s essential to achieve the manufacturer’s recommended cutting speed for the material and the thickness. 

Overcoming Challenges Seen When Plasma Cutting Thick Metal Plates

Metal plates thicker than 1-inch are considered thick and pose a challenge when plasma cutting. Powerful plasma cutters can easily slice thick plates, but most portable plasma cutters struggle with very thick plates.

Challenges Associated With Thick Metal Plates

Not only are thick metal plates heavy and challenging to prepare before cutting, but they often require a far longer cutting time. As a result, the power source’s duty cycle becomes even more critical since making pauses as you cut is not desirable — it’s challenging to continue the cut from where you left off, resulting in a less accurate cut line.

Frequently cutting thick metal plates will result in more consumable replacements since the arc-on time will be significantly higher per cut inch compared to thin sheet metal or medium-thickness plates. So, it’s necessary to account for additional consumable wear when planning to cut a large batch of thick material. 

Very thick metal plates above 5-inches have unique challenges that require a special approach and engineering when plasma cutting. Cutting such thicknesses requires lag angle management techniques to manage considerable plasma lag created by the material’s thickness. In addition, it’s necessary to employ advanced techniques to pierce them properly.

Selecting A Suitable Plasma Cutter For Thick Metal Plates

You will need an industrial-grade plasma cutter to cut thick metal plates. The Hypertherm MAX200 plasma cutter has a maximum steel cutting capacity of 2-inches (50mm) at 6 IPM. It can output 200A (30 kw) of power at 100% duty cycle for all-day production. It’s our best recommendation for materials up to 2-inch thickness for manual or mechanized cutting. It supports dual gas input (plasma and shielding gas), which allows you to use the most optimal gas for the cut material and thickness.

The second best and portable solution for cutting thick metal plates is the Hypertherm Python 125. It has a 100% duty cycle at 125A output and can cut up to 1 and 3/4-inch thick steel at 10 IPM. The Hypertherm Python 125 requires a 480/600 3-phase input, so while it’s portable, please consider the available power if you want to use it on-site. You may need a diesel-powered generator like the MMD PowerPro 65 to use the Python 125 in the field. 

Consider using argon-hydrogen gas for plasma cutting thick stainless steel and aluminum plates. The 35% hydrogen and 65% argon mixture provides the hottest plasma arc and improves the cutting speed.

Safety Measures Specific For Cutting On Thick Metal Plates

Heavy metal plates pose a significant safety challenge. Workers can get injured by lifting these materials or by plate falls, pinches, and improper use of the lifting equipment. 

Ensure that all workers follow large plate handling safety protocols and that the load is not swayed when moved with cranes. 

Plasma cutting equipment for cutting thick metal plates outputs significantly higher energy than less powerful sheet metal cutters. Therefore the risk for burns and electrocution is higher, and every precaution must be considered to avoid worker injury. For example, the Hypertherm Python 125 has a rated output voltage of 175V, while the Hypertherm Viper 65’s voltage output is rated at 139V. Add in the significantly higher amperage, and the total energy produced by high-end plasma cutters is far greater. 

Since cutting thick materials takes longer, their cut edge will be extremely hot. Therefore, workers handling these metals should wear all appropriate PPE, like heat-resistant gloves, boots, and overalls. 

Get Your Plasma Cutting Equipment From Red-D-Arc

Our plasma cutter rentals fleet includes small, handheld plasma cutters, and industrial-grade machines for all of your metal cutting needs. Contact us today, and our experts will help you find the right plasma cutting equipment for your application.

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