Tag: maintenance

Achieving top-notch cut quality with plasma cutting involves understanding the main factors that impact the results. In this blog guide, we’ll explore these crucial elements to help you get the best possible cut every time.

The 7 Key Factors: 

1. Amperage (Cutting Current)
2. Gases Used for Plasma Cutting 
3. Arc Voltage
4. Torch Height
5. Cutting Speed
6. Kerf Width

1. Amperage: The Power Player   

Amperage measures the flow of electrons in an electrical circuit. Higher current levels can reduce dross (the unwanted material that forms on the edge of a cut) for a given material thickness. For instance: 

I_c = 260 Amp; Thickness 1 inch, mild steel, cutting speed 66 inches/min

A lower current level usually results in better edge quality and squareness for a given thickness, but maximum dross formation.

I_c = 260 Amp; Thickness 1 inch, mild steel, cutting speed 66 inches/min

Bonus tip: Lower current consumables generally last longer, especially when cutting with oxygen.

To ensure optimal amperage performance, it’s also essential to maintain a clean and dry air supply system, with regular checks on air quality, gas quality, and CFM (cubic feet per minute) flow rate.

2. Choosing the Right Gases

The purity of gases used in plasma cutting is critical for maintaining cut quality and consumable life. Here’s a quick guide:

Oxygen (O2) and Nitrogen (N2): O2 at 99.5% purity, N2 at 99.99%.

Argon-Hydrogen (H35) and Nitrogen-Hydrogen (N5): H35 at 99.995% purity (65% Argon, 35% Hydrogen), N5 at 99.98% purity.

Air: Should be clean, dry, and oil-free.

Methane: 93% pure.

Typically used plasma gases include Compressed Air, Oxygen, Nitrogen, and Argon-Hydrogen. Shielding gases help in arc constriction and cooling, enhancing the cut quality by reducing oxidation at the cut edge. The choice of gases depends on the material you’re cutting and the desired cut quality. Always refer to the manufacturer’s instructions for the best results.

3. Arc Voltage: The Balancing Act 

Arc voltage is crucial for controlling the torch height and, consequently, the quality of your cut. Higher arc voltage means a taller torch height, which affects the bevel angle and overall cut quality.

Keep an eye on the cutting speed—it directly influences arc voltage. As speed increases, voltage drops, and vice versa. This relationship is vital for maintaining quality cuts, especially around corners and intricate contours.

Relation between the arc voltage and cutting speed.
(Note: Graph is dependent on system and metal thickness)

THC (torch height control) reacts like this: The torch will lower as speed decreases, or rise as speed increases. THC must be turned off or “AVC Disabled” when speed decreases.

4. Torch Height: The Perfect Distance 

Getting the torch height right is key, especially during piercing and cutting.

Piercing Height: Set at 1.5-2 times the ideal stand-off distance.

Cutting Height: Maintained during the cut for optimal results.

How does it work? The torch height control system (THC) adjusts the torch based on the surface, ensuring consistent cut quality. Remember, the THC is “blind” before cutting starts, so it must first touch the material to detect the initial position.

5. Cutting Speed: The Sweet Spot

Speed is everything when it comes to plasma cutting. The correct cutting speed minimizes dross and ensures a clean cut. Follow the cutting charts provided by your equipment manufacturer to find the optimal settings for amperage, arc voltage, and torch-to-work distance. Proper handling and storage of consumables is also crucial to prevent damage and contamination.

Example of plasma arc formation
From left to right: Low cutting speed, Correct cutting speed, Fast cutting speed

6. Kerf Width: Precision Matters

Kerf width, the void created by the cutting process, is crucial for the dimensional accuracy of your parts. A wider kerf is often the result of slower speeds or higher power settings. Typically, kerf width is about 1.5-2.0 times the nozzle’s orifice diameter. Regular torch maintenance and proper mounting on the gantry arm ensure accurate kerf width control.

7. Coolant Condition

Regularly replace the coolant (every 6 months or quarterly for heavy use) and completely flush the system to prevent performance issues and torch failure.

By considering these critical factors, you’ll be well on your way to achieving top-notch plasma cutting quality and optimizing your workflow. Remember, attention to detail is key to producing precise, high-quality cuts.

Text:               Thermacut®
Photo:            Archive of Thermacut, k.s.

Plasma cutting systems are becoming increasingly used in a wide array of applications. Any Investment in new cutting equipment is a significant decision where major breakdowns or minor performance decreases can affect overall productivity.

Budgeting, assessment of market offerings, and consideration of return on investment are all important factors to ultimately make a well informed decision in purchasing any product and particularly when choosing the right plasma cutting machine.

Proper maintenance and regularly checking vital components ensure equipment maintains excellent condition. Regular service, upkeep, and adhering to manufacturer recommendations all support the optimal performance levels and promote high quality results.

In this brief guide we’ll highlight some maintenance ideas and intervals that can help to ensure components in your plasma cutter keep operating smoothly.

Why is maintenance important? 

Maintenance for plasma cutting machines is crucial, falling into three key categories: safety, ROI, and performance. Safety is paramount, ensuring industrial machinery operates without risks. Regular maintenance extends machine lifespan, improving ROI, and maintains top-notch cutting quality and efficiency.

Before each use

1. Inspect the torch body and handle. If the torch body is cracked, it will collect more debris affecting safety. Any damaged components should be repaired or replaced to prevent gas leaks and ensure safe operation of the plasma cutter.

2. Check the power cable and leads for any cuts, fraying, or exposed wires. Repair or replace if damage is found. Any twists or high-strain points in the wire should be further inspected for damage that could affect performance of the plasma cutting system.

3. Ensure the correct installation of consumables. Check the orifice is round and free of any debris lodged between the shield and nozzle. Apply a thin coat of dielectric to the torch O-ring if it is dry. If the O-ring is missing or damaged, replace it with a new lubricated o-ring.

4. Connect the system to the input power supply, release pressure on the gas regulator, connect the air line, switch the system to the “ON” state. After the automatic diagnostic check, inspect and if needed, adjust the air pressure to the desired value. Once all checks and necessary adjustments are made, proceed with usage.

Daily checklist

1. Inspect the torch body for cracks or exposed wires. Check handheld torch safety trigger for debris and test proper operation.

2. Remove power and Inspect cap sensor safety switch behind consumables. Ensure free of debris.

3. Check all cables for strain relief and power cords for wear, and exposed wires. Correct issues and replace cables or wires if needed.

4. Check connector hoses, and connections. Ensure fittings are secure and free of damage. Replace if necessary.

5. Check the work lead clamp and ensure tight fit to avoid arcing and contamination.

6. Check torch consumables for wear.

7. If your machine has any sensors, ensure proper operation.

Weekly Maintenance

1. Ensure proper operation of safety switch to prevent accidental firing during use of handheld or mechanized torches.

2. Clean machine with degreaser and a rag to remove any excess metal, dirt, and grease.

Monthly Maintenance

1. Maintain primary air filter and any accessory air filters.

2. Inspect fiilter for dirt and o-ring for wear, cracks and pinches.

3. Verify clean, dry, air free of oil or contaminates from air compressor to plasma cutter, purge excess moisture buildup.

Every 3 Months

1. Check the cutting torch exposed wire or cracks in the torch body.

2. Check the gas hose, filter elements and connections for leaks.

3. Check with your manufacturer to determine if any new maintenance is recommended, cleaning with compressed air can keep your machine at peak performance.

Annual Maintenance

1. Have a professional safety inspection performed by a trained technician if removing the cover.

2. Examine maintenance logs and assess future maintenance requirements.

If any damage is found during an inspection, always identify and assess any damage to the input power lead/plug, torch, torch lead, airline hose, connectors, or filter components. When necessary, repair or replace the damaged components accordingly. Do not operate the system unless it fully complies with safety standards. Always take necessary precautions to avoid exposure to dust and contaminants. Prioritize your safety, the safety of your colleagues, and the environment. Wear the appropriate Personal Protective Equipment (PPE) as required by your organization and local laws.

Text:               Thermacut®
Photo:            Archive of Thermacut, k.s.