Plasma & Oxy Fuel Cutting Machine

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Plasma & Oxy Fuel Cutting Machine

How To Choose The Metal Cutting Machine? (Plasma, Oxy-Fuel, Laser Or Waterjet)

In metal processing applications, users are often faced with the problem of choosing the most suitable metal cutting machine.

In fact, the mainstream metal cutting processes nowadays have their own characteristics in terms of cutting thickness, cutting accuracy, metallurgical performance and productivity.

This article cannot cover all the details of the above features, but can only summarize them in an overview, hoping to bring you a better understanding and facilitate your best choice.

Before we discuss the technology and capabilities of each process, we must first define what needs are most important to users in the metalworking industry.

Equipment purchase cost

Each of the cutting methods requires different CNC, dust removal equipment, CAD/CAM software, etc.

For example, laser requires higher speed and accuracy on thin sheets compared to the slower cutting speed of waterjet and flame. These requirements can directly lead to a huge difference in equipment costs.

Cutting cost per unit part or unit length

This cost includes gas, nozzles, electrodes, electricity and water.

In some cases, equipment acquisition costs and labor costs (e.g. loading and unloading) are also shared.

So it is important to be aware of its scope when making comparisons.

The cost per part or unit length covers cutting speed and productivity and is a more realistic reference than the cost per time.

Ease of use

This requirement lies primarily in software (especially CAM) and CNC.

Learning times are now being reduced and reliance on experience reduced by integrating professional experience built-in.

For example, Hypertherm, the leader in plasma cutting, has built the full set of Hypertherm plasma process parameters directly into Hypertherm’s own nesting software and CNC control, allowing new users to quickly master them and maintain the same cut quality and productivity as professional veterans.

This need is difficult to quantify, but should never be ignored for practical production.

Productivity

Also called production capacity.

Cutting speed is often the determining factor for the output capacity.

Accuracy of cut parts

There are many ways to measure the accuracy of a metal part.

Usually, lower tolerances are required for the outer contour as opposed to the inner bore.

That is why many metal cutting suppliers are now introducing a process for cutting higher quality bores.

In addition, users usually measure only the top surface in their measurements, but in reality, the dimensions of the bottom surface can vary greatly because of the slope of the cut.

In this article, for the sake of simplicity, it is recommended to use the positive and negative tolerance values measured for the top surface and then consider the cut slope for each process.

Edge quality, metallurgical properties

All the above processes have different effects on metal machinability, forming properties and weldability.

Maintenance requirements

The maintenance of these different processes and the ease of maintenance needs to be considered in the long-term cost of ownership.

Below is a brief description of these different processes, including flame cutting, fine plasma, 3 kW fiber laser and waterjet.

For comparison purposes, I will use the purchase cost of a complete system including a 5′ x 10′ (approx. 1.5 x 3 m) cutting area, an industrial CNC machine (neither entry-level nor maximum configuration), and CAD/CAM software.

1. Oxy-fuel (Flame) cutting

Oxy-fuel (Flame) cutting

The oxy-fuel cutting process is the simplest of all the cutting techniques we are discussing here.

The principle is to first heat the steel with a combustible gas to the “ignition point” temperature (approximately 1800F), and once this temperature is reached by preheating, pure oxygen is injected to create an exothermic reaction with the hot steel, which rapidly erodes the steel.

The flame can only cut carbon steel, mostly in thicknesses of 1/4″ (about 6.35mm) to 6″ (about 150mm).

The cutting speed is faster than other processes for thicknesses over 2″ (approx. 50 mm).

It is easy and inexpensive to install multiple flame torches on a CNC oxy-cutting machine at the same time, which doubles the capacity.

5′ x 10′ flame cutting machine Cost:

RMB 80,000 – 120,000 (relatively simple type machine with low speed)

Cost of cutting per unit part or per unit length:

Using quite a lot of gas and slow cutting speed.

The thicker the steel plate, the more advantageous the cutting cost is relative to plasma.

Typically higher cost per foot cut than plasma, and relatively lower cost for thicknesses over 2″ (~50mm).

Ease of use:

Flame CNC cutting machines require a very experienced operator to achieve the fastest cutting speed and the best cut quality.

It also usually requires constant monitoring of the cutting process.

Productivity:

Oxy-fuel cutting has low productivity due to long preheating time and slow cutting speed.

Cut part accuracy:

A good operator with the most appropriate speed, height, gas, and nozzle will cut parts with an approximate dimensional tolerance of ±0. 030″ (approximately 0.76mm) and less than 1 degree of slope.

Edge quality, metallurgical properties:

The heat-affected zone of flame cutting is large.

The section is rough and has hanging slag.

Maintenance requirements:

Maintenance of the flame cutting bed is relatively simple and can be mastered by the user himself.

2. Fine Plasma

Fine Plasma

Fine plasma uses high temperature ionized gas to produce a high energy density cutting arc, so it can cut all conductive materials.

The latest technology requires no operator experience.

Fine plasma is best suited for cutting carbon steel from 26 gauge (approx. 0.45mm) to 2″ (approx. 50mm) thick, and stainless steel and aluminum up to 6¼” (approx. 160mm) thick.

5′ x 10′ plasma cutting machine cost:

150,000 – 250,000 RMB (faster, equipped with height adjustment and dust removal)

Cutting cost per unit part or unit length:

On carbon steel from ¼” (approx. 6.35mm) to 2″ (approx. 50mm) thick, plasma cutting costs are the lowest relative to other processes.

Ease of use:

When equipped with the latest CNC and software, plasma is very easy to learn and use.

Since professional process parameters are already built into the nesting software, there is no experience required of the operator.

Productivity:

Cuts faster than laser for thicknesses greater than ¼” (~6.35mm).

Cuts faster than flame at thicknesses less than 2″ (~50mm).

Plasma is the fastest and most efficient of all cutting processes.

Cut part accuracy:

Dimensional tolerances for carbon steel cut pieces are approximately ±0. 015″ (approx. 0.38mm) to 0.020″ (approx. 0.5mm).

For thin plates less than 3/8″ (approx. 9.5mm) thick, the slope is 2-3 degrees.

For thicker boards than 1/2″ (approx. 12.7mm), the slope is within 1 degree.

Edge quality, metallurgical properties:

Heat affected zone is very small, usually less than 0.010″ (about 0.25mm).

Good weldability of the section, smooth and no hanging slag.

Maintenance requirements:

Maintenance is relatively simple and can be mastered by the user himself, or only requires telephone support from the manufacturer.

3. Fiber laser

Fiber laser

Fiber laser is the latest laser technology available.

It uses a solid-state laser generator that is more efficient than the traditional Co2 laser, and the wavelength of the fiber laser is suitable for conduction in the thin, flexible fiber, which is more flexible and easier to maintain than the Co2 laser, which can only be conducted by mirror reflection.

The high-energy laser is focused to melt the material being cut, and an auxiliary gas (usually oxygen when cutting carbon steel) blows off the molten metal.

A 3 kW fiber laser is equivalent in cutting power and speed to a 4 to 5 kW CO2 laser. Its cutting capacity is typically up to ¾” (about 19mm) thick carbon steel.

5′ x 10′ fiber laser cutting machine cost:

300,000 – 500,000 RMB (laser cutting bed requires higher motion accuracy and shade protection)

Cost per unit part or unit length cut:

Laser cutting costs are most advantageous for thicknesses less than ¼” (about 6.35mm).

As the thickness increases, the cutting speed decreases significantly and the cutting cost is higher than plasma, although the quality and accuracy of the cut are excellent.

Ease of use:

Similar to the latest plasma systems, when equipped with the latest CNC and software, laser cutting machines are just as easy to learn and use, as all settings are automatic.

Productivity:

Highest productivity on thin sheets, equal to plasma as thickness increases to ¼” (~6.35mm).

Cut part accuracy:

The best fiber laser cut parts have dimensional tolerances within roughly ±0. 01″ (about 0.25mm).

Better than plasma and equivalent to waterjet.

The slope is within 1 degree.

Edge quality, metallurgical properties:

The heat affected zone is slightly smaller than the plasma.

Maintenance requirements:

Compared to the previous CO2 laser, the fiber laser is substantially less difficult to maintain and can generally be mastered by the user with telephone support from the manufacturer.

4. Waterjet

Waterjet

Waterjet technology has been around for decades and has been used on a wide range of materials from cake to granite.

Soft materials can be cut with pure water, where a high-pressure stream of water (40,000 to 60,000 psi) is compressed by a nozzle, increasing the flow rate and energy density.

Sand can also be added to the water stream, which acts like the teeth of a saw, cutting under the impetus of the water stream.

Current state-of-the-art waterjet pumps can reach 100,000 psi of high-pressure water.

Higher pressures mean faster-cutting speeds, but certainly more downtime for maintenance, as the pump seals need to be replaced regularly.

Two of the biggest advantages of waterjets over other cutting processes are the lack of heat affected zone and the ability to cut virtually any material.

In addition, the waterjet cutting accuracy is very good. However, the biggest disadvantage of waterjets is their slow cutting speed.

Cost of 5′ x 10′ waterjet cutting machine:

200 – 350,000 RMB (low motion performance requirement due to slow speed, cheaper than laser bed, slightly more expensive than plasma cutter)

Cutting cost per unit part or unit length:

Since waterjet cutting is so slow, the cost per part cut is the highest compared to other processes.

Ease of use:

Similar to the latest plasma systems, when equipped with the latest CNC and software, waterjet cutting machines are just as easy to learn and use. Very little experience is required of the operator.

Productivity:

Very slow on carbon steel and stainless steel, cutting aluminum will be faster.

Cut part accuracy:

The accuracy of the waterjet is the best of all cutting processes, with dimensional tolerances of cut pieces within approximately ±0. 005″ (approximately 0.13mm).

The slope is within 1 degree.

Edge quality, metallurgical properties:

No influence on the metallurgical properties of the material to be cut.

Smooth section, cutting quality is related to the grit and cutting speed (the slower it is, the smoother it is).

Maintenance requirements:

Maintenance is relatively simple and can be mastered by the user himself.

Conclusion

Clear your needs and practical applications first, and consider the various process characteristics described in this article, I believe you will be able to choose the most suitable metal cutting process and equipment.

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