posted in Processes in the Spotlight
CNC Plasma cutting is used to cut shapes and contours through the full thickness of flat sheet or plate metal and through the wall thickness of sections such as pipes and structural beams. It is this output of a 2 dimensional profile or a profiled section that has earned Plasma Cutting it’s general categorisation as a “Profiling” process.
Plasma is, very basically, gas heated by an electric arc to form a plasma beam capable of melting metal almost instantaneously. The combination of the heat of the plasma, and the pressure of the concentrated stream of gas forms the cutting mechanism - the plasma melting through the thickness of the material, whilst the pressure of the gas removes the molten material.
CNC Plasma Cutting Configurations
CNC Plasma Cutting capability can be broken down into 3 main groups which can be found across the UK, varying in stock forms and number of control axes available. So let’s get into it...
2D Plasma Cutting
Also called flat-bed Plasma Cutting, produces flat profiles from plate or sheet, with straight cut edges at 90 Degrees to the profile surface. Typically, high powered Plasma Cutting beds are configured in this way, giving the largest depth of cut of between 100-150mm.
3D Plasma Cutting
Similar to 2D Plasma Cutting, and also commonly referred to as flat bed Plasma Cutting, this variation adds a third dimension through the introduction of an angular cut or bevelled edge through the sheet or plate material. Typically, High Definition Plasma Cutting beds are configured in this way, giving the greatest flexibility, accuracy and / or speed.
Tube & Section Plasma Cutting
The stock material and the cutting axes are the major changes and enhancements in comparison with flat bed Plasma Cutting. The Plasma Cutting Head is typically stationary whilst the section or pipe is manoeuvred under the beam creating not only end profiles, but slots, tags and holes within the section or pipe.
These machines may or may not be fitted with a tilting head or 3rd axis, enabling not only the cutting of the section, but the bevelling of its edges or countersinking of holes - as with the above described “3D Plasma Cutting”
What processes typically accompany plasma cutting?
Fabrication, Bending, Rolling, Welding...
Plasma cutting is commonly used to cut profiles to be used in fabrication, including bending, rolling and welding. In the manufacture of large diameter pipe and section it is possible to plasma cut pipe end profiles, and partially cut holes and junctions from the flat plate material. Later, when the flat profile is then rolled and seam welded the formed pipe doesn’t require any further shaping, other than to fully cut the partially cut holes and junctions.
Plasma cut profiles are also a common stock material for further processing by a multitude of machining processes. In this instance Plasma cutting is acting as the bulk material removal process, providing the machinist with stock material that includes some machining allowance. It’s possible in many cases that profiles require minimal machining such as drilling and tapping after being plasma cut, this is due to the high level of accuracy and the quality of the cut edge that is achievable with plasma cutting.
In instances where the material being plasma cut needs increased flatness, plough grinding or “Lumsden” grinding can be performed. This increases the flatness of the profile, whilst providing the added benefit of removing the material skin and cleaning up it’s appearance. Only the planar surfaces of the cut profile are processed during plough grinding, the cut edges are left unaffected.
A Tilting head or 3rd Axis on a CNC Plasma Cutting machine allows the creation of bevelled edges, contours or countersinks in the stock material, whether it be flat or of 3 dimensional section. This can be highly useful in instances where plasma cut pipes and profiles are designed to form angular junctions, or weld preparations are required. However, not all CNC Plasma cutting systems offer this 3rd axis, or tilting head, so it is common for profiles to go through an edge preparation process after Plasma Cutting. This can be applied along the long flat edge of a profile, or the contoured edge of a hole or slot formed in a pipe or section. Using CNC Edge Preparation a huge variation of preparation shapes can be achieved, as opposed to a simple angled cut possible with Plasma Cutting.
Cleaning & Preserving...
Sometimes the material being processed has a crust or skin which needs removing, in these cases the plasma cut profiles can be cleaned or processed in a number of ways to suit your needs. Cleaning processes such as pickling or abrasive blasting can be employed, whilst it’s also possible to paint profiles to prevent further corrosion, or providing a final finish. One benefit of these cleaning processes over plough grinding is that all surfaces are treated, inclusive of cut edges.
What processes are alternatives?
Plasma cutting competes with all profiling technologies in the processing of sheet and plate metal materials. This is due to its wide range of applications in terms of thickness and flexibility. Most commonly it will compete with flame cutting and laser cutting technologies, but does offer some significant advantages over both.
Plasma Cutting vs Flame Cutting
Plasma Cutting vs Laser Cutting
What to consider when choosing and specifying Plasma Cutting
Plasma cutting does form a heat affected zone on the cut edge of a profile, this is due to the fact that the cutting mechanism is by the melting of the stock material. The level of energy used in plasma cutting is significantly lower than flame cutting due to it’s cutting speed, and therefore the Heat Affected Zone is smaller with plasma cutting.
Although CNC Plasma Cutting can cut sheet metal materials, in many cases laser cutting is stronger in the cutting of these materials from a cost and performance perspective. This is particularly true for very thin sheet metal materials.
Plasma cutting can be used for plate, sheet and grate or mesh materials, however sandwich form materials such as honeycomb, which have voids throughout their thickness cannot be cut. This is due to the breakdown of the plasma beam as layers are cut and voids are exposed to the cutting head.
Plasma cutting is applicable to a wide range of metal cutting situations, from flat plate materials through to 3 dimensional sections.
CNC plasma cutting is a process that is typically applied to large stock forms of material such as large plates or sheets of material. The plasma cut profiles in most cases are themselves a stock form for further processing.
Sourcing plasma cut profiles could offer an improvement through the reduction of heat affected zones and distortion over profiles currently flame cut. Reducing the cost and difficulty associated with further processing such as machining the hard cut edge of the flame cut profile and combatting distortion and stress due to heat input during the cutting process.
Where can I find a Plasma Cut Profile Supplier?
In the UK we have a vast range of material stockists, fabricators and value-add stockists who can provide the exact service, or combination of manufacturing services you require.
You can start your search today - need Plasma Cutting, Plate Rolling and Welding from one supplier? No problem - just head on over to the Manufacturing Network Supplier Search Engine and you’ll find suppliers offering the exact combination of processes you require.
You’ll be amazed at how you can start improving and simplifying your supply chain through using our Supplier Search Engine to find suppliers with capability that matches your exact needs.
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