- XXL Laser cutting of oversized metal sheets
- Working area of 16,000 x 4,000 mm
- Chamfer cutting up to 45 degrees
CNC laser cutting has been possible for us in a new dimension since 04 May 2012. We started up a laser machine, with which sheet metal blanks up to 16,000 x 4,000 mm are possible. We decided to make this investment, as we wanted to be able to cut large parts, which we bend on our 16 meter long press brake, too. Our new machine is also suitable for machining small parts. There is room on the cutting table for up to 32 small format (2x1m) metal sheets, which are cut to size fully automatically without monitoring.
What our new machine can do:
- XXL laser cutting of oversized metal sheets and plates
- Laser cutting within the working range of 16,000 x 4,000 mm
- Laser cutting chamfers up to 45 degrees
- The CNC laser cutting is now faster and enables a quality we were previously not able to achieve.
- Loading and laser cutting take place simultaneously, which means that job processing times are also reduced.
- The new machine is very robust and is far easier to service. In this way, downtimes are reduced to a minimum.
- It has a Chamfer head, with which chamfers up to 45 degrees can be cut. In this way the chamfer cutting and cutting the material to size take place in the same work operation.
- With our new machine we extend our CNC laser cutting capacity many times over. This means that we are able to process your orders even more quickly.
Sheet machining with the speed of light
It is an acronym for Light Amplification by Stimulated Emission of Radiation… The acronym laser has established itself as the commonly used word.
In order to cut workpieces with a laser beam, an energy beam must be generated in the laser source, which is highly focused using a lens. The CNC-controlled beam liquefies the material within the preprogrammed cutting joint. In this way very complex contours can be cut out with maximum precision, which would hardly be possible with conventional machining methods. We use CNC laser cutting to machine steel and stainless steel sheets and plates from 1.0 to 25.0 mm thick or aluminium sheets and plates up to 15 mm.
CNC laser cutting – what types are there?
Flame cutting (aka gas cutting)
In this method, oxygen is blown into the effective area of the laser beam. Oxygen is a very reactive gas and causes the molten material to burn instantaneously. Flame cutting is faster than fusion cutting, as oxygen die amplifies the heat generation of the beam and assists the cutting process. However, reactions between oxygen and metals are also disadvantageous. The oxidised cutting edges frequently have to be cleaned and descaled. Flame cutting may only be used for steel products.
CNC laser cutting at Rime
We opted for this method as it offers advantages compared to flame cutting, which benefit you as the customer. The material is first melted by the laser beam. But instead of oxygen, nitrogen is blown into the kerf. The highly concentrated gas jet removes the molten material from the kerfs and also prevents slag and scale from forming.
Nitrogen does not form any compounds with other elements. Gases with these properties are called “Inert gases” or “shielding gases”. Apart from nitrogen, argon and helium also have properties, which are frequently also used as a gas mixture for CNC laser cutting.
Cost-affecting factors of CNC laser cutting?
Choosing the right material thickness
Our laser cutting machines have an output of 4,000 and 6,000 watt. The cutting speed must be adjusted to the material thickness. Laser parts made of thinner metal sheets are cut out quickly. The speed must be reduced for thicker sheets and plates, in order to obtain a smooth cutting edge. For this reason, laser cutting of thicker sheet metal parts is more time and cost-intensive.
Recesses / openings and contours
It goes without saying that cutting out complicated contours requires more time than creating simple geometric shapes. If cutouts or openings also have to be made in the workpiece, the time required increases considerably. First, the beam cuts through the metal sheet (Arrow 1). This process is called cutting in and takes place with reduced laser power. If the laser beam were to hit the smooth surface of the material with full energy, part of the laser beam could be reflected from the surface.
In unfavourable cases, this can damage the lens of the cutting head. To obtain clean cutting edges with CNC laser cutting, the laser cuts through the material in the middle of the cutout, the machine guides the beam along the programmed edge (Arrow 2), and cuts out the cutout with a clean cutting edge (Arrow 3).
The effect of different gases
The choice of cutting gas has a direct effect on the production costs. A gas pressure of 1 bar is sufficient for the oxygen supply to achieve optimum results. As the liquefied metal is blown out in fusion cutting nitrogen has to be brought to a pressure of 20 bar. A lot of nitrogen is required to build up this high pressure, which affects the costs.
What are the advantages of CNC laser cutting compared to other cutting methods?
Different materials can be cut with the same machines. Theoretically it would even be possible to work wood or plastics. Thanks to its computerised controls, the machine is able to cut out different shaped laser parts from a metal sheet panel. This means that several jobs can be machined simultaneously. Every conceivable form or shape is possible, which is a large advantage compared to Shearing.
There are no limits to creativity. Computer programs help to position the workpieces. For example, smaller laser parts are arrange in areas which would remain unused with conservative metal machining. If nitrogen is used there is no need for time-consuming rework of the cut edges. Our flexible use options also enable individual parts or small series to be produced.
Are there any disadvantages?
Despite its many advantages, laser cutting unfortunately also has a few economical and financial disadvantages.
- The acquisition costs for a machine are very high.
- The health and safety requirements are very strict.
- CNC laser cutting uses up a very large amount of energy.
- Shielding gases must be used.
Nitrogen is used for fusion cutting, and is blown into the kerf at high pressure during the cutting process. The gas consumption of large machines is extremely high and is a decisive cost factor.
Another challenge is the thickness of the material. Our laser cutting machines can cut through steel up to 25 mm thick. The thicker the sheet the slower the cutting has to be to cut through the metal completely. The more slowly the laser beam cuts through the material, the more heat is transferred to the metal sheet. The additional heat causes more material to be melted on in the cutting clearance than is wanted. At the same time, knurling, characteristic for laser cutting, occurs which can be so marked that material edges have to be reworked, in order to ensure the best possible product quality.
This reworking is very time-intensive and causes additional costs. This is also the reason why laser cutting thicker materials is no longer so economical.
Another problem can also occur with thicker workpieces. On cutting in the laser beam is deflected by a minimum amount and therefore produces a slightly inclined cutting edge. This can have a negative effect on the dimensional accuracy of the product. It is therefore frequently not possible to do without reworking. Unfortunately, correcting the material edges takes time and costs money. In the case of smaller material thicknesses the deflection of the laser beam does not play any noteworthy role.
The tape shot
In order to prevent angle deviations in advance, it is necessary to ensure that the laser beam is guided through the lens with the most precise alignment possible.
Before starting the cutting process the exit angle of the beam must be checked, by getting the laser beam to cut through an adhesive strip. The “tape shot” enables best possible adjustment, in order to produce products with excellent quality. The CNC laser cutting does not start until the beam exits the cutting head in an absolutely centred position. It is only with greater material thicknesses that the deviation is so large that reworking is necessary.
What does a laser machine consist of?
Design and function
Our laser machines are suitable for cutting flat metal sheets or plates to size. They cannot be used for laser cutting plastics and other materials due to the high output, as they burn easily. Only metallic materials can be machined.
In principle, all laser machines have the same basic design. The heart of the machine is the laser cutting head, which is moved via guide rails in three axes. By adjusting the Z-axis, the cutting head adapts to the height of the workpiece. Controlled feeds of X and Y axis control the laser cutting head in any arbitrary point.
As our laser machines know the precise position of the material, it is sufficient to place the metal sheet on the workbench. If the alignment deviates by a few degrees, the computerised controls correct his fully automatically.
Laser beams are reflected off glossy surfaces. With the high power involved, even reflected beams can cause skin burns and/or eye injuries. For this reason the laser cutting is shielded by a protective enclosure or cabin.
The enclosure should not only protect against radiation, but also emissions of dust and gases. Our machines develop a total power output of 10 million watts in the focal point. This power heats the sheet metal so much that it vaporises. High-alloy mild steels contain a large number of elements such as chrome, nickel, copper or titanium and in a gaseous state have a harmful effect.
Fine duct with a particle size of one to five micrometres can also be dangerous for the human body. The enclosure is equipped with an extractor and a professional filter system to minimise emissions.
Our laser machines have automatic pallet changers with two pallets each. These are located in the exit position, outside the protective cabin. In this position both pallets are stocked on top of each other.
The workpiece is placed on the top pallet by a crane and is moved into the cabin for laser cutting. During the cutting of the metal sheet the workpiece can be placed on the second pallet first. Following completion the pallets are exchanged.
The photos were taken in test mode and show how the chamfers are cut. In normal operation the laser head is shielded from the outside world for safety reasons so that the cutting of the parts is not visible.