Robot-based CO2 laser cutting

Citation

(2008), "Robot-based CO2 laser cutting", Industrial Robot, Vol. 35 No. 5. https://doi.org/10.1108/ir.2008.04935eaa.002

Robot-based CO2 laser cutting

Robot-based CO₂ laser cutting

Article Type: Viewpoint From: Industrial Robot: An International Journal, Volume 35, Issue 5

Jeff Franks Laser Resources, Melbourne, Australia

Keywords: Robotics, Material-removal processes

Laser cutting is a well established application for metals, plastics, wood and even paper in almost every area. The first systems were installed in the 1970s for 2D applications. Later this process was also used for more complex parts and stepped into the third dimension. Many mirrors where needed to cover the necessary beam guidance in the five axis of such a system. With the well established robots as manipulators for almost every job in automation it was just a short move to get lasers involved with robots as system technology.

There are instances where parts are manipulated by the robot in front of stationary laser beams. Such as the partial cutting of dashboards for airbag applications (due to the complicated sensors required to ensure only a specific depth partial cut is achieved). This is however not so common and most robot-based CO₂ laser cutting applications involve the robot carrying the process head (delivering focused laser beam and cutting assist gas). Several configurations of which are possible.

Where higher power is required the use of an optical arm with typically five articulated joints is well known. Almost any type of high-power CO₂ laser can be used with these arms (e.g. from Arnold Maschinenfabrik) the limiting factor being the cooling system on the mirrors of the arm. But, the better the beam quality of the lasers applied, the better the results in cutting. The process head can be fitted with an additional linear axis with capacitative height control if it is to be utilised on metallic parts where focus position and stand off height are critical. For non-metallic (typically plastic) a less costly and lighter cutting head can be utilised. In addition to the process head, a break away mounting for the arm is common to avoid expensive damage to the arm in the event of a robot crash. This is due to the limited movements the robot can make when fitted with an optical arm.

It is also possible to carry the entire laser on or as part of the robot. This method took off after the introduction of sealed slab lasers as these could be carried by the robot. In position on top of the robot with RF PSU, then the beam redirected via a small optical arm on the robot. This format is inexpensive as the robot is standard, but you also carry over the limitations on robot movement due to the optical arm. Options are therefore available with customised robot types either still carrying the laser on top with optical path through the centre of the arm and a fourth and fifth axis specifically designed to deliver the beam into tight work area’s or to do away with the top arm of the robot altogether and replace this with the an encased laser and an endlessly rotating fourth and fifth axis which also carry assist gas and cooling. These systems are already available with laser powers up to 600 W.

A new development with these systems is for them to be equipped with a beam deflection head and focus optic. Allowing processing of s/w controlled shapes (up to 100 × 100 mm) in a single robot position. This is mainly suitable for plastics due to the limitations focused spot size, and lack of gas assist during cutting.

Robot-based solid state laser cutting

Solid state lasers are developing at a rapid rate in recent years due to big advances in the beam quality of the laser sources. Of course, these lasers have always had one significant advantage over CO₂ lasers and that is there capacity to be delivered through a flexible fibre optic. With the development of diode pumped Nd:YAG lasers a much improved beam quality was available and these lasers saw systems put into production that could both weld and cut. The robot carries the all important fibre and is able to pick up the required processing head depending on the job required.

With the development of disc lasers in more recent years, this beam quality has been even further enhanced enabling high-quality cutting finish and at even greater laser powers. Some “Q-switched” disc lasers have been utilised with robots and optical arms (as the peak power is too great for fibre delivery) for very specialised automotive small cutting applications of painted body panels with no damage to surrounding paintwork!

Recently, perhaps fibre lasers offer the greatest new potential and there is great interest in the laser industries ability to produce high-power fibre lasers with single order modes for cutting applications. Not so long ago these lasers would never have been considered for the industrial cutting market, but with all of the major manufacturers developing products and with the market for these lasers predicted to double in the next few years, it already started its success story in the robotic cutting applications next to welding and other purposes.

Robot-based laser usage is generally state-of-the-art. The laser source is chosen based on the applications and hundreds of theses systems are installed globally.