Most fabricators have the same goals in mind: to produce better parts, retain and attract customers, and grow their business. There are many steps required to meet these goals, but few are as critical as investing in quality equipment.
With so many equipment options to choose from, particularly in the world of laser cutting, how does a fabricator narrow down the list? A good starting point is to take a closer look at a machine’s accuracy and precision, both in terms of quantifiable specifications and in features like machine vision-based alignment.
Accuracy and precision
Simply stated, precision allows fabrication of parts that are highly consistent. Accuracy, on the other hand, compares a finished part to the ideal dimensions. With these two conditions there are four possible outcomes.
Low precision and low accuracy. The worst possible outcome. The part features are neither repeatable nor sufficiently close to their measurements as defined by the part specifications. The process must be changed or improved dramatically to produce high-quality parts and maintain throughput.
High precision and low accuracy. In this case, part dimensions differ consistently and predictably from specifications. Sometimes rework can make up the difference but this process impacts throughput and efficiency.
Low precision and high accuracy. In this case, part dimensions often match specifications but a lack of consistency results in many out-of-tolerance parts. Some parts make it into the next manufacturing step while others must be reworked or scrapped.
High precision and high accuracy. The best of both worlds. Part-to-part repeatability ensures consistent output and results that can be steadily passed onto the next manufacturing step. High accuracy means that parts are sufficiently close to their ideal dimensions. High consistency and quality enable smoother operations and better products for the end user.
Start with performance
To achieve the gold standard of high accuracy and precision, fabricators should look for laser cutting equipment that is stable and robust. In the case of IPG Photonics’ LaserCube fiber laser cutting system, several aspects stand out, including the high-performance components, assembly method and supporting technologies.
As the world’s leading manufacturer of fiber lasers, it goes without saying that IPG views laser quality and performance to be an essential part of any advanced laser system. A focus on beam quality, long-term power stability and matching laser parameters to the job helps systems like the LaserCube produce excellent results cut after cut.
Accuracy and precision also require a stable platform, and natural granite is the foundation found in many of the turnkey laser systems manufactured by IPG, including the LaserCube. Natural granite offers a number of superior material properties, primarily high strength and stiffness that enable excellent absorption of vibrations caused by machine motion. Natural granite also has a low coefficient of thermal expansion — approximately half as much as that of steel and cast iron.
The motion system of the LaserCube is driven by non-contact brushless linear motors and high-precision linear encoders, both critical elements for high-performance cartesian systems. The LaserCube uses a gantry configuration with two motors and encoders powering the Y-axis with a single motor driving the X-axis. This design enables high acceleration due to the lightweight design of the cross axis. Minimization of moving mass dramatically reduces following error at high speeds and accelerations to allow for rapid traverse and contouring velocities.
Alternative motion systems like ball screw and rack-and-pinion systems require periodic maintenance and they eventually wear, compromising system performance. Systems that utilize rotary encoders often suffer accuracy issues due to manufacturing variations in the pitch of the lead screw or rack. In the longer term, wear of the recirculating ball bearings in the ball nut will reduce repeatability.
High-performance components can only do so much, however, if they are not assembled with sufficient attention to detail. The assembly of each LaserCube is performed using precision metrology tools and assembly techniques to measure critical features like straightness, flatness, squareness and parallelism of the guideways. The result is unmatched cutting accuracy and precision.
Sticking the landing
Still, external factors can result in parts and features that are out of spec. Poor part fixturing or tolerance issues caused by previous non-laser manufacturing steps can result in incorrect cut placement even when the laser cutting system is performing as intended.
With this in mind, the LaserCube can be equipped with a vision system that automatically adjusts laser targeting to position cuts where they belong relative to existing part features. While machine vision has been around for decades, manufacturers have more recently begun to recognize its value in laser cutting applications.
The LaserCube’s vision system scans parts prior to firing the laser to automatically account for the effects of dimensional deviations or operator error, reducing process requirements prior to laser cutting. For complex and pre-processed materials such as screen-printed plates, punched parts or chemical-etched components, vision registration minimizes rework and helps ensure high-quality results.
Although cutting has become one of the most common applications of lasers and laser systems, optimizing feature quality and throughput sometimes requires additional considerations.
In addition to turnkey laser systems, IPG also offers application evaluations and process development. Global application labs and laser processing experts work with fabricators to ensure that systems like the LaserCube will meet, or exceed, their expectations. The process often starts with samples, which are processed by IPG before the lab delivers a report and the recommended system configurations. IPG will also develop a full process for fabricators to use with their laser system to ensure a smooth and effective implementation.
