Application Changes at a Press of a Button

Drive Technology in Woodworking Machines

Machine Operates at the Push of a Button

Machines with a high degree of automation and the greatest possible customer benefit are trending in woodworking. “A machine’s program change should, in principle, be possible at the push of a button,” emphasizes Denis Lorber, Head of Research and Development at Holz-Her in Nürtingen. “Customers generally want the machine to be pre-set and pre-positioned.” What used to be a unique feature of large industrial machines now applies to all series – including entry-level machines. This is made possible, among other things, by decentralized drive technology.

Automated units are now being offered even for simple edge banding machines up to the entry-level segment. “A few years ago, this would have been taboo because customers did not expect it,” Lorber explains. The increasing automation for entry-level machines is also a response to the skilled worker shortage. “In the past, skilled workers on-site knew how to set machines; our customers today rely on machine operators who may only know where to press a button.” This accelerates the pace of automation, reaching into the entry-level segment. This phenomenon is not only observable in Germany but worldwide.

Demanding Drive Technology

For automation to meet its high expectations, control and drive systems that use uniform interfaces are needed. The systems must be able to network with each other without problems. Holz-Her, therefore, relies on CAN and Ethercat. The networking extends to every single drive in the woodworking machine. Accordingly, the requirements for drive technology are high. “It ranges from high-end AC servo drives, which we use in many of our products, to three-phase asynchronous drives, to small positioning drives that we need in high quantities to position our machine units very precisely to a hundredth of a millimeter without operator assistance.”

Integrated Stepper Motors

A drive solution found in almost all Holz-Her machines is the stepper motors with integrated electronics from drive manufacturer STXI. Dr. Markus Erlich, Vice President of Marketing and Portfolio Management at STXI, explains why this solution is particularly effective: “The integrated converter operates the stepper motor with an encoder like a servo motor. That is, the stepper motor is commutated as if it were a high-pole servo motor.” This offers advantages over traditional stepper motors. “The drive has no step losses and high energy efficiency, as only the currents required for the demanded torque flow – not always full currents as with the classic stepper motor,” Lorber adds. “We also perform position control. So, the motor holds its position and behaves essentially like a servo motor.” Currently, these drives are prominently featured in edge banding machines and CNC machining centers.

These drives are particularly suitable for edge banding machines. “Because these machines have many different units with sometimes up to six or eight axes per unit. For customers, it’s important to quickly switch between different edges and processes without having to open the hoods. Manual intervention in the machine is undesirable. What counts is not losing time when switching from one workpiece to the next,” Lorber says. “We are now so fast that we can even switch in the gap between several parts in the machine.”

Integration of the Drives

To ensure smooth operation, Holz-Her involved STXI very early in the engineering of the machines. Lorber says, “There is also a Holz-Her specific firmware that we have frozen. This prevents sudden incompatibility with our control world during software revisions.” The integration is regulated in detail. “It extends to various functions, e.g., the behavior during referencing, behavior and colors of the LEDs. All positioning commands are captured. The software developers of both houses have done a great job. They have quickly reacted to every change in the market. It was a model collaboration,” praises the Holz-Her development head.

But it was not only about software. “We also developed a hardware variant specifically for Holz-Her without a heatsink,” recalls the STXI Vice President. “The often sharp-edged heatsinks of motors protruding far out of the machine could injure operating and service personnel. Therefore, these motors now run in variants with one or two stacks without cooling fins.”

Connectors were also a matter of coordination. “Together we defined which connectors are used and in which direction they are installed. The goal was a space-saving design as well as simple installation during the initial commissioning at the production plant,” Denis Lorber explains another detail.

How this works with STXI, Erlich explains. “In the early phase of product development, we try to meet all customer requirements. At this stage, we can still make corresponding adjustments in standard products. Customer orientation is very important to us. We are not a catalog company – that’s why we make changes in a product line that we offer as standard if necessary. With the Holz-Her drives, a connector could be completely eliminated by dispensing with the I/Os connected there.”

Heat Development and Commissioning

For Holz-Her, the decentralization of the drives was also a compelling argument. Lorber explains why this is necessary: “We rely on decentralized drive technology because we had to combine a relatively high density of drives with comparatively little space in the control cabinet.” Besides reduced cabling effort, the thermal behavior of the machine also favors decentralized drives. “It’s always good if you can let the thermals escape into the atmosphere where they are generated, and ideally, they shouldn’t enter the control cabinet at all.”

Both partners have learned from each other in this aspect. “We produce almost 700km from Nürtingen, in Austria. Therefore, our commissioning technicians must be able to commission all drives without the help of a software developer,” explains Lorber: “When a machine is switched on for the first time, many drives report in that are not initially known. Therefore, we have built in intelligence that enables quick commissioning. Together with STXI, we have thus adapted the type plate.” The ID is now included in the QR code. The number on the label corresponds exactly to the one with which the motor registers on the bus. Thus, during serial commissioning, the motor is practically scanned via the barcode reader. The motor then directly connects to the specific axis through the commissioning software. Crucial to this was, of course, that the Holz-Her software development department coordinated with STXI. The goal has been achieved. Almost everything runs at the push of a button.

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