Customers of linear modules are like car buyers at times. Some want the basic model and others want all of the features to meet their needs, or their pocket. This is why Bosch Rexroth is offering its Omega modules with ball rail guide under the brand name Rexroth in various sizes and is equipping them with optional safety dampers to protect the end positions.
The timing belt that embraces the drive wheel in an "Omega shape" gave the Omega modules their name. Their drive is found on the carriage in contrast to the standard modules. This allows variable fixing and mobility options for the carriage and main body depending on the arrangement. The solution from the Rexroth Bosch Group is therefore particularly suitable for longer strokes in a vertical and horizontal direction. The system, which was primarily developed for the areas of handling and assembly, allows increased dynamics with higher loads over longer travel distances. Drives mounted in a fixed position with a travelling main body are perfect as the vertical axis. Due to the low travelling dead weight, this arrangement makes it possible to delve into large working ranges. The three sizes with main body widths of 55 mm, 85 mm and 120 mm achieve an optimum process with high repetition accuracy and good rigidity at the same time. To increase the customer's flexibility even further, it is also possible to mount additional motors. As a variation, the user can mount the main body in a fixed position and operate several carriages with their own drive independently of each other.
Constructors from the Rexroth Bosch Group considered an industrial impact damper to protect the Z-axis against damages due to uncontrolled movements. The developers located in Schweinfurt have been cooperating with the Nürnberg company Roth GmbH & Co. KG for more than 20 years on this issue. Their customer advisors were integrated in the Omega module construction business. "Development of new timing belt linear axes within the Rexroth Bosch Group with the special arrangement of drive element took place in 2009 for which our engineering was requested for design and consultancy. After successful completion and the first successful prototype test runs, the three new axes were standardised and introduced to the market as the Omega module OBB", reminisces Reinhold Michl from the Roth project team. The team considered special industrial impact dampers from ACE for the safety elements required by the Rexroth Bosch Group: "ACE is an innovative company with a good structure and vision. We experienced this from the beginning of our cooperation in the year 1996 and we wanted to incorporate it in this project", says Michl's colleague, Edyta Urbanska, who is responsible for commercial customer support at Roth GmbH & Co. KG.
Trust is decisive
There were nine months between the task and the initial orders for the impact dampers alone. During this time, numerous on-site visits with samples took place on one hand while the best solution was tracked down in design calculations on the other hand. This shows how the company in Schweinfurt wanted to be very certain when it came to protecting the Omega modules. After all, this element intended to provide a certain something extra for particularly demanding customers. From the number of possible damping solutions, the Roth-Team advised the use of safety dampers from the company ACE from the very beginning. These are suitable as a more affordable variation for use only an emergencies in comparison to the standard industrial impact dampers. However, due to the fact that three different load ranges between 20 and 90 kg needed to be covered and with an impact speed of up to 5 m/s in the worst case, several safety dampers solutions came into question. These resulted from the designs made with the help of a calculation program from ACE Stoßdämpfer GmbH after entering all relevant parameters. A slightly higher impact speed was assumed in all cases to give the Omega modules some leeway.
While the ACE type SCS33-50 impact damper with a maximum energy absorption of 620 Nm per stroke would be sufficient for low load ranges, the evaluation showed that the larger variation, type SCS45-75 would be required for the higher moving mass of a maximum of 90 kg for the 1,654.6 Nm per stroke. This means they are more than well-equipped from the impact damper point of view for the purpose of only providing a reliable service in an emergency. However, the experts from Roth say that accidents should certainly not happen to the Omega modules with their high quality control and the proven drive solutions. Trust in the dampers from the market leader ACE ultimately clinched it with one of the leading market companies for drives, control and movement. The automatically adjusting, compact safety dampers provided with a fixed impact point have therefore been installed in the Omega modules since 2011. And it proves to have been a good decision; when they were asked about the experiences gained with the products used, Michl and Urbanska unanimously agreed: "They fulfil the task reliably just as expected. Our customer would have otherwise certainly already heard complaints. But we don't know about any problems at all."
