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Curvic Plate prevents replacement of complete gearbox

Innovation from APEX Dynamics increases maintainability of new bending machine Dynobend

An email with seven design specifications. That was in fact the start of the collaboration between Dynobend and Apex Dynamics on Dynobend’s “125 Power Boost”. The specifications concerned the large forces that would be generated in this new, fully automatic bending machine. The drive mechanics had to be able to transmit these forces effectively and ensure low maintenance. Solutions were found in close consultation.

By Martien van Zaalen

The new machine is completely customer-specific, but it is made up of a number of “ideas” that have the opportunity to be reused later in other machines for different customers. Said Mark Luttikhuis, global sales & marketing director of the machine builder from Haaksbergen. A machine that, with a bending moment of 105 kNm (kilo-Newton meter, a unit for torque) and a roller force of 200 kN, generates very large forces for an electrically driven machine. To determine the correct gearbox, pinion (a certain type of gear) and rack (a toothed bar), Dynobend engineers contacted their colleagues from Apex Dynamics in the Netherlands.

FIVE DEGREES OF FREEDOM

The development process for the machine started earlier with a request from an automotive customer, Luttikhuis explains. This party was looking for a solution for the automated production of a certain type of symmetrical profiles. Profiles that, so far, required a lot of manual work and resulted in quite a few failures. Luttikhuis can not be more specific than that because of the Non Disclosure Agreement that this customer had Dynobend signed. To do that work effectively and efficiently, a machine that combines bending and rollingwhile offering five degrees of freedom for the roller was required. The machine is intended for 24/7 production of large series and must therefore be able to run completely independently. So the automated and integrated systems for supply, removal and cleaning also were to be supplied. A machine that can be programmed based on the 3D CAD drawings of the product that need to be produced. “Our software generates all control software fully automatically from that drawing. This applies to our machines in general: we want to make the work preparation of the customer as easy as possible. If required with auto-correction: produce a single product and digitally scan it in our measuring cabinet. Then it is checked to what extent the scan result differs from the CAD file and based on that the system adjusts the control system fully automatically, so that the second product is perfect.

DETAIL ENGINEERING

The 125 Power Boost also had to be powered electrically. While greater forces can be generated hydraulically, an electric drive with servomotors can be controlled and adjusted much more precisely. “Electric is therefore the trend in our business. The first concept therefore immediately included servo drive and a planetary gearbox. “But how and with which forces had to be transferred exactly, from servo motor to bending work, that was discussed in the detail engineering phase. After some searching in the range of gearboxes from different suppliers, Apex Dynamics became involved, a supplier which Dynobend had previously done business with, according to Luttikhuis.

CHALLENGE

That first question was posed in a brief e-mail with the design specifications. Thom van Oss, general manager of the Benelux branch of Apex in Helmond, brought the A4 sheet to the interview in Haaksbergen. That served as the starting point for a configuration process during which a certain type of relatively small servomotor and a large, low-backlash gearbox was selected in a weeks-long collaborative process. “Such a small motor on a large gearbox – that actually does not look the prettiest,” says van Oss. “But this combination can handle those forces and torques. A considerable challenge was the customer requirement of maintainability. Because of these great forces, wear of the toothed ring (a kind of round rack) occurs in any case. It needs to be renewed after millions of cycles. We had to make sure that we didn’t have to replace the entire gearbox of about 170 kilos. Because that is a costly and time-consuming job. “The solution was found in the fact that Apex was prepared to develop and produce “ a customer-specific pinion based on the curvic plate”.

CURVIC PLATE

In a bending machine, a rotational movement needs to be converted into a linear movement. This is done by rotating the pinion over a rack. The pinion is mounted on the output shaft of the gearbox and with that connection the problem was solved. Van Oss: “You prevent mechanical wear by eliminating backlash. So the pinion is usually welded to the output shaft. But at some point you have to replace the pinion. If it is welded, you have to replace the entire gearbox. That is why we have developed the curvic plate. The pinion is mounted on this curvic plate in the new machine. Backlash-free thanks to the convex and concave-shaped cams that this round plate has. The plate itself is mounted on the output shaft of the gearbox with high strength bolts, van Oss explains. “When replacing the pinion, that curvic plate will also be replaced. In a fraction of the time and costs required to replace the complete gearbox. ”

MAINTAINABLE

“The maintainability,” Luttikhuis adds, “is one of the strengths of our bending machine and is something that the customer attaches great value to. Already in the first design phase, we take the accessibility of the wearing parts into account, we ensure that engineers can easily reach them with a crane. And that they can then quickly exchange these wearing parts. Together with Apex, we have also succeeded in making this new machine very maintenance-friendly. In addition to this gearbox, Apex Dynamics also supplies the drive mechanics for the 125 Powerboost supply and discharge systems.

STANDARD IS NEVER STANDARD

Standard is never standard, says Mark Luttikhuis. It rarely happens that two exactly the same bending / rolling machines leave the factory in Haaksbergen. At least there is a difference in the tooling that is on it. “Our standard machines consist around 80 percent of parts and modules that we use more often and 20 percent of customer-specific parts. These machines are standalone and distinguish themselves through their flexibility. “They are easily convertible and suitable for single pieces or small series”, Luttikhuis promotes. In addition, the manufacturer develops and builds custom work: fully automated machines that, integrated in a complete production line of, for example, an automobile company, perform bending and rolling work fully automatically. “They usually consist of no more than 60 percent standard parts.” These two machine types are developed and assembled completely in Haaksbergen, where also the tools are produced. For that, Dynobend works with a large number of suppliers. One of them is Apex Dynamics. This Taiwanese manufacturer of gearboxes, racks and pinions has its own branches with distributors and engineers worldwide.

Sources:
www.dynobend.com
www.linkmagazine.nl

Picture:
Com-magz