igus develops energy supply solution for rotational and linear motion

Customer requirements for turning machines have changed and now demand shortened processing and tooling times, reduced amount of effort needed for process development and integration and, at the same time, an ability to handle the increasing degree of complexity. The new Multisprint from DMG MORI meets all these challenging requirements. Nozzles for fluid power equipment, implants for dentistry and shafts for motor vehicle manufacturing are just three examples of complex components that can be made. The result is a manufacturing solution for scalable requirements from initial series production to the high-volume production of complex workpieces.

The heart of the machine is the spindle drum with six spindles for simultaneous machining of several workpieces. The main spindles in the drum have a travel of up to 180mm. The drum moves the workpieces to the tools quickly and very precisely. It only takes 0.65 seconds for one of the six spindles to travel to the next position. For spindles to return to the starting position after machining has been completed in the six stations, the drum must turn 300 degrees in reverse. For this, the unit, which weighs over three metric tons, only needs one second. The rods are pushed out of the loader through the drum to get into position for machining. How did DMG MORI manage to implement the different types of movement with this speed and precision?

Custom-made

In summer of 2016, DMG MORI invited tenders for the catalogue of requirements and the Cologne plastics specialist igus was awarded the contract. Mirko Passerini, Technical Director at DMG MORI's Italian location GILDEMEISTER Italiana S.p.A. and responsible for the development and production of the MULTISPRINT, explains the decision in favour of igus: "We have a lot of confidence in the many years of experience that igus has in the development of custom-made energy supply systems. As well as in the company's extensive, high-quality testing facilities."

The first meeting of the experts from the two companies took place in January 2017. Plans for the sheet-metal design were made and suitable cables and hoses for supplying the drum with energy, data and fluid were chosen. "The readychain solution from igus was the breakthrough for us", adds Passerini.

The unique energy supply system rotates with the drum and enables the linear movements of the spindle drums. Consisting of a metal frame, cables, hoses and chains, the system is located in the middle of the machine and is suspended from the drum, which rotates at high speed. The rotary energy supply system rotates along with the drum. The standard rotary modules consist of two circular guide elements. One part of the guide trough is attached to the stationary part of the system and the other to the rotating part. The reverse bend radius enables movement of the energy chains in two directions. Here, a rotation angle up to 540 degrees on one plane is possible.

The drum in the Multisprint rotates in a range of 300 degrees and consists of two rotation systems. In the outer system there are the hoses, as they need a somewhat larger bend radius, which is 160mm. In the inner circle, twenty-four cables are guided – twelve encoder cables and twelve servo cables. For each of the six linear chains, there are two encoder cables and two servo cables. One of the servo cables supplies the energy for the linear movements of the main spindles in the drum and one drives the spindle motor. They can move at a speed of 0.66m/s and with a maximum acceleration of 10m/s².

Modular components

The engineers from igus had three months to develop the system. During development, a lot of value was placed on the modularity of the individual components. The linear chain systems can be plugged in and the sheet-metal parts designed by igus, for attachment to the machine, are made of several parts. This facilitates handling of the readychain on the customer's premises and makes harnessing in the igus factory easier.

“Before delivery, the entire system was tested extensively,” says Lukas Czaja, Head of Industry Management Machine tools at igus. At its headquarters in Cologne, igus operates the industry's largest test laboratory, which is 3,800 square metres in size. A specially developed test stand simulates the movements of the multi-spindle automatic turning machine. In the realistic environment used, the readychain has already completed more than 800,000 cycles without any problems.

Today, the Multisprint combines the productivity of a production turning machine with the precision of an automatic turning machine and the complexity of a universal turning machine. It is therefore able to make complicated turned and milled parts in the areas of bar machining and chuck machining - without a lot of effort being needed to retool the system. Today, dozens of Multisprints are in use in Germany, Italy, the US, Spain and other countries. “The customers are thrilled and understand the concept of the new machine immediately,” explains Passerini, “and they especially like the ease of maintenance that the igus energy supply system enables.”