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The Rupp Report: (R)evolutionized Dobby And Jacquard Weaving

Jürg Rupp, Executive Editor

Up to now, a dobby or Jacquard machine has always been connected with the weaving machine. Every weaver knows the problems with high-speed weaving. Stop-and-go is just one problem; marks in the fabric after a stop or a restart contribute to inferior-quality products.

Any inconsistency in the process causes problems, and the higher the speed of the propeller shaft during production, the higher the forces. Consequently, the wider the machine, and the greater the distance between the harnesses of the Jacquard machine, the greater are the vibrations on the entire system.

For decades, the weaving community around the world has asked for a system that would avoid all these problems. A new development called SyncroDrive from Germany-based weaving machinery producer Lindauer Dornier GmbH might be the solution.

For the first time, there is a possibility to separate the weaving machine from the dobby or Jacquard machine. This means there is the possibility to have an independent shed. All limits are eliminated in weaving, because the weft insertion is freely programmable.

Separate Drives
In conventional weaving systems, the weaving machine and the Jacquard machine have separate drives with servo motors. In Dornier's SyncroDrive system, there is no shaft drive, but there is a connection via an electronic beam. Air-jet machines have a drive connected directly to the main shaft.

Also, the rapier weaving machine with a nominal width up to 290 centimeters (cm), like the air-jet machine, has a direct drive. Rapiers with a nominal width from 300 cm up have a direct drive with a flywheel connected directly to the main shaft. The Jacquard machine has a direct drive with a flywheel on the main shaft. For the shedding device, relatively small motors are needed — 6 to 8 kilowatts, depending on the number of boards.

The patented SyncroDrive is a low-maintenance drive system without clutch-brake unit, with a separate motor for the shedding device. The inventor of the SyncroDrive was Valentin Krumm, the former head of weaving technology at Dornier and predecessor of Gerhard Bögl, the current head of the Technology Center for Weaving Technique in Lindau, Germany. Krumm is also the mastermind behind Dornier's positive rapier weaving machine. The intelligent drive design has extremely small speed variations compared to conventional direct drives.

The SyncroDrive reads the desired weft insertion and stores it. The last weft insertion remains memorized during the next startup. The Jacquard machine's shed formation speeds up, for example, over eight to TEN insertions to reach the specified speed. Similarly, the weaving machine speeds up over one weft insertion to reach the specified speed. The synchronization of the two machines starts when both have reached the specified speed. Then, the true weaving process — the weft insertion — begins. If the job is completed or stopped, the last insertion is memorized while the machines shut down. The shed formation shuts down over eight to ten insertions to a full stop. The weaving machine shutdown is carried out over one weft insertion to a standstill.

Through the use of the SyncroDrive, the propeller shaft is eliminated, so problems such as start and stop marks no longer exist, which has a very positive impact on the whole weaving system. The SyncroDrive does not operate with cams, because a cam motion can't be run independently.

Thanks to the machine's soft start and stop, start and stop marks are avoided. Also, the last reed beat-up is perfectly executed because the SyncroDrive memorizes the last weft insertion. The Jacquard machine is separated from the weaving machine and can shut down smoothly.

The propeller shaft used in conventional weft insertion is replaced by an electronic beam. Therefore, vibrations in the Jacquard machine's frame are minimized. The ground vibrations are reduced, and speed variations are less than 3 percent. In a top-class weaving mill, using SyncroDrive, the oscillations were reduced by more than 50 percent. When the author physically tested the machine, the vibrations were very low.

Dynamic Warp Guide
Dornier mentions that the highly dynamic warp-yarn guide unit (DWG) enables weaving with the lowest possible warp tension level, leading to a significant reduction in warp-end breaks. Through its synchronous movement with the shed motion, this patented, roller-free unit guarantees an ideal tension balance between the opening and closing shed motions even at maximum machine speeds.

More detailed information will be provided in an upcoming issue of Textile World .

July 30, 2013