Warp beam control – a short history

The evolution of warp beam control from 1947 to today

Let’s start with an overview

Warp beam control development and use since KAST 483 (1983)

1947 — Willy Grob AG is established

Willy Grob founded his company for weaving machine accessories in Zurich in 1947. The manufacturing programme included various accessories for weaving machines, including warp beams. In order to achieve the necessary tension in the warp threads, the warp beams were braked with chains and ropes.

1960 — Invention of band brakes

This type of warp tension control did not always meet the requirements, as there was no shed compensation. Willy Grob then developed and patented a band brake in which the warp tension was generated with springs and a shed compensation was also integrated. This design was intended for warp beams with lower warp tensions.

A little later, a braking unit for ground beams with higher warp tensions was added to the range.

1979 to 1983 — Patent “Positive warp let-off device” to the Kast 483

40 years ago, the first positive warp let-off device was developed by Willy Grob AG.

With the increase in weaving machine speeds and the use of synthetic warp materials, some of which have a high elasticity, the band brakes previously used proved to be disadvantageous. These facts gave rise to the idea of feeding the warp threads to the weaving machines in a positive manner.

On April 9 1979 Willy Grob AG applied for a patent with the title “Positive warp let-off device”, the patent was granted on April 30 1979.

The KAST 483

After several failed attempts, Leo Kuster, together with the company REGATRON, succeeded in developing the first marketable warp let-off control KAST 483. At that time, the basic beams of the weaving machines were equipped with negative, mechanical warp let-off devices and there was no need to change anything.

For the high beams, however, band brakes were still used. The KAST 483 was designed to replace these belt brakes. After a short time, warp let-off controls KAST 483 were also used on ribbon weaving machines.

1986 — Development of the KAST 186

The introduction of the KAST 483 was very successful, and more and more requests came in to also positively feed the warp threads of the ground beam for sensitive fabrics to the weaving machines.

As the warp yarn tensions in the ground beam are higher, the application limits of the KAST 483 were quickly reached. Therefore, a warp let-off control had to be developed very quickly to meet the new requirements. This is how the KAST 186 came into being.

1992 — From analogue to digital: the DIGI-KAST

The KAST 483 controller was also used for the production of technically demanding and sensitive ribbons in ribbon weaving mills. Since several warp beams often had to be controlled in ribbon weaving mills and the cost of the KAST 483 was too high, the idea was born to be able to control up to 4 warp beams with one controller.

At the same time, the time was ripe to change from analogue to digital warp beam control. This idea was patented on August 16 1993 and granted on May 31 1996. The result: the DIGI-KAST.

For small warp beams the power units were integrated into the control system, for larger warp beams and warp yarn tensions external power units could be used.

1996 — Microcontrollers and servo motors: the KAST 696

Due to the rapid development in the field of semiconductor technology and modern microcontrollers, it was possible to develop the KAST 696, which allowed the use of servo motors.

The control was designed for the operation of 3 servo motors, two of them for the warp let-off and one for the fabric take-off. With motor torques up to 14 Nm, solutions were possible that were not offered by the weaving machine manufacturers.

1997 — Make it simple: development of the Solex 297

The cost pressure on electronic warp let-off systems in ribbon weaving mills is extremely high and to meet these demands the idea of a low-cost design was born.

In the spirit of lean production, the control system has been reduced to the essentials to keep costs down. An attempt was also made to reduce the mechanical components to the essentials. For example, the warp beam was no longer positively connected to the gearbox, but was driven by a tangential friction wheel, which drove the warp beam peripherally, as had previously been the case on the SOLEX mopeds.

However, it was not long before a new product was developed using this control. This was the selvedge thread feed on wide weaving machines.

1997 — Development of the KAST 197

The KAST 186 controller has been in use for more than 20 years. Now the end of an era is foreseeable and decided. The replacement is in full swing. The KAST 186 will be replaced by the KAST 197.

2008 — Universally adaptable: the UKAST

After only about 10 years, the KAST 197 was also replaced by the UKAST. The U in the type designation stands for Universal. Unlike the KAST 197, the control does not have an integrated frequency inverter, but is equipped with an interface so that various commercially available frequency inverters can be used. This means that the control can be universally adapted to customer requirements.

2012 — Intermediate solution: the KAST 912

The KAST 696 was developed in 1996 in cooperation with the company DEIMO S.p.a. in Italy. With the takeover of DEIMO by Stäubli, the KAST 696 was replaced by the KAST 912.

2017 — Switch to ERGOTRON: the KAST ERGO

Sales of the KAST 912 did not meet Stäubli’s expectations, so production of the control was discontinued. Since then, CREALET has been using the control from ERGOTRON, Italy, for servo applications.

The result: the KAST ERGO.

2017 — Visualize, simplify and access remotely: the KAST BLDC

The warp let-off devices used so far for selvedge thread feeding on wide weaving machines and for warp tension control on ribbon weaving machines were equipped with spring-loaded dancer rollers. The warp tension was adjusted by mechanical springs. The reproducibility of the settings was not guaranteed and thus the fabric quality produced was not constant.

These were reasons to measure the warp tension by means of load cells in order to visualise the respective warp tension and to simplify the adjustment of the warp tension.

In addition, a solution was sought to provide customers with remote access and remote support via TeamViewer. All these new requirements resulted in the new KAST BLDC warp let-off controller.

The KAST BLDC also marks the start of the cooperation with BRUNNER for all types of drives.

2021 — For higher warp tensions: development of the KAST LCM

The KAST LCM warp let-off control was developed as a supplement to the KAST BLDC for higher warp tensions. All functions of the BLDC have also been integrated into the KAST LCM.

2023 — The latest development: the KAST ECR

At the ITMA in Milan, the new KAST ECR warp tension control is presented to the trade for the first time: the idea is that the warp beam does not need to be driven, as the warp tension is sufficient and the warp beam only needs to be braked.

In the past, this was often achieved with weight-loaded rope brakes. As the warp beam diameter decreased, the weights had to be changed. In order to avoid this non-value-adding work and at the same time to keep the warp tension constant from the full to the empty beam, the KAST ECR was developed.

The warp tension is monitored by load cells or distance sensors. Either the tension or the position of the pendulum is displayed on the control panel. Many functions of the BLDC have also been adopted for this control.