Compact automation for small parts production

As a specialist in product and high-performance automation, Austrian machine manufacturer Stiwa, headquartered in Attnang-Puchheim, has been developing automation, production and software solutions for 50 years. One example of this is the modular LTM-CI compact automation system, which shows how high-performance automation works in the smallest of spaces. It is designed for products with a diagonal space of up to 30 mm and is itself the result of a drastic downsizing, as Roland Schiermayr, Head of Automation Research and Development at Stiwa, reports: "A customer who produces many millions of dampers for a furniture store every year wanted to purchase a new machine for production. The existing one was 10 m long and disproportionately large for the production of small components just a few centimeters long due to the limited production space. For us, this was the impetus to exploit all the possibilities for miniaturization."

Function modules for different work steps

The result of the development work is the compact LTM-CI, a flexible automation platform that can be 3 to 4 m long, depending on the design and equipment. A rigidly interlinked transport system forms the basis, while the other equipment is adapted to the individual application requirements. Up to 22 function modules, each 90 mm wide, can be integrated for different work steps, for example for pick-and-place applications, laser welding with up to five degrees of freedom, for screwing, press-fitting, labeling or for testing and measuring processes. This makes compact automation suitable for small parts production in a wide range of industries. A major car manufacturer, for example, uses it to produce valves for an anti-lock braking system.

The valves are just 8 mm long, consist of just a few components and are produced in seven-figure quantities every year. Production has to work at half-second intervals to cope with this quantity. First, the individual parts are fed from storage containers, separated using a vibrator and placed on a conveyor system for the first production step. The components then travel to the appropriate station, where delicate grippers pick them up and fit them together or process them in some other way. The cycle times have been significantly reduced with the LTM-CI, which in turn enables a considerable leap in productivity.

Driving force of the actuators

The drives of the actuators in the function modules play a key role in this. The mechanical engineers discovered the drives from Faulhaber for this purpose. The LM 1247 linear motor, for example, plays an important role in the LTM-CI. It is installed at up to 20 points in the system, including in stop units, i.e. slides that interrupt the material flow, and in grippers. A particular strength of this linear motor is its high speed. This drive also delivers enormous thrust: at just 12.5 mm wide and 19.1 mm long, it develops a continuous force of 3.6 N. "At its peak, it even manages 10.7 N," emphasizes Roland Schiermayr. "There is no other small linear motor on the market with this power density."

The brushless DC motor from the 2250...BX4 series also impressed the machine builders. It drives the swivel units in the gantry handling of the compact automation system, which are used to bring tools or components into a specific position. In addition to high dynamics and compact dimensions, an accessory was also important in the selection process, recalls Schiermayr: "We need very high precision and repeat accuracy at this point. It was therefore an important argument for us that Faulhaber can supply this motor with a matching multiturn absolute encoder. Its signals are required for the high quality of production and quality assurance."

Trouble-free over 60 million strokes

However, the decisive parameter for Stiwa is the durability and long-term reliability of all components. This is because the company guarantees its compact automation customers trouble-free operation over 60 million strokes. All moving parts, including the motors, have to play their part. "We subject our own parts as well as the purchased components to endurance tests," says Roland Schiermayr. "We try to destroy them through wear and unfavorable conditions. We only install them in the machines if they pass this endurance test. Faulhaber motors have proven that they can withstand such extreme demands. They help us to achieve our own requirements for reliability and service life with minimum space requirements and the shortest cycle times."

Hanover Fair, Hall 6, Stand B22