The manufacturing industry, particularly the automotive sector, today relies more than ever on automated production in multi-shift operations. However, automated production is efficient only if the technology can be controlled and the investment and operating costs are manageable and can be calculated in advance. Two very important aspects in this respect are the technical availability and the process safety in multi-shift operations, and a prerequisite for these are the full and complete monitoring of all functions and processes.

Today, the automotive industry plays a leading role in the area of automated production. This is done primarily with the aid of industrial robots in all parts of the factory and, especially, in the bodywork production.

Here, the raw sheets of metal and the semi-finished parts are handled, as are the welded assemblies and the complete car bodies. In many cases, technical reasons dictate the use of vacuum gripper systems. These are the ideal solution due to their many positive characteristics: flexible utilisation, high suction forces, secure gripping, low weight, suitability for highly dynamic motion, the widespread use of standardised components for relatively low manufacturing costs, high reliability to ensure the necessary process safety and relatively low operating and maintenance costs.

The enormous cost pressure forces the process engineer to increase the efficiency of the robot and handling systems even further, while maintaining the process safety in all imaginable situations. This means that more and more process parameters have to be monitored, not only for the above reason but also to optimise the process, to avoid faults, to reduce the maintenance costs, to improve the performance and availability and to ensure the necessary flexibility in use.

As a central element of a handling system, both vacuum technology and the vacuum gripper system are also affected by these considerations because the rapid establishment and maintenance of a reliable vacuum in every possible situation plays an important role in the overall handling process. The same applies to the achievement of the shortest possible cycle times for gripping and releasing the workpieces, and this is the reason why distributed actuators and sensors are being used to an increasing degree. This is the only way the vacuum gripper system or vacuum generator can react quickly enough to such things as gradual maladjustment, leaks or defects and initiate the necessary countermeasures.

Integrated sensors increase
productivity and process safety

In order to increase both the process safety and the dynamic operation of a handling system, without incurring other drawbacks, the vacuum specialist J. Schmalz GmbH in D-72293 Glatten has developed a very innovative mini-inline vacuum valve, which can also be equipped with a miniaturised vacuum sensor. This worldwide unique design makes it possible, for the first time, to measure and control the vacuum directly at the suction pad.

The body of the inline valve of the series IV3-3/8AG-3/8IG or IV3-3/8AG-1/4IG is similar to that of the well-known Schmalz SVK check valves. One flat of the hexagonal body carries a 4-pin, M8 plug connector via which the solenoid valve is supplied with power.

This means that the standard Schmalz cables with elbow connectors can also be used for the miniaturised inline valve, helping to keep the costs for purchasing and for keeping spare parts as low as possible. The inline valve has a normally-open (NO) contact, since the air flows axially through the valve body, with minimum flow resistance, when no current is flowing. When the valve is energised, the so-called plate armature opens an axial vent hole and simultaneously closes the axial hole through the solenoid. The armature chamber, and thus the suction pad, are now vented to the atmosphere via the radial holes to prevent a vacuum from being generated in the suction pad as it is pulled away from the workpiece. The workpiece can now be removed, but the vacuum in the hoses of the system is maintained.

This fact, and the fact that only the internal volume of the suction pad, and not the complete hose system, has to be evacuated, the time needed to grip the next workpiece is reduced to a minimum. The same flat of the valve body also carries a threaded M5 connector which lead directly to the hole which opens into the suction-pad connector. This permits the new vacuum sensor VS-V-SD60-M5/VS-V-SA-M5 to be mounted for direct measurement of the vacuum in the suction pad.

The 3/8“ screw connector contains a sieve to prevent dirt from entering the armature chamber, where it could cause malfunctions of the valve.

Inline vacuum valves – modular components
for intelligent handling solutions

The advantages of the integrated valve and sensor technology of the inline valves from Schmalz speak for themselves:

• the vacuum is measured where its value is important;
• incorrect measurements which could result from blocked vacuum lines are a thing of the past;
• the control system can react directly to the measured values by, for example, deactivating a defective suction pad while maintaining the vacuum in the rest of the system;
• the combination of inline valve and vacuum sensor permits individual adaptation to changing process parameters;
• the compact valves can be mounted directly between the spring plunger and the suction pad, without the need for adapters;
• in the form of a combined inline valve and vacuum sensor, these standard vacuum components form the basis for intelligent vacuum systems with distributed control of the suction pads and the process.

Possible applications, some of which have already been implemented, exist in the production of sheet-metal parts in the automotive industry and in the production of kitchen appliances. A typical example is and intelligent and flexible system for loading the machines with metal sheets, with the aid of which the expensive press systems can be operated 24 hours a day with the necessary process safety.

Since it is now possible to measure and control the vacuum at each individual suction pad, universal and flexible vacuum spiders can now be designed to handle a whole range of different parts by deactivating the suction pads which are not in contact with the workpiece. This, in turn, reduces the costs for compressed air and other sources of energy, which means that the maintenance costs for compressors and other devices are also reduced. Of course, such vacuum spiders with individually controlled suction pads are used in other sectors of industry for handling, for example, wooden parts, furniture components, sheets of plastic, cardboard boxes and sheets and many other similar objects.

A further possible application  for the inline valve is to use it on a "calibration suction pad" when a new handling system is being set up and adjusted. The above-mentioned combination of an inline valve and a vacuum sensor makes it possible to measure the vacuum at each individual suction pad, to optimise the hose lengths or suction-pad positions as necessary and, finally, to improve the programming of the sequence of operations for handling the parts. This results in far shorter running-in times and the related shorter system standstill times during the installation or modification of handling systems.