In the late 1960's PLCs were first introduced. The primary reason for designing such a device was
eliminating the large cost involved in replacing the complicated relay based machine control systems.
Bedford Associates (Bedford, MA) proposed something called a Modular Digital Controller (MODICON) to a
major US car manufacturer. Other companies at the time proposed computer based schemes, one of
which was based upon the PDP-8. The MODICON 084 brought the world's first PLC into commercial
production.

When production requirements changed so did the control system. This becomes very expensive when
the change is frequent. Since relays are mechanical devices they also have a limited lifetime which
required strict adhesion to maintenance schedules. Troubleshooting was also quite tedious when so
many relays are involved. Now picture a machine control panel that included many, possibly hundreds or
thousands, of individual relays. The size could be mind boggling. How about the complicated initial wiring
of so many individual devices! These relays would be individually wired together in a manner that would
yield the desired outcome. Were there problems? You bet!

These "new controllers" also had to be easily programmed by maintenance and plant engineers. The
lifetime had to be long and programming changes easily performed. They also had to survive the harsh
industrial environment. That's a lot to ask! The answers were to use a programming technique most
people were already familiar with and replace mechanical parts with solid-state ones.

In the mid70's the dominant PLC technologies were sequencer state-machines and the bit-slice based
CPU. The AMD 2901 and 2903 were quite popular in Modicon and A-B PLCs. Conventional
microprocessors lacked the power to quickly solve PLC logic in all but the smallest PLCs. As conventional
microprocessors evolved, larger and larger PLCs were being based upon them. However, even today
some are still based upon the 2903.(ref A-B's PLC-3) Modicon has yet to build a faster PLC than their
984A/B/X which was based upon the 2901.

Communications abilities began to appear in approximately 1973. The first such system was Modicon's
Modbus. The PLC could now talk to other PLCs and they could be far away from the actual machine they
were controlling. They could also now be used to send and receive varying voltages to allow them to enter
the analog world. Unfortunately, the lack of standardization coupled with continually changing technology has made PLC communications a nightmare of incompatible protocols and physical networks. Still, it was
a great decade for the PLC! 

The 80's saw an attempt to standardize communications with General Motor's manufacturing automation
protocol(MAP). It was also a time for reducing the size of the PLC and making them software
programmable through symbolic programming on personal computers instead of dedicated programming
terminals or handheld programmers. Today the world's smallest PLC is about the size of a single control
relay!

The 90's have seen a gradual reduction in the introduction of new protocols, and the modernization of the physical layers of some of the more popular protocols that survived the 1980's. The latest standard (IEC
1131-3) has tried to merge plc programming languages under one international standard. We now have
PLCs that are programmable in function block diagrams, instruction lists, C and structured text all at the
same time! PC's are also being used to replace PLCs in some applications. The original company who
commissioned the MODICON 084 has actually switched to a PC based control system.

Cartesien Robot Palletizer 

Takes part of a new family of manipulators / robots for palletizing, developed to satisfy the hight and medium requeriments of production lines, since 400 to 1200 bags / hour. With the maximum rubustness, efficiency and economy. According to most actual demands of automatization it is intelligent, modular and adjustable to the particular needs of each production line.

In this kind of machine, a the arms are moved through three Cartesian Axles and rotate on vertical axle. The bags are caugh one by one from the rollers conveyor to the designed point by the control program. This process has no limit for the the shape of the bags, the degree to which they are filled, or by the type or nature of the materials.

The utilisation of a PLC control system permits the complete automation of the operating movements and the automatic regulation of the position of the mechanical parts which move the bags and the pallets.

The bag dimensions, the number of bags by layer and the coordinates at which they are to be placed, as well as the pallet dimensions can be recorded in the memory, and all this data can be allocated with a program number.

On simple recall of this program number through the interactive screen allows the change of the memorised pattern and automatic adjustement of the machine. This system simplifies the programming and reduces the configuration time.

The intuitive commands in the tactile screen make easier the programing and adjustment of the robot, also, gives a detailed information of all the incidences with the diagnostics program.

The RC 600 Robot palletizer comes complete with safety devices compliant with current EC standards.
 

TECHNICAL DATA

• Maximum speed: 450 - 750 b/h, depending on the number of bags per layer
• Workable bag weights: from 10 to 50 kg
• Minimum pallet dimensions: 800 x 1200 mm
• Maximum pallet dimensions: 1100 x 1400 mm
• Maximum palletized load height: 1800 mm, including pallet height
• Operating system: PLC
• Power supply: 380 V- 50 Hz / 440 V-60 Hz

OPTIONS

• Stainless steel finish of the trapdoors.
• Parts in contact with the bag (rollers, plates, etc.) in stainless steel.
• Dispenser for placing cardboard sheets on the pallets.
• Possibility of working with pallets higher than 1800 mm.

For non-standard pallet dimensions, the technical feasibility of the plant must be confirmed.