Bringing colour to the street

By Michael Selle

The wide range of colours available for automotive paint finishing provides vehicle owners with the personalization they want. In order to achieve this, flexible paint supply systems are needed in the paint shop.

For the first time, Durr is set to equip an entire paint shop in the USA with an EcoSupply P special paint supply system. The piggable system’s low paint loss rate, low flushing agent consumption and rapid colour changing will ensure efficient processes in the paint shops.

The ever-growing range of colours in body painting entails not only special paints but also increasingly small-batch colours. For such applications, Durr offers the EcoSupply P standardised modular paint supply system. The system, which employs pig technology, is equally suited to water-based paints and solvent-borne paints.

“Durr has installed special paint supply systems for automobile manufacturers all over the world. Now, we’ve received our largest individual order for the EcoSupply P yet. For the first time ever we are equipping an entire paint shop for body and bumper painting in the US with a total of ten systems,” said Dr Hans Schumacher, president & CEO of Durr’s application technology division, describing the global success of the efficient system.

Compared with the previous ring-pipe systems, Durr pigging systems consume considerably less paint and flushing agent. With the rising prices of special paints, this gives piggable systems* a decisive edge - investing in special paint supply systems will pay off very quickly.

In the project, the car bodies are to get fourteen additional small-batch colours, including two applied using what is known as tri-coat premium painting. The process applies different colour shades to the body in direct succession during base-coating. Because the existing robots’ paint-ring-pipes can only be supplied with a maximum of twenty colours, the automobile manufacturer is upgrading to piggable systems.

Paint recovery and cleaning using pig technology

The small-batch colours are painted in batches of 15, 30, or 60 bodies. While the painting process is underway, a second system is already performing the next paint change. TheEcoSupply P system delivers the paints by sliding cylindrical pigs through hoses to the paint spray booth - with extremely low paint loss.

The pig destination modules are integrated directly into the Durr EcoMCC3 colour changes**, which are installed in the trolley docking station of the existing thirty-two robots on the base-coat lines and the six robots used for bumper painting. When the paint has been applied, the pigs push the remaining paint back out of the hoses. This leaves almost no residue in the process returning it to the paint tanks and cleaning the hoses. The system houses the paint supply stations in a separate paint mixing room beneath the paint spray booth.

Simple to use

Durr is also supplying the system’s visualisation function and the control unit that will in future communicate with the existing plant and robot systems. The visualisation function tells the system operator which paint spray booth needs, which colour. After connecting the paint tanks, a simple push of a button suffices to start the filling process and automates pig-based painting.

The current project takes the number of EcoSupply P systems deployed in the USA to twenty-five in total. In European plants, Durr’s special paint supply systems have been in use since 1999.

During that time, more than 420 systems have been installed at various automobile manufacturers and in plastic parts paint shops in the industry’s supplier sector.

Customer requirements

The customer requirements for these special paint systems are very different:

• There are customers who can continue to use the paints after initial painting

• Customers who cannot use the paints again, i.e. painting with genuine, so-called small-batch colours that are only needed once

• The available ring pipes that can be connected to the robots at most no longer suffice for customers and their new vehicle models with their different colour palettes that are supposed to be painted on the same painting lines.

• Likewise, EcoSupply P systems are already being used in several paint shops for the currently increased number of colours available in the clear coat area (matte and coloured clear coats).

• Moreover, the number of colour changes per day for special colours plays an important role when selecting a system. This ranges from 3 to 100 colour changes per day. In the truck business, for example, every driver’s cabin or its plastic components are successively painted in different colours on several painting lines.

It requires intensive communication between the control, conveyor and robot technology, as well as the paint mixing room, in order to have the right colour available in time for each painting cycle. Likewise, the paint systems and the pigging lines must be flushed in time for a new colour so that the necessary system number can be minimised.

Durr’s product range features a variety of pigging systems for these different customer requirements and different kind of applications. All these systems allow almost 100 percent of the paint to be recovered.

• Basic main pass system: One 9-mm pig hose is looped through the robots on each side of the paint booth. A simple yet effective system for connecting a small number of robots.

• Main pass system: The system is for connecting many robots. One 16-mm pig hose is laid on each side of the paint booth. The robots themselves are connected by separate 9-mm pig hoses.

• Single pass system: Each robot is connected by a separate 9-mm pig hose. This allows the robot to be supplied with only the colour required for the painting process. This is becoming more and more important due to the increasing number of special paints.

The EcoSupply P system’s modular design enables different paint supply units with capacities of 10 to 500 litres to be combined in a highly flexible way which also allows for the use of effect paints. Durr offers various handling concepts:

• Fully automatic systems for 1-x paint systems, which are connected to 1-x pigging systems. The customer changes the colour in the paint systems only rarely or uses one or two separate small systems for genuine small-batch colours. The overall system processes the paint spray booth’s colour requirements independently and on time.

• Fully automatic paint cabinets for 20- to 25-kg tanks. The customer only has to load the paint cabinet with a new colour whenever a colour request is made.

• Some manual work steps must be performed in the semiautomatic systems to flush the paint system during a colour change.

• So-called pigging is done fully automatically by the control system in all of the above-mentioned systems.

High efficiency

Using Durr robots that mount the colour changer on robot front arm allows paint loss to be reduced. Depending on the number of robots, this is as little as 300 ml per colour change. Depending on the technology used and the tank size, flushing agent consumption lies in the range from 6,000 to 20,000 ml per colour change, dropping the colour change times between 15 and 60 minutes per colour change.

* Pigging technology is a conveying method that almost completely removes any paints and flushing agents from hose systems. A fitting body tapered in the middle - the pig itself - is pressed through the hose system with compressed air. (Pig = pipeline inspection gage)

** The colour changers from our competitors can also be equipped with Durr pigging technology by using an adapter or short hose as the connection.

Author: Michael Selle is Product Manager Special Paint Supply Systems, Durr Systems AG

© Coatings Special by Chemical Today magazine

Read More: Bringing colour to the street