Reciprocators and anthropomorphic robots, alternatives to manual spraying

In the woodworking sector, on the other side of those who promote the manual manufacture of objects, there are those who are irrevocably won over by the technical side, by machines using the latest technology. This is also the case in wood finishing. Unlike those who apply oil or wax with a brush, cloth or trowel, they prefer modern finishing materials applied with the most advanced systems. In the case of spraying, the complexity of the guns is determined by the complexity of the technologies, how 'manual' or automated they are. There are simple guns for simple technologies, but also reciprocators or anthropomorphic robots when the technologies are more dependent on machines than humans. I propose to talk about these spraying systems, about their choice according to performance, but also according to the needs of the plant.

Spray finishing lines

Spraying can be done manually or with automatic systems. With manual application, the emphasis is not primarily on productivity but on the human ability to apply the varnish as well as possible to all parts of the object. When using automated systems the main requirements are productivity and reproducibility of the final result.

In automatic systems the parts to be finished pass at a calculated and constant speed through the right of one or more guns. They are called finishing lines and comprise several operations that are done automatically by machines. Basically it is a system that transports the parts (conveyor belt, chain), moving them automatically from one operation to another (sanding, grinding, varnishing, drying).

The making of these lines depends on the shape of the objects to be finished. In the case of smaller objects or dismountable furniture, conveyor belts are used on which the components are placed and varnishing is done with guns mounted in an enclosure through which the belt passes. We have already talked about this type of finishing linesso I won't insist.

However, there are also larger objects that cannot be lacquered on such lines (fitted chairs, windows), in which case chains are used to hang the objects. Varnishing is done when the object reaches the point where the application system is located.

Types of guns used on chain finishing lines

Basically, application systems fall into 3 categories:

• manual application - application is done by a person wielding a simple gun or pump;
• automatic application by vertical translation movement - the application is done automatically, the gun moving in a vertical direction (up-down) while the parts to be coated pass in front of the gun. Basically it is a 2-axis application system: horizontal (conveyor) and vertical (gun). Such guns are called reciprocating guns;
• automatic application by 6-axis movement - this is done by a robot that copies the movements of the human hand, applying the material from any angle. The robot can be programmed to repeatedly apply the material to any shape. These robots are called anthropomorphs.

For all these systems the guns can be airless, airmix, electrostatic or for application of powder paint.

Manual application

In such applications, the sprayer is positioned at a fixed point and the objects pass right by him. Application is done with guns mounted on pumps. This is how window frames or chairs are finished. There are also lines on which furniture is finished, but they move on conveyor belts with wheels.

Manual application makes the system cheaper than an automated one. The disadvantage is reduced productivity and the possibility of not achieving the same result for all objects being finished.

If the objects to be finished are more difficult, requiring more attention, this system is very suitable. The sprayer can constantly see the surface of the object, intervening immediately if defects appear.

Reciprocal

The system is used for less complicated objects. It's basically a 2-axis application - vertical and horizontal, with the gun moving only in one direction. This restricts quite a lot the range of products that can be finished this way.

It is possible to combine several such systems so that the object is covered from several sides. If a face-to-face application of a panel is desired, one reciprocator will be mounted in one direction and the other 180° to the first. In this way the panel moving with the chain will pass through the right of the 2 reciprocators and will be covered on both sides.

The system has a much higher productivity compared to manual application and the result is the same all the time, independent of human intervention. The disadvantage is, as already mentioned, that it cannot be used for coating more complicated objects. However, by combining several such guns, the range of products is considerably diversified.

Anthropomorphic robots

We are already talking about state-of-the-art machines with outstanding performance. Such a robot 'at work' looks like something out of a science fiction film. The gun is mounted on the end of a robotic arm capable of replicating the movement of the human hand and arm. The movements of such a robot are on 6 axes.

The movements required to cover an object perfectly, no matter how complicated, are "translated" into a computer program, allowing the robot to reproduce them identically whenever necessary. This is a system with very good productivity and reproducibility. The disadvantage of such machines can only be the price.

Designing an automated solution

Before choosing one or other of the options, it is best to make an analysis of the parts to be covered. The analysis may result in a variant that is more affordable in terms of price or better in terms of performance. An example of such an analysis can be found at Falk Consulting the distributor of the French manufacturer of spraying equipment Sames Kremlin in Romania

Falk and Sames Kremlin suggest a series of questions to answer before you start designing your finishing line. It is important to know the dimensions of the objects to be finished, whether they will be fixed or movable, the pitch between them, etc. This is the starting point for designing and sizing the finishing line.

Purchase of a finishing line

You don't buy a finishing line after a visit to a trade fair or a presentation. That's where you see the possibilities, compare them, gather information, dictate options. The choice of line is always based on the data available in the factory.

First, the need for it must be determined. The investment in such a line must be worthwhile and, above all, must be recouped. Don't invest in a high productivity finishing line if that's not what you're looking for in the first place. Also, if you are one of those who make one-of-a-kind furniture or items or small series, certainly not high productivity finishing lines is what you need.

For series production, especially large series, a finishing line is a very good choice. Depending on the desired productivity, the type of product produced and last but not least the budget, you can choose a finishing line where the application is manual or automatic. How automatic is up to you. I can only wish you the best choice.