Automatic trace spraying means the spray gun will spray on loaded objects while they’re moving forward on a conveyor system. The painting machine or robot will follow the conveyor speed and complete the spraying before objects move out it’s effective working area. When everything setup well, it seems pretty easy. However, things are not always as expected due to various conditions.
When we configure a robotic spray painting system, we always need to automate the setup as much as possible regardless the spraying method. But it’s not always so easy to make it working as design principle due to technical limitation or the onsite operator skills. In this article we will briefly explain the concept and required technology in order to configure a full automatic trace spraying system by industrial standards.
Spraying accuracy control
Accuracy is the primary concern for trace spraying. When it’s an offline setup, we can easily set the spraying speed and frequency as objects are fixed in place. However, when it’s moving on conveyor system, the speed and frequency is limited by machine effective working range. That means we either make this working area extra bigger or slow down the conveyor speed. But we will have to consider how to load the next objects in proper way, or else there will be conflicts.
In some cases, we stop the object in spraying area by elevation while conveyor keep moving. The spraying can be handled much easier as offline logic, but we have to give proper signal to loading station. After the object is properly sprayed and moving to next station, the followed piece must be in place to make the process continuous. Normaly we install a 3-color light at loading station. When the object is spraying in paint booth, the light will be red so we can’t load another piece untill the spraying done. Once the previous object moves forward after painting, light will be turned green, so we can load new pieces.
Concurrent control among different devices
When it’s trace spraying, there will be multiple devices to be functional concurrently such as spray gun, conveyor and might be some kind transfer machine among different stations. Programmer must be familiar with the logic with sufficient actual performance so he can give a clear logic program to handle each device in right way. Because when a single device fails, it will bring issues to the whole system. For example, if the painting machine signal failed to detect object, the loading station light will always be green. If the worker is new on this job, he will keep loading and then jam the conveyor.
The only solution is to set a reliable program with reliable components to make sure everything functional good. And the actual requirement is to have an experienced programmer who be able to deal with professionally.
Flexibility issue
For trace spraying system, it’s hard to store multiple programs over different products painting. Most of the time we only set a single program that can handle a bunch of similar pieces. Sometimes when the product is more complex and requires more spraying time and frequency, unless the effective working area is extra big, it’s hard to work with.
Curing problem
It’s a serious issue when it’s UV based painting system. Because UV curing is pretty fast, if we set higher or lower speed, it’s big quality issue on surface. Because of this, it will limit the painting machine. Means the spraying time and frequency is fixed under a fixed conveyor speed. If we want to increase this, the only way is to build a bigger paint booth with bigger reach while it’s a big issue sometimes.
In a word, if we’re going to build a trace spraying system, we must evaluate our products carefully and the factory space then work closely with a professional machine supplier to choose a suitable technology. When the setup is more than expected complex, it’s not just about painting but an intelligent construction.
