Overspray Issues and Its Solution

Overspray is a common issue where the ink is not properly sprayed on the material and as a result you can identify small dots in the borders of your print. Here you can see some examples of how does this issue looks like.

This issue occurs due to improper configuration of the printing parameters such as temperature, voltage, negative pressure, and printing height. Fortunately, the changes on the parameters that need to be made in order to solve this issue can be easily be performed by any printer operator.

To solve this problem, we have created a series of steps that you may follow

1. Printing Height. When you are going to print, having a proper gap between the material surface and the printheads is a fundamental condition in order to get a good result. The Z axis measure tool on the printer software should allow you to reach a proper height to print in any specific material, however, if you are still seeing a big gap, you may decrease it manually.

Using the down bottom on the console you can manually decrease the distance between the trolley and the material. The distance between these two surfaces must be around 1.25mm or the same thick a as quarter dollar coin. 

2. Constant Flow of Ink. Sometimes, one of the factors that contribute to the overspray phenomena is the concentration of air on the hoses and printheads. As a regular process, we can get rid of the bubbles by opening the frontal hoses of each of the printheads and holding the purge bottom for a couple of seconds. Following this, we should be able so see a constant flow of ink with no bubbles at all. We can repeat this procedure 2-3 times for each hose to make sure all the air is getting out of the lines.

In the next link there is a video of the process of elimination of air

https://drive.google.com/file/d/1JPAzc753ZJ0arVHP0AQOkXtKuvU3AXLd/view

 

3. Dirt on the Surface of Trolley. Rarely the overspray is caused by dirt that have built relief on the trolley surface, this dirt acts like a brush, touching the material and spreading the ink before being cured. The solution for this is as easy as to rise the trolley and clean the metallic surface to remove any dirt that may stick out.

4. Changes of Voltage and Temperature. Most of the overspray issues are solved by changing the voltage and temperature parameters on software. In this case is good to keep in mind that the values that we can increase or decrease on these parameters depends on the type of ink and printheads we are using. In general terms, the values of voltage can be changed from 0 to +3 or -3, that means the values (-3, -2, -1, 0, 1, 2, 3) on the voltage offset for each printhead. The temperature of the printhead may be changed between 45C to 55C for BesJet ink, and 35C to 45C for Korean ink.

To perform a change in these parameters we click the Voltage tab on the PrintExp software. Voltage changes are to be made on the Voltage offset section. You can modify the voltage individually for each printhead in the section shown in the next picture

After a change made in the voltage, press Set Voltage Temperature and then press Save on the top right corner of the screen.

To perform changes on temperature we will head to the Head Temperature section, and as the same as previously, any change on temperature must be followed by pressing the Set Voltage Temperature and Save options.

Now that we know how to change the Voltage and Temperature, it is required to modify these values so we can find the ones that correct the overspray. 

In order to find an appropriate combination of values for voltage and temperature, we recommend you to print a sample with your current parameters. Then, print the same file with variations of the voltage going from -3V up to +3V (-3, -2, -1, 0, 1, 2, 3) and compare the results with your initial reference print. Once you see a variation on the result of the print because of voltage you can keep the value that improves the most the result and start changing values of temperature.

Following the same logic, we will change values of temperature keeping the voltage constant to the previous value that you got. You can perform changes in temperature with 5C variations (45C, 50C and 55C BesJet ink) (35C, 40C, 45C Korean Ink)

The logic of these changes and tests is the same whether the parameter that solves it at first is voltage or temperature, this procedure is performed to discard all the values that don’t improve the result until reaching the one that improves it the most. 

5. Changes of Pressure. If the parameters of voltage and temperature have been changed and overspray effects still persists on the prints, changing the pressure is something you may consider to perform. Increasing the pressure slightly (-0.2 each time) on the system that has the issue (color or white) may improve the result. Keep in mind that if the pressure is too high the printheads may struggle to spray the ink properly so the changes must not increase significantly the work pressure.