Automatic sealant application



Our client asked us to create a demo for automatically applying sealant to a soldered object and a ceramic object. This is to ensure the soldered object does not let loose. This needs to be checked visually, one check before applying the sealant, and one check after. The client only automates this part of the process, modules will be placed in a buffer station by hand and will be returned in a buffer station after the sealant is applied.


The result is a system that includes a buffer station which has a side to put in the modules and shows status of the modules with led-lights. It also includes a robot that picks up the modules and moves them to the vision and sealant station.


To seal the module correctly, a first inspection has to be done. This is done by a digital microscope and a Halcon program. The first inspection checks if the wire is placed correctly against the ceramic cylinder, see Picture 1. If the program rejects the module, the robot will put the module back in its original place in the buffer system. If the program accepts the module, the robot will continue with its progress and apply the sealant on the modules.

After the sealant has dried for three hours, the robot will pick the module back up to inspect the first seal. This is done by comparing the original image with the new image. The program checks whether the original wire is in the sealed area or not, see Picture 2. The program will give feedback to the main program which decides what the next move of the robot will be.

Sealing station

For applying the sealant, we use a pneumatic system. The system contains of electric controlled magnetic valves, a Venturi valve and 2 adjusted syringe barrels. The barrels contain the sealant which can be filled from the top of the syringe barrel. When the valve gets signaled to open, pressure will press the sealant out of the syringe. After the right amount of sealant is applied the pressure is released. After a few seconds the Venturi valve will be activated too and creates a vacuum that pulls back the hanging sealant.


The trays (which contain the modules) are transported by a robot. This robot is a cobot from Universal Robots. A cobot does not need special cages as protection and is designed to collaborate with humans. The robot runs a program which receives commands from the PLC via a TCP connection. All the points/locations of the robot can be easily changed manually on the teach panel. This insures that changing the location is easy and can be done without reprogramming the robot or PLC. Multiple emergency stops are implemented to increase the safety of the robot.


The PLC (programmable logic controller) is the heart of the installation. It makes sure all the elements of the system do their thing when needed. To reach the goal of applying sealant to the module the program follows five steps:

  1. Waiting for a tray (which contain multiple modules) to become available. This waiting is because there are no modules inserted or the modules are waiting for their sealant to cure.
  2. Getting the tray from the storage.
  3. Camera check.
  4. Applying sealant.
  5. Returning the tray to the storage.

All steps are checked on error and if one occurs the program is paused and an error is shown on the panel. The complete system, including communication, can be simulated. This ensures easy testing when implementing new features.


The operator can control the machine with the HMI (human machine interface). A HMI is a screen which displays information from the process and can control the PLC. When the machine is in operator mode the view is simple. This view shows information about the status of the process and the process can be started and paused. Also, trays can be disabled and enabled manually, so the modules can be inspected if needed. To make the HMI more accessible to everyone the language can be changed between Dutch and English.

In addition to the operator view there is also an admin mode. This mode is protected with a password. In this mode the system can be controlled manually. Furthermore, important settings or the current program flow can be changed and the program and tray buffer can be reset.

Database with visualizer

To insure the quality of the modules all the checks are registered. These results are sent from HALCON to the database system. This system is running a webserver, NodeJS and a MySQL server. The information flow is visualized on a webpage. This page is updated when new information is received and shows the status of the modules. Also, the pictures of the last four checks are shown on the page, so a operator can confirm everything is working properly. A separate page is designed to show the history of the modules. This history includes the result of the checks, when the check was done and the picture of the check.


The system works as planned. The modules will be checked for proper installment, is sealed, buffered for drying and checked if the sealant is applied properly. Data about applying sealant is saved, information is given to employees about the status of the modules by led-lights and system status is shown on the HMI.

Brad Kitt.