BIT Hotmelt Technology & gluing mattresses
Over seven billion people populate Earth and there are even more mattresses. Many of these mattresses are glued together, To produce this amount of mattresses with a high quality standard, an automated production system is required.
The foam top and base are provided with glue. Currently, all sizes of mattresses are being glued using an automated process after which they are assembled by hand. However, every size mattress uses the same glue track. This means that the smaller mattresses are getting same amount of glue then the bigger ones, which is not necessary.
Mistakes that are taking place during the process of gluing, to match the standards, the mistakes are being fixed by hand on the moment. You can imagine this takes a lot of time for the workers to fix the mistakes. Keeping both the workers occupied as the regular process is aborted. Furthermore, multiple processes are required to glue multiple sizes of mattresses.
Goal of the project
During the project, the main goal was to make the process “smart”. To make a automation “smart”, it has to have some self-fixing features on it. In our automation the “smart” feature means, that the automation has to be able to fix its own mistakes. It’s also smart because it can handle multiple sizes of mattresses.
The following requirements were taken into account for the project:
- Mattresses can have different colors
- Mistakes during the process should be fixed autonomously
- Sizes may differ between the limits of scaled 1:4
According to us the best solution was to make use of the following subsystems:
- Detection system
- Movement system
- Glue system
- Operating system
- Human Machine controller
The movement system is required to move the glue system over the surface of the mattress to glue on the right points. We used a Universal robot to move the glue system. For the proof of principle we used this type of RRR robot.
The glue system consists of a setup of four glue nozzles on a mounting plate operated by valves and connected to the operating system. In the proof of principle we used a cold glue system, instead of the regular used hot melt glue. This because of the ventilation in the classroom isn’t sufficient for this type of machine.
The detection system is the most important part of the system. The detection system is required to find the mattress and to find potential mistakes. The camera makes a photo to send to it to the controller( the robot). It creates valuable data to find for example, the position, orientation and mistakes of the mattress. We are using UV reflecting background, to create a high contrast between the mattress and the background. We use the same principle for detecting the glue, by adding UV to the glue.
Challenges during our project
The vision part was a big part of this project. We choose to use UV light to determine the contrast between the mattress and the glue. It looked ideal, but it had some big challenges. The big pitfall was the UV fluid that is added to the glue. The UV containing hotmelt gives a perfect difference between the glue and the mattress. But the UV fluid, we’re adding to our cold glue, is a bit unpredictable, which results that the system is not robust.
Dynamic speed is a feature we use to ensure a certain open time for the glue. Also the dynamic speed enables the system to control the glue track width. By preforming tests on site by BIT Hotmelt, we collected data to create a formula that results the ideal speed by the size of mattress.
Our requirements that were set at the start of the project:
- Mattresses can have different colors Done
- Mistakes during the process should be fixed autonomously Done
- Sizes may differ between the limits of scaled 1:4 Done
We can conclude that UV works very well. It is important that the glue is reflecting UV to be visible by with the camera. Be aware that the camera has limits and cannot see everything, we see.
In the real situation a camera is not the ideal solution. The disturbance increases when the detection area increases. The size of the mattress can also be determined with distance sensors. For the glue detection of the hotmelt a height measurement could be ideal. Because the foam rises, it should be detectable. It could be ideal, but that has to be tested.