Our goal this year is to create a cell that can preform the screen printing process in an semi-automatic manner. Our cell will start with pre-made screens and continuously produce T-Shirts with a custom design. By using a standard size screen, we can create a modular system that will allow us to print a variety of colors and images. An operator will be required to add and remove shirts with every cycle of the cell. This reflects the majority of modern manufacturing. Automation is used to do dull repetitive tasks; however more complex tasks, such as lining up a shirt so the image is centered, need a human operator. It is possible to completely automate the system, but this would be very difficult and very expensive. As is often the case, the additional cost of creating a fully automated system is not far exceeds the cost savings of removing a human operator.
This project was selected for a multitude of reasons. The cell is a complex and rewarding design and will be an excellent challenge for our club. Along with the challenge of creating this cell, we believe that it can also provide important functions for years to come. The cell can be brought to events and used for fundraisers, providing funding for future SME projects. The cell can also be used to promote manufacturing; we can use the cell as a demonstration piece to show not only the capabilities of RIT SME, but also to create interest in manufacturing in prospective students.
Throughout the years, textile products have been used for art, advertising, personal expression and more. These textiles can be produced through a variety of ways; weaving, stitching, and embroidery have been vary popular historically. A more recent method is the process of screen printing. Screen printing is a very common, cost effective way to create repeatable designs on textile products. The process offers nearly unlimited possibilities for design, everything from simple one color shapes and text to complex multi-color patterns and images.
The process begins with a design such as our club logo:
The number of colors in the design determines the number of screens needed for the print. As our logo has two colors, orange and white, we will need two screens. The next step is to split the design into it’s component colors. The two patterns can then be printed on transparent film. These transparencies are called “Positives”.
A layer of fine mesh fabric is stretched over a wooden frame to create the screen. The screen is then coated in Photo Emulsion, this turns the screen into a very basic film. The positive is placed in front of the screen and the screen is exposed to a bright light. This captures a negative of the image. The screen is then washed and all of the uncured photo emulsion is washed away. Just like in photography, the negative can now be used to create many final images.
Once the screen is made, printing can begin. The screen is placed on whatever flat textile product you wish to put an image on. Ink is placed on the screen and a squeegee is used to apply a layer of ink onto the fabric. The first screen is removed and the second is placed on the fabric. Ink is once again placed on the screen and squeegeed through the screen onto the fabric. The screen is removed and the ink must be heat set into the fabric to create a permanent bond to the fabric.
Here is where we will keep you updated on the progress of our project. We will keep this page updated as we create functional requirements, reach project goals, and create new deigns. So be sure to check back from time to time!
We began design by creating a flow chart of the flow of material through the system. This allowed us to break this project into five subsystems; loading/unloading, ink dispensing, printing, curing, and mobility. A list of functional requirements was made for the overall system and each subsystem. For the past few weeks we have worked to create multiple concepts for each subsystem and use the functional requirements to create a paired comparison in order to select the best concept to move forward with.
We have selected a concept for each subsystem and have begun to do designs in CAD. We have a long way to go, but we have reached a point where the basic functions of the system can be shown. Please enjoy the GIF below showing the basic motions of our project!