Printing over raised areas on substrates can pose many problems. here are a few examples of what has worked for me.
By: Mark Berryman
I have never seen anyone able to print over the buttons, if you were to print the buttons this is what you would encounter. as you pull the squeegee across the screen and approach the button, the screen will ride up on the top of the button causing the ink to be deposited all around the button leaving a huge amount of unwanted ink on the substrate. the result would be quite messy and very unprofessional looking. try to avoid these kinds of jobs, I have never seen or known any printers who could pull it off! NOT on buttons.
Printing over the zipper or small buttons can be done several ways. if you have script that runs horizontally across the shirt or sweat shirt, divide the artwork in half, or simply cut it in half and measure the space between the buttons or zipper, burn your image the same way.
You will have to make a board so the zipper and seam will rest into. think of this like a trench. I have done this by cutting two boards that are the same size of your current platens. Usually 16x16. I used 1/4" thickness for my trench boards. when you have your boards prepared, mark the board with a center line and split the difference between the zipper measurement, you can use a little spray tack to hold the boards in place, at this point I would recommend using a heavy tape( duct tape) to re-enforce the boards, tape around the sides and extend the tape over the board and platen, this should keep the boards secure. You will have to adjust the off contact to compensate for the additional 1/4" height. you may want to re-enforce the area of the screen that will come in contact with the zipper or buttons by using a heavy tape, run a thin piece down the middle of the backside of the screen. do this to avoid damaging the screen, I have seen screens split when they have come in contact with the zipper or buttons! OK, let's get on to the printing phase. spray the boards with a little spray adhesive. Place the zipper or buttons into the trench, make sure the zipper and seam are nice and flat. NOW print the substrate, you should have a nice smooth print. the only drawback to this method is the image will be divided.
Printing directly on the zipper. Again you can use the same trench board as described before, you may need to use slightly thinner boards. the concept here is to get the surface as flat and even as possible.
This time the art will not be separated and you will be printing directly onto the zipper. one approach I have done is to print from side to side as opposed to the regular pull stroke toward the top of the screen, this is helpful because you can use additional pressure when your stroke meets the middle of the zipper, that will help even out the deposit of ink on the surface of the substrate.
It will take some practice to get the hang of it, some of the prints may not be 110% perfect but that's the price you will pay when printing over uneven surfaces.