Intermittent Image Blurring
By intermittent image blurring, I am referring to an image that normally prints sharp and every once in a while, the edges will be blurred on a few prints and then seemingly correct itself, or the press operator will have to stop and clean the back of the screen and then the problem goes away for the rest of the day. The problem could be due to a number of the 547 variables of the screenprinting technologies, but if you have not found the answer among the known variables, I would like to introduce you to yet another variable – Vibration.
This morning in a telephone conversation with another screenprinting technologies consultant, while we were swapping road stories, I was reminded of this story and thought I would share it.
Decades ago, a friend who owned a blueprint company that used a large — 40-inch x 40-inch — process camera called me to ask if I could stop by and help him with a problem. Upon arrival, he explained that, although he had checked everything he could think of, he was faced with a waste factor of rejected camera shots several times a day, where the image would be blurred. Everything was tight on the camera and the vacuum was working well. He had a voltage regulator to take care of electrical brownouts, caused by intermittent decreases and increases of power.
As we stood there looking at the camera, I felt the floor vibrate. I was used to being in areas where there were mild earthquakes caused by fracking and had even been in a few major earthquakes with massive destruction and deaths, so I am aware of the feeling. I turned to my friend and asked him if he felt the floor vibrate. He gave me that funny look and said smiling said, “No!”
Knowing that the area was not prone to earthquakes occurring several times a day. I went outside and looked around. Just behind their building and probably no more than 20 feet from the building were the railroad tracks. It seems that everytime a train came down the tracks, the camera would vibrate and cause the image to be blurred.
Moving forward to a year ago, I was in a graphics screenprinting shop that had a similar problem on their M&R Saturn press. Every so often they would experience a blurred image on a few prints. When they asked me if I knew what could cause the problem, I only had to ask if there was a train track nearby.
You guessed it! It was right behind their building and the freight train would pass by on a daily basis. While the reason was correct, solving the problem is not so easy. They opted to simply listen for the train and cease printing for a few minutes. Sure it slowed production for a few minutes, but they avoided the waste and cleanup time.