Analysis: Reasons for poor image quality of silk screen products
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Expert advice on dealing with elastic decay issues
You may often face such a question: "What is the cause of the elastic decay of the screen?" The question is simple, but it has no answer. There are many factors that affect it, and there are often several factors at the same time, making the answer to the question ambiguous. Next, we will unify the materials and screen making factors that often lead to the elastic decay of the screen, focusing on how to prevent and reduce the elastic decay of the screen.
Elastic attenuation: source vs. reason
The low elasticity of the screen is the main reason for the poor image quality in screen printing products. Common problems associated with low flexibility of the screen include incorrect overfeeding, constant sound during printing, uneven printing ink layers, images such as stains or loss of detail. For multi-color printing (such as three-color printing), it is also important to maintain a high level of elasticity and a stable level of elasticity. Otherwise, overprinting, moiré, mesh marks and associated image defects may occur.
All elastic attenuation can be combined into two basic sources and some secondary causes. Note the distinction between the terms "source" and "cause". Each printed screen contains only two important physical elements: the frame and the mesh. In either case, the elastic attenuation is nothing more than one or two sources. In addition to these two factors, external factors that cause the elastic to decay or disappear are called "causes."
For example, if a truck hits your frame, the frame may be damaged and weakened, and the mesh elasticity cannot be supported. In this hypothesis, the physical damage to the frame is the cause of the elastic attenuation, but the frame itself is the source of the problem.
Wooden frame
The most common frame material is wood. A wooden frame with a reasonable structure and design can fully meet the printing requirements, but the wooden frame is more likely to cause problems than the metal frame.
Regeneration
For wooden frames, the main cause of elastic attenuation is the recycling of wooden frames. The frame is generally recycled and washed with water or some solvent to remove the old emulsion. In some cases, even the mesh frame is placed in a soap bath to soak the emulsion and easily peel off the screen. The problem is that when the frame is immersed, it absorbs water and cleaning fluid, reducing the strength of support and the ability to tighten.
Under the strength of the screen, the wooden frame (especially the longer side of the frame) may bend inward. This phenomenon is called angular distortion. This phenomenon occurs in any frame including a hard, resilient, resilient metal frame, but it is more noticeable for water-absorbing wooden frames.
The more the frame is distorted, the more relaxed the mesh becomes. Therefore, a fully acceptable wire mesh stretched onto a dry wooden frame may become unacceptable after being treated, cleaned or recycled. And if the wooden frame is bent as soon as it is wet, it is difficult to return to its original shape, and even if the wire mesh is removed, it cannot be recovered.
Heating
Screens are often dried and heated in a drying oven or house with a dehumidification device. The problem is that hot wood does not have the strength of cold wood. As a result, the frame will exacerbate the tendency of the bezel to bend inward after heating. The most obvious phenomenon is the roof of the old house that is recessed downwards. The degree of subsidence of the tin roof frame is the most common, the reason is very obvious, the tin roof is hotter. Humidity also has an effect when using wooden frames.
Frame size
The question mentioned above means that the wooden frame is not a satisfactory material for making the frame? the answer is negative. The problem with wooden frames is that the wood size used is not suitable for the job. The traditional frame is made by a typical lumber mill. The general wood size is 2x2, 2x4 and so on. However, these size specifications are not a precise true width and depth, but are convenient to use. For example: "2x2" refers to 11/2x11/2 inches. It is known from experience that a 23x31 inch frame made of 11/2 x 1 1/2 inch wood has a mesh elasticity of 35 N/cm at the edge. If the frames are kept dry and stored in a constant temperature room, it can be used to make 23x31-inch automatic printing screens or 25x36-inch screens (manual or automatic) without any problems. The edges of these frames should be at least 11/2 inches deep and 21/8 inches wide. Such a frame is twice as strong as a conventional 11/2 x 1 1/2 inch frame and is not easily bent after stretching.