Dr. Anderson's sage advice still rings true today with this flashback to 2003.
Rigid-frame summary The ideal stretching system to employ for screens affixed to rigid frames can be summed up as follows:
• The system would rely on small, pneumatic stretching clamps;
• It would allow sideways (lateral) motion of the clamps during tensioning;
• It would stretch the mesh through a series of short tensioning cycles with brief rest periods between each stretching stage;
• It would apply random deflection and vibration forces at multiple points around the mesh during rest periods;
• And it would target a narrow range of stable tension values for the final mesh.
Automating as much as of this process as possible by using computer-controlled stretching equipment could further increase the consistency and repeatability of your stretching results. But if this is the route you plan to take, make sure that automation doesn’t become a substitute for skilled screen-stretching personnel.
With the multistage stretching procedure recommended here, screenroom employees must have a great understanding of the stretching process in order to measure the progress and effectiveness of the system. These employees should be able to carry out all of the stages of the process manually and recognized and understand problems before taking steps to solve them. With such skilled operators, production of high-quality screens can continue, even if equipment breaks down. When tasks such as screen stretching are deskilled through automation, you’ll eventually see the results in reduced print quality and, possibly, lost customers.
Many of the tension issues that arise with screens on rigid frames also occur with retensionable frames (Figure 4). This article doesn’t distinguish between the various types of retensionable frames available today, but focuses on the thread deflection and realignment concerns that apply to all frames in this category.
[Figure 4: Retensionable Frames
Retensionable frames hold each edge of the screen mesh secure during stretching, which prevents a screen’s thread count from shifting but creates unequal distribution of forces and maximizes thread deflection. Fiber realignment can be accelerated on retensionable frames by running a hard-rubber roller over the mesh immediately after stretching.]
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