Metal screen printing frames

Metal frames are usually made of steel or aluminum and are much more often used in professional screen printing than wooden frames. The main reason for that is that they provide much better stability, which is important for large formats and/or multicolor printing.

Steel frames are characterized by the highest stability and durability, but they are also much heavier than frames made of aluminum (specific gravity of steel is 7.8 g/cm3 whereas for aluminum it is 2.7 g/cm3.) Therefore for printing large formats aluminum frames are usually preferred. Steel frames are used mostly because of their lower price, as well as due to better dimensional stability in the printing process.

The greatest technical advantage of steel frames is that they’re twice as resistant to high temperatures than aluminum frames. The coefficient of linear expansion is 0.000012 for steel, while for aluminum it is 0.000024. What that means is with an increase in temperature of 20 °C one meter of steel profile will extend its length by 0.24 mm and one meter of aluminum profile will lengthen by 0.48 mm. After cooling back both frames will return to previous dimensions, but the aluminum frame will cool down faster. Considering the changes in linear dimensions is particularly important in case of big screens, when where high accuracy of color registration is required.

Aluminum frames are more resistant to corrosion than steel frames, but they aren’t resistant to sodium hydroxide solutions and for this reason they have to be properly protected if sodium hydroxide is used for degreasing the meshes.

Aluminum frames’ dimensional stability is improved by increased wall thickness. It’s worth noticing, that even with thicker walls aluminum frames are nearly a half lighter than steel frames of similar format.

Aluminum frame screen

Aluminum frame screen

How to choose a screen printing frame?

Properly selected screen printing frame ensures uniform stress distribution over entire surface of the mesh. Too small a cross section of the frame will cause the profile to curve to the inside after the mesh is stretched and the tension will be higher near the corners than in the middle of the stencil. In such cases mesh, stencil and squeegee are exposed to excessive stress and wear.

The table below provides guidance on the parameters of aluminum frames published by European Screen Printing Manufacturers Association.

Print area (cm) Internal dimensions of the frame (cm) External dimensions of the frame (cm) Profile dimensions and wall thickness (mm)
35 x 35 65 x 92 73 x 100 40 x 40 x 2.8/2.0
55 x 75 90 x 110 100 x 120 50 x 40 x 3.2/2.0
75 x 105 110 x 135 120 x 145 50 x 40 x 3.2/2.0
100 x 140 133 x 163 145 x 175 60 x 40 x 3.0/2.0
120 x 160 158 x 198 170 x 210 60 x 40 x 6.0/3.0
140 x 180 174 x 214 190 x 230 80 x 40 x 6.0/3.0
160 x 210 210 x 250 230 x 270 100 x 40 x 6.0/3.0

 

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