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Clamps Help Tension Silk over Frame
Problem
The successful performance of screens used for silk screen
printing depends significantly on just how tightly they
are stretched. The tension range used for most silk screen
printing frames is somewhere between 4 to 28 lb/in. (7 and
50 N/cm), depending on the size of the frame. The tensioned,
or stretched, silk or other material cannot distort when
the ink is forced through under some considerable pressure
either manually or by some other process. While this may
sound simple, the problem lies in how to tension the screen
properly while is it is glued to a strong wood or metal
frame. |
CHT
pneumatic stretching clamp system |
Solution
Cosmex Graphiques, St. Laurent, in Quebec, Canada, a major manufacturer
of aluminum frames, furnishes ready-to-use screens to the screen
printing industry, We have solved the problem with the unique
use of modified DE-STA-CO hold-down toggle clamps. The clamp
chosen for the job is the classic DE-STA-CO Series 207 manual
hold down action clamp. The clamps can accommodate any 5/16
in. (7.93 mm) spindle. The clamps have a holding capacity of
up to 500 lb (227 kg). In this application, the hold-down U-bar
is fitted with 10-inch (25.4 mm) clamp jaws covered with non-slip
rubber. The clamp jaw can be adjusted within the range allowed
by the U-bar. Now that there is a means of securing the screen
material, a means has to be at hand to tension the material.
Cosmex designers mounted the modified clamp to a rail-type device
that can then be retracted by means of a pneumatic cylinder.
Result
A high capacity air cylinder allows the system to achieve the
highest recommended tensions and more. There is choice of 4-inch
as well as 6-inch stroke for larger graphic screens. The clamps’
angled design helps prevent them from opening even at the highest
tensions. Depending on the size of the frame, as many as 10
of the clamping units may be used to manufacture a frame. The
operator places the screen material loosely between the clamp
jaws of each of the clamps and closes the clamps manually. When
all the clamps are closed, the pneumatic cylinders are actuated
simultaneously and the screen material is tensioned prior to
gluing the frame. |
