STAPLES JUMP THROUGH CANVAS DURING STRETCH
During a stretch the artwork will tend to rise because the end of the canvas is being held securely in-place by the “clamp bar”. As the artwork rises the canvas SHOULD stretch over the edge of the “wood stretcher bar”. If it doesn’t stretch the most likely causes are a poor radius on the “wood stretcher bar”, heavy gauge canvas or improper stretcher block set-up. Any one of these things can cause the artwork to rise more than the recommended 3-4” creating a slightly larger “gap”.
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BASIC OPERATION:
The goal is to allow the artwork to lay a little flatter. Normally, we do not recommend pushing down on the artwork because it is equivalent to increasing the stretching pressure, however, it could help to minimize or even eliminate the “gap”. Just be warned that doing this will cause the canvas to slip from the grip of the clamp, if you have enough excess canvas this will not be a problem.
COMMON PROBLEMS:
A slight gap can be overcome by tilting the staple gun toward the operator and firing the staples further away from the “gap”.
The “clamp bar” will tend to rise during a stretch because we are exerting a tremendous amount of upward force during a stretch. The amount that it rises depends on a number of variables mentioned below. As long as the ‘clamp bar” drops back down after a stretch than it is working correctly.
The “stretcher blocks” must be properly positioned to allow just enough travel to allow the staple gun to apply the staples. The artwork must travel far enough forward to produce about a ½” gap. Anything less than ½” will result in a larger “gap” in the canvas. Moving your ‘stretcher blocks” slightly forward will allow that much more travel
Heavy canvas has very little give and it tends to form a “gap” much more than lighter gauge canvas.
Using wood stretcher bar with little or no radius will most definitely cause the canvas to not travel enough
TROUBLE-SHOOTING:
If your “clamp bar” has shifted upward due to loose “jamb nuts”.
With all air removed see if your “clamp bar” moves up and down…it shouldn’t. If it is loose then take an 11/16” open end wrench to the rear “jamb nut” on each of the “clamp bar” cylinders and force the bar downward while tightening all of the “jamb nuts” .