Rapid-Air SERVO FEED: 200T & TX - Manual (Page 17)

16
FEED ARC
To explain how the “feed arc” is related to the servo feed calculation, we must first explain
what the feed arc is in relation to a press.
The press has a die that has two halves. The lower half is stationary and the top half is
moveable in an up and down motion which is one cycle from the full open to the full closed to
the full open again. The component that makes all of this happen is named “crankshaft”. The
crankshaft makes a 360 degree revolution for one cycle of the die from open to close to open
again. When the die is fully open, the crankshaft would be at “0” degree position. When the
die is fully closed the crankshaft is at 180 degrees or one-half of a revolution.
We ask that a switch be set at 270 degrees to activate the feed because at this position, the
die is completely clear of the material. This is also a good starting point to explain the “feed
arc” portion of the auto calculation in the Rapid Air program.
If the feed input switch was tripped at 270 degrees of the total revolution of the crankshaft and
the arc calculation was 180 degrees then the servo feed would complete it’s feed by 90
degrees of the press cycle or 180 degrees past the 270 degree mark.
The feed arc could be set at 90 degrees so the feed cycle would be complete by 360 degrees
or when the press was at the top of the stroke.
The feed arc could be set at 270 degrees so the feed cycle would be complete when the
press was at 180 degrees. This example would not work if the feed cycle started at 270
degrees as the feed would still be trying to move the material when the die was closed or
together. To use a 270 degree feed arc the feed would have to start at 230 degrees or 240
degrees to be finished moving the material before the die was closed or together. This
example could not be possible if the die had pilot pins installed in it for precise locating of the
stamped part. The cam switch drawing in the back of the manual will help you visualize the
above feed arc explanation.
In essence, the larger the feed arc number up to 270 degrees, the lower the acceleration/
deceleration rate. The smaller the feed arc the higher the acceleration/deceleration rate and
the fewer strokes per minute for a given feed length.