Originally Posted by
ube quilting
The reason to put the feed dogs down is to reduce wear and tear on the mechanics of the machine. You don't need the feed dogs when FMQ so why have them working.
There's no reduction in "wear and tear" as the entire mechanism still moves the parts through the entire range, except the lift is reduced in the FD down position.
The "feed dogs up" allows for the sandwich to be compressed as the needle is on the upstroke to eliminate flagging and dropped stitches. This functions much the same way as a hopping foot one might normally use. The drop position is actually for darning.
Yes, a longarm doesn't have feed dogs but it controls the layers with a "hopping" presser foot, much the same as feed dogs up.