Differential feed is one thing that if you can get it figured out in your mind how it
works, and when you need it you'll understand it.
First off, if you lift up your foot you're going to notice you have two sets of feed
decks.
Two in the front and two in the back and they are actually separated with a break.
Older sergers without differential feed had one long feed deck all the way back here,
and so it just pulled your fabric in normally and you couldn't adjust how that happens.
Because your foot is so long, a good inch plus between the front of the foot and where
the needles will actually stitch the fabric what happens is is that sometimes the pressure
of the foot stretches the fabric out and it comes out all wavy.
Another issue is that on satin fabrics, slippery fabrics, the fabrics tend to gather and crinkle.
The bottom layer is fed faster than the top layer.
What I'm going to do is just quick kind of ... We're just doing a four thread; I'm going
to actually sew on a diagonal here.
I'm going to get it started so that diagonal gets pulled in just fine.
So what we have here is that this starts to curve and it doesn't really let the fabric
lay flat when it comes out.
What's happening is is that there is too much pressure ... As that's going through it's
stitched and it's almost like space it all the way out.
Let's try this one.
It's kind of a funky fleece.
See if we get a little bit more.
Okay, so see.
Sometimes it looks fine but look, I'm curving it but when I put it straight that's when
I see the curves.
Again, stretched out.
Also too on this fabric I'm seeing some of those loops off the edge so I want to take
and move my cutting width, move it away from the needle so it fills more in as I surge
there.
How do we fix this?
Over here in the back corner, that's why we're viewing back here; it has a N, a 1.5 and up
to 2, and then it goes minus or a 0.8-0.6 setting.
If you think of N as a one to one ratio, these two feed decks are pulling in simultaneously.
What's happening is that if we could take the front feed dog and actually help ooze
it in, like make it come faster than the back one it would actually pull the fabric in before
it actually gets stitched and it will help keep the fabric actually at rest when this
stitch is actually formed.
With stretchy fabric the tendency is usually to take it up to about a 1-1/2 all the way
up to 2.
Fleeces, sweatshirt fabric, and then the machine will do the rest for you.
You really just have to kind of try one.
What it's doing is it's kind of pushing the front of it into where the needle is and oh
yeah, totally, much flatter.
It's actually even easier to stitch.
See how ... Well, it just comes out perfect.
Now on the flip side, when we have two pieces of fabric that is like shiny and slippery
and we put those right sides together ... I'm going to go ahead and put my differential
feed back to normal.
When I stitch these sometimes my edge at my ends come out at different lengths.
Okay, these weren't the same length when I started but let's take a look at what's happening
underneath here.
So the front is probably going to look fine but on the backside I'm starting to get some
wrinkles back here on the seam.
That's because the bottom layer is almost getting fed too fast.
It's kind of like starting to gather, which you can use the differential feed to gather
and it works beautifully with a gathering foot you can put for the serger.
In opposite we can go ahead and to go point 0.8 or even 0.6, and that front feed dog set
is going to say whoa.
It's going to kind of hold back that bottom layer and kind of resist it, so when you go
from a seam at one end all the way down to the other end they will come out even as planned.
If you don't remember which way to go, one will make it worse, one will make it better.
Do a couple samples and just see what kind of results you have and know that differential
feed is your friend and will often help fix the problems you're having on these difficult
fabrics.