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--- when_things_go_wrong [2016/02/21 20:12]
192.168.1.35 [Move it, move it, move it.....]
+++ when_things_go_wrong [2016/02/21 20:34]
192.168.1.35 [Get to know the feed dogs]
@@ Line 48: / Line 48: @@
 ==== Move it, move it, move it..... ====
-Another important cause of skipped stitches is stitches getting too short because the fabric is not feeding adequately. The stitches may get shorter as I sew over a hump or they may get shorter because there are an uneven number of layers or heavier fabric underneath the pressure foot.
+Another important cause of skipped stitches is stitches getting too short because the fabric is not feeding adequately. The stitches may get shorter as I sew over a hump and to compensate for that try [[Hemming#Snipping the side seam|this]].
+Sometimes irregular movement will not show up as visibly short stitches but translate into skipped stitches more subtly.
 Please notice the rick rack trim I attached with the coverstitch in the images below.
-Both examples were done on my Babylock Coverstitch machine. the top image shows the 2 needle narrow coverstitch going over rick rack trim. This did NOT work well, I had several skipped stitches. The reason I used my BLCS machine was that I had the right color thread in it and my sewing machine was threaded with adifferent color for other parts of the same project. i would normally not choose to use my coverstitch machine for this but I learned something valuable. Do you notice the stitches sometimes going through the rick rack and sometimes only going through the cotton fabric? That's where I got skips, the difference in number of layers caused the skip. My best guess is that with this constantly changing number of layers there is an irregularity in the feeding/needle penetration, much like left and right tyres going over different surfaces, and this difference may translate in a skipped stitch.
+Both examples were done on my Babylock Coverstitch machine. The top image shows the 2 needle narrow coverstitch going over rick rack trim. This did NOT work well, I had several skipped stitches. The reason I used my BLCS machine was that I had the right color thread in it and my sewing machine was threaded with a different color for other parts of the same project. i would normally not choose to use my coverstitch machine for attaching trim but I learned something valuable in the process. Do you notice the some of the stitches going through the rick rack and some of them only going through the cotton fabric? That's where I got skips, the difference in number of layers caused the skip. My best guess is that with this constantly changing number of layers there is an irregularity in the feeding/needle penetration, much like left and right tyres going over different surfaces, and this difference may translate in a skipped stitch. So unfortunately the width of the rick rack and the width of the the two needle narrow coverstitch are not compatible
 {{:going_wrong:topstitching_rick_rack_with_2_needle_narrow_skipped_stitches.jpg?|}}
-In the second sample I used the chain stitch and stitched 2 rows close to one another so that the needle was always penetrating the same number of layers and I didn't have a single skipped stitch. Something worth remembering.
+In the second sample I used the chain stitch and stitched 2 rows close to one another so that the needle was always penetrating the same number of layers and I didn't have a single skipped stitch. Something worth remembering!
 {{:going_wrong:topstitching_rick_rack_trim_with_the_chainstitch.jpg?|}}
@@ Line 65: / Line 67: @@
 On my Janome and my Pfaff machines I need to increase both the stitch length and the differential to enhance the feeding.
-Even feeding is most likely to happen when the bulkiest part underneath the pressure foot is right there where the longer continuous feed dogs are. In the image below you can see that these longer feed dogs are on the left and right side. In the centre there are several short feed dogs but there is a large space where there id no feeding to allow for the needles to move up and down.
+Even feeding is most likely to happen when the bulkiest part underneath the pressure foot is right there where the longer continuous feed dogs are. In the image below you can see that these longer feed dogs are on the left and right side. In the centre there are several short feed dogs but there is a large space where there is no feeding to allow for the needles to move up and down.
 {{:going_wrong:feed_dogs.jpg?|}}
-Now imagine topstitching a seam and the bulkiest part is in the centre. The longer feed dogs may get little or no hold of the fewer layers of fabric beside and feeding will not be even.
+Now imagine topstitching a seam and the bulkiest part being in the centre, being fed by those short feed dogs? Beside it, going over the longer feed dogs, there may be just one layer of fabric or fewer layers of fabric. When that is the case the risk of irregular feeding increases and with it the risk for skipped stitches. So I prefer to do topstitching so that the bulkiest part of a seam is being properly gripped by those longer feed dogs.
+I intend to expand a little on this in the chapter on [[Top stitching#Top stitching and feed dogs|Top stitching]].
-When I pick a differential setting that is suited for the fabric and application, the fabric should move evenly. When the number of layers changes, the feeding may slow down, resulting in the stitches getting shorter and eventually the looper thread not being connected properly to the needle threads. Another reason for poor feeding is the degree of stretch of the fabric. As the lycra content goes up, the fabric gets more and more elastic and this often results in short stitches, because between each movement of the feed dogs, the fabric has a chance to recover its natural  with the looper thread skipping. Lycra knits vary between moderately to VERY stretchy and only the extremely stretchy ones are a challenge when coverstitching.
-How come? I get less (a lot less) skipped stitches with my Babylock CS and in part I credit the Babylock feeding system for that.
- bunching up underneath th pressure foot. I notice that I do not have this problem with my Babylock, so I wanted to understand the difference because that might help me find a way to solve the skips on the Janome.
-The feed dogs are different. They differ in length, width and type (the Babylock seems to have more little points that grip the fabric). The major difference IMO is in how far the pressure foot extends BEYOND the feed dogs. The back edge of the Babylock pressure foot lands 1mm behind the feed dogs and the edge of the Janome pressure foot lands 4,5 mm behind the feed dogs. THAT is what can easlily cause the fabric to slow down or stop moving.
-One solution is to make the stitch longer because then the feed dogs make a larger movement and the risk of bunching up is reduced. In fact if you try this, you will probably notice less skips. But the disadvantage is that as the stitch gets longer it gets less stretchy, a hem f.ex. risks snagging and eventually the thread may break.
-My conclusion is that on the Janome VERY STRETCHY fabrics perform best with a stitch length around 3 and simultaneously supporting the movement at the back by gentle guiding the fabric away from the pressure foot while stretching in front of the pressure foot with the other hand. I stretch the fabric in front so that the maximum amount of thread goes into the stitch and once the fabric recovers, the stitch will look shorter and be very stretchy.
-Please note that for most lycra fabrics this is not necessary, I am talking about the very loosely knit and stretchy ones.
-Is that clear as mud?? smile emoticon

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