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Needle Flex and Tension


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If you can understand how a longarm quilting machine works through its stitch formation and how that process affects your stitch quality and tension, you can learn to use just about any thread in your APQS quilting machine!Needle flex plays a critical role in how successful you will be with your stitches. Anything that can cause the needle to "flex" or "bend" has an impact on your tension. This includes factors like:

    [*]How quickly you move the machine[*]The direction you move the machine[*]How taut you have the fabric between the rollers[*]The batting thickness[*]The fabric's weave or texture[*]The thread's thickness and composition[*]The needle's size[/list=1]Watch this video to learn more about how your machine operates and how to make good choices to produce a high quality stitch every time you use your machine:
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Very helpful video. One thing that I learned is that even though I may see a bit of contrasting thread in the needle hole on the quilt it doesn't mean that my tension is off, but more that it may be fine thread in the needle hole. I'm going to try heavier thread and see what happens. Wish I'd know that the past few days, I wouldn't have stressed so much over seeing bobbin thread on top in the needle holes. :)

I had a problem today with thread goobers (technical term :D ) building up on the backing in the points of my stitching. I was testing tension and couldn't eliminate them by adjusting bobbin and top tension, new M.R. 4.0 needle, changing threading path, increasing stitches per inch, and I was careful to pause a bit in the points. I changed to a different top thread and all was fine. Is there something else that I should have done?

Thanks, Dawn, for the great videos and all the help that you give us!

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  • 4 years later...

Debbie:

 

The directions that Dawn describes in the video is 180 degrees out or opposite of what is described in the video as we move the fabric instead of the machine.  To complicate things further , we rotate the machine 90 degrees and sit on the side of it.  

 

Dawn first says the best quality stitch will be moving the machine Left to Right, because the needle is deflecting to the left.  On a George this will be moving the fabric Front to Back.  Remember George is mounted 90 off of where you would stand on an table mounted machine.  Thus when you move the fabric Front to Back, you are deflecting the needle Left as described in the video.  

 

Dawn then says the best quality will be when you move the machine towards you.  On George this is when you move the fabric Left to Right.  That is to say the needle is being bent to the right, towards the hook or towards the throat area of George.

 

Remember the needle flexes because of the drag on the fabric.  That is to say, the needle is still depressed into the fabric when it is moving, thus the needle bends in the direction the fabric is moving.  So to clarify, when you move the fabric Front to Back, you move the needle away the hook assembly as it makes it rotation around the bobbin, tying the knot slightly later.  The same the holds true when you move the fabric Left to Right, you close the space between the needle and the hook, so the hook has an easier time of grabbing the thread.

 

When Dawn describes moving the machine away from you, she says it opens the space up between the needle and the hook assembly.  On George this would occur when you move the fabric Right to Left.  That is to say you move the fabric away from the throat of the machine, the fabric will pull the needle ways from the hook or away from the throat area of George.  If deflected enough, the hook can miss the top thread forming a missed stitch.  

 

Finally, when dawn says you move the machine right to left, it moves the needle towards the hook.  Thus tying the know a little earlier than planned.  On George this will occur when you move the fabric Back to Front.  The fabric move towards you, the fabric will bend the needle towards the hook or towards you as you sit in front of George.

 

Clear as mud?   I believe I got all the directions corrected for how we move the fabric, and for how we are sitting 90 degrees to the right of how you would stand in front of a longarm.

 

Cagey

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No, I do not believe you are saying that correctly.  

 

The needle flexes in the direction you are moving the quilt top, and per Dawn's video I believe the best direction would be moving the fabric towards you sitting in front of George.

 

Though a true longarmer will have to chime in here, from reading the APQS Blog post "What causes railroad tracks?" - Railroad tracks also happen due to needle flex – something that happens with all sewing machines but is most noticeable with longarms simply because of the speed at which you move the machine.

 

I am not so sure if all George quilters move the fabric so fast they get much needle flex.  The longest quilt top movement I could see on a George might be 12 inches side to side  before you have to stop and reposition your hands.  I am not sure how much needle flex that would generate.  Hopefully some of the more learned quilter will let us know what they think on the topic.

 

Cagey

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Needle flex is by stitch, not by inch.  That is to say the needle flexes whenever it changes position in relation to the fabric.  As the stitch is repeated the needle "rebounds" to it's original position as long as the tension on the thread allows it to do so.  Moving the fabric (in sit down machines) or the machine (in long arms on a frame) produces the actual stitch.  If there is no movement, the needle goes up and down in the same place.  The faster the movement, the longer the stitch.  Its this movement that flexes the needle.  How the needle flexes in relation to the hook, affects the machine's ability to make the stitch, and the quality of the stitch.  If you move the machine (or the fabric) so fast that the needle cannot rebound to it's stitch making position, you'll hit the hook with the needle and break it.  If it "rebounds" to stitch making position, but not all the way to the optimum hook/needle position, it will affect the tension and the the stitch quality.  The ease of return to optimum is affected by the direction of the movement. (front to back and left to right on the sit down machine is the easiest)

 

I hope this helps explain directional tension changes.  Jim    BTW, needle flex is caused both by fabric and thread.

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Jim:

 

Thanks for the explanation.  My question for you and the group, is if a sit-down quilter is moving the fabric slowly and in relation with the needle movement, the only needle flex would be from thread drag?  Which should be fairly minimal, correct?

 

Cagey

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