Juki DU-1181N thread tension keeps messing up when i sew over a fold

[Skylicking]

Hi I have a Juki DU-1181N and I've been sewing denim with it but recently the thread tension would get loose on the underside EVERYTIME I sew over a fold or thick part. I was wondering if anyone would know what could be wrong? 

 

Thank you for your time. 

[nylonRigging]

that machine is walk foot and use a 135x17 needle  ? . also assuming your using 69E thread ?
could be not enough thread tension, and presser foot tension ?
or when your step-up on top the stack folds of the thicker seam, you might be getting some needle deflection  ?

if your satisfied with your machine setup, but not satisfied with the bottom stitch looks.  You might also try a ( height shim ) . placed for the foot and dogs to all level out on level plain , just at the point you walk/step-up on the thick seam stack. 
Your sewing a folded seam/hem, that is ( 3 piece ) thick , and then your machine has to negotiate a side-seam that is rolled out of Hem.  that is a good jump and the shim really helps to give machine a easy road to lay nice better stitch.  you are barely getting the foots toe on top of the high seam stack, but now the thinner fabric below is suddenly unsupported.  Same stepping off the high stack, your foot is running off but thinner material below is unsupported until the Heal drops off the edge.
I have a few I keep in machines drawers and they come in handy from time to time.  I also make my own, and in different heights, for running feet/dogs  parallel on different height material.
 
But common sold nylon/plastic ones for a straight stitch jump / they look like this .
and you just slide (open needle slot ) in-front of stacked seam to jump down big, and then remove when the foot just clears the stack  . .  Or slide Shim in from behind to jump up big, when your needle is on the down stroke sitting in-front of the stacked seam
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Edited October 8, 2020 by nylonRigging

[nylonRigging]

Also Add ;

I was just back sewing and something else did just pop into my head . ( slight chance? )  maybe worth checking ? , that when you raise your foot to a height to engage that large step-up . maybe ? , your Tension Disk push-Pin,  is just cut a little long, and you just barely tapping it on the high lift, and loosing a bit your top thread tension setting . It Something you Maybe ? not noticing till you pushing the upper end of you Foot lift.

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Edited October 9, 2020 by nylonRigging

[Skylicking]

Hi @nylonRigging

Thank you so much for responding and the helpful tips! i reset my tension to see if it would be better. It works for some parts but still happened on some thicker parts. It's interesting cause this was never an issue before so i don't know why it started doing that. My stitch would be good the whole time until it goes over a fold (doesn't matter how thick it is). Resetting the tension def did help tho. 

For my projects I've been patching upycycled denim so their thickness is all different. Using your advice i made a step using extra fabric and placed it behind my feed when i got to the thick parts which really helped but sometimes the last stitch off would still get loosen. I'm trying to loosen up my feed a little and i think my machine foot can be lifted up more so i'm going to try that next.. just looking for the correct size wrench. 

I was wondering do you know what the tension knob on the top is for and how to set it correctly? Also what do you mean by needle deflection? 

 

Again thank you for your time and advice! Really appreciate it. 

[nylonRigging]

4 hours ago, Skylicking said:

I was wondering do you know what the tension knob on the top is for and how to set it correctly? Also what do you mean by needle deflection? 

One knob has to be the foot pressure + / -  .. and the other ( i don't have that model juki ? ) . but could be foot height Adjust ? maybe remove front cover and look to see if obvious adj. something ?  or look in the manual ?
that another thing is ?  have you adjusted your foot stepping height at all to step easily to negotiate the higher seams .

Deflection . is when your needle is punching threw multiple layer, and it will plunge going off center slightly. It makes your bottom stitch look like crap and if bad enough deflection you can strike the needle plate . that's why needle plates are sold cheap and needle are sold by box's of 100 ....LOL
Keep the needle sharp, and also you might want to bump up a size maybe at least a 135x17 ( 20 ) . You might be sewing great with a thinner blade and smaller eye . But when you jumping on top a seam that is 3X thicker than what you were just sewing.
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