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Juki 1541S Inconsistent Tension

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Picked up a new-to-me Juki 1541S and initially it sewed wonderfully. Machine was very dirty from being used in a factory environment. I'm afraid my good intentions of cleaning and oiling everything has caused some serious inconsistent tension issues. Oiled all indicated points per the manual, removed needle plate cover and evacuated all the old factory lint. Cleaned out bobbin case area with compressed air and a brush.

For this project I'm sewing nylon with Tex70 bonded nylon thread. Visually, it appears that the top thread goes from having too much tension, to too little tension. This happens at all sewing speeds. Whether I'm crawling slowly or ripping through at max speed. Bottom side fares a bit better but is also not entirely inconsistent. Any thoughts or recommendations would be helpful. I've ripped my hair out all day over this!

• I have checked all the thread paths and they are clean and clear, no snags.

• Needle is fresh - Size 21.

• Bobbin case holder is not Juki OEM - it's made by Haya (problem?)

• Bobbins were cheap $0.50/ea from Amazon in a 20pk (problem?)

• Hook timing appears to be correct

• Check spring path is clean and clear

• Tension disks are clean and clear

rGRMB3o.jpg

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Not that the textile weave wont close up! But the needle size is to big, in that the recommendation from mfg.’s is size 16-18 for tex 70, size #69 threads. 

Sometimes its easiest to back off bobbin case thread tension screw. Adjusting this where its very lite! tension. Then working with the top more easily. Your stitch can waver a bit I think first with the needles hole making ability. Then followup with tension checks.

Carefully notice any case tension screw. In their ability to be consistant in applying or reducing. I've had one with threads very very screwy, from new. Uncommon i think. 

I do feel we all consider, or maybe i should just say me. I feel the big brands we know of do in fact have better consistancies in their products. This sometimes bothers me afterward, when i have these very same issues. But hey, I many times relearn :bike:

Something I heard and started is keeping a few different bobbin cases extra. Also more importantly is keeping some separate if you can for different thread sizes. This I find criticaly handy in using threads of same size, but different types. In examples, high heat or solarfix marine. 

In closing I wouldnt do anything without changing the needle size first, to at least close as possible to 18.

Good day

Floyd

 

 

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Could be as simple as a bad spool of thread with the thread on the spool temporarily binding or uneven unravelling from spool. I think the size of needle may also being playing a factor, 18 or 20 g depending on thickness of material). I have had the problem when I over loaded the bobbin combined with incorrectly threading the bobbin. I needed to adjust the stop on the bobbin winder and re thread a fresh bobbin correctly ( in through the hole of the bobbin disc bracket from the spool, around the disc, out through the same hole then to the bobbin case on the winder. A couple photos of your top threading may help to spot something.

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Just to add to my previous post. How I check the tension on my Juki 1541S is with the bobbin in the case I pull out about 6 inches and hold the end of the tread and let the bobbin / case rest flat in my other hand. I then try to lift the works up by the thread. If the bobbin case and bobbin doesn't stand up vertically and the works remain flat in my hand with the bobbin spinning easily  I tighten the thread tension spring screw. If it lifts off my hand with no thread coming off the bobbin, I loosen the thread tension spring screw. I like the bobbin case to stand up and the bobbin spin with a little resistance in the case. I only thread the bobbin to about 80 percent.

kgg

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45 minutes ago, brmax said:

In closing I wouldnt do anything without changing the needle size first, to at least close as possible to 18.

 

Changing down to a Size 18 did help with consistency to some degree. 

bPFPv6L.jpg

There's still a few spots where it it gets tight for a single stitch. 

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57 minutes ago, kgg said:

A couple photos of your top threading may help to spot something.

Here's the top threading. The guard in the last photo was removed to better see the thread path.

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gJOf5CE.jpg

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The thread path is looking good from my point of view.  Whats a priority for myself is keeping a consistant pattern of how I thread through all the guides and holes. 

Everyone can do it in any method by the book, but as everything having a known consistant pattern helps.  Especially in any situation of multiples and or monitoring these for troubleshooting. 

Your onto the issue for sure, if its possible look or video the spools usage or thread coming off during this issue.

When you notice an irregular stitch, you may count until the next. Maybe its a visible moment off the spool where you see something. Narrowing further I have made marks on the thread just off the spool to help in different situations.

Its crazy how a lite! thread issue coming off the spool makes it a pain for a bit. 

 

Good work there

Floyd

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In your last photo there is a thread retaining screw, spring and flat plate that is missing in the last large guide before the needle (where there are two threads). This holds the thread flat against the guide before the thread goes through the guide hole just above the needle. I think this is to keep the thread in a consistent position during up and down stroke of the needle so it don't flap around.

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In my last posts I said ' (where there are two threads) " it should have said (the large guide just below where there are two threads in the guide).

kgg

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33 minutes ago, kgg said:

In your last photo there is a thread retaining screw, spring and flat plate that is missing in the last large guide before the needle (where there are two threads). This holds the thread flat against the guide before the thread goes through the guide hole just above the needle. I think this is to keep the thread in a consistent position during up and down stroke of the needle so it don't flap around.

It was interesting I noted this part missing from nearly all the machines in the factory where I got this from. Perhaps removed for a reason or it's easily damaged in production. Looks like it's ~$25 in parts to get that piece replaced. Certainly won't be seeing the daily grind in my home shop that this machine saw for the first few years of its life.

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I’d also check every edge that the thread passes over for grooves or burs.  The only part you apparently physically moved is the needle plate - I’d take it off and look closely at it as well as how the bobbin case interacts with it.

Have you taken off the tension disks to look at their condition?  

Have you grabbed the thread coming out of the tension assembly and pulled out a few feet looking for changes?  

With the bobbin in the machine and fed up through the feed dog pull the lower thread to feel for binding on a number of bobbins.  Cheap bobbins are famous for being inconsistent in almost all dimensions and I recently had to toss out a handful of new ones that would bind in the bobbin case.

I hope you figure it out - it’s always fun solving a mystery!

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Nylons are tricky sometimes. You definitely want to use the smallest needle possible, and adjust the needle and bobbin thread tensions in very small increments. Never hurts to back the tension way off, then add it back slowly (both needle and bobbin threads, little by little).

As DonInReno mentioned, cheap bobbins can be problematic, especially when trying to find a fine balance of tensions. Also, too high tension when winding a bobbin can make the thread hang up in spots. Makes for mystery stitches where suddenly the bobbin tension goes wacko for just a few stitches.

Like others said, 69 thread typically calls for 18 needles, maybe 19 if it's tough nylon and you need to punch many layers.

Where you have the thread snaking through the guides, make sure the thread is winding through "clockwise". You have it going one way through the first guide, then the other way through the next. The thread may hang up a bit from this from un-twisting then twisting back. (or maybe not but consistency helps rule out other issues)

 

 

 

 

 

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Is there not another small hook between the needle bar and the needle to hold the thread close to the top of the needle

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What type of needle are you using? It's generally recommended that for nylon etc a "standard" round point garment needle is best.

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7 hours ago, DonInReno said:

I’d also check every edge that the thread passes over for grooves or burs.  The only part you apparently physically moved is the needle plate - I’d take it off and look closely at it as well as how the bobbin case interacts with it.

Have you taken off the tension disks to look at their condition?  

Have you grabbed the thread coming out of the tension assembly and pulled out a few feet looking for changes?  

With the bobbin in the machine and fed up through the feed dog pull the lower thread to feel for binding on a number of bobbins.  Cheap bobbins are famous for being inconsistent in almost all dimensions and I recently had to toss out a handful of new ones that would bind in the bobbin case.

I hope you figure it out - it’s always fun solving a mystery!

I've removed and cleaned the tension disks and there are no obvious defects - they are smooth and clean. 

Pulling the thread coming off the tension assembly seems to be fine as well. Every different type of thread feels a bit different. Some bonded nylons come off in a silky smooth fashion (Coats Tex70 Bonded Nylon is smoother than A&E) but the same problems creep up regardless of thread vendor or thread age. I have some old spools of Coats Tex70 bonded nylon from 2008 that are significantly smoother than stuff from November of 2017.  FWIW... Running Tex90 bonded polyester with a size 21 needle has far less issues - still not perfect, but the results are closer to being acceptable. Not sure what this means.

I'm going to attempt to source some Juki OEM bobbins and a OEM bobbin case as well.

 

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7 hours ago, R8R said:

Nylons are tricky sometimes. You definitely want to use the smallest needle possible, and adjust the needle and bobbin thread tensions in very small increments. Never hurts to back the tension way off, then add it back slowly (both needle and bobbin threads, little by little).

As DonInReno mentioned, cheap bobbins can be problematic, especially when trying to find a fine balance of tensions. Also, too high tension when winding a bobbin can make the thread hang up in spots. Makes for mystery stitches where suddenly the bobbin tension goes wacko for just a few stitches.

Like others said, 69 thread typically calls for 18 needles, maybe 19 if it's tough nylon and you need to punch many layers.

Where you have the thread snaking through the guides, make sure the thread is winding through "clockwise". You have it going one way through the first guide, then the other way through the next. The thread may hang up a bit from this from un-twisting then twisting back. (or maybe not but consistency helps rule out other issues)

 

 

 

 

 

I'm going to try some prewound bobbins and see if that helps at all. From what I've seen they're wound at the factory with much more consistent tension.

I will be sure to double check my twist direction as it's going through the thread path - I hadn't thought of twist direction as being critically important. Muscle memory serves to make me do it the same each time but I've not really paid attention to the orientation.

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23 minutes ago, dikman said:

What type of needle are you using? It's generally recommended that for nylon etc a "standard" round point garment needle is best.

Groz Beckert round point. I have been using Size 21 needles for the past year with great success on my 111W and on a shared 1541S at another workshop. I have a feeling that stepping down to 18 or 19 is going to be problematic when stepping over thick assemblies or sewing over zipper tape. I may have to swap needles depending on what operation I'm working on.

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I bought a 1508NH that had a similar uneven stitch problem.  It turned out to be the surface finish on the tension disks.  The quick solution was to use a piece of leather and jeweler's rouge to polish the contact surfaces of the tension disks to a mirror finish.  Problem solved!  These machines are designed for course thread. However the thread that I typically use has different friction characteristics.  This creates a jerking because of the change between static and dynamic friction on the threads.  Polished disks solve the problem.  I find that I have to polish the disks periodically when the stitch quality starts to decline.

Dave

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44 minutes ago, DDahl said:

I bought a 1508NH that had a similar uneven stitch problem.  It turned out to be the surface finish on the tension disks.  The quick solution was to use a piece of leather and jeweler's rouge to polish the contact surfaces of the tension disks to a mirror finish.  Problem solved!  These machines are designed for course thread. However the thread that I typically use has different friction characteristics.  This creates a jerking because of the change between static and dynamic friction on the threads.  Polished disks solve the problem.  I find that I have to polish the disks periodically when the stitch quality starts to decline.

Dave

Dave- I'll have to give this a try. They feel smooth to my touch  but that may not be as smooth as they can possibly be. 

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Quick update - What "seems" to have solved my inconsistent tension issues is winding my bobbins on a different winder. The common variable previously was that all bobbins were wound on the onboard winder on the 1541S. I tried winding them on my 111W's side mounted winder and have had several hours of successful sewing with consistent tension.

 

My 111W side mounted winder does seem to have more tension on the disks than what the 1541S disks are able to apply. I've tried maxing out the 1541S bobbin winding tension spring and it still isn't as tight as my 111W's. Would this cause a significant difference in the quality of the wound bobbin?

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Any chance of showing the thread path from the spool of thread to the bobbin tension discs onto the bobbin winder.

kgg

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i have a juki dnu 1541 machine and have issues with the machine not sewing intermittently, i have removed plates and oiled all the wicks then manually move the needle to get everything oiled up . it will sew then it wont. the caution light will start blinking, need help

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9 hours ago, BKB69 said:

i have a juki dnu 1541 machine and have issues with the machine not sewing intermittently, i have removed plates and oiled all the wicks then manually move the needle to get everything oiled up . it will sew then it wont. the caution light will start blinking, need help

I am assuming you mean the caution light is for your motor as most of the Juki dnu-1541 don't have a caution light unless you have a DNU-1541-7 with the box of electronics mounted on top of the machine. Since you have oiled and cleaned the machine I would go back to basic's to narrow the problem down.

1) what size of needle are you using for what size of thread?

2) thread path from the thread spool to the needle is it correct?

3) thread caught inside the bobbin case holder?

4) With the machine threaded up and some material under the presser feet

i) remove the drive belt from the machine to the motor

ii) turning the handwheel towards yourself does the machine sew

I would say your problem lies with the motor so check that the motors power cord. Is it in good condition and fully plugged in to a good wall receptacle? The connection from the motor to the on/off switch or the control box in good condition? Also most motor arrangements have a built in fuse which may not be fully seated or faulty.

A couple of photo's of your thread path and motor setup could be helpful.

kgg

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