Tuesday, May 25, 2010

It's a Juki Disastro

Well, not really a disastro ... I've just been listening to CocoRosie lately.
Though, my brand-new Juki DNU-1541S is still not working and that's close to a disaster.
After hours of contemplation and watching the hook spin round and round I've figured out that the hook assembly is most likely defective, or was damaged somehow at the factory. Either way, there's a rough spot in the rotation of the hook that causes the assembly to seize up when there's enough lateral pressure applied to it.

Hook assembly pictured above. The inside part with the post is called the basket. It rocks back 'n' forth slightly while the hook rotates around it and is held in place by the bobbin case holder.

The first time I was sewing with this machine, I was going slowly over some number-eight cotton duck, everything's going well, beautiful stitches ... sewing over a few more layers of duck on top of that, and then boom! the machine jams up.
I thought it must've been a bad needle strike, or something like that, and the safety clutch went off. But it wasn't that at all. It took me a while to figure it out -- days -- but here's what's going on:

When there's force on the basket, such as when the machine is handling heavy material, the basket and hook lock up. This makes the basket pop outta place and rotate with the hook. (Note the top red arrow above: This is the li'l nubbin that keeps the basket in place [the finger on the bobbin case holder]. With the second arrow, above, you can see the needle coming down through the slot in the basket.)
Here the basket has popped out of place and is rotating with the hook. The needle is continuing to descend...
...and will collide with the basket ... now! Your needle will now be missing its tip and your case opener (that lever on the bottom of the photo) will now be pointing to the right, knocked outta place.

The great tragedy of this is that Juki sewing machines have such a good reputation that no one believes me when I tell them that I'm having trouble with my hook assembly. They usually try to blame the problem on me, or tell me to call someone else ... in circular fashion.
And since this only happens with heavier material, it wasn't caught at the factory during the final sew off.
Fortunately Juki America has been fairly helpful, and I've sent my hook in for inspection.
[Note: I've received my replacement hook and I've just installed it. So far so good. Thanks, Juki! [Keep reading for more updates]]
Though, I swear this machine must be cursed. First I received a defective table leg, then the motor belt was too small to match the drilled holes, now a crummy hook assembly.
Sheesh. Give me a break.
Lucky I still have my 111. Almost half the price and sewing strong.

So here's me taking the hook assembly off:
I was hoping to just move the feed base up a bit and slide the whole assembly out, but the thing's so complicated on the 1541s, I just took the assembly apart and got it out that way.
[Note: I figured out you can just loosen the bobbin finger/holder (that piece with the nubbin on it) and swing it out of the way and that leaves just enough room for the hook assembly to slide out. That's when the feed dog is at its highest point.]
Above and below is the hook with no basket.
Made a li'l mark on the machine so I can roughly line it back up ... though, there's a groove in the hook shaft...
[Note: Lucky there's a groove 'cause I forgot what position the needle was at. You need another reference point, otherwise this is useless. Ha.]
Needle plate removed. The hook just about to come back up. This is where the hook would snatch the thread loop.
No more hook assembly.

UPDATES 5/10/15
Probably should've updated this years ago, but I only use this machine occasionally now, mostly just for thick foam applications ... but I've recently received some emails from people with this same problem and seen this problem come up on some forums, so here it is.

After I installed my new hook assembly back in oh-10 I still experienced hook jam, though not as much as with the original hook asm. I've thus concluded that these hooks are bad -- bad to the bone. [If I can't get other hooks in other sewing machines to jam the same way by pushing on the bobbin, and I can with the 1541S, there's definitely something wrong with this hook.] Though, I've figured out a way to work around this handicap. First, let's look at the threading diagrams for the 1541 and 1541H (heavy duty):


 Above is the threading diagram for the 1541 and 1541S (safety clutch). Note the sliding thread guide (red star). This is used to adjust how much thread goes around the bobbin -- or something like that. I can't find it addressed specifically in the manual.
 

Now look at the threading diagram for the heavy duty class. No sliding thread guide! This is key. Here's what I think is going on:

These machines are set up to sew through a couple layers of upholstery material, and when you go to sew through anything heavier, there isn't enough thread to go around the hook assembly smoothly, putting inward force on the bad bobbin basket, which binds.

To avoid locking up the bobbin, I've been threading the machine the H way (or similar) with good results. This is how I was threading it the last time I used it, sewing 1/2-inch closed-cell foam and Cordura. I've skipped the sliding thread guide and the square thread guide, leaving plenty of thread to travel around the bobbin.


Notice the sliding thread guide is oriented the wrong way. I'm pretty sure threading it like this will actually take up more thread. I was playing around with different guide configurations a while back. I should set it back the way it was...
Here is another look at the hook assembly and related parts. Juki has a real nice database. You just need to set up a user name and password.



If this happens to you, the hook assembly will catch the needle and the machine will jam. If you're sewing at speed, your needle will be shorn off. Clean out your ruined needle and thread and turn the handwheel backwards till the hook asm pops back into place on the finger and then look for issues (you will most likely have to reset the case opener lever (on an S class). You may have to adjust your threading, as shown above. Or it's possible thread has been pulled into the hook raceway and caused the jam.
This might be caused by another issue, brought up by a sewing tech on Upholster.com (2/7/11):

Re: JUKI 1541-S shuttle/hook assembly out of whack, help me fix it!

I know exactly what is wrong, and I can explain how I know; because I check every Juki DNU-1541S before it leaves my shop for this known (by us) issue with this model, out of the box.
I can't tell you how to fix it, as I do not care to go head to head with another sewing machine mechanic. They may have a different resolution to this that I do, and I don't want to get into a tit for tat, he said she said brouhaha.

But, I can tell you what I know for absolute sure; the hook supporting plate/bobbin case finger that holds the bobbin case/inside hook from spinning is hanging on by a finger nail, and does not go in far enough. Unless this is taken care of, this will be an issue that will continue to plague this machine.

I've reset my hook placement before, and tested it by hand to make sure it was solidly engaging with the finger, and still had it pop off. There is quite a lot of force behind that hook when it jams. The finger-placement problem explains why it comes freely on certain 1541s, though -- and is maybe further proof of a larger quality issue with these machines.

And here is a thread on Leatherwork.net where the hook assembly popped free.

I'm hoping, as I use this machine more, the hook breaks in and never does this again. I oil my hook manually now, and I'm pretty cautious when I sew heavier stuff. Hopefully one day I can relax while I use this machine. :)

Update (5/25/16). I've been informed by a sewing machine mechanic that there is a break-in period for hooks -- even high-speed Juki hooks. He recommends turning the hook oiler all the way up and going full throttle for a while.

If you've had a similar experience or have any suggestions, send 'em my way @ coryleif [at] gmail [dot] com.


15 comments:

Mallory said...

This blog post is amazing! I work at a sewing machine dealership in CoMO, and I LOVE how well you've explained all this. I also know a guy who services industrial machines, like you Juki and can get parts for them. ROCK ON!!!!
Oh, and I feel like we are kindred sewing spirits in a way, because ever since I was 15, I've been sketching (both on paper and in fabric/thread) out the perfect bag for all my needs. Lots of products have emerged, but I can sense that making the perfect bag for other people would be extremely satisfying.
And if you need a job as a sewing machine technician, I think I know where you can find one ;)

Mallory Donohue
Zede's Sewing Studio
573-874-2500

cory said...

Thanks, Mallory!

Eric said...

Hiya!

Thanks for the great blog! Love the 1541S build post.

Can you tell me how the 1541 was fixed? I am about to get my new 1541s and want to double check it as I assemble to make sure there's no problems. I have actually been reading that there are a few of these machines with hook problems out there. Just want to be safe!

And finally, how are you still liking the 1541s? It is your main machine? Love to know.

Eric

cory said...

Hi Eric,
I received a replacement hook from Juki. It was doing pretty well for a while...then it started locking up the same way. The only two things causing pressure on the hook assembly are the thread and the case opener. I think sometimes the thread was too tight when it was coming around the case. You adjust this by sliding the skinny thread guide up or down. When I'm sewing 1/2" foam I'll take the thread out of that guide so there's even more thread available for each stitch.
I also disengaged the case opener in case that was causing trouble. I think the opener really only helps when using heavy thread--heavier than 92. My 111 doesn't have one and it stitches great.
I haven't heard of anyone having this sort of problem before and I've been looking for a while (though maybe in the wrong places). I still find this problem extremely weird and still don't understand it fully. Though, for a bit, I installed a 241 hook in the 1541 (they're fairly compatible) and never had it jam. In the older hook the thread-cutting grooves in the hook raceway are cut diagonally, while on the current hook the grooves are perpendicular to the raceway. Just a thought. Though there could be any number of other reasons for this...

Yes, the 1541 is my main stitcher. It's a great machine when it's behaving--the foot lift on it is awesome. Though I still use the 111 a bit too...it feels more comfortable to me.
Anyway, I'm sure you won't have any problems with your 1541S. Just make sure the hook is lubed and make sure the thread guide is adjusted to suit the material thickness. Also remember to hold the thread ends when you start a stitch--the Juki is touchy about that.
Have fun with your Juki!

Eric said...

Oh! I see what you mean about holding the thread ends on the 1541. Dang loops! I thought I was going crazy there for a moment, thinking my bobbin tension was too loose...

Is your needle tension on the 1541 super tight? Mine seems to like it very high. I'm going through two layers of nylon tube webbing and it seems to be really pulling the fabric together more than I'd like. Maybe I need to work with tensions again...dang! How are your tensions setup?

Thanks again for the great blog. Hope all is well.

Eric

PS No bobbin issues to date. Zamir set everything up before it was sent out. Seems like a good guy to work with.

cory said...

Eric,
I don't think my tension's super tight. First of all I'm using T90 thread. If you're using much heavier it's possible that you might need to loosen the bobbin tension.
For heavier stuff I tighten the dial down till can see one or two threads of the post. For lighter stuff I back up till the post end is about flush with the dial.
Needle size can affect tension...if you're using too big a needle you can get wonky tension.
Hope this helps.
Lemme know if you have any other questions. You can email me at coryleif@gmail.com
Happy sewing!

Martin Stahl said...

Wow ... Reading through this I suffered with you with all the staring problems you had with your machine. I probably would have given up. Actually it make me think .... Waht odd you do, if you have a problem that you can't figure out yourself. This kind of machines are not very portable to take them on the backside into the next towns service place..

Martin

cory said...

Hi Martin,
Yes, this is not a fun situation...especially with a new machine. You just try to be patient and figure out what's wrong and how to fix it and hope you get it right.
Juki is more helpful than most large sewing companies, I believe.
I've since found Leatherworker.net, a great forum and resource for industrial problems. Among its members are a number of shop owners who answer questions. Though, sometimes a machine is in so much trouble you have to ship it to a pro. Fortunately I haven't had to do that yet.

Shannon said...

I just want to say THANK YOU so much for this post. My 1541S broke down yesterday, today is Labor Day and I was desperate to get it going again. I looked all over for information because I knew the problem was in the hook but my inexperience kept me from figuring out where the problem was. You're awesome pictures showed me what needed to be fixed and I got it going again! I can't thank you enough for the great pics and explanation of the key factors to make it work properly. YOU ROCK!
Shannon

Unknown said...

This is mee to the T! Just brought my Juli 3 days ago and have the exact same problems.took it back 2 times and all the time they blame me! Did i drop it they ask! No! And I cant convince them its not me its the machine

rchauffe said...

Great info, thanks for taking the time to post. Same issues!

What did you mean by disengage the opener for lighter threads?

Thanks,
Ron

cory said...

Ron,
By "disengage" I meant I didn't reset it. It's hanging loose, touching nothing. Its purpose is to push on the bobbin case and make sure there's a gap up top so the thread can pull smoothly around the bobbin case finger. With lighter threads there's more room, so it's not an issue. As noted, the safety-less 1541 does not have an opener. Though, I should probably reset mine some day...
Good luck!

Unknown said...

I have to start by saying I love you. Your blog has calmed my shattered nerves more than once. Will you throw out a few thoughts as to why I can't pick up the bobbin loop on my 1541S? Timing is good, finger tightened. Opener adjusted...I think.....

cory said...

Hi Unknown,
Glad the blog's been helpful!
If you can't pick up the loop, try these things: Put in a new needle. Make sure the needle is inserted correctly (all the way in, groove facing left, thread going in left to right). Make sure you're holding onto the end of the needle thread when you're picking up the loop. Double check the threading on the machine all the way back to the thread stand. Make sure you have proper needle-thread-size compatibility. It's usually something small and simple that's causing the problem. Hope this helps! If you have any other questions, email me at coryleif on g-mail.

Janet Gannon said...

OMG.. this is exactly my problem Basket case comes loose and spins around, needle breaking, etc. New machine. I need to contact Juki!! Thanks, I'm not crazy.