Suggestion on bottom stitch issues on my new Juki DNU1451S

[LunarConcepts]

Hello, I recently purchase a Juki DNU1541S and I am having an issue with my bottom stitch making a loop whenever I make a turn (generally a 90*). I am sewing a heavy nylon webbing. I have been through increasing and decreasing both top and bottom stitch tension to the extreme. I have to run a decent amount of top stitch tension as this stiff is rigid and has a very tight weave. When I have the top stitch tension tight, it pulls the bottom stitch loop up through the material excessively to the point that my 90* corners are not crisp but rounded off. I can work with the top and bottom stitch tensions till it no longer pulls the bottom stitch through the material but then the loops start forming on the bottom side.

This is normally only an issue for the first stitch after turning the material. All this is better shown in the picture. This is an issue I don't have on a Brother LS2- B837 and I am not sure if it has something to do with horizontal vs. vertical axis machine. Its almost like I am getting an excessive amount of slack when knee lifting the presser foot when turning. I did try actually just spinning the material under the foot without lifting and it made no notice improvement and in one instance made it worse

I appreciate any suggestions. Thanks for a great forum.

 

 

[Tejas]

The problem might be lifting the foot too high, opening the tension disks. You might try lifting the foot only high enough to turn the material. The needle should be buried and just on its way up.

[Russ]

I agree with Tejas.  I have a 1541S and a couple of other machines, and the Juki is unique in that it wants the needle almost all the way down when making a 90 degree turn.  My other machines like the needle much higher.

 

[Gregg From Keystone Sewing]

I'll look into it as well, I'll try what Russ said.  This is not the 1st time I've seen this issue before.  

[LunarConcepts]

Thank you all,

I will try turning the material prior to going past needle bottom. I always went past bottom on the Brother to make sure I didn't deflect the needle away from the hook and miss catching the corner stitch. This seems to be more of an issue when I am only sewing through a single layer. It is very frustrating as its usually right a the end of the project. It certainly kills the feeling of a successful finish.

I have tried not raising or barely raising the presser to make sure it wasn't releasing the thread tension at all but really there is no load on the thread so I am not sure how it would?

Gregg, Loving the new machine. All is well, I just need to get this last little thing figured out. The repair on the Brother has made it better than ever.

Thanks for any additional input!

 

 

[Gregg From Keystone Sewing]

On 11/26/2016 at 2:20 PM, LunarConcepts said:

Thank you all,

I will try turning the material prior to going past needle bottom. I always went past bottom on the Brother to make sure I didn't deflect the needle away from the hook and miss catching the corner stitch. This seems to be more of an issue when I am only sewing through a single layer. It is very frustrating as its usually right a the end of the project. It certainly kills the feeling of a successful finish.

I have tried not raising or barely raising the presser to make sure it wasn't releasing the thread tension at all but really there is no load on the thread so I am not sure how it would?

Gregg, Loving the new machine. All is well, I just need to get this last little thing figured out. The repair on the Brother has made it better than ever.

Thanks for any additional input!

 

 

Glad to hear it, thanks so much.  Keep on me with the DNU-1541S and turning the work while in seam, I want to get to the bottom of this.  Again, not the 1st time I've had this brought to my attention.

[TinkerTailor]

Just drawing at straws here but this came to mind:

Have you tried with a needle a size up or down? I know webbing can tighten down on the needle and the hole closes back up. I wonder if the act of turning the work causes the thread to wrap around the needle a little and get slightly tighter, or perhaps stopping the needle motion to turn allows the webbing to collapse the hole, effecting the ability of the machine to pull the top tight at the end of the stitch cycle? Also, just curious, what happens if you turn a 90 the other way? I wonder if it makes a difference whether you turn towards or away from the hook. If it is the same both ways i would lean to a needle/thread/lube issue but if it changes with direction i would suspect something going on in the hook with loop formation. Again, just a shot in the dark.
Thread lube may help as well.

 

[LunarConcepts]

On 11/28/2016 at 0:55 PM, TinkerTailor said:

Just drawing at straws here but this came to mind:

Have you tried with a needle a size up or down? I know webbing can tighten down on the needle and the hole closes back up. I wonder if the act of turning the work causes the thread to wrap around the needle a little and get slightly tighter, or perhaps stopping the needle motion to turn allows the webbing to collapse the hole, effecting the ability of the machine to pull the top tight at the end of the stitch cycle? Also, just curious, what happens if you turn a 90 the other way? I wonder if it makes a difference whether you turn towards or away from the hook. If it is the same both ways i would lean to a needle/thread/lube issue but if it changes with direction i would suspect something going on in the hook with loop formation. Again, just a shot in the dark.
Thread lube may help as well.

 

Thanks for commenting! I have this almost entirely eliminated primarily through increasing the bobbin tension to what I would feel would be way to much but if it works....

Basically I got pissed off at the Juki and went back to my old Brother. I managed a relaxing 2 hours of making belts and when my head was in a good place I sat back down with the Juki and backed everything out and started working my way in. I would roll over to the Brother and give the top thread a pull and then back to the Juki to adjust the tension till my calibrated elbow felt they were the same for both machines. I did the same for the the bottom stitch and realized how much less the Juki was even after yo-yoing the bobbin case to get it into the normal tension range. I went for broke on the bottom tension and dialed it tighter with positive results and without an impact on the top stitch.

I am going to give a thread luber a shot. This webbing sews up rock hard and the smoke rolls off the titanium coated needles. I would love to eek out a bit more top stitch tension which I am hoping will snug up the last little bit of slack on my corners

Thanks again!

[Tejas]

Here are links to how to measure, and reliably set, tension with a spring gauge.

http://sew24.blogspot.com/2012/11/how-to-measure-thread-tension-with.html

http://jukiindia.com/Item-List/Adjustment_Procedue.pdf

[brmax]

+1 on the links,  I like Juki's method of measuring the bobbin. I thought I was abstract in a similar method, not so much now  (snap finger) darn it

Being interested in all the in's and outs or why,s to my understanding the machine, other than me hittin the go pedal. Here's what I tried in my first machine and subsequent 1541 and one can use it handily with other machines. Though tensions change it was a good mark or judge point for myself on a consistent material; I sewed a very small bag "almost closed" cut the top thread leaving bobbin thread attached and insert weight or weights in sewn bag, let it position over the operator side edge and adjust weight to slowly drop down.

I measured this in different ways and was 27grams, or 417grain for my particular job and machine, remembering what someone mentioned it can change with material n threads. So for this I adjusted a couple and put in a Ziploc, and can be a handy idea.

With that mention behind, I have been curious of the winding effect on thread at the needle as re positioning materials, and at points thought this is tougher than normal. It may be possible to be losing a stitch.  In some ways if we look at videos of thread at certain points through the sew cycle when the needle returns to go up its in free state or thread is sliding through eyelet.

As mentioned this can be a top drawer adjustment with needle selection for a specific action when known, no doubt worth further discussion. So in short a small eyelet could have enough tension in thread to pull up some and or in a repositioning remove the normal amounted loop of thread usually waiting on the hook.  That was deep, so coming up for air!

out for coffee

Floyd

[TinkerTailor]

36 minutes ago, brmax said:

+1 on the links,  I like Juki's method of measuring the bobbin. I thought I was abstract in a similar method, not so much now  (snap finger) darn it

Being interested in all the in's and outs or why,s to my understanding the machine, other than me hittin the go pedal. Here's what I tried in my first machine and subsequent 1541 and one can use it handily with other machines. Though tensions change it was a good mark or judge point for myself on a consistent material; I sewed a very small bag "almost closed" cut the top thread leaving bobbin thread attached and insert weight or weights in sewn bag, let it position over the operator side edge and adjust weight to slowly drop down.

I measured this in different ways and was 27grams, or 417grain for my particular job and machine, remembering what someone mentioned it can change with material n threads. So for this I adjusted a couple and put in a Ziploc, and can be a handy idea.

With that mention behind, I have been curious of the winding effect on thread at the needle as re positioning materials, and at points thought this is tougher than normal. It may be possible to be losing a stitch.  In some ways if we look at videos of thread at certain points through the sew cycle when the needle returns to go up its in free state or thread is sliding through eyelet.

As mentioned this can be a top drawer adjustment with needle selection for a specific action when known, no doubt worth further discussion. So in short a small eyelet could have enough tension in thread to pull up some and or in a repositioning remove the normal amounted loop of thread usually waiting on the hook.  That was deep, so coming up for air!

out for coffee

Floyd

If you want to get really accurate,  they make trigger pull digital scales for gunsmiths that measure grams/tenths of ounces of pull. Some have used luggage scales and fish scales for the same thing. The methods of hanging weights on the thread are just ways to get it close without the measuring tools. Before digital, these types of tools were really expensive...

Lyman makes a great one and it can be had for under 50 bux on sale. Not cheap but worth it in time saved if you are frequently setting tensions on machines. If you write down the numbers that work for a particular thread/material/needle combo, you can replicate it exactly very quickly.

The advantage to the trigger pull ones over the luggage and fish scales(which also work) is the trigger pull scales usually have a function to save the peak value. This allow you to pull and look, while a luggage scale required you to read it while it is moving. One way around this is to set the tension too tight, pull the scale to the known value you want the thread to be at, and then loosen the tension until the thread moves.

You do want to look for a scale that measures in fine enough increments. Many trigger scales start at 8oz and measure in 1 oz increments. The lyman digital one starts at 0oz and measures in 1/10oz (or metric). Many luggage and fish scales are only good for pounds/kilos.

http://www.cabelas.com/product/Lyman-Digital-Trigger-Pull-Gauge/740429.uts

 

 

[TinkerTailor]

22 hours ago, LunarConcepts said:

This webbing sews up rock hard and the smoke rolls off the titanium coated needles.

If you are seeing smoke from the needle, you need to slow down and/or mitigate the heat. The metal needle will not smoke, it is thread/webbing/oil burning that is causing it. If you stop a hot needle, it will melt the material in the hole, and then cool. This will cause the hole and the thread to fuse some, close up around the needle and get tight. This could easily be the cause of the pre-corner loop, if the top thread is melted into the hole, it can't pull tight when the machine finishes the stitch.

If you are sewing to a safety/military etc standard, you will probably fail due to material damage.

Thread lube is a must, and since staining is not an issue, not reason not to. Another way to reduce needle heat is a needle cooler. It is basically an air nozzle pointed at the needle. Not much air volume needed at all. An airbrush compressor and an old airbrush zip tied to the machine will work dandy. I had a picture somewhere of a ghetto needle cooler setup but i can't find it right now...

[gottaknow]

23 hours ago, LunarConcepts said:

Thanks for commenting! I have this almost entirely eliminated primarily through increasing the bobbin tension to what I would feel would be way to much but if it works....

Basically I got pissed off at the Juki and went back to my old Brother. I managed a relaxing 2 hours of making belts and when my head was in a good place I sat back down with the Juki and backed everything out and started working my way in. I would roll over to the Brother and give the top thread a pull and then back to the Juki to adjust the tension till my calibrated elbow felt they were the same for both machines. I did the same for the the bottom stitch and realized how much less the Juki was even after yo-yoing the bobbin case to get it into the normal tension range. I went for broke on the bottom tension and dialed it tighter with positive results and without an impact on the top stitch.

I am going to give a thread luber a shot. This webbing sews up rock hard and the smoke rolls off the titanium coated needles. I would love to eek out a bit more top stitch tension which I am hoping will snug up the last little bit of slack on my corners

Thanks again!

If you're getting smoke, you are melting the webbing. Nylon webbing that has been melted during the sewing process become harder and can abrade the thread make for a weaker seam. The thread also sustains damage which weakens it. We use webbing on a lot of our products. If I see smoke, I set up lube reservoirs. If I'm using poly/cotton thread, I soak the needle threads in silicone. If I'm using bonded nylon, I run the needle thread through an inline dip. The easiest ones to use are a small plastic box with thick felt pads inside. You fill it with silicone and as the needle thread passes through, it coats the thread right before it's sewn. Bonded nylon doesn't absorb the silicone if you soak the cone. It just needs to be coated and the thread path lubricators work fine. Here's one, (yellow box) installed on a chainstitch machine. We were making leather welding jackets using Kevlar thread. These small boxes are nice because they have magnets that hold the on the machine without drilling holes. You can also see my air cooler I made to further lower the heat I use an air switch connected to the treadle so it only blows air while you're sewing  

Regards, Eric

Edited December 4, 2016 by gottaknow

[Tejas]

Here's a link to the thread lubricator I use.

http://www.sailrite.com/Magnetic-Thread-Lubricator

 

[TinkerTailor]

7 minutes ago, gottaknow said:

If you're getting smoke, you are melting the webbing. Nylon webbing that has been melted during the sewing process become harder and can abrade the thread make for a weaker seam. The thread also sustains damage which weakens it. We use webbing on a lot of our products. If I see smoke, I set up lube reservoirs. If I'm using poly/cotton thread, I soak the needle threads in silicone. If I'm using bonded nylon, I run the needle thread through an inline dip. The easiest ones to use are a small plastic box with thick felt pads inside. You fill it with silicone and as the needle thread passes through, it coats the thread right before it's sewn. Bonded nylon doesn't absorb the silicone if you soak the cone. It just needs to be coated and the thread path lubricators work fine. Here's one, (yellow box) installed on a chainstitch machine. We were making leather welding jackets using Kevlar thread. These small boxes are nice because the have magnets that hold the on the machine without drilling holes. 

Regards, Eric

I knew you would comment on this as well, just didn't think it would be simultaneously......Do use needle coolers much? Machinists have moved away from flood coolant in many situations and moved to these micro misters that spray a microscopic mist right at the cutting edge. Way less mess. I wonder is this could be adapted to sewing? It would be a very  tiny amount of atomized water, which cools when it evaporates. For jobs like webbing where there is no risk of damage at all from the water, this may be the ticket... I mentioned the airbrush hack for an air cooler, how are they done in yer neck of the woods? Any other recommendations? I Imagine you guys use air actuators as well for some automation operations, and the machines have an air supply near which makes things easier.

[gottaknow]

I use air needle coolers on my feed off the arm felling machines, (Union Special 35800's), certain bar tack machines, and anytime silicone isn't enough. I make my own by flattening the ends of 1/8" copper tubing. Easy to shape and solder as needed. I do have air line ran through out the factory. It takes a mere 10-15 psi of air through a tiny orifice to create significant cooling, no atomized mist required. My compressor is a Quincy 15 hp which gives me about 35 cfm at 90 psi. I have zero moisture in my system thanks to a refrigerated dryer and two 80 gallon tanks. It's amazing how much heat sewing 4 layers of 26 oz. wool generates. 

Regards, Eric

[Gregg From Keystone Sewing]

Really interesting thread.  Gottaknow, what are you doing with that brass tube junk; One answer for that is Loc-Line.  Easy to install, lots of options such as inline flow controls, various nozzles, and relatively inexpensive to use.

[gottaknow]

Lol Gregg. I've seen that, sheik. I use the copper tubing because I have miles of it. 

Regards, Eric 

[billybopp]

Gotta ask .. Is the belt mechanism to help pull material through?  Is it powered / synchronized with the feed?   I've never seen one o' those before.

Bill

[TinkerTailor]

20 minutes ago, billybopp said:

Gotta ask .. Is the belt mechanism to help pull material through?  Is it powered / synchronized with the feed?   I've never seen one o' those before.

Bill

Yes and yes. When you are sewing a 30 foot sail or a bigtop tent for instance, the feed dogs/machine operators cant handle the material weight so pullers are used.

[Gregg From Keystone Sewing]

11 hours ago, gottaknow said:

Lol Gregg. I've seen that, sheik. I use the copper tubing because I have miles of it. 

Regards, Eric 

We use what we have available to us as well!

My dad has stuff all over the house fixed up with sewing machine parts, like the base of lamp is a Singer 68 class steel cam, common stand parts to fix things around the house, all kinds of stuff, the possibilities are endless!