Outer Presser Foot Stutter on Cobra 4

[MrLentz]

Hello,

I just purchased a new cobra 4 sewing machine and have been noticing that when sewing slowly the outer presser foot comes up in a very jumpy manner. Kind of like a stutter. It kind of concerns me that the rod holding the outer foot might be off in some way - and I don't want to continue any damage to this new machine if something isn't set right. Anyone have this issue with that outer presser foot when it is pulling up? Still does it even when I pulled the foot off.

The rod is pushing up on the large tension spring on the inside of the case, so my thoughts are that this could just be some physics about the slow speed against a high pressure spring. Any thoughts? Just want to make sure either way before moving forward!

 

[JREESER1]

If you just purchased a new machine, call the dealer and describe your concerns. I'm sure they can ease your mind and find a solution if there is a problem.

jr

[Wizcrafts]

Lol, the jumping of the presser bar is probably caused by an off-axis hole bored into the top tension adjuster bolt. Just loosen the lock nut and rotate the adjuster a little until the presser bar moves freely.

[MrLentz]

16 minutes ago, Wizcrafts said:

Lol, the jumping of the presser bar is probably caused by an off-axis hole bored into the top tension adjuster bolt. Just loosen the lock nut and rotate the adjuster a little until the presser bar moves freely.

I did try that in 1/8 turns to see if there was a good location, but doesn't seem to make a difference. That's my concern though - is a poorly drilled hole in the case, would that mess up the machine in the longrun? Kind of bummed because I also am having a problem with the needle holder and bar. Apparently the needle is skewed off to the right by about 1/16 inch and just about hits the holster plate even when installed entirely to the right. I am getting a new needle holder to see if that is the issue, but overall it's starting to seem like I might have a lemon.

23 minutes ago, JREESER1 said:

If you just purchased a new machine, call the dealer and describe your concerns. I'm sure they can ease your mind and find a solution if there is a problem.

jr

I have been asking Steve at leather machine co, but no answers on this part so I wanted to see if anyone else had a similar issue

[Uwe]

I'd take the faceplate off and carefully observe how everything moves as you slowly turn the hand wheel. Give it a good oiling while you're at it. You might be able to tell where it catches and causes a stutter.

Sometimes the foot lift linkage needs to be adjusted a little to line things up just so for smooth movements. Also check if a screw may have worked itself loose during the break-in period, which happens on occasion with new machines no matter how careful the technician is.

The vendor's tech support is your first line of problem solving, be sure to keep trying to give him a shot a fixing your problem. The dealers keep saying that it's their setup work, initial adjustments, and after-sale support that makes the difference between all these virtually identical clone machines. If you're going to end up doing the work yourself, you might as well order a machine on alibaba.com and save a chunk of money up front. At the same time, even the best vendor has absolutely no control over which screws the user turns, which may cause issues.

It's not yet time to lose sleep over potential off-center holes and lemonade.

But it is time to break out the camera phone, dust off your youtube account (or get one) and post a video snippet of the problem. The only thing that's certain is that this won't be the last time words alone will not sufficiently describe a problem.

 

Edited March 24, 2017 by Uwe

[Uwe]

As a follow-up, I actually caused a similar problem on my Adler 205 once, where the foot lift linkage started making odd clicking noises. I took me a while to realise where the noise came from and that I myself had caused the machine to make these noises after adjusting the manual foot lift height. A very subtle tweak to lower the manual foot lift height a small amount brought the machine back to silky smoothness and banished the clicking noise. In my case the clicking noise was caused by an internal sliding block that was stuttering as it moved on the shaft. The Adler's mechanism is different enough from your 441 class machine to not be of help in debugging your case. I'm just mentioning it to illustrate that small adjustments can have unintended side-effects, and that some issues only manifest themselves at very slow speeds and could easily be missed during initial setup. The clicking noise actually went away when speeding up the machine. No off-center holes or lemon castings, just plain old user error was the root cause in my case.

Here's a video snippet of my Adler 205 making the clicking sound:

 

[MADMAX22]

Regardless I would still leave it alone till you talked to someone at Cobra. Looks like they have a limited lifetime warranty but dont know the details so who knows what voids it. 

[brmax]

If when you sit next to it and manualy lift up on the foot at the mounting is there noticeable drag. You could remove the side for a better oil app possibly. I had a great talk with the tech at leather machine so do give them a shout back in the shop

good day

Floyd

[MrLentz]

Thanks everyone for your replies. Yes I am getting back in touch with them to keep troubleshooting this. I know from this forum they have good support which is why I chose to buy from there. I have wiped out the interior of the case and oiled every moving part, so it's probably a bit more technical at this point.

Here are two videos of the stutter.

https://dl.dropboxusercontent.com/u/277783/IMG_0203.mp4

https://dl.dropboxusercontent.com/u/277783/IMG_0202.mp4

 

 

[MrLentz]

Ok, just to clear this problem up - it has been solved. Leather Machine Co got back to me after seeing the videos, it turns out the problem had to do with the steel plate on the inside back of the case where a roller bearing rolls up and down it as the presser bar lifts. Turns out the plate was not close enough to the bearing, so I loosened the top screw on it, applied pressure pushing it closer to the bearing, then tightened the screw back down. Problem solved!

 

[JLSleather]

So the "fix" for a bushing with too much "play" is to "one-side" it in the hole?  Okay ...

 

 

 

[brmax]

Its dry. 

It may be possible to remove the top presser spring retainer nut totally. In doing this a better oiling of these parts surely could be tried.  This seems to be a new machine fit type issue though a pain i think a bit of time and youll be off n stitching.

I had earlier tried myself manually lifting the presser foot on mine  at its mount point and this is handy. 

Have a good weekend

Floyd

edit: oh the ole  chatter roller ya!

Edited March 24, 2017 by brmax

[MrLentz]

4 minutes ago, JLSleather said:

So the "fix" for a bushing with too much "play" is to "one-side" it in the hole?  Okay ...

 

 

 

Yeah - I am not sure, it did stop it from skipping. My guess is that when the outer foot is going up, the inner foot is pushing down - and due to how the linkage is set up there must be some lateral force on the outer foot bar with the spring. Both feet use that same spring for tension, so the inner foot looks like the lateral force is counteracted by applying equal force using the bushing against the wall. Without enough pressure on the bushing plate, the rod probably bends ever so slightly. Same with too much pressure is my guess as well.

[Uwe]

I think the vertical plate adjustment is just a normal adjustment for this machine's design and does not indicate a loose bushing or some other defect.

The bearing wheel presses against the vertical surface as it rolls up and down. That vertical surface needs to be in the right plane to keep things aligned properly and provide a leverage surface for the bearing wheel. If the vertical surface is too far away the linkages put horizontal pressure on the presser foot bar and deflect it or press it sideways against the upper and lower bushing walls, rather than guide it straight up and down without sideways deflection or pressure.

 

Edited March 24, 2017 by Uwe

[brmax]

Thats what gets my goat, i got all worked up on mine and so got ready. Did work outs! Push ups everything. Even brang all the tools in, a new pot of coffee. 

I made the call and like : do this, i did and it was fixed and done. Dam coffee in my cup was still steaming. 

Floyd 

[JLSleather]

From the video, I'm thinking that the noise (which is more obvious when you slow the video down to 1/4 speed) is from the SPRING contacting teh casting in the low end. "One-siding" the shaft in the busing wouldn't be my first "plan", but ..   If the shaft is off by that noticeable amount, a guy might think about an eccentric bushing to allow it to pull back in the right place.

Question is, does it look like the needle itself is moving laterally with each stitch?  

[Uwe]

I vote for letting the man enjoy his stutter-free machine.  

[JREESER1]

I second that motion, Uwe! If he is happy with the fix, that should be all that matters.

jr

[MrLentz]

haha, well as long as it is not a patch for a bigger problem i'm fine with it!

[Uwe]

I really do think the fix was a normal adjustment and I don't see any indication of some major flaw that needs to be worried about.

[brmax]

There maybe somewhere an illustration on the adjustment here but its not in the Juki engineers manual where i have noticed. So any of you are more than welcome to share the typical adjustment and or measurements. I certainly would appreciate the information. 

Thanks

Floyd

[MADMAX22]

1 hour ago, brmax said:

There maybe somewhere an illustration on the adjustment here but its not in the Juki engineers manual where i have noticed. So any of you are more than welcome to share the typical adjustment and or measurements. I certainly would appreciate the information. 

Thanks

Floyd

I didnt notice it in the chinese version either. Doubt you will find any mention of this "normal adjustment" and since it doesnt seem to pop up here much I doubt I would consider it normal. It may be normal for the suppliers when they get them from china but didnt see it in any of there videos either. 

Glad it was posted though so atleast now there is something searchable if someone runs into the same issue.