Adler 269-373 missing stitches

[Yanni]

Hello,

 

We have 4 x Adler 269-373s in our factory and one of them skips stitches just one at a time and totally at random.

I have done the timing in all of the other machines so I am quite competent to sort them out but the last one I can't work out what is wrong with it...

The puzzling thing is that it skip stitches on straight lines usually you get missing stitches on curves etc when the leather is stretched and bends.

I've got an EFKA motor on it, hook is brand new, and checked distance between hook and needle is great, I have tried various tensions, for both thread and thread spring, 

alter tension on the bobbin....really puzzled..also machine restricted to 650 max speed. Most of the parts are brand new original Adler too I bought from Germany( spend £1000 on it recently ).

The only thing I can see is the thread flying out a bit more when it misses the stitch and I've got the feeling it does it either when decelerate or accelerate.

 

Any suggestions?

 

Thanks

Yanni

 

[Constabulary]

First I would check it the needle hight and bobbin case opener, I would assume it has to open a bit earlier. It´s just a guess from her distance.

Edited May 8, 2016 by Constabulary

[Uwe]

Gravitational waves. That machine is clearly a gravitational wave detector that senses when a gravitational wave, generated by a supernova in a distant galaxy, causes a distortion in times-space and deflects the thread loop away from the hook. I see a nobel prize in your future.

[sandyt]

Another guess from overhere.

Have you tried other needle types or sizes? Or thread? Maybe it doesn't like your needle/thread combo.

Checkspring like Constabulary mentioned could be something. 

You could play with the timing a tiny bit. I know it's not the way to go, but most of the times I time my machines on feeling. I rarely use the factory settings. BUT (!) I only have old and  sometimes half worn machines.

Good luck! Hope you can finish the puzzle.

 

[Yanni]

Thanks, all the adlers in factory are identical and use the same needle/thread. 

I don't use the factory settings for the timing as I found them slightly incorrect. Again the other 3 are working fine with my settings.

I will try another bobbin tomorrow and see what happens...

[sandyt]

I overlooked you have 4 identical machines. Sorry about that.

You could try switching the bobin indeed.

Good luck.

[billybopp]

Does the problem child machine always have the same operator?  

 

[Uwe]

The operator of the trouble machine may stop the machine more often than the others. Every time you stop the machine, there's a slight chance of a skipped stitch, depending on exactly when in the stitch cycle you stop the machine (that brief moment right after the needle starts to rise again, when the thread loop is forming but the hook has not yet caught the loop is the worst time to stop the machine in terms of potential skipped stitches). Pull up a chair and observe that operator and machine for a while - you may see a pattern that contributes to the problem. If the machine's Efka motors have needle positioners that stop in the down position, perhaps that machine's programmed down position has a slightly higher chance of a skipped stitch. If they're using huge spools of top thread, the trouble machine's cone of thread may be a little more lumpy/sticky/rough/brittle than the others and occasionally tug at just the wrong time.

Edited May 8, 2016 by Uwe

[brmax]

I might take a look at the bobbin case height in relation to its clearance in the needle plate, if at minimum I wonder.

Also the thread size is this easily changed smaller for a test for added above check.

a question, even if this is random is this repeated in the same 2' run, jus curious here.

Good day

Floyd

[gottaknow]

Random skips are usually the hardest to troubleshoot. You need to rule out not having enough foot pressure. When you hit a harder section of leather, it can stick to the needle and push the foot up, not forming a loop and skipping. Your check spring could be too tight as well. If you can rule those things out, retard and advance the hook timing a bit each way. I do repair machines on the side apart from my regular job. Send me a ticket and I'll get it settled down for you.

Regards, Eric