Durkopp Adler 8967 issues

[BurkBags]

I recently picked up a DA 8967 cylinder bed machine that used to be used in a blue jeans factory for the cuffs.  I am going to use it for some heavy multi layer cordura projects as well as leather.  I got it running and with a new needle got it sewing with my bonded 69 nylon thread really well in terms of making a nice stitch.  However, my issue is with the thread cutter and also auto backtack.  

When I use auto backtack, the stitch length knobs both jump to maximum (6) when its used.  They jump when the machine shifts from rev back to fwd.  I also noticed they will do the same thing if I manually push down the lever and let it spring back.  If I gently move it down to reverse and let up gently, stitches stay the same length.  

The thread cutter seems to try to work, but when its used, the top thread remains uncut and when I pull the piece out, there are 3 threads coming from the bottom also uncut.  Very strange.  Attached pics of bobbin, maybe I'm threading wrong.  Pics in manual aren't terribly clear.

 

 

 

[Uwe]

I've never even heard of this machine until just now, but it looks like a very nice - and very complex - machine. 

You'll need to spend some quality time with the service manual for Durkopp Adler 8967 (8967_instructions_for_service.pdf)

I'm not an expert on thread cutting mechanisms, but I was just working on the thread cutting mechanism on my Adler 467 yesterday. It also did not want to cut the thread reliably - I had to advance the hand wheel a quarter turn to complete the cut. On my machine the fix ended up being an adjustment inside the needle position sensor. My NP sensor has one disc that is used for positioning during thread cutting operation. I had to rotate this disc a little to change how far the knife moves during the cutting cycle.

[BurkBags]

Ya, I'll have to have a look at that.  It is a VERY complex machine!  I was excited that its automatic in terms of auto-backtack and threadcut as I have a flatbed with those options.  But the DA is on another level.  Like there's something like over 300 parameters you can program and you can dial in certain functions to the millisecond.  I have been going over the service manual but I might end up having a local tech come out as some things are a little over my head.  

I did figure out the thread cutting mechanism is a circular rotating disc with a knife on it so possibly its a timing issue with the needle like yours was.  I also noticed when going to "home" position, the motor is currently setup to send the needle home, but then reverse a tiny bit so the needle is at its highest position so its above the foot to prevent snagging material when pulling it out.  I might try to turn that off and see if it helps thread cutting.

Thanks!

[Gregg From Keystone Sewing]

I may be incorrect, but it sounds like it's jumping to the longest stitch length because the control box is telling it to do so?  Just a guess tossed out there.  What model is the motor?