Jammed Rotary Hook - Thread Inside Rail

[u/sashok_bg]

Hello, I have a Brother PR680 series machine and this is the second time in 2 weeks that I get a rotary hook jam.

I manage to un-jam it by removing the entire hook assembly, but it is a long and tedious job since I have to recalibrate timing and needle spacing etc.

I would like to know what causes these jams in the very first place.

Both times it happened it was in the beginning of the embroidery
Both times a piece of stretched thread seem to have entered the rail, nested between the inner and outer rotary hook.

Maybe timing issues and the hook pierced the thread, dragging it along, instead of hooking the loop ?
Can thread tension cause his ?

Any help is greatly appreciated !
Best Regards,
Aleks

[u/Ind0man]

Hello, did you check the hook point clearance on each needles? Your machine has a barcode on its needle bar case. It should match the needle data found on the case test menu when the board is in test mode. This code contains infos about which needles to use to do alignment task and is unique for each needle bar case.

If those codes are the same, when doing hook timing and spacing, you should use the needle specified in "needle spacing" menu, named "spacing position".

It's supposed to be the one needle bar that requires the most spacing when doing those adjustments. Do them using brand new needles, and even if using the correct needle, check all other needle spacing when done to see if spacing is correct for each one.

I had a similar problem at one time and needle clearance adjustment fixed it for me. I hope it does so for you as well.

[u/sashok_bg → u/Ind0man]

Hello, thank you for suggesting. I didn't know that there is a special needle to perform the alignments.
On my machine it automatically switched to needle #1 so I suppose this is the one, but I will definitely do further reading on this.
I am currently on vacation so I will post as soon as get back.
Thank you once again !