Fraying thread while reversing

[buellfire]

I have a Consew 255-rb3 with a family servo motor and box style speed reducer. I sew vinyl for medical upholstery,  currently having a problem with reverse while locking the thread. While reversing the thread will start coming apart almost instantly, this happen while starting a run or after forward sewing. I can sew all day going forward but reverse will shred the thread. I am using this thread Bonded nylon v-69 T70. Any help would be appreciated. 

[CowboyBob]

This could be a timing issue but we'll start with the easier causes first.Check your needlebar thread guide by taking some thread & pulling through it & see if it shreds,also check the bottom of your inside foot & feed dog for burrs or sharp spots.

 

[buellfire]

Thanks Bob! I will check those pieces. My thread guide does seem loose and the thread doesnt stay in there, maybe that is the problem. 

[Pintodeluxe]

I agree with Bob, that is a good place to start.

If the thread isn't staying in the needle bar thread guide, then you've already found the problem.  That will 100% cause thread fraying because the needle just stabs its own thread.    

Other things to check...

1.  Check spring position.  Check spring needs to control the upper thread until the eye of the needle reaches the material.

2.  Check spring tension.  Check spring needs adequate tension to perform #1 above.

3.  Needle bar height.  Hook needs to intersect needle about 1/16" above the eye.  If it crosses too close to the eye of the needle, it will split the thread and cause fraying.  

4.  I'm assuming you're using about a #18 needle for the bonded 69 weight thread?

 

Best of luck with it.