Nests on the back are usually a result of not pulling up both threads to the front of the quilt and lightly holding them in place before starting. If you do that, you shouldn't get a nest. I have a HV Designer with D Cards. In my tension (upper) disc, it is easy to get the thread behind the tension disc. Also, when you thread the machine, make sure the "thread take up" (see design) is ALL the way up. That opens the tension discs. Also check that your thread is feeding easily - not wrapping around the top of the spool etc. For free motion - how fast or slowly you go should not cause "nests." You may have bigger or shorter stitches, but not nests. If it persists, take a sample of your stitches and machine back to where it was cleaned. They should have checked the timing, and clearly it is not working.
Good luck.

I agree here with Deb (except the part about shutting off the machine). Rethread the machine. Those nests are caused for a reason. My nests are usually because I sew at top speed and when I stop, the thread doesn't. Somehow it manages to jump out of the discombubulator thingy that goes up and down before it is threaded into the needle. When that happens, this causes the thread to unleash itself from the tension disc. If you are getting thread buggers, then something has come undone. If your fabric is trying to go on a reducing program, then something is bound up. Give it a good laxative by rethreading both the top and the bobbin thread. What ever response you get, just remember this: Nothing can tighten it self on its own. If you feel you must fix a tension issue then something has jumped it's boundaries, or there is a clog of lint somewhere. This is NOT a personal issue, nor is it a machine issue if you just remember that "things" do not tighten themselves. ;)

I don't have any luck quilting with 100% cotton bobbin thread. I use an all purpose or poly and it seems to have fixed the problem. Also, make sure your bobbin is going in the right direction. Lastly, there are at least two clear plastic bobbins, one is flat and the other is slightly rounded. If I accidentally use the wrong bobbin, I get this too. I wonder if it's the minky... I would try a poly thread if all else fails.

sometimes i rewind my bobbin onto another....it can be wound too loose.

Check your thread and see how it is wound on the spool. Some theread must be in the up right position and some need to be in a horizontal position to feed correctly. Check Cindy Needhams website, I think she has information there. If not she is great at reaponding to email questions.

My old machine did this if I put the bobbin in the case backward. Take out the bobbin and flip it over.

How does your machine act if you just do a small test run with a regular cotton quilt sandwich - could it be the minkie causing the problems with all those great bumps?

I had the bird nest type pile up of thread some time ago. I know how frustrating that is. As one person has said, it might be the bobbin. That was my problem. I hadn't used my newer PFAFF in awhile and had not threaded the bobbin correctly. Looked at the machine manual and discovered what I was doing wrong. Good luck. ~Fran

Make sure you presser foot is up when threading top thread. This will allow tension to grab hold. To test if top tension is alright put down presser foot and gently tug thread in needle. Thread should bend needle slightly if top thread is in tension mechanism correctly.

You must pull your bobbin thread up to the top. Here is a youtube video explaining that.

http://www.youtube.com/watch?v=JfIle...eature=related

This information is about 2 1/2 minutes into the video.

There are other videos in this series (4 total), plus many others on youtube that might help you with your FMQ.