I just inherited another Huqvarna (this is a model 630). It was working great until I wound a bobbin on it. After I removed the filled bobbin the machine won't move the needle up and down (but the bobbin spindle keeps turning)! The manual is no help. I wound the bobbin per the instructions. HELP!!

Is it smoking out of the casing or is the bobbin plastic and its melting?

Well, you COULD get this fixed -- or you could purchase an inexpensive bobbin winder and skip the whole issue. Does a better job, too.

First, remove the bobbin and clean the entire area; if your machine model has a bobbin case, be sure to remove any lint from between the overlap. Change to a new bobbin in case the bobbin is wound poorly (happens even to pre-wounds).

Check thread paths of bobbin and top threads and be sure tension isn't too loose in bobbin or top; sometimes the auto tension changes erratically when stitching on thick fabrics, check your manual for resetting it to default or for making adjustments.

Be sure the needle is one that is the right size and type for the fabric you're stitching on and use a new one; bent needles happen easy, and a slight, almost undetectable bend will cause this type of issue.

Hi, not familiar with this machine, but a few tips -
Unthread the machine fully. Remove the bobbin. Is the bobbin thread the same as the top thread? Is it a Quality thread (yes, cheapie thread can give big issues!!) Do you have several different threads wound onto the bobbin?? Is the bobbin thread wound on quite tight? If you push your finger nail into the thread wound onto the bobbin, it must not feel soft or spongy. .... hope this in general helps some!

Some how the bobbin got wound too tight. The thread must have been caught along it's path or something. You will have to unwind the thread off the stuck bobbin. Once enough thread is off the bobbin it should pull off. After that, throw that bobbin in the trash, it is now deformed and most likely will not work anymore. If you wind your bobbins with the machine threaded always make sure you have your presser foot up and Always use a metal foot.

it sounds like the machine may need to be serviced

Mine stopped working too. Gave up and wound bobbins by hand for a while until I broke down and took the machine apart -- an ordeal to figure out. I found that a pliable ring on the winder was completely disintegrated (gummy plastic-like stuff). An online search found this -- a bobbin "tire" which I THINK is the part I need: http://www.sewingpartsonline.com/bobbin-winder-tire-brother-x55238051.aspx. Hope this helps. --Also cleaned all the lint out when I had the machine opened up. They don't make it EASY!

Not sure what a 4D machine is, but guessing you have a Designer of some kind. Have you put in a new bobbin since you sewed out the successful design? Did you wind it yourself or is it a pre-wound? If wound yourself, maybe the tension on the bobbinfill was not correct and the bobbin is not wound properly as a result. Wind a new bobbin - take the machine speed down three clicks and wind the bobbinfill around the round metal tension bit in a figure-of-eight instead of around once only (i.e. go under the disc, around to the left then over the top then across to the bobbin filling mechanism).
Floss out the bobbin tension slot with a piece of strong sewing thread to be sure there is no fluff in there, and when you re-load the bobbin be sure to listen for the "click" as the thread goes into the tension slot.
Sometimes designs are badly digitised and they will not sew out nicely. If you are sure your fabric is correctly hooped, the bobbin is correctly wound and securely in the bobbin case, try loosening the upper thread tension by two clicks and see if that helps the problem to go away. (SET menu, numbers and plus and minus signs under the icon that looks like a DNA thread - minus to decrease tension.)

buckmanfamil....I use my finger to keep tension on thread when i fill my bobbin.i also pusu thread slightly up & dwn to even it out on bobbin.works for mine ! I luv my Baby Lock !!

Recently had same problem. Underneath the bobbin area on the bottom of the machine is a small white plastic piece that resembles a fan. Singer calls this the bobbin cam actuator. It is usually cracked along the sleeve that fits over the metal pin, bar? This is the mechanism that lifts the bobbin when it is wound. When its broken it can't lift the bobbin to be wound properly.