Can you tell me what the bobbin image on the artista 640 means? It will only sew for a few stitches and then stop

Bernina calls this the stitch plate (where the feed dogs come up and the needle goes down). To remove the plate, turn off the sewing machine. Remove the sewing table if it is in place. Take off the presser foot and remove the needle. Open the free-arm cover (bobbin cover in the sewing machine front view, page 4) by tilting it down towards you. Press down on the back right corner of the stitch plate and lift the stitch plate off to remove it. See page 68 of the manual for the Bernina Artista 170 for the pictures that go with the above steps. Bernina has the manual on the product page: https://www.bernina.com/en-US/Machines-US/Series-Overview/BERNINA-artista/BERNINA-artista-170 . The current link to the manual is https://www.bernina.com/BERNINA/media/Support/Sewing_Quilting_Embroidery/artista/artista_170/Documents/EN/008853-73-04_Naehen_a170_EN_online.pdf .

I hope this helps.

Cindy Wells

Suggest taking it for service. This could be a machine problem.

Perhaps I'm not understanding your question. When doing applique, I use a very tight zigzag stitch with a satin stitch foot or open-toe embroidery foot (so the thickness of the stitches do not create buildup under the presser foot). Set the tension so the bobbin thread stays mostly under the fabric so the top thread is the only thread that shows on the top (sometimes threading the bobbin pigtail will help).

Fuse the cutout fabric to the backing fabric. Then zigzag so the raw edge of the fabric is covered by the zigzag (helps to use a thicker thread so the coverage is easier).

Some newer machines have the ability to miter corners. On my 930, I set the needle position to the outside of the raw edged. Then when I near the corner, I gently, but consistently, narrow the stitch width to an an outside point, since the needle on the outside edge, turn the fabric and gently, but consistently, widen the stitch to full width. This creates a nice mitered corner.

When making curves, stitch small lengths and then sink the needle on the outside of the curve, and gently turn the fabric to follow the curve and repeat while going around the curve.

https://books.google.com/books?id=MQneD8cQ5KAC&pg=PA13&lpg=PA13&dq=mitered+applique+corner&source=bl&ots=1sHsUrkVAz&sig=1WZ-i2-T3RtvUEW797sHxTKiq4E&hl=en&sa=X&ved=0ahUKEwiaoZeiwunKAhVslYMKHewdDFEQ6AEIKzAC#v=onepage&q=mitered%20applique%20corner&f=false


How to Appliqu Like Pro Sew4Home (FWIW, IMHO, the satin stitch on the bird is really a poor example. The stitch is not very even at all--could be the sewing machine.)

How to Make and Apply Appliques (The giraffe is a better example, although choosing a simple design to applique usually yields better results.)

Practice, practice, practice!

...

the feed dogs need to be checked on the machine, they are the ones that move the fabric thru the machine.

make sure you're using the appropriate bernina bobbin, others can confuse the sensor. This video(by Bernina Boys) shows how to clean lint to prevent this problem which is what often causes this error. Or go into settings by pressing the diamond with right hand arrow inside of it. The eye with the speaker next to it should get you where you need to go to turn it off.
The manual on Bernina's website is here:
https://www.bernina.com/en-US/SupportData/BERNINA-Nah-und-Stickmaschinen/artista/Manuals/031508-50-04_0601_a640_EN

page 98 has the information you want.

Make sure your needle is inserted into the machine correctly
It could be the design with the density of stitches is too high.

Cheers,
Kelly
San Diego, CA
Embroidery Services

There is one video that MAY help.

https://www.google.com/search?q=Bernina+Artista+630.+It+sews+for+about+15+stitches+and+stops+and+and+error+screen+comes+up+and+says+a+thread+is+broken

,,

To wind the bobbin, select straight stitch, thread the machine up as normal making sure the presser foot is up, open the slide plate, push the little button over to raise the winder, take the thread and wind it round the presser foot screw a few times, press on the foot control slowly and the bobbin will wind, when you have enough, stop, close the slide plate to drop the winder down, pull the threads to the back and start sewing. for manuals try www.tandtrepair.com

try using a straight stitch plate, this will help resolve some of the eye lash effect. 

see your local dealer and tell them you have a bad power board. or l-print. this is a known issue and bernina is covering it under there 5 year warranty. the 5 volt output is faulty on some some models