Causes:

Improper Thread
Try re-threading the machine; make sure the thread goes through all guides.

Burrs
There may be burrs in the needle's eye, on the thread guides, needle plate or the hook. Replace the needle and try buffing the thread guides and needle plate. Buffing may alter the timing, so it's a good idea to replace a damaged hook.

Dry Hook
Because it dries out faster, the hook needs frequent lubrication. The hook assembly should be lubricated every 4-8 hours of machine running time.

Needle to small
You may have to change to a larger needle

Too much Adhesive spray
You should be using only Embroidery designed adhesive sprays, never over use them. Too much adhesive build up on the needle can cause them to drag and break threads. If this is happening you should examine the way you use your adhesive spray

Improper timing
If your machine isn't timed properly, it can cause many probems in addition to thread breaks. Such as broken needles, poor stitching or sometimes no stitching.

Old Thread
Thread can become brittle with age and long exposure to light, air and heat. You should store your thread in a cool, dark place to lengthen shelf life.

Bruised cone
A bruised cone of thread can occur if the thread falls on the floor, causing the lower winding of thread to loosen and catch as the thread spools off. You can take off the affected part of the thread or replace the cone.

Machine speed
Some of the designs increase the stress on thread. You should lower the machine speed as needed

Lint build up
A lint build up on the tension discs, needle plate or bobbin cases can cause breakage. These areas should be cleaned frequently with air or a brush.

Bent needle
This can happen after the needle hits a very hard object such as a Hoop, needle plate or the hook. If this happens you have to replace the needle and check for burrs and the timing.

Improper tensions
If the tension is too tight, it can cause pulling, puckering and thread stress. If the thread is too loose it can cause the thread to pile up and loop. You have to adjust the tensions to achieve a flat smooth look.

Using Tape for loose ends
Using tape can leave a residue and this can cause friction and thread breakage.

Holding the thread
If you hold the loose end of the thread when you start up the machine and you are pulling the thread too tight, it can cause the needle to bend or break and can also cause the thread to break.

Stitches form wrong or not at all

Causes:

Empty Bobbin
replace

Retaining finger in wrong position
loop can not form

Improper Timing
the bobbin hook won't catch the loop

Needle position is incorrect
can cause the timing to be off

Damaged hook
replace

Missed stitches

Causes:

Wrong Needle Size
in relation to the thread and this can make it difficult for loops to form

Thread is to tight or to loose
causes irregular loops to form

Timing is incorrect
can cause the bobbin hook to not catch the loop

Needle breaks

Causes:

Bent needle
replace

Dull needle
will bend and eventually break, replace

Timing wrong
damage to needle and hook and poor stitch quality

Holding thread during startup
can bend the needle and break the thread

Needle is inserted wrong
insert all the way up the needle bar shaft and needle screw is tight

Needle cuts holes in garment

Causes:

Dull needle
difficult to pierce garment causing tearing

Needle point is wrong type
wrong point can damage some fabrics, try a ballpoint

Needle to large
can stretch fabrics

Fabrics are to delicate
may have to use a topping

The design is out of register

Causes:

Garment is hooped to loosley
re-hoop but do not stretch fabric

The fabric is unstable
you may have to use a heavier backing

Garment is puckering

Causes:

Tensions to tight for a particular thread or garment

Improper hooping

Unstable fabric

Dull needles

Too many stitches in an area

These are some of the normal problems you may experience during the Embroidery Process.