Some embroidery machines have an automatic thread cutter (at the end of each color, but also within the same color when necessary). However, this option is not always suitable.

When is automatic thread cutting not suitable?
When the design contains very narrow and repeated satin embroidered parts
The rule: Each time the machine begins a new part of the pattern, it begins this embroidery with a few stitches and ends with a knot before cutting the threads.

Problems encountered :

The priming of these small parts does not work well and small loops of thread can form, thus causing excess thickness on the back.
The beginning fails and the pattern only begins after a few stitches. Not cutting the thread therefore allows for cleaner and better embroidery. Finally, a reduced embroidery speed is the guarantee of a better result.
Not cutting the threads can therefore be a good option when sewing fine text as well as fine satin stitching repeated on a design. This allows these parts to hold together better and thus have a nicer look.

When the pattern is visible on the back:
Indeed, when there are a lot of thread cuts in a pattern, you will find as many small knots on the back which is not always very pretty. (ex: tea towels, towels, scarves…)

By removing the automatic thread trimming, you will also remove the knots on the back of your embroidery, and instead get the bobbin thread taut between each part of the design. So fewer knots, so a flatter and cleaner result.

Cut all these little threads by hand, the result will be even prettier!