What is the difference between a stop and a colour change?

On the machine, nothing: both halt for the operator. In the file, a colour change advances to the next thread in the list and a stop keeps the same thread, which is how applique placement stops and mid-design pauses are written. DST has only one code for both.

Why does my design have jumps everywhere in the viewer?

Every move between two separate parts of the same colour is a jump. Turn on show jumps to see them; the ones that matter are longer than 12 mm without a trim before them, because those leave a thread on the surface.

Does the machine trim automatically?

Machines with a trimmer cut at every trim command. Some also trim automatically after a jump longer than a setting on the machine, typically 3 to 12 mm; DST relies on that behaviour by writing three jumps where it wants a trim.

How many colour changes is too many?

On a single-needle machine every change is 30 seconds of operator time, so a 5,000-stitch design with 12 changes spends as long changing as stitching. Merging same-colour blocks that follow each other removes the pointless ones.

Jumps, trims and colour changes: what the commands in an embroidery file do on the machine

Between the stitches, an embroidery file carries commands, and the commands are what make the machine stop, cut, or carry thread across the fabric. Most problems that are "in the file" but are not density are here: a loose thread across a gap, a machine that halts for nothing, a run that takes twice as long as the stitch count says.

The four commands

Stitch. Move the frame and put the needle down. The only command that sews.

Jump. Move the frame without stitching. The needle stays up; the thread goes with it, lying loose across the fabric. Jumps connect separate parts of a design in the same colour, get the frame from a colour change to the next block's start, and in some formats split stitches that are too long to encode in one record.

Trim. Cut the thread. On machines with a trimmer, an explicit command; on older machines, a stop for the operator to cut. After a trim the thread is free, so the next stitch starts with a tie-in.

Stop / colour change. Halt the machine. A colour change halts and advances to the next thread in the file's list. A stop halts and stays on the same thread, which is what a design uses for "place the fabric now" or "pause here". Multi-needle machines turn colour changes into needle switches automatically and only halt for stops.

How formats write them

Formats agree on stitches and differ on the rest:

| Format | Jump | Trim | Colour change | Stop | |---|---|---|---|---| | DST | jump record | three jumps in a row | stop code | same code as colour change | | PES / PEC | flagged move | flagged move | colour change record | duplicate colour = stop | | JEF | jump record | jump of zero length | colour record | colour record with a 0 palette entry | | EXP | 0x80 0x04 | 0x80 0x80 | 0x80 0x01 | same as colour change | | VP3 | no jump; long move | explicit | block boundary | none | | XXX | 0x7F 0x01 | 0x7F 0x03 | 0x7F 0x08 | same as colour change | | U01 | jump | explicit | needle change | explicit | | TBF | 0x90 record | 0x86 | needle change | 0x40 |

Converting translates between them. DST's three-jump trim becomes an explicit trim in EXP; a VP3's long move becomes a jump in PES. The stitches around them do not move. Formats explained has the full picture.

Jumps that leave thread

A jump carries the thread across the fabric on top. Short jumps, under about 3 mm, are hidden under the next stitches or are shorter than a trim would be. Long jumps leave a float that has to be cut by hand after the run, one per jump per piece.

The pre-flight check lists jumps over 12 mm that have no trim before them. For a design meant to be sewn on a machine with a trimmer, those are the ones to fix: cleanup inserts a trim before each. For a home machine without a trimmer, they become manual cuts either way, and the count tells you how many.

Many machines can be set to trim automatically after a jump longer than a threshold. That is also how DST-only machines handle trims at all: three consecutive jumps trigger the trimmer.

Colour changes that cost time

A single-needle machine stops at every colour change for the operator to change thread: about 30 seconds each, plus a trim and a restart. Twelve changes on a 5,000-stitch design is six minutes of changes on eight minutes of stitching. Run time works through the arithmetic.

Two kinds are removable in the stitch file:

Same colour twice in a row. Object-based software exports every object as its own block, so two adjacent objects in the same thread produce a change between them that changes nothing. Cleanup merges those into one block and replaces the change with a trim.
A change with nothing after it, or before anything is sewn. Readers drop those on load.

The rest are design decisions. Reordering colours to reduce changes is possible in editing software, with care: the order decides what sews on top of what.

Stops and multi-needle machines

A multi-needle machine handles colour changes on its own, so a design that halts on a Brother PR or a Tajima is halting on a stop, not a change. Files converted from PES sometimes carry stops that were pauses for a single-needle operator (to place an applique, to fold a hood out of the way); on a multi-needle machine those still halt. The viewer's colour block list shows stops as blocks with the same colour repeated, which is the cue to remove them if they are not wanted.

Trims per thousand

A trim is a few seconds on an automatic trimmer and a chance for the thread to pull out of the needle on restart. Designs with a trim every hundred stitches are usually auto-digitised from images, and the count is a warning sign about the rest of the file. The pre-flight check flags more than one trim per 150 stitches. Cleanup cannot remove trims that separate real objects, but it does remove the trims and jumps that merging same-colour blocks makes redundant.