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How it digitizes

This page explains what the engine does with a shape, in the order it does it. The numbers are the defaults, tuned against professionally digitized files, and are adjusted by the fabric. Published practice from Wilcom, Embrilliance and Ink/Stitch was followed.

#The pipeline

artwork / picture / typed text
   -> shapes (fill rule applied, clips applied, millimetres)
   -> layering: merge near-identical colours, scale, centre
   -> each shape: satin columns, fill, or run
   -> sewing order: shapes, strokes, travel, trims, ties
   -> pieces joined into one design (layout), hoop check
   -> DST written -> read back from disk -> safety check
   -> preview + report + worksheet (+ design file, other formats)

#Choosing the stitch

Every satin shape is checked before it is used: its stitches must stay inside the shape and cover at least 85% of it, or leave only small pieces (a serif, the stub where strokes meet) that are sewn as patches. If not, the engine tries one unsplit column, then a single straight satin for a dot, then falls back to fill.

Distressed or grunge lettering (specks, chipped edges) is first traced as the clean letter.

#Satin columns

• Splitting: a shape is split into strokes at forks and sharp corners. Branches tuck about 0.8 mm under the stroke they join. Rounded turns stay one turning column.
• Mitres: at a corner each column's stitches stay square and get shorter against the mitre line, as a hand digitizer mitres (no fan round the inside corner). Ends cut more than 25° off square are sewn the same way.
• Very sharp junctions (top of an M, point of a V) run the longer stroke through to the outline and tuck the other under it.
• Crossings (X, K): one stroke runs straight through; the other's halves tuck under.
• Stitch placement: evenly along both edges; each column's ends set its direction; short stitches on inside curves.
• Spacing by width: 0.46 mm (narrow) to 0.39 mm (wide); 0.45 mm or more for small text.
• Pull compensation: 0.15 mm (2 mm wide) to 0.25 mm (6 mm and wider), times the fabric's pull factor, plus push compensation at the ends.

#Underlay by width

Fabrics other than twill add more (see Fabrics).

#Tatami fill

• Rows 0.2 mm apart, 4 mm stitches.
• Needle holes shifted about a third of a stitch per row, drifting so they never line up into stripes.
• One edge hole per row turn.
• Angle: each fill shape gets the angle with the fewest row breaks (fill_angle_auto). Setting an angle in the app or with --angle turns this off.
• Sewn as one continuous path: travel runs under rows not yet sewn, or under shapes sewn later.
• Enclosed pieces (letter counters, slivers inside a star) are sewn on the way past while the route is still hidden.
• Holes narrower than 0.8 mm are filled over; they would close up.
• Underlay: edge run and cross-hatch.

#Layering

• Fills first, satin on top.
• Fill is cut out under lettering over 6 mm, running 0.4 mm under its edges; it is kept under smaller lettering.

#Sewing order

• Next shape: the nearest. On caps: bottom row first, each row from the centre out.
• Letters that touch (under 0.8 mm apart; they touch once sewn) sew one after another, each finishing near the next.
• The dots and accents of a word sew with it.
• Inside a shape: a search over stroke order, start end and direction, tried from each free end, against an auto-route plan (one main path end to end, every side branch out and back: travel out hidden under it, satin on the way back).
• Tucked strokes go before the stroke covering them where that costs nothing.
• Each satin finishes on the edge nearer the next stroke.

#Travel, trims and ties

• A move follows the planned path when it is hidden; otherwise it travels under stitching still to come (at most 1 mm over bare fabric or on top of finished stitching, 0.7 mm grace where it leaves or lands). Ground that a later shape covers counts as hidden.
• If it can't hide, the machine trims. There are no untrimmed jumps.
• Tie-off: 4 stitches of 0.9 mm before each trim only (the pro files have essentially no tie-in after).
• Between pieces of a design: always a tie-off, trim and jump.

#Tiny typed text (run)

The medial axis of a 20 mm copy of each letter, keeping each branch that sticks out past the strokes it joins (a t's crossbar, a 4's foot, a V's point). Walked out and back from the leftmost tip: bean out, single run back in the same holes, needle points at every tip, join and sharp corner. Trims between letters, ties 0.4 mm.

#Only what changed is sewn again

Each colour pass's stitches are kept. A change to one colour's angle or spacing redoes just that pass (Five Star's red fill: 1.6 s instead of 7.5 s), and switching a colour back on is instant. Switching a colour off redoes the colours under it, since they now fill the space it covered.