Heat transfer vinyl is cut mirrored, and ordinary vinyl is not
Cut HTV the right way round and you press a backwards logo onto a shirt. Cut ordinary vinyl mirrored and you weed the wrong side. Only the operator knows which is on the roll.
Why the two are opposite
Ordinary adhesive vinyl is cut face up, weeded face up and applied face up. What you see on the cutter is what ends up on the sign.
Heat transfer vinyl is cut on its carrier, weeded, then turned over and pressed face down onto the garment. The carrier stays on top and peels away. Because it is flipped once between cutting and pressing, it has to be cut mirrored to come out the right way round.
Overcut, and why the corner looks rounded
A drag knife is not driven around corners. It trails behind the carriage on a swivel and rotates into line as the carriage moves. At the start of a shape it is pointing wherever it finished the last one, so the first millimetre or two of the cut is not fully through.
The fix is to run past the start point by a small amount, usually 0.25mm to 1mm, so the blade covers that stretch properly once it has swung into line. Too little and the piece will not weed cleanly. Too much and you cut into the shape next to it.
A weeding border saves more time than it costs
A rectangle cut around the whole design gives you something to lift. Without one you are picking at the edge of the sheet with a hook. With one you peel the surround off in a single piece. It costs a few seconds of cutting.
Blade depth and force, before you blame the file
A cut that will not weed is usually not a file problem. The blade should protrude about the thickness of the material plus a hair - for 60 micron vinyl that is barely more than the bevel showing. Too deep and you cut the backing and the whole thing tears when you weed.
Force follows from that. Standard vinyl is typically 60 to 80 grams, HTV a little more because the carrier is stiffer, glitter HTV more again. Run a test cut of a small square inside a larger one and weed it before committing a sheet.
Small text is where jobs fail
Below roughly 6mm cap height, letters with counters - a, e, o, R - stop weeding reliably because the middles come away with the surround. Thin serifs go first. If the design needs to be that small, use a font with thicker strokes rather than scaling a thin one down, and expect to pick out counters by hand.
A checklist before you send the job
- Is this HTV? Then mirror. Is it adhesive vinyl? Then do not.
- Overcut set, usually 0.25mm to 1mm for a drag knife.
- Weeding border on, unless the sheet is going straight into a roll feed.
- Paths closed. An open path on a cutter leaves the piece attached.
- Test cut done, at the material and blade you are actually about to use.