A roll has a fixed width and an open length, so the goal on a roll is the shortest length. Estimates always nest on rolls, imposition jobs can use Roll media, and the nesting API accepts a roll container.
The parts of a roll#
- Width and side margins: pieces stay inside the printable width, the roll width minus a margin on each side.
- Lead-in: roll used before the first piece.
- Lead-out: roll used after the last piece.
The length used runs from the start of the roll through the lead-in, the pieces and the lead-out. The material used is the roll width times that length, which is what a nested estimate is priced on. The yield is the parts' area divided by it.
A part wider than the printable width in every allowed rotation doesn't fit. Estimates (and API requests that ask for panelling) split it into overlapping panels that run down the roll; see Nesting and yield. Imposition jobs report it as a part that doesn't fit.
Beds#
A flatbed cutter with a conveyor cuts a long roll one bed at a time: it cuts what lies on the bed, advances the material by one bed length, reads the registration marks and carries on. The bed length is the cutter's Working length. Roll cutters, and flatbeds without a working length, feed continuously and have no beds.
What happens at the seam between two beds is the Bed boundaries choice:
| Choice | What the nest does |
|---|---|
| Keep parts within one bed | Every piece lies wholly on one bed. An empty band one spacing wide runs across the roll at each boundary, and each bed is nested on its own. |
| Parts may span bed boundaries | Pieces are placed anywhere. The cutter splits contours that cross a boundary across the feed. |
| Automatic (the cutter's default) | Keep within beds on a flatbed with a conveyor and a working length; let parts span otherwise. |
Keeping parts within beds costs some roll length, the empty bands, but no piece is cut in two passes, and the cut file can be split into one page per bed for software that feeds page by page. Letting parts span gives the shortest roll. A part longer than one bed can only be nested with parts allowed to span.
Set the default on the cutter (see Cutting machines). An estimate's material group or an imposition job can override it with Bed boundaries: Cutter's setting, Keep parts within one bed or Parts may span beds. In estimates the choice is only shown when the group's cutter works in beds.
The nest view draws each Bed boundary and, when parts stay within beds, the Bed keep-out bands. The cut time counts the beds: registration marks on every bed and a conveyor advance for every bed after the first.
Space for marks#
Marks that must never depend on luck, such as registration marks and cutter codes, reserve their space before the nest runs:
- Marks along a whole side of the roll widen its side margins.
- Marks at the start of the roll keep that area of the first bed clear, and marks at the end of the roll lengthen the lead-out, so they sit just past the last piece.
- Marks drawn on every bed, such as a bed's corner marks, keep the same areas clear on every bed. With parts allowed to span beds, marks drawn per feed keep the same areas clear in every feed length along the roll.
- Labels attached to each copy make each piece's footprint larger, so neighbouring pieces keep clear of them. The cut line doesn't change.
Every nest is checked against these areas before it is kept: a layout with a piece in a reserved area is never shown.
Strips on a roll: lanes and bands#
The Strips method of imposition keeps items in straight strips between slit lines. On a roll the strips run one of two ways:
- Lanes run down the roll, side by side across its width, so the roll can be slit into narrower rolls.
- Bands run across the roll, one after another along its length, so the roll can be cut into lengths.
Auto picks the better of the two. A roll strip layout can't keep pieces within cutter beds yet: use True shape, or let pieces span beds. Mixed strips, which put different items in one strip, need sheets.
What rolls don't support#
- N-up (guillotine) and offset runs need sheets.
- A maximum roll length isn't supported yet: the length is open.