What is the difference between double knife removal and double line removal in ArtiosCAD diemaking?
Knife to Knife layout
A layout can be created that is knife to knife meaning that edges (cut lines) of one design align directly over the edge of another design. Even though the single design has a valid edge, in the dieboard only one knife, called a common knife, is required to separate the abutting oneups. Here is a basic design laid out knife to knife. The green arrows indicate where common knives would exist.
A laser or router is used to create the dieboard slots which will contain the rule. To prevent the machine from creating a slot with two passes, thereby extending the time it takes to slot a dieboard and more importantly increasing the risk the slot width is enlarged, use the Double knife removal tool in the Dieboard toolbar so that only one pass is used.
Below, note that the edges comprising the overlapping dust flaps overlap but are not coincident. There is a bit of extension between the two flaps as pointed to by the blue arrows. The Double knife removal tool will create one new straight rule that will become the common knife as shown by the aqua line as pointed to by the red arrow. The algorithm decides which overlapping edges are removed and/or shortened/combined and a new knife is added to a special section within the .MFG file. The layout looks the same to the user, but its underlying knife or rule structure has changed.
In the context above, the overlapping cut lines for diemaking are semantically known as knives. The term double line may be used in these cases, but it isn't technically correct. It is a more generic instance of any two lines, whereas double knives refer to overlapping cut lines that become one knife in the dieboard.
A tool exists within diemaking called Designer's Fix-it that can be accessed via Manufacturing > Designer's Fix-it. It can be used to remove double lines. Any double lines.
In this case, diemaker's Fix-it finds coincdent line and/or segments, lines that exactly overlap.
From a .MFG file, these lines are not selectable and cannot be "fixed" as this tool was not designed to create common knives but only find any double lines. The pushing of these buttons takes no action because changes to the underlying die should not be made at this stage. The algorithm knows only about the coincident lines, not how to create a common knife.
Common file import
If a layout was imported as a DDES, CF2, DXF or some common file format, the Designer's Fix-it > Double line could be used to help ensure double mismapped lines were not created in the resulting die.
Useable sheet edge
Lines that overlap sheet edge will be considered selectable double lines and could result in the deletion of the portion of the sheet edge.