Crops: Edge Start and Edge Stop
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Cutting Tool Settings
Crop and skeleton crop cuts can be controlled to deal with how they cross plate edges, and how the interact with part cuts. Each cutting tool has the following settings in the Crops: Edge Start and Edge Stop group:
This causes crop cuts to not pierce on the edge of the plate, but instead to pierce in the "meat" of the plate and cut towards the plate edges.
Some crops obviously extend edge to edge, and these are automatically split into two cuts, both piercing in the middle and cutting towards the edges.
Known Edge Overshoot, Unknown Edge Overshoot
Plates normally have a nominal size which is not exact. For example a nominally 2400mm wide plate may be measured to be 2422mm wide in actuality, while another may be 2415mm wide. In fact the width can vary along the length of a single plate, and plates can be slightly cambered, all depending on the quality of the milling. As a result when we cut these plates, we may not know exactly where the edges of the plate are.
When the plate is positioned on the machine the location of the plate origin typically defines two "known" (or datum) edges, whether these are pushed against stops, or whether some kind of alignment procedure is performed. Primecut allows you to specify a smaller overshoot value for these datum edges versus a larger overshoot the unknown edges.
This is similar to the Edge Overshoot above, but explicitly specifies the leadin length to be applied. There is no distinction between known and unknown edges at this time.
Edge Start Shrink By, Edge Stop Shrink By
As described above plate edges are often not exactly known. Usually they are further out than we expect, but sometimes due to plate alignment inaccuracies, or plate edge camber, the plate edge may be closer in. This setting allows any special commands (for example disable height control, or disable loss-of-arc detection) to be issued a small distance inside the expected edge of the plate. Edge Start Shrink By also enables piercing to be moved onto the plate away from the edge if desired, for more reliable starting..
NOTE If you are wanting to stop the cut short of the edge, you must set the xxx Edge Overshoot to a negative value, as well as the Edge Stop Shrink By to a positive value! Otherwise if xxx Edge Overshoot is 0 and Edge Stop Shrink By is set to a finite positive value, a leadout will be added extending the cut back to the nominal edge.
Example 1: We want the cut to finish 1/4" from the edge of the plate: set Edge Stop Shrink By to 1/4", set xxxEdgeOvershoot to -1/4".
Example 2: We want the cut to to insert a M61 code 1/4" from the edge of the plate, but cut to the edge: set Edge Stop Shrink By to 1/4", set xxx Edge Overshoot to 0", set Edge Start Pre-Leadout to M61.
Edge Start Pre-Leadin, Edge Start Post-Leadin
Allows special commands to be added to the program before an edge start leadin.
Edge Start Pre-Leadout, Edge Start Post-Leadout
Allows special commands to be added to the program before an edge start leadin. Edge Start Pre-Leadout is particularly useful as the place to insert codes to disable height control, or disable loss-of-arc detection
Allows for adjustment of the minimum distance between the crop and the part, in addition to the kerf of the part and default cropping tool. Defaults to 1mm, adjust to suit.
Cutting Process Settings
On cutting processes we have Edge Start and Edge Stop settings.
When Edge Start is in effect, the Shrink Start By setting is not adjustable, it is fixed to the Edge Start Shrink By tool setting above. Primecut will automatically set a straight leadin of length Edge Start Leadin Length (above).
Similarly, When Edge Finish is in effect, the Shrink End By setting is not adjustable, it is fixed to the Edge Stop Shrink By tool setting above. Primecut will automatically set a straight leadout of length (xxxEdgeOvershoot + Edge Stop Shrink By) (above).