Corner overcut

[raemin]

Hello, is there any simple way to perform corner over-cuts ?

On the other software I am using this is straightforward, but i cannot seem to fin an easy way to do it in QCADCAM ?

[andrew]

I can confirm that this is not currently supported by QCAD/CAM.

[raemin]

Just curious as how others are handling such requirement?

A "proper way" is to draw a circle and offset it using the "Manual Distance" snap but this is quite time consuming when many angles are involved.

CornerOvercutProperWay.jpg (15.63 KiB) Viewed 11175 times

The quick and dirty approach would be to drill at the angle, unfortunately I just cannot find how to automatically centre the drill tool to such angle. (The drill tool button is not available unless an element is selected.) As a last resort I could place a "dot" in the angle and use this dummy element as a reference for the drill.

As said I would be interested in your feedback on a "proper way" to handle this.

[CVH]

Just curious as how others are handling such requirement?

Hi,
cutter-path-wise:
With line segments the angle of the 'overcut' path is the opposite of the angle bisector.
The 'overcut' length is merely a relation of the cutter radius and the enclosed angle.

Somewhat harder with arc segments ...
I would set up the math and write a script ... See PM (Private Messages)

That is when you define the cutter-path yourself and mill on path ...

The easiest way in drawing an 'overcut' boundary corner is to construct a circle with cutter radius tangent to the boundary segments.
(Draw .. Circle .. 2 Tangents and Radius) (CTR)
Draw an auxiliary line between the circle center and the boundary corner.
(Draw .. Line .. Line from two points) (LI)
Move the circle with reference, choosing the intersection of the auxiliary and the circle as reference and the boundary corner as target.
(Modify .. Move/Copy) (MV)
Delete auxiliary line and trim where necessary.
This works for any enclosed angle between two line segments.

Regards,
CVH

[raemin]

Thanks for the detailed feedback.

I think one could make it do with updating the cutting path only as this is somehow easier to implement that drawing the actual contour of the object. The following would make it do : an additional path that would follow the bisector of the angle, over a length that is equal to the radius of the drill bit.

Overcut.jpg (37.95 KiB) Viewed 11089 times

I must admit however that it's nice to have a drawing with the "actual" contour of the shape.

[CVH]

The following would make it do:
an additional path that would follow the bisector of the angle, over a length that is equal to the radius of the drill bit.

Correction:
As already said, the 'overcut' length is not equal to the cutter radius ...
... Yes, default overcutting with R would work out fine for enclosed angles above 60°.

The 'overcut' length is merely a relation of the cutter radius and the enclosed angle.

Overcut = R * (1/sin(enclosed angle/2) - 1) for enclosed angles of 0-180° excluding 0°.
See dxf:

OverCuttedPath.dxf

(105.94 KiB) Downloaded 686 times

Regards,
CVH