Drag Knife Tool

We are manufacturers of numerical controls and used to propose and support our customers with SheetCAM in almost all plasma applications.
At this stage we are trying to run some tangential cutting applications with the DragKnife plugin but I am finding difficulties.

The cutters we are required to adopt have the following configuration:

As can be seen in the picture, the rotation fulcrum of the cutter, equivalent to the Tool Center Point (TCP) is off-center from the actual cutting point because the blade has a negative offset in X (variable according to blade type) and in the drawing shown as TCP.X = TCP.X - 3.52 mm.

By changing the blade size this offset increases or decreases.

Perhaps mistakenly, I thought Offset in DragKnife meant exactly that offset between TCP and cut tip:
Creating the path in NC code, I realized that it is not what I expected.

I have used other CAMs in the past, but they are incredibly expensive to make the machining of a simple cutter where there was this kind of “compensation.”:
I await clarification if DragKnife plugin can support this type of tool or what is designed into the plugin as a tool.
Best Regards,
RosettaCNC Support Team

As you thought, the offset is the distance from the TCP to the cut tip. What issues are you having with the tool path? It looks like you are using a Donek knife. This plugin was originally written for Donek.
You can specify an offset in the cut operation. This offsets the tool paths inwards or outwards and should not be confused with the tip offset. This offset is useful for instance if you are cutting inlays. It allows you to adjust the dimensions for a perfect fit.

Well I fixed a few things that I had misrepresented.
It seems to be working fine except for the extra rotational movements with the blade in the up position that are to be understood.

It’s all still a bit of a work in progress but I attach a video of what it does.

When the knife does it’s relignment move it lifts to the swivel depth before plunging back down to cut depth. You have the cut depth set to 10mm, which seems very deep for a knife. You have the swivel depth set to 0.1mm.

Ok I will check the tools parameters.
I’ve entered randomly because I was not able to find a manual about the plugin and tool description.

PS my knife tool is motorized in rotation so don’t need of to be dragged to be in right angle. It lift up, a little, rotate, then lift down and can start to cut.

I thought this was a drag knife. If your have a motorised C axis, why do you have an offset between the TCP and cut point? Thst’s only normally done for darg knife.

I have to provide, both in the numerical control firmware and in the post-processor that the cutter is perfectly in axis with the vertical rotary axis and that there is an offset, as present in a typical DragKnife. In fact, in our case, the applications will always have a rotary motor, typically a small stepper motor, and the axis is constantly interpolated with the other motion axes.
The fact that Sheetcam handles the offset is very valuable.
In that case I need it to continue to work as it does now but when it gets up to start a new cut it just has to: get up a little bit, rotate the C-axis in the desired direction, go down and cut. Then during cutting the C-axis is constantly kept in line with the path.

That’s an unusual setup. Try the ‘Mach3 tangential’ post processor. It is set up for tangential knife.