Loss of time

[Jibeji]

Hello,
I have defined a simple profile path of 20mm depth, 1 mm per pass, with a Z-safe set to 5 mm.
Each time the mill goes deeper, it always goes back and starts from the Z-safe height at plunge rate which is of course very slow ie:

Z-1
mill
Z5
Z-2
mill
Z5
Z-3
mill
Z5
...
Z-19
mill
Z5
Z-20 (25mm at Plunge Rate !!)

Is there a way to optimize that?

[Adrian]

Are you sure it's a profile toolpath you're doing and not a pocket one?

[Jibeji]

Adrian,
Yes I am.
Please view the attached file, and the end of the according gcode :

[...]
G0Z5.0800
G0X-26.0000
G1Z-19.0000F200.0
G1X0.0000F1200.0
G0Z5.0800
G0X-26.0000
G1Z-20.0000F200.0
G1X0.0000F1200.0
G0Z5.0800
G0Z8.0000
G0X0.0000Y0.0000
M30

[Adrian]

Which Post Processor are you using? Do you have any ramps set?

When I create a toolpath like that it goes from 1mm to 20mm without retracting until it's finished.

[Jibeji]

I am using Grbl 0.8c (mm) without any ramp set.

[Jibeji]

I have just tried with LinuxCNC post processor, same result.

[Adrian]

Could you attach the actual Cut2D file?

[Jibeji]

Hi,
You will find the file attached.
For information I am running the latest release: 8.020 built the June 18th.

[Adrian]

Sorry I completely forgot that you might be machining an open vector. For some reason when you said a profile toolpath I automatically assumed you were machining a closed vector.

That is correct behaviour for an open vector. It has to return to the start point to respect the chosen cut method (climb/conventional) and it can only do that by retracting from the material.

One way around it is to make a vector that goes back on itself so that the start and end are in the same place.

[Jibeji]

One way around it is to make a vector that goes back on itself so that the start and end are in the same place.

I ignored this.
Would you please tell me how to do that?

[Adrian]

The file I attached to my previous post has the modified lines in it.

You use the polyline tool to draw a line as normal you then move the mouse back to the start so the line is on top of itself and the start node and end node are on top of each other.

[Jibeji]

Brillant!

Thank you very much Adrian.