CNC question: travel speed and height of Z axis to first cut,,,

[jamesbeckett73]

Good day, perhaps someone can be of help?

I am CNC-ing material which is at the limits of the height of my machine. This means I need to set my zero postion quite high (Z axis). When making my first cut, the bit immediately drops below the zero postion, and moves at high speed through the stock, to arrive at its first actual cut postion. When returning to home position, it is also dropping below the set zero position. You can imagine the mess made!?

I have altered clearance and retract heights to no avail,

I would like to effect initial speed of machine, when moving to first cut postion (this alone would be a solution) and the height of Z axis, during this initial motion.

I do not see the possibility to effect these parameters in the GRBL settings of the machine itself.

Thanks in advance for any clues!!

(apologies for luddite terminology)

Greetings,,,

Workbee CNC, MacOS Mojave 10.14.3

[seth.madore]

What post processor are you using, and can you share your Fusion file?

File > Export > Save to local folder. Return to thread and attach the .f3d file.

Where is your WCS zero set from, and how do you establish your tool offsets?

[jamesbeckett73]

Thanks for asking Seth,

File is too large for allowed attachment (photogrammetry model), so I made a download link if you have the patience:

https://wetransfer.com/downloads/3e0a841c0a56c8947b2f65d292b3504220190826114600/82aa90e99950cc9e1507... 

You will notice only one path is calculated, and is floating above model geometry. This is the current file I am using. It is a fix, as stock is warped (wood), so I am basically using the path to level the stock first.

Post processor is "Open Hardware Desktop CNC Router" which is a variation on the AD 360 pp, which basically only takes out tool changes (if i recall a command M6 or TM, something like that)

The WCS is set by manually jogging the bit to position.

I establish offset in the geometry tab of a parallel pass, but this is at "0"

much appreciated in advance (apologies for lack of proper vocabulary)

[jamesbeckett73]

Found a work around, 

in the gcode, there is a command at the beginning of the job "Z-10"

I delete this and the problem is solved, no odd plunge.

Not the most elegant way, but it works