Hi

I am new to CNC work, but am a design engineer and have designed and coded loads of industrial machines over the years.

So, I have designed and built a small CNC mill that I have used a couple of times and it ran fine (cutting pockets). It uses a Pi 3 with bCNC linking to an arduino. Cad and CAM is done in Fusion 360.

However, now that I am trying to make more advanced operations I have an issue I dont understand.

Essentially, I have a piece that is machined from a 190 by 62 by 6mm blank and I created 2 30 x 30mm pocket operations at either end, followed by 8 holes using the 'bore' operation in Fusion (the first time I have used this function

I zero by selecting the left front corner of the 190 by 62mm blank and the setting X, Y, and Z to zero. Start the code and it works fine as It cuts both pockets. But when it then moves tot he holes, the Z axis zero seems to be offset to 5mm above the material so the hole boring spirals down until it finally removes 1mm of material at the bottom of it cut (the display reads -6 for Z at this point) .

If I then stop the machining and tell it to return to home, it is now great in X and Y, but 5mm above the top surface in Z

The simulation in Fusion does not how this and neither does the NC code when simulated using an online simulator


Any ideas?

any thanks