NEED HELP - bcnc and fusion 360

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

Can you post your file here? File, Export to your computer, then upload it here (you may have to zip it first, don't recall).

David

You are losing steps on Z axis! Check the pockets are correct depth.

Quote:

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Originally Posted by imola_s3

Hi

I zero by selecting the left front corner of the 190 by 62mm blank and the setting X, Y, and Z to zero.

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How are you setting zero in Z? Do you have a probe? Did you touch a tool? Are you using one tool to do both operations?

If you share your .f3d file with us, I'm sure it won't be a problem to resolve.

PM

It appears to me you either loosing steps in Z axis as pointed out by Breezy1849, or your End mill is not clamped correctly and creeping out or your motor is moving.

Are you using screws or belt for your Z Axis? Many small home built machine as a bit flimsy, and losing steps due to lack of rigidity.

GST

Unless you upload your file it is literally pure guesswork from everyone, I suspect it will be somewhere in a possible combinations of Height Tab settings/Linking settings/Safe Z settings, they are all possible areas to look at.

In Fusion go to File > Export > Select f3d format to save out as to a location on your PC and then put it in a Zip file and use the "Go Advanced" option and then you will be able to attach the Zip file :D

Stay Safe!!
Regards
Rob