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Strange part offset using 3d Adaptive clearing

Message 1 of 14
564 Views, 13 Replies

Strange part offset using 3d Adaptive clearing

Hi, first time posting to the forum so go easy on me ๐Ÿ™‚ i'm really stuck on something and would appreciate some advice from fellow Fusion360 CNCers. I am milling crank cases for small model engines and thought I'd give 3d adaptive clearing a try since it seems best suited to roughing out complex shapes. Trouble is, when i go to mill the part, the part is off centre vs the model point I'm using as the origin. 


some facts:


In fusion.

- The simulation looks perfect i.e the part is centred around the origin as it should be.


On the machine (MACH4)

- All axes homed. Offset G54. Secondary DRO zero'd on the origin too.

- After the incorrect/off-centre part is made, If i do a G0 X0Y0, the machine goes back to the true zero as evidenced by the secondary (glass scale DRO). This in my mind rules out mechanical or Mach issues causing missed steps or things lie that. 

- Looking at the GCODE for a drilling operation, the coordinates are spot-on. These use the same set-up as the 3d Adaptive Clear so potentially have ruled out an issue on the way I have created my setup or selected the model point.


This is a real mystery to me and have never had any trouble like this before (and frustrating as I've wasted a lot of time and aluminium on this already). My gut feel is that there might be some issue with the mach post processor or some incompatibility with a particular 'mode' set on the machine.


Model Link:


Some pics below. 





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Labels (1)
Message 2 of 14

Can you share the Fusion file AND the posted g-code?

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 3 of 14

Oh, and you currently have to you the "post reply " small window at the bottom of this thread to attach stuff, not the "Reply" button on each response to the thread, in order to attach stuff. Forums are broken (again)

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 4 of 14

Model URL:

GCODE attached



Message 5 of 14

done thanks for the hint... i was looking for the attach button everywhere!

Message 6 of 14

You'll have to export and share your Fusion file, as Personal Users aren't able to share A360 links that can be downloaded.

That said, I'm not seeing the issue in the backplotter:




Seth Madore
Customer Advocacy Manager - Manufacturing
Message 7 of 14

Hi, apologies for delay, things have been busy at work and I've only just managed to take a look at this again.


I simplified things by creating a simple 20mm square to carve out of the top of some scrap using the same face-->3DAdaptiveClear-->2D Profile workflow and it shows the same issue (good). The file is attached,


I also created the same 20mm square using Aspire VCarve and, running the GCode created by that, the square is perfectly central to the workpiece as expected. This rules out any mechanical issues in my opinion.


My thoughts are that this might be some funky tool offset thing or other part of the MACH4 post-processor script that might be the culprit. I will try to delete and reinstall also perhaps go with the MACH3 post as this seems more widely used/supported?


The picture attached shows the results of the test. The two test pieces on the left are using Fusion, the one on the right the VCarve Gcode.







Message 8 of 14

UPDATE: I just tried deleting my local post processor and using the vanilla MACH3 post processor from the fusion library and the same issue: The square is not central to the workpiece by between 1-2mm.

Message 9 of 14

Can you share your V-Carve code so I can compare the output from both Mach3 and V-Carve?

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 10 of 14

attached below. Thanks.


PS: ready for this to be some extremely embarrassing user error!  ๐Ÿ™‚

Message 11 of 14

I understand that the control is a Mach3, but what is the actual machine, it's spindle limitations (torque and rpm) and overall machine strength?

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 12 of 14

Hi Seth, sorry i missed the reply notification. The machine is a Sieg SX3 1000W and 146KG weight. So at the sturdier end of the hobby range but still very flimsy by industrial machine standards. I've been adjusting feeds and speeds so i feel we're at the limit but these are still very light cuts required. 


I tried the program I sent you again today after a more extensive strip-down and examination/retightening of all the ball screws/bearings etc. The result was less backlash and therefore a more accurate 20x20 square but still not in the centre of the stock.


Tearing my hair out!






Screenshot 2021-09-26 at 14.15.46.png



Message 13 of 14

Hi, The only other info I thought it was worth sharing was my Mach4 motion settings. The crazy think is that this has been working fine for years.  The only thing which I'm not too sure about here is the incremental vs exact stop and the arc centre. 




Message 14 of 14

Hi Guys, in the end I deleted my Mach4 installation and the SmootStepper plugin and started from a clean install. This seemed to cure the issue. 


Please accept my apologies for wasting people's time on here and thanks for the replied in the thread. 


Lesson learned about DIY CNC: You do spend as much time getting/keeping it working correctly than actually making parts. When I grow up i might need to treat myself to a dedicated CNC machine. 




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