Collisions with Stock on Deep Carvings

I have an MPCNC Primo, DW611 and am using a 1/8" ball nose bit from V1 for this. I’m trying to carve the spoon you see in the attached photos (grabbed the model from a kind soul on Reddit).

The issue I’m experiencing is collisions between my holder/shaft and the stock during simulation. My stock is somewhat deep and my bit is not but I think it should be able to theoretically carve itself down to where I want it to go. How does Fusion’s CAM allow for the presence of the shaft/holder as it carves items into deeper stocks? I thought that is what the Shaft & Holder mode is under the tool tab but I’m not sure what I’ve done wrong.

I’ve attached photos of the model, an example of the collision location and what my parallel toolpath tabs currently show. The six holes you see on the sides are used with dowels to flip the stock over and continue on the backside as a two-sided carve.

If you see anything I’m doing wrong, please let me know. Thank you!

If your bit is longer than simulated, the make it longer in the tool library. It does look like the collet might crash cutting that part shown in the pic; it is against the stock wall and fairly deep. Ultimately if you are sure it will clear then just cut it, otherwise longer bits may help.

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I use Fusion 360 for my CNC work, but the CAM side of things is so complicated that typically I just thrash round until I get what I want. If you save your fusion 360 file to your local drive, put in in a ZIP file, and attach it to a post, I’ll work with it to see if I can figure out how to address your issues. BTW: I really appreaciatge all the work you went to in posting your question.

Here are a few things you may or may not know.

  • In simulation mode, if you look at the bottom of the screen, there is a bar with a base color of green. The red bars are collisions. You have a lot of them. You can click on any of the red bars to move your simulation to that point.
  • When simulating, if you turn off the Models before starting the Simulation Mode, turn off the Toolpaths, and turn on Stock, you can watch the bit carve your stock. It is much easier to see a collision problem this way.
  • Under the stock tab, there is a “Stop on collision” checkbox allows you to find collisions.
  • If you are at a collision point in a simulation, select the Info tab at the top of the simulation dialog. In this mode, you can click your mouse down and move left/right/up/down. These mouse movements (while the left mouse button is held down) scrubs back and forth in the simulation makiing it much easier to see what is going on during the collision.
  • I’ve not use the Shaft & Holder settings, but accoring to my intrepertation of the text on the help screen, your 10mm Holder Clearance effectively shortens your usable bit by 10mm, which is typically a lot with using a 1/8mm bit, and which may account for collisions where visually there are none.
  • If this first toolpath you will be running, then Rest Machining can be unchecked. If this is a later toolpath, then I would “Use as Computed” as the Adjustment in the Rest Machining settings.
  • In the few instances that I’ve done this kind of double-sided milling, I’ve started with an Adaptive Clearing toolpath and then use a Parallel toolpath for as a finishing pass.

Thanks a lot. Let me work through your feedback.

Question: I found the DW 660 model that you posted a few months back. Have you implemented that as your holder model in your Fusion 360? Where is the option to do that? I found a menu that lets me create a geometry but not actually import an STL or the STEP that you uploaded. Does that also perform collision avoidance for you?

No, I’ve not implemented the DW660 model as a holder model. It is not something I’ve explored.

Robert’s post is on the money. I was short on time to post earlier, so never mentioned details of f360 simulation. I also don’t use the holder setting under tools, but f360 is correctly simulating with the holder I have configured in my tool settings. I did not make a precise stl for my Bosch collet, but there was a default holder that was similar in size so I just use that. I never cut things too close with respect to holder clearance anyways. So the model I am using is slightly larger than my Bosch collet, which means the simulation will show red if the collet gets too close (but not actually touching).

I also always check the simulation using stock, which also helps to visually catch errors in gcode besides just collet crashes. Like if I have something configured wrong and travel slices deep, the stock simulation will show that deep cut.