Z-axis raising to router screw extents when ran

Hi All!
1/4" carbide
Ridgid Router R22002 with z-axis pitch measured at 3.17mm (0.125")
HSM for Inventor CAM
Test file attached.10500.nc (42.9 KB)

In GC, I am setting my carbide just above the wood and defining z-axis zero position. In the CAM setup, I have 0.2" raise for traverse/clearance. When I hit play, the z-axis motor is raising the top of the router height lock adjustment (the thing that connects the raise/lower screw to the router body) to the point where it appears that it will top out and bind. I have stopped it before it gets to the end so it does not break anything. From just touching the wood to full raise of the router screw, I should have slightly over 1/2".


  1. Does “Define Home” in GC only define XY location?

  2. In z-axis settings in GC, what values will “Save and Traverse” set? After selecting this option, the carbide moved away from the wood between 1/4" to 3/8", as an observation. I pushed play again and the z-axis appeared to try and top out again so I stopped it before it did.

  3. Any ideas why the z-axis travel appears to want to top out when I hit play while “zero” and “save and traverse” seem correct?



Seems like a post processor thing to me. I could not find -Z in the code. All Z are 0 or above.
Camotics shows all cuts above the material. :thinking:

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Do you think it is the way HSM handles Grbl post?

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No idea. Do you have a chance to set Z 0 at the top of the material and the ‘final depth’ to Z -18mm?

Edit: I had to look up HSM, BTW. I first thought of an orchestra with 100 singing Maslows.


AH! I think you clued me into the issue. I just checked in Inventor and bottom was set to stock top for all operations. DOH!!! :slight_smile:

I will fix this and update.


Correction - it was set to contour bottom which I assumed meant the selection on the model. I thought this should use the geometry and not worry about stock bottom. Anyway, I made the changes to all point to stock bottom and will check it out.


Corrected file. 10500-1.nc (43.0 KB)

@Gero - Does this show correct for you now in your viewer?

Sorry no and if you look at the g-code all Z is above 0.

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I’m not sure I should mention this, but here I am. If you put a ‘minus’ in the settings in GC infront of the z-pitch and reverse the z-direction, would this temporary work?

Edit: I souldn’t have posted it. :see_no_evil:
With untested g-code the results can be dangerous.
Do not try this on your Maslow, find your closest neighbour :sunglasses:

Edit2: A fearless chipmonk has actually tried it and it was a bad idea! Do not do it!

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It worked, sort-of. Changing the value to negative plunged the carbide all the way to the bottom of the material, which is not what I intended. I set this up to take multiple steps on plunge. I intended it to take 0.2" plunge steps. I will change it back to a positive value and go from there.

I see in your screenshot, far above, that the incremental plunge depth is shown though.

For what it is worth, the cut is very smooth but it was squawking really loud and started jumping, which supports my need to plunge in stages. :slight_smile:

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Sorry for that. It tried to reach safety hight down there I guess. I ow you a ply sheet.

BTW bCNC also shows all moves above surface

There are online tools to check g-code but I don’t have links nor time to search.
The friends here will jump in for that.

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HA! I wonder if my setup is the issue. In HSM I had the work coordinate system set to the bottom of the part. In this image below, I moved it to the top. This would support why you show the material above the plane in bCNC.

I will give this a go and see what it does.


That is going to make a difference :crossed_fingers:

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No luck. Changing this origin to the top only made the external contours visible. I also noticed I am out of date on firmware so going to update all of this and try the steps again.

Really appreciate the help so far!


I’m far over bedtime and will opt out for today. Sure the Fusion360 Maslowians will bring you faster forward then I could.
Wish you all the best! (waiting for pictures of projects :slight_smile: )

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A quick and easy way to check each file would be to open it in a text editor and just check to see if the z-axis values are negative or positive like @gero shows here:


Just so I have a little more clarity, does Maslow assume that plunging into the material is a negative Z Direction?

Yes, into the material is a negative direction, out of the material is a positive direction. Zero is where the z-axis was when the “set zero” button was pressed

Cool. I will do some more tests with the HSM set up in Inventor to make sure that Z axis values being reported in the NC file are negative. Right now I think part of the problem is the way I defined the world coordinate system in HSM. I assumed that the zero XY plane was the face of the material that I can touch with positive Z coming out towards me to produce negative Z values but it looks like the NC file at post did not record those values that way. It might be measuring things from what is called bottom of stock in HSM which would give a positive Z value in the output.

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Are you using the Maslow post processor with HSM? I have created a couple of parts with HSM in Inventor and had no problems. I am not versed in it well enough to offer much support without having the program in front of me, but I can try to help you troubleshoot.

Also, I am not sure if it was answered earlier, but you asked if “Define Home” only defines XY coordinates, and I believe that is the case. You need to go into the Z-Axis settings to define the Z axis zero.

If I remember right, this should not matter. HSM will have you define the stock as being around the part (you can also define extra stock on one or more faces) and then you should be able to select the geometry to cut out of that stock. Make the stock partially transparent so it will be easier to see. Define the top of the stock as Zero in HSM and then all the cuts will be in the -Z region if the part is located inside the stock (I mirrored a part to make two of the same and nest them, and the mirror operation ended up putting the second part a thickness of the part higher than the first part. I ended up finding this out by looking at the stock end on and noticing that the 1/4" thick stock was located between the two parts so that each was only embedded in the stock 1/8". Moving the second part down solved this).
Also, when you run the simulation in Inventor, you should be able to see the stock being removed as each operation is performed. Rotating the view to edge on should also give you an idea if your part is actually inside the stock or sitting on top of it.

I’ll try to get on my computer in the next couple of days to get a clearer step by step.