Z axis running above work surface

Hello again, Noobie still stumbling along! I’ve finally got my PRO48x48 running the full g code, I’m able to use the touch-plate without a problem, I’ve set my origin to the work surface in the setup with Fusion360… I load the g code in Mach4, hit start and off it goes. Spindle revs up, Z axis drops down and everything starts to follow the path shown, except it is cutting the air above the worksurface. I ran the entire code twice, both times the router bit never touched the surface. So, what obvious, simple thing am I missing this time??? LOL

A question. Immediately after using the touch plate what is the value in your Z dro? Should be 2” I think. Then bring the tool down to the surface with the keyboard and see if the Z dro reads zero. If that all checks out, create a simple tool path with Fusion and post it here.

You can also use the MDI to run simple commands like “g1 z0 f1” this should bring the tool slowly down to the surface of your material. Maybe start with “ g1 z1 f1” then measure to see if your tool is 1” above your material.

Thank you for your help! So, in order, immediately after the touch plate, the value is zero. Bringing the tool down thru the MDI command (thank you for that tidbit, I had not learned that trick!) left it somewhere near 1/16" above the surface.

I tried adjusting the z offset in the toolpath to zero (it was at 1mm) and ran the new test gcode and set it to run. This time, the bit started its helix just above the surface (about where the zeroed z axis with the MDI Z0 command put it, but it did penetrate the surface and carved the pattern. The end result was that for a 1/4" deep pocket, it was about 1/16" too shallow.
The test gcode i used was a simple circle with a straight line. But I’m embarrassed to admit I dont know how to upload it here. I could upload a pdf of the code???
Thank you for taking the time to help!

If your z-zero is showing 1/16" above the material, then that is your problem! Something’s not right with how you are using the touch plate. Maybe record a video of you using it…and verify with calipers the height of the plate, and the height set in the settings for it.

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Not sure what you mean by adjusting the z offset means but I agree with Corbin. The tool should be touching you material at Z0. Many people do not use the touch plate but rather move the tool down a known reference or just touching the material and press the zero z button. Avid has a good video on that.

The helix should start above the material. That keeps the tool from plunging into the workpiece before starting the helical motion.

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Another note. You can copy and paste gcode from your file into the reply to these posts. You can also drag and drop fusion files or pictures or pdfs into the post window to share info with others. For fusion, export the project into their .f3d format then drag and drop or use the upload icon found in the top line of the post editor (a little square with an up arrow. Very useful to help us all figure out what you are trying to do. Good luck.

Well, one slip of the finger just plunged my bit into the surface and snapped the bit! Oops.
BUT, I reset the touch plate, still don’t know how to upload a video or anything like that here. I follow the Avid instructions of jogging the spindle to just above the center of the plate, roughly 1/2" above, open the touch plate command, set the tool diameter, choose the lower left corner. After it touches the plate, I turn it 90degrees, hit okay, repeat for the next axis and it retracts above. I remove the probe and plate.

In fusion360, when I created the 2d pocket, in the 3rd tab “HEIGHT”, under Top Height, using from “Stock Top”, I then set its offset to 0 rather than 1mm.

That change got the carve started last time, but left that 1/16th offset still. Have to get myself some calipers to measure it.

We may be getting there. By default when creating a new setup in Fusion Cam/Manufacture section the stock setting (second tab) will add 0.04 “stock” material on the top and bottom “model”. If you stock is actually 3/4" thick and you model is 3/4" thick you use “No additional stock” in the Stock Offset Mode dropdown. This may be your problem.

The Add Stock setting is more for the metal world where you start with a rough cut piece, face the top, then start your pockets etc. I assume that you are starting with material that is final thickness. This would account for being around 1/16" (actually 0.08") or so off.

Top Height in your case should have an offset of 0. Another thought is that many people use Model Top instead of Stock Top. This can be less confusing. Matches the wood/plastic working world where you actually start with material that is the correct thickness.

As far as getting files/pictures into these posts. Try just drag and drop or left click “copy” of gcode then left click “paste” while editing (in Windows).

Finally, after doing your lower left probe with the touch plate the Z dro should read 2" and the X and Y dros should read 1.1025" according to my touchplate. The spindle is left directly over the center of the touch plate and raises up enough so that you can remove it.

Overall it sounds like you are getting there. Alway fun to be learning multiple things at the same time (Mach4/Avid/Fusion360). Keep it up!

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I knew there would be a learning curve, just wasn’t expecting a hairpin turn!

Hopefully, after I’ve gained some experience, I can be able to pay it forward. I’m discovering that all the things that have seemed impossible are actually rather simple once explained.

Thank you again! Rest assured, I may be back again soon!

We’ve all done that at least once :slight_smile:
What I do is MDI the Z to, say, 3" above the workpiece. Then I slide in a 1-2-3 block to verify that it’s 3". That gives me plenty of reaction time if it’s going to hit.

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This is so simple yet so genius!