Z raises up, nobody asked it to...

[lskuared]

Hi,

Using F360 hobby edition and Mach3. 

I am trying to cut a shape out of foam on my CNC router. I am using 2D contour as it allows for tabs. Simulation runs great but when I post and run in Mach3, I get a soft limit warning. I do not have physical limit switches, only software limits. I have not had issues in the past.

In Fusion, I have selected the contours from the top and bottom of the model, same result. I have tried G53, G28, and Clearance Height for safe retracts. I have adjusted the Heights tab numerous times with the spindle raising a maximum of .25 inch above the model. When I look at the gcode, excerpt below (full code attached), I see a Z move as 1.25. This is the issue. I don't have that much room to raise Z. 

When I set my spindle coordinates, I have the lowest left corner as X,Y 0,0 respectively. I then move Z down to just touching the model (paper technique). I then zero out Z in Mach. Then I raise Z 0.3 inches so that during travel to the first plunge, it doesn't drag along my stock/model. All is good to this point. Once the spindle reaches the first plunge point it wants to raise Z beyond my limits. It doesn't need to and I don't want it to. 

I have read many similar forum entries but nothing exactly like this. I have included a png of my Fusion screen with the desired outcome from the stock.

Top section of code:

(Forum NC)
(T4 D=0.25 CR=0 - ZMIN=0 - flat end mill)
G90 G94
G17
G20
(When using Fusion 360 for Personal Use, the feedrate of)
(rapid moves is reduced to match the feedrate of cutting)
(moves, which can increase machining time. Unrestricted rapid)
(moves are available with a Fusion 360 Subscription.)

(2D Contour3)
T4
S5000 M3
G54
G0 X3.472 Y12.4056
Z1.4
G1 Z1.2 F12
Z0.725 F20
G19 G2 Y12.3806 Z0.7 J-0.025 K0
G1 Y12.3556
G17 G3 X3.497 Y12.3306 I0.025 J0
G1 X4.2296 F12
G2 X4.354 Y12.1937 I0 J-0.125
G1 X4.3521 Y12.1734
X4.3518 Y12.1701
X4.3491 Y12.1485
X4.3487 Y12.1456
X4.3454 Y12.1229

Please help!! Haha

Thanks,

Jim

[engineguy]

@lskuared 

You have Z1.4in as your first Z height so that would likely be that you are using the "Clearance Height" option when Posting code, that would be how you have set that value in Fusion.

Check again your settings in the "Heights" tab for your Operation in Fusion, if you have Top Height/Retract Height/Clearance Height remember that they are added together to give a total clearance height.

Check also your G54 setting in your Fixtures in Mach3 as that is the first location the machine will go to 🙂

I loaded your code into Mach3 here and as you can see in the image below the first Z height is the 1.4in, so, if that is the correct Clearance height that you wanted then it will likely be a setting at your CNC.

[engineguy]

@lskuared 

I did a small test, I set a G54 in the Fixtures to a value of -2.0in and when I ran the code in Mach3 the first move was to Z3.4in which is the original Z1.4in plus the G54 Offset, see images below.

Value of -2.0in in Fixtures

Gives value of 3.4in

[lskuared]

Thanks for responding!!

The clearance height seems to be adding the thickness of the model/stock too. My heights above stock add up to 0.8. See pics. 

If we can back up a step, should I be indicating the contour line at the top of the model or base of the model as these are through cuts? I did try both ways and had same issue but maybe I need to start at the correct point and then move forward. I hope that makes sense. 

I looked at old g-code from successful projects and don't see what I did differently - no luck. Guess this is what happens when you run the CNC router twice a year, haha.

[engineguy]

@lskuared 

Select the botom edge of the Model for the Contour, that way it defaults to "Selected Contours" for the "Bottom Height" and it can be left at that.

Next, set your WCS to the Top of your Stock in Fusion and Front Left corner, that is your X/Y/Z Zero, you then need to do exactly the same at the CNC,  then all your values will be from that point so that is where you need to "Touch Off" at the CNC.

If you would like to upload your Fusion File then go to :-

File > Export > Select f3d Format > Save to a location on your computer > Then attach to your reply using the "Attachments" facility below your reply box.

[lskuared]

Ok, I'll give it a go. F3D attached. Thanks!

[lskuared]

 Here's a pic of the beast if needed.

[lskuared]

Hi

I moved WCS to bottom left etc in both interfaces. I zeroed my spindle where I wanted it and checked "Fixtures" and it showed a value. No matter what value I put in for G54 (I did 0 to 1 to -1) fixture setting, the spindle still trips soft limit on Z lift at first plunge. I even moved my "router" up in the fixture to give the carriage more room to move up. So lost. 

[engineguy]

@lskuared 

What is the tool length that you have in your Tool Table?

Try the attached G Code file in your Mach3 and check your G54 setting is correctly set using the "Offsets" screen in Mach3, I have set the WCS to the Front Left corner for the X/Y and top of stock for the Z.

It runs correctly in Mach3 here so if it is not correct at your CNC then it is your settings at the machine 🙂

[lskuared]

Thanks. Can I get your F3D file please? I think you put the coordinates at the opposite end of the direction my table runs. The pic above of my machine shows X,Y 0,0 position. 

[lskuared]

My end mill sticks out 1.25 inch from the collet. 

[engineguy]

@lskuared 

Yes, of course, if it is of any help to you then you are most welcome to it  🙂 🙂 🙂

Also attached is the Mach3 Post Processor that I used 🙂

[engineguy]

@lskuared 

Nope, I didn`t move the WCS to a different end, I only moved it from the "Selected Point" to the nearest corner and top of stock just as in your last image. You will see that in the f3d file 🙂

For your tool length you should use the "Settings" screen in Mach3 to set and save the tool length offset, if you do that as well as the Work Offset on that screen then it should all work 🙂 🙂

[lskuared]

I still hit soft Z limit. I don't get it. Worked fine last time I used it too. Sigh

[engineguy · Accepted solution]

@lskuared 

Are your "Soft Limits" correctly set and are they enabled and working, do you have a Box around the Toolpath in your Mach3, if they are not enabled then there is nothing to stop the machine from going overtravel. See Images below, the settings I used are enough for the Soft Limits to work OK on screen but they are obviously not the same as your machine but big enough to allow the Soft Limits to be enabled, I don`t know if they will work in your version of Mach3 but worth a try, the dotted lines are the Soft Limits Box, sometimes called the "Machine Work Envelope", hope this gets you nearer 🙂 🙂

 In teh above image you can see the dotted line box is fully around the toolpath

 Above image shows the Soft Limits enabled, Green outline

The values shown above are big enough to make a box around the toolpath, you can make these values to the amount of travels you have on the CNC, then the box will always be big enough, you may need to change the Z axis to Positive "Home" direction 🙂

[lskuared]

Yes, soft limits set correctly, see pic.  So, I ignored the limit warning and ran it and this time it was a Z min limit. I let it run until it was about to gouge my bed and stopped it. 

I'm going to accept your offerings as a solution so you're eligible for the free toaster at the end of the year (or whatever prominence that affords) but I hope to still be able to pick your brain on this. I'm going to make some adjustments and try again in a bit but I'm tired of looking at it for now, haha. 

[engineguy]

@lskuared 

Nope, no toaster, not even any "beer tokens", which as I don`t use the stuff wouldn`t be of any use anyway 🙂 🙂 🙂

Yes, I see the X and Y of the limits are OK but I can`t see the bottom of the box, if it isn`t set to the bottom of the toolpath or lower then you will likely get the Z warning, all good fun 🙂

[lskuared]

Ahhh yes, the model falls below the limits. 

 

[lskuared]

Welcome to Mach3 forum...

No matter what value I put in Fixtures for G54 I hit Z min/max error. I've used positive and negative values. Thoughts?

Still don't understand how everything worked fine last use. Things did what I told them to do...

[lskuared]

Are you giving up on me?