CAM Generation toolpath that goes outside of CNC limits

[Anonymous]

Hi, I have included the file I'm working on, and a picture showing the start of the toolpath.

My problem is that I would like to keep my stock bottom left corner at my CNC mechanical zero, and keep my software limits activated in my GRBL controller. (I'm using an X-carve)

There is also quite a bit of stock to remove from around the part, something like 2 passes side-by-side with a 1/2" end-mill.

When I post the NC file, and open it. I can see the first moves takes the cutter to some negative values (both in X and Y) which trigger my software limits alarm.

Is there any way to make Fusion no go below zero??

I have checked my machine configuration and under kenematics my x and y axis minimum are set to 0.

Thanks

Patrice

[Matthew-R]

@Anonymous

Hello and thanks for posting your question to the Fusion CAM forum. I have this same machine in my home shop and have gone through some of the same things as you have.

Regarding machine configuration and how you have it set up with 0 minimum and 980 maximum, that looks like it should limit, or let you know of an error when the code posts out. It's not doing that, so I'll investigate this further with our development team to see if this is a defect of some kind, if something is setup wrong, or if we're misunderstanding anything.

About the part, I would approach things a bit differently with how you have it programmed. The 2D Adaptive operation is meant more for removing large areas of material when it is absolutely necessary and also when you want to make sure the your tool's flute length is fully engaged.

For most wood parts, especially panels or profiles, I would rough the part out with a 2D contour operation rather than a 2D adaptive, this will be much faster for you. This will cut your machining time in this instance from about 6 minutes to about 2 minutes. Also, think about your work holding. If you are securing this part to your table with any clamps or fixtures, you can't mill away those fixtures, so keeping your tool close to your contour might be necessary. You may even need to add some more stock to your sides for this. One more thing that might help in the end is using tabs in the 2D Contour to keep that part secured in the stock when your final pass cuts through the material.

Then for that slot you have modeled, I've added a tangential pass extension to move the cutter out past the end of your model. This will give a nice smooth exit from the slot.

I hope this helps getting you cutting in the meantime. I'll update you with what I hear back regarding the machine configuration setup. 

Kind regards,

Matt Reineck

Technical Support Specialist, CAM

WWFO CSS Technical Support

[Anonymous]

Hi Matthew, thank you so much for a very rapid response.

The extra stock on the 4 sides is because it’s a leftover from a previous project. And rather than having to remove the tabs, all the while testing the machine and software.

I’m holding the stock with 2 screws to the wasteboard, don’t worry the wasteboard has holes with screw-in inserts.

The tangential extension you added is a nice touch.

Another work around that I found was to create a sketch somewhat smaller than the stock defined, but still bigger than the part itself, and use the edge of this sketch as the stock contour.

Than another was to turn off software limits, and set zero at 50 mm away from mechanical zero.

In the meantime, I’ll continue to try different setups. Im not sure where to start. Is it machine configuration, post-processor or my drawing that’s wrong. I doudt it’s the post, cause the NC file is not even done yet, and we can see the toolpath away from the machine zero.

[dave_lawrence]

i have a very similar issue, i am new to CNC, and recently got a Xcarve to play with and it seems that if i set my 0,0,0 at the homed location and the z at the spoil-board, the first move makes a direct line to the first cut and often digs into the the spoil-board as if my z zero point was on the top of my wood. I have to set the Z as if it is the top of my stock, the only problem is i mill that away and i want to flip my stock. so how can i set my 0,0,0 to the 0,0,0 of the machine and have it not dig into my stock or spoil board. i actauly cut an extra piece of stock so i could re zero. that  works well but i would like to zero to the spoil-board. i know i have a lot to learn on the tool paths but i need the set up to work.

[seth.madore]

Simplest thing is to simply jog the tool well above the top of the stock. Next thing would be to edit the post to have the Z move occur BEFORE the XY move. I'm not keen on that approach, but can understand why people would want that.

[dave_lawrence]

i guess im trying to understand if i can set up a fixture or a solid to avoid, so that the endmill goes to the clearance level first. 

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[seth.madore]

Negative. This is a function of the post processor.

The post REALLY should be tweaked for this processor, imo. It's not equipped to handle limit/homing switches, so it will just ignore any G91 G28 Z0 callout. The thing to do would be to have it traverse in the Z axis to a known safe spot and then move in X/Y. The issue with that is if you have clamps or different size stock..

[dave_lawrence]

i guess part of my frustration is that in Easel i can not find a way to read out the current location, so setting it to the same start point is painful, that's why i want to home it on a know point preferably with my homing switches and my z probe. you are correct it will not accept the G28 callout. i have toyed with adding a z move manually at beginning to move the bit to the z max/home and that seems to work, but it would be really nice if i could add that in as part of my standard post export so i dont forget. or can i add a step to go to z home in fusion? is it possible in fusion to add a move to a specific location in setup like a separate tool path that moves to a specific spot?

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[seth.madore]

What code will send the Z axis to a home position, and is that further away from the material, or further into it?

Yes, the post processor and easily be manipulated to add this code so it's not forgotten