Cutting tool doesn't retract

[Anonymous]

I can't seem to get my retract heights correct.  

The ORIGIN is set at the corner of my Stock block.  The first toolpath is at the diagonally opposite corner.  Regardless of my retract height on the first toolpath, the cutting tools drags across the surface of my stock, then retracts to the retract height before entering the material.  Is there a way to set a retract height before it starts the first toolpath?  I've attached my model and gcode. 

  

[Matthew-R]

@Anonymous Thanks for posting your question to the Fusion 360 CAM forum. One initial suggestion that I have would be to make your origin point pointing in the positive x and y positions toward the model, unless you have a compelling reason not to.

Regarding your question about the tool being dragged across the model, have you tried disabling the G28 function in the GRBL post processor dialog, as pictured here.

Here's a screen capture of the posted GCode with G28 disabled.

Let me know if any of these suggestions are helpful or if you have any other questions. Thanks again!

[Anonymous]

Hi Matthew, thanks for replying.  

Just based on the size and shape of my stock piece, it was easier to have the origin in the upper left corner.  I suppose I can move it.  

On the retraction issue, I did have G28 Disabled and it still dragged across the stock piece.  When I look at your code, on line 13, it looks like the first move command is an X-Y position.  Doesn't that mean it will do that same thing.  

I've temporarily solved it by adding a G0 Z0.5 to line 12, but I would like to understand why this is happening.

Thanks. 

[Steinwerks · Accepted solution]

This is happening due to your controller and/or machine not supporting a home position, which is how HSM was developed (for industrial machine tools that start at a machine home which is generally Z0 in either G28 or G53). If you do have homing switches I would highly recommend using them.

If you set your workpiece height and then jog your tool up a bit it should clear before moving to the clearance height of the first toolpath.

Alternatively the post can be edited to input a basic retract height if desired.

[subteblu]

The same problem for me. The cutter does not retract before the first movement. Is it possible to edit the Post Process to add a value before the first movement? Editing the gcode every time is annoying. Im using grbl machine.

[LibertyMachine]

What sort of value would you be looking for, and would it/can it always be the same value, or would it have to change depending on thickness of stock, length of tool etc?

[subteblu]

I just need to add a Z5 before the initial move, ever the same valor. I use an external controller, it set the Z0 when send the gcode to the machine, have not limit switches.

G90 G94
G17
G21
G28 G91 Z0
G90

(2D Pocket1)
M9
T1 M6
S10000 M3
G54
Z5
G0 X28.098 Y20.041
Z5
G1 Z2.5 F300
Z-0.2 F133.3
G3 X41.709 Y20.148 I6.736 J8.979 F400

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