I occasionally have this issue when cutting multiple items (linear array or otherwise)…the Z does not retract and cuts a contour all the way to the next item. This particular file I’m cutting .030 deep and my retract height is .3940. The first tool path cut with no problem at all. The second path (stars) scratched/etched all the way across my acrylic to the next star, ruining two items. Fortunately I was standing there when it occurred. What am I missing? Is anyone else having this issue?
The retracts are in the G-code:
Which machine do you have?
Are all the connectors in good condition and secure? All the wiring in good condition?
I’ve noticed thinner stock will bow up in the middle if clamped down to hard Tape and super glue work really well in avoiding this.
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I have the Pro XXL and all of my connectors appear to be in good condition. I will look them over a bit closer today. It’s not a “bowing” issue. If this were the case, it would be a problem on all the toolpaths in that area of the cut. This issue is certainly intermittent. Up until now, I’ve had total confidence in the machine and running projects. Now I’m a bit nervous :).
This is the traverse (rapid) move to the first star. Clearly 10mm above the part.
Here’s the section in the G-Code [My comments in square brackets]
This is using the Carbide 3D Shapeoko post.
X3.9835Y13.2978
X3.9898Y13.2917
X3.9971Y13.2871
X3.9872
G0Z-0.0202 [Lift 0.010]
Z0.3940 [Lift to 10mm]
(Toolpath: Contour Toolpath 4)
M05 [Spindle Off]
(Move to safe Z to avoid workholding)
G53G0Z-0.197 [Lift to 5mm below the limit switch. G53 = Machine Coordinates]
(TOOL/MILL,0.001, 0.000, 0.394, 45.00)
M6T503 [Load Tool]
M03S1 [Spindle On, 1 RPM]
(PREPOSITION FOR RAPID PLUNGE)
G0X18.2734Y6.0611 [Rapid to XY position. Should still be 5mm below limit switch]
Z0.0098 [Rapid to just above part]
G1Z-0.0300F350.0 [Plunge to -0.030]
X17.6765Y5.6291 [First cut move in star]
X17.8996Y6.3344
This looks correct. Are you cutting very near the upper limit of your Z axis? Or very near the bottom limit? I had some issues early on where the Z axis was getting stuck near the bottom limit.
great question…I’m likely working near the bottom limit. I’m running the Carbide spindle at the moment so an adjustment there wouldn’t be too difficult…plenty of room. Your response is very helpful…thank you!
Ok, it does not appear to be an issue of working too closely to the Z limits, top or bottom. I ran an “air cut” and it after it cuts each star it retracts and then lowers again to the cutting level to move to the next star. It is doing so with each star. Can you descipher this in the gcode as it moves out of the cut of each star to the next?
The G-code seems fine — the one concern is the final contour toolpath where things are cut out — you are cutting to a depth of 0.21" w/ a tool which is just 0.125" in diameter — best practice would be to add geometry and cut as a pocket down to tab height or the penultimate pass.
Good to know on the flute length…appreciate that feedback. Would that have anything to do, though, with the issue at hand?
Here are the lines between the first & second star…
X18.8722Y5.6291
X18.2734Y6.0611 [Last cut move on 1st star. Z-0.030"]
Z0.3940 [Retract Z to 10mm]
G0X11.2734 [Rapid to start of next star]
Z0.0098 [Rapid down to Z+0.25mm]
G1Z-0.0300 [Feed down to cut depth Z-0.030"]
X10.6765Y5.6291 [First cut on 2nd star]
X10.8996Y6.3344
Unless your G-Code is different than mine, this looks correct.
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So it should be moving to the next star at a 10mm height, which is my retract height of .3940. I’m at a loss. It is very clearly producing a rapid down move to Z-.030 and moving to the first cut of the next star…on each image (uniformly). hmmmmmmmmm
Any chance you have a little vertical slack in you Z axis?
I was doing an advanced vcarve on a 3/8" piece of walnut. It was a long carve and I was working around the shop. I came over to notice that the back side of the walnut had risen up. that made the carving a little deeper than wanted. I was still able to use the piece. I got my OOPS clamps out and clamped down the corners and finished the carve.
If you look at the top corner pieces you can see that they are fatter then they should be. This carve was about 4 hours with a 15 degree vee bit and a 1/32" flat mill. Likely only I would notice the mistake but a mistake it was.
Sometimes during carving a board will warp. Not sure if it is heat or the internal stresses on wood being released during cutting but it happens. Usually 1/4" plywood is the worst for me about bowing up during carving.
The piece was 12 X 10 and I thought my cam clamps would hold it against my L bracket but I was wrong. Luckily I did not have to start over.
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