Unexpected Plunge

Unexpected Plunge

Postby Dale1944 » Thu Dec 29, 2016 4:53 am

I am a rank beginner, and I can't make sense of Gcode. I was trying to cut an circular opening for an 80 mm spindle. I was using a 1/4" end mill with 1/4" depth per pass in 1/2" mdf. By the time the cutter made about 150 degrees of the first pass, it plunged from the original 1/4" to about 3/4" before I managed to stop it.

I went back to look at the toolpath, and everything looks right to me, but clearly . . .

Code: Select all
( Profile 1 )
( File created: Wednesday December 28 2016 - 03:05 PM)
( for Mach2/3 from Vectric )
( Material Size)
( X= 11.000, Y= 5.500, Z= 0.500)
()
(Toolpaths used in this file:)
(Profile 1)
(Tools used in this file: )
(3 = Down-Cut Bit 1/4"                57-910)
N100G00G20G17G90G40G49G80
N110G70G91.1
N120T3M06
N130 (Down-Cut Bit 1/4"                57-910)
N140G00G43Z0.8000H3
N150S13500M03
N160(Toolpath:- Profile 1)
N170()
N180G94
N190X0.0000Y0.0000F90.0
N200G00X1.9500Y4.2000Z0.2000
N210G1Z-0.2500F30.0
N220G2X3.4000Y2.7500I0.0000J-1.4500F90.0
N230G2X1.9500Y1.3000I-1.4500J0.0000
N240G2X0.5000Y2.7500I0.0000J1.4500
N250G2X1.9500Y4.2000I1.4500J0.0000
N260G1Z-0.5000F30.0
N270G2X3.4000Y2.7500I0.0000J-1.4500F90.0
N280G2X1.9500Y1.3000I-1.4500J0.0000
N290G2X0.5000Y2.7500I0.0000J1.4500
N300G2X1.9500Y4.2000I1.4500J0.0000
N310G00Z0.2000
N320G00X8.0000Y3.8565
N330G1Z-0.2500F30.0
N340G2X9.1065Y2.7500I0.0000J-1.1065F90.0
N350G2X8.0000Y1.6435I-1.1065J0.0000
N360G2X6.8935Y2.7500I0.0000J1.1065
N370G2X8.0000Y3.8565I1.1065J0.0000
N380G1Z-0.5000F30.0
N390G2X9.1065Y2.7500I0.0000J-1.1065F90.0
N400G2X8.0000Y1.6435I-1.1065J0.0000
N410G2X6.8935Y2.7500I0.0000J1.1065
N420G2X8.0000Y3.8565I1.1065J0.0000
N430G00Z0.2000
N440G00Z0.8000
N450G00X0.0000Y0.0000
N460M09
N470M30
%


Obviously, I messed something up. Can someone make sense of where I went wrong?
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Re: Unexpected Plunge

Postby martin54 » Thu Dec 29, 2016 5:17 am

Could be a number of reasons for a sudden plunge, so may not be a gcode problem at all, I can't tell as I don't read gcode either :oops:
Often helps to post the Actual file as well so if you post the crv3d file the forum experts can more easily identify the problem :lol: :lol:
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Re: Unexpected Plunge

Postby FixitMike » Thu Dec 29, 2016 8:50 am

A spiral upcut cutter that is not adequately tight in the chuck will work its way out so it cuts deeper.

However, at the end of the G-Code there is a command to plunge to .80 depth. "N440G00Z0.8000"

Post your Aspire file so we can see what toolpath settings you used.
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Re: Unexpected Plunge

Postby Adrian » Thu Dec 29, 2016 9:30 am

The 0.8 is the home retract isn't it with the 0.2 being the clearance? The cutting depths are -0.25 and -0.5.
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Re: Unexpected Plunge

Postby BrianM » Thu Dec 29, 2016 9:31 am

FixitMike wrote:...
However, at the end of the G-Code there is a command to plunge to .80 depth. "N440G00Z0.8000"



That is the tool RAISING to 0.80" not plunging. The only cutting Z depths are at -0.25" and -0.5" so either the tool has slipped or the machine is loosing steps. The tool slipping is probably most likely as Mike said.

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Re: Unexpected Plunge

Postby Dale1944 » Thu Dec 29, 2016 3:10 pm

I was doing a practice run for the top portion of a dust shoe. I used mdf because it is cheap and on hand. I cut the four pockets first with no apparent problem. Later I measured them and one pocket was about 0.030" shallower than the others, otherwise fine. So I tried the second file which was the profile cut to clear the spindle and the vacuum outlet. That was the gcode above.

After sleeping on it, the only thing I can come up with is I was using a shop vacuum to clear the saw dust. Static electricity could have scrambled things, but I used it in the same manner on the pocketing file. (Depth variation?) No change in set up, same bit with the collet untouched, and only the time to load the second file elapsed (perhaps 10 minutes.)

Top Element.crv3d
(117 KiB) Downloaded 46 times
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Re: Unexpected Plunge

Postby martin54 » Thu Dec 29, 2016 4:10 pm

Static electricity could have scrambled things, but I used it in the same manner on the pocketing file

Static problems can happen at any time :lol: :lol: , just because it didn't happen when you cut the first bit doesn't mean that you should rule it out. One pocket being shallower could be down to the material not being completely flat, you could try running some air cuts, set the z high enough that if it does start to plunge you have time to hit the emergency stop :lol: :lol: :lol:
Run both files again without the aid of a hoover & see what happens :lol: :lol:
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Re: Unexpected Plunge

Postby Dale1944 » Fri Dec 30, 2016 4:14 am

Static electricity from the shop vacuum seems to be the most likely culprit. I re-ran both files as Martin suggested, without the "Hoover." Both files ran correctly.
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Re: Unexpected Plunge

Postby TReischl » Sat Dec 31, 2016 1:52 am

You do not have to be an expert to "read" gcode.

For problems like this I suggest you load the file into an editor, then tell it to search for "Z".

It will go through and find all the Z's for you. Then it is just a matter of looking at the value.

If you have your Z zero set to the surface, all minus values are in the work, all positives are above the work (non cutting).

Pretty easy to do.
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Re: Unexpected Plunge

Postby Dale1944 » Sat Dec 31, 2016 4:54 am

TReischl -- Thanks for the idea. I loaded it into Word 2010 and did the search. The "Z" values were as they should be. I still would like to get an explanation of what is going on without becoming an expert. Being able to stumble around would be enough!

I want to thank everyone for their efforts to get a nescient neophyte beginner on the right path.
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Re: Unexpected Plunge

Postby TReischl » Sat Dec 31, 2016 4:07 pm

Dale,

As others have suggested here you need to check the mechanicals/electricals of your machine.

It is usually easier to start with the mechanical things first. Like check your couplers to make sure they are tight.

After that, I would take a look to see if it is losing steps. Not sure what control software you are using? If it is Mach, then the easiest thing to do is reduce the accels/decels and the overall speeds.

Hopefully (and usually it is) the problem will be solved by doing the above.

After that you have to start looking for electrical interference. Much more difficult IMHO.

Good luck, and let us know what you discover!
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Re: Unexpected Plunge

Postby cws » Mon Jan 30, 2017 10:45 pm

I had this problem and I was advised to updated my software. Haven't had it since. I think it was in V-Carve 7.5.
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