Possible bug?

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31 Oct 2010 12:27 - 31 Oct 2010 12:29 #4977 by 2e0poz
Replied by 2e0poz on topic Re:Possible bug?
Still confused here????

I set up code again using DXFtoGcode and GCNCCAM (tried both) and still get the same results with smaller cutters. Silly question now but surely if the cutter is smaller in diameter than the smallest hole or curve you want to cut it should work right?

I like using QCAD as it is quick and simple for the 2D type drawings.
DXFtoGcode and GCNCcam keeps things simple for creating the code

Am i just using the wrong software tools for the job?

I've been trying to keep everything in Linux and don't really want to be using Windoze for anything if i can help it. Any suggestions?

Thanks

Paul
Last edit: 31 Oct 2010 12:29 by 2e0poz.

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31 Oct 2010 12:58 #4978 by andypugh
Replied by andypugh on topic Re:Possible bug?
I am no expert on this, I write all my G-code so far by hand (and I tend to not use diamter compensation, partly for reason of the complexity you are finding)
It is possible that the diameter of the cutter needs to be smaller than the radius of the hole, not the diameter. However that would only be the case if EMC checked the tool outline against the metal already removed, not the path, and I am pretty sure that EMC doesn't try to do that.

I wonder if this line:
"If the tool is already covering up the next XY destination point when cutter radius compensation is turned on, the gouging message is given when the line of NC code which gives the point is reached. In this situation, the tool is already cutting into material it should not cut."

from:
linuxcnc.org/handbook/gcode/diacomp.html

Is the problem?

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31 Oct 2010 13:25 #4980 by 2e0poz
Replied by 2e0poz on topic Re:Possible bug?
Andy

That explains things much clearer, like most people i am always in huge rush with never much time to spare. Writing code by hand will be possible for me as it is not that difficult to learn. i spent a lot of time getting to a point of cutting with my build and not had the opportunity to spend a lot of time on the software aspects. X/Y movements are easy to see visually but the arc movements are not. This is why i think it is easy to misinterpret with what you think is happening. I WILL calm down now and learn more and understand there are limitations with free cam software.

Thanks again

Paul

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31 Oct 2010 13:29 #4981 by BigJohnT
Replied by BigJohnT on topic Re:Possible bug?
2e0poz wrote:

I set up code again using DXFtoGcode and GCNCCAM (tried both) and still get the same results with smaller cutters. Silly question now but surely if the cutter is smaller in diameter than the smallest hole or curve you want to cut it should work right?


When you say "I set up code again" does DXFtoGcode want to know the cutter diameter? I've not used either of those programs yet so I'm in the dark here. Is it generating software offsets in the post processor part? Did you change the cutter diameter in the tool table before running the code?

Can you attach the dxf file so we can look at it?

John

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31 Oct 2010 14:41 #4984 by BigJohnT
Replied by BigJohnT on topic Re:Possible bug?
I just ran a dxf file through dxf2gcode and if the start radius was not bigger than the tool diameter it didn't generate a long enough entry move and EMC politely complained that I was a dufus and didn't know how to write g code B) .

You might play with the settings in dxf2gcode a bit.

John

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31 Oct 2010 16:46 #4985 by 2e0poz
Replied by 2e0poz on topic Re:Possible bug?
Yes John it does ask for the diameter and also GCNCAM it also asks which you set up in the template. With this you have to match the tool table in EMC against tool numbers. It's a shame that these projects don't seem to be still running as for simple stuff they are ideal.

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31 Oct 2010 16:49 #4986 by 2e0poz
Replied by 2e0poz on topic Re:Possible bug?
Here is the drawing

File Attachment:

File Name: 22mmbearing.dxf
File Size:18 KB
Attachments:

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31 Oct 2010 17:54 #4988 by andypugh
Replied by andypugh on topic Re:Possible bug?
You might want to give SheetCAM a go.
It is commercial software, but you can do some stuff in the demo mode. (And there is a Linux version)
www.sheetcam.com/index.shtml

Do the CAM packages you are using have an option not to use diameter compensation (ie to do the compensation in the CAM package). Diameter compensation is great if you want to run the same G-code day after day and simply measure the tool and adjust the tool table for wear, but I have generally found it to be more trouble than it is worth.

The problem I have found with G42 is the requirement for entry moves, and it may be that the CAM software is not doing those very well.

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31 Oct 2010 18:25 #4989 by 2e0poz
Replied by 2e0poz on topic Re:Possible bug?
Andy

i think there maybe some confusion here, the code that has been generated has been done purely from the cam software (available from this site). The only input required is specifying the tool diameter and length, speeds and feeds etc. This is not done in the G code directly.

DXFtoGcode

specify tool diameter, speeds, feeds, etc. Which side to cut of the line done on the drawing then export the code.

GCNCCAM

You create a template of the above then open the drawing, specify which layer is cut first then build the code automatically and save. Any compensation is done buy the CAM software.

This is why i find it strange that if create a new machine profile and run the code generated from either of these it works fine first time. If i then load up some new code generated from either of these it errors with the gouging corner etc etc. I don't feel i have been doing anything different from last year on my first machine using 8.04 and never saw errors like this.

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31 Oct 2010 18:34 #4990 by andypugh
Replied by andypugh on topic Re:Possible bug?
2e0poz wrote:

Any compensation is done by the CAM software.

I am not sure that is true, the first file you posted had a G42 at the beginning, which turns on diameter compensation.
It is possible that the two bits of software are fighting each other, with one using G42 compensation, and the other offsetting those lines again.

Does the output look OK if you comment out any G41 and G42 statements?

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