How do people handle the lack of tool radius compensation in

Discussion about the arduino based g-code interpreter, grbl
Baxter
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How do people handle the lack of tool radius compensation in

Post by Baxter » Sat Feb 09, 2019 6:33 pm

I have a large number of cad 2-D plans, and eventually got an eShapeoko to cut them out accurately. But it uses an Arduino running GRBL, and this turns out not to have tool radius compensation.

It would be a huge job for me to redraw all my plans - created over many years - all slightly wider. But if I don't, all cutting will be slightly too small by the tool radius.

One way of minimising this problem would be to use a very small tool - sub-millimetre - but that would be very delicate, and I can't find many around.

Does anyone have any other suggestions? Or should I go for using something like LinuxCNC and redo all my electronics?

WillAdams
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Re: How do people handle the lack of tool radius compensatio

Post by WillAdams » Sat Feb 09, 2019 8:37 pm

Does Gsharp support this feature?

https://github.com/NRSoft/GSharp
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Baxter
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Re: How do people handle the lack of tool radius compensatio

Post by Baxter » Sun Feb 10, 2019 7:52 am

This would be something you would use instead of G Code Sender?

If it supports macros then I suppose the user should be able to write their own compensation routine even if it is not natively supported. That would get round the Arduino limitations for GRBL.

I was wondering if someone had ported GRBL to a Raspberry, where there would be more available memory for extensions...

WillAdams
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Re: How do people handle the lack of tool radius compensatio

Post by WillAdams » Sun Feb 10, 2019 2:22 pm

You would use Gsharp as a pre-processor for your code.

There have been a number of ports of Grbl.

Does LinuxCNC have a mode where it will control a machine over USB?
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Baxter
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Re: How do people handle the lack of tool radius compensatio

Post by Baxter » Sun Feb 10, 2019 7:39 pm

I'm not sure.

Being a beginner at this game is like exploring Africa in the 1850s - there are no maps and you have to discover everything for yourself. When you spoke about handling tool radius compensation outside GRBL, I looked at DFX2Gcode, which is what I am using to generate G Code, and I think that it has some kind of compensation - it certainly lets you fill in tool diameters. Why would it do that if it did not do something with the data?

But the documentation is so poor I will have to run it with various settings and try to work out what it does by trial and error.....

Baxter
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Re: How do people handle the lack of tool radius compensatio

Post by Baxter » Sun Feb 10, 2019 7:43 pm

Ah... all it seems to do is embed G41/G42 commands to the GRBL - which, of course, won't work.... And G Sharp just looks like some code libraries...

cgallery
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Re: How do people handle the lack of tool radius compensatio

Post by cgallery » Sun Feb 10, 2019 9:40 pm

So your “plans” are in the form of existing gcode?

If you have CAD that you can import into a CAD CAM package, it will handle your cutter radius.

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Re: How do people handle the lack of tool radius compensatio

Post by WillAdams » Mon Feb 11, 2019 4:57 am

Also, you can use G-Code ripper from Scorchworks to convert the G-Code into a DXF or other format --- there's an opensource vector file conversion tool which does this as well.
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Baxter
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Re: How do people handle the lack of tool radius compensatio

Post by Baxter » Mon Feb 11, 2019 8:55 am

My 'plans' are in an old proprietary CAD package format. They are 2-D line drawings of parts to make model boats.

I can output them as .DXF - and then I use DXF2Gcode to generate the cutting commands.

Are you saying that the drawing package is the correct place to handle tool radius compensation? The package I use at the moment doesn't do this - but it's archaic, so that's not surprising. So I should be looking to get a new CAD package...?

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Re: How do people handle the lack of tool radius compensatio

Post by twforeman » Mon Feb 11, 2019 5:12 pm

The CAM that you use to create the tool paths should handle the cutter compensation.

If your current drawings are drawn to the actual scale you want, then you should be able to import the DXF files into a CAM program and the CAM program will handle the cutter compensation when it generates the G code.

You just tell the CAM program what the diameter of your tool is and which side of the curve you want to cut on.
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