topic No G20 or G21 in output file in Fusion Support Forum

No G20 or G21 in output file

jim_holloway — Mon, 19 Dec 2022 18:14:13 GMT

I am very new to Fusion 360 but after building a small project and taking it through the post process, it generated the expected .nc file. The project was a 40 inch wide panel but when I attempted to run it on the machine, it became apparent that the machine was attempting to make a 40 MM wide panel instead. So I reviewed my setup making sure that I selected "inches" in the post setup. Same result at the machine.

Did some research and found that G20 and G21 were the G-code output for Inches or MM respectively to the machine.

So I reviewed the generated G-code but did not find a G20 or a G21 command anywhere in the file. Is this a fusion 360 error or did I miss a step somewhere ?

Re: No G20 or G21 in output file

seth.madore — Mon, 19 Dec 2022 18:15:39 GMT

What post processor did you use, and what is the controller of the machine?

Re: No G20 or G21 in output file

jim_holloway — Mon, 19 Dec 2022 19:20:42 GMT

The Post processor is UCCNC. I am not sure about the controller as its a friends machine but I will find out.

Re: No G20 or G21 in output file

seth.madore — Mon, 19 Dec 2022 19:52:38 GMT

I actually think that the code you shared IS in Imperial, but it's your machine that is in Metric. Reason for saying that? Number of decimal places. An MM program would cut off (typically) at 3 decimal places (xx.xxx) and your program has xx.xxxx, thus indicating that it's the machine, not the program.

Nevertheless, I would have expected to see a G20/21 in either case. This can easily be added to your post processor so it's there at all times, or you can manually add it into your code (at the beginning). Downside would be that you have to remember that each time.

Can you confirm that your machine accepts a G20/G21?

Re: No G20 or G21 in output file

jim_holloway — Mon, 19 Dec 2022 21:15:42 GMT

I can manually add the G20 and try to run it again. I will let you know.

Thanks

Re: No G20 or G21 in output file

jim_holloway — Wed, 21 Dec 2022 02:09:14 GMT

Seth,

I manually modified the code with a G20 with no change in output. So I checked the help file and apparently this machine does not accept either G20 or G21 as a valid code. So I changed the project to MM, tried again and it worked this time. I appreciate your help in this matter.

Re: No G20 or G21 in output file

seth.madore — Wed, 21 Dec 2022 09:02:53 GMT

Well, that is certainly interesting and....unfortunate. Well, our teachers (in the USA) have been preaching for years that "metric is coming", so now you get to work only in MM!

Re: No G20 or G21 in output file

jim_holloway — Thu, 22 Dec 2022 18:56:42 GMT

Yes I was surprised as well that it would not accept imperial measurements. Fortunately Fusion 360 makes the conversion to metric relatively painless. As for the US conversion to metric being imminent, I was hearing that drum beat as a teenager and that was in the late sixties. It seems no closer today than it was then.