G93

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G93

Postby Greolt » Thu Aug 31, 2017 6:44 am

Wondering if implementation of G93 mode might be on the agenda.

Maybe hopeful is a better word. :D
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Re: G93

Postby Greolt » Thu Dec 07, 2017 6:22 am

Made a couple of mentions of G93 over the last months.

Had no responce at all.

Is this possible?
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Re: G93

Postby Greolt » Thu Dec 21, 2017 1:46 am

Still no response.

Perhaps I just do not ask the right questions or in the right manner. Would not be the first time. Words are not my strong point. :)

Wondered if people just don't know what G93 is, or why it is used. Inverse time feedrate mode.

I don't know if this is why it was originally devised but it is typically used when there are both angular and linear axis combined in one movement.

Rotary axis velocity is measured in angular units per minute. Often, but not always, degrees.

Linear axis velocity is measured in linear units per minute. Most often inches or mm.

The two do not play well together when combined in one movement.

So instead of going from point A to point B in units per minute. (G94)

With G93, the time that move should take to complete is included in each line of code.

This overcomes the limitation of mixing different types of units per minute.

Basic CAM software like Aspire, that I use, does not have the ability to produce G93 code but there are fairly simple post processors that will convert G94 code to G93.

Mach3, that I still use for rotary work, has G93 capability. It also has an inbuilt rotary axis velocity compensation which works quite well. That is what I use.

Being just a carpenter I have no idea which of the above would be simpler to include in UCCNC. It would be great to see one of them and G93 would be a great start.
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Re: G93

Postby cncdrive » Thu Dec 21, 2017 6:58 pm

I have never used G93 so I just read after it and so now at least I now know what it is. :)
I'm not sure how hard or easy to implement it, will have to think it through first and talk to the collegues.
But I'm curios to ask that what is the practical reason to use the G93? I mean in what application and for what exact reason or reasons is this code is used?
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Re: G93

Postby Greolt » Thu Dec 21, 2017 11:58 pm

cncdrive wrote:But I'm curios to ask that what is the practical reason to use the G93? I mean in what application and for what exact reason or reasons is this code is used?


OK lets take what I would consider to be a typical UCCNC user with a rotary axis in a router or similar. Using inches and degrees.

The problem with G94 in this situation is the F60 means 60ipm movement of the tool though the work on a liniear axis.

Rotary axis is 60 dgrees per minute at F60

With the tool at 6 inches from the centre of rotation (12" dia), the tool movement through the work becomes 6.3 ipm

The tool at one inch from the centre of rotation (2" dia), the tool movement through the work becomes 1ipm. That is a LOT different from the 60ipm required.

One of the ways to deal with that is the use of G93. Inverse Time Feedrate Mode

A lot of the typical low end CAM software cannot produce G93 code but there are converters.

Look at this youtube video which is promoting one such converter. It als has a good explanation of the issue when using G94 on rotary axis work.

https://www.youtube.com/watch?v=d0ffiCekhpE
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Re: G93

Postby velvetpig » Mon Jan 01, 2018 4:41 am

I also would like to see G93 implemented.
If not, will have to switch between UCCNC and MACH3.
Cheers
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One in Office and One in Jail.
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