# Circular Interpolation

• posted

Now I need to figure out how to do circular interpolation on the YZ plane instead of the XY plane in Mach 3. G2 G3 & G12 G13 are interesting and each have their uses, but none of the documentation I have found shows how to translate that to any plane other than the XY. Some says results will be unpredictable if you try. I thought about just swapping my motor connections. It might be simpler. And of course make sure that I change the speeds to match.

• posted

For anything more precise than engraving I am writing all my code by hand.

• posted

Plane selection:

G17 - XY plane G18 - XZ plane G19 - YZ plane

Arc (circular interpolation):

G2 - Clockwise arc G3 - Counterclockwise arc

Documented in the Mach3 documentation, G and M code reference.

There should be nothing unpredictable about selecting which plane to circular interpolate in.

• posted

And yet there I was totally surprised each time with where my code went off to. In fact the MACH documents didn't even document the various variables of the commands. I had to search them out from other sources and experiment. There seems to be this assumption by some that everybody who is playing with Mach3 is an expert machinist with 20 years experience writing g-code when in fact for some of us it's the exact opposite.

For example:

G02 = Right hand circular interpolation. This is meaningless to most beginners.

Makes an arc from the current point to the point defined by X, Y, & Z variables in the command line with a center of circle defined by I(offset from current X) and J(offset from current Y). (Yes I know I truncated the variable list. I did that for simplicity to illustrate the point.)

And then even without an example that doesn't mean much. The only reason I understand that definition is because I figured it out by working backwards. Not saying it was hard, but I am saying that the Mach documentation doesn't define that. Certainly not the G-codes and M-codes definition in the software itself.

Now when you try applying that with G18 or G19 it gets really complicated because first off none of the documentation I have found indicates which way is the top (positive direction) of the axis or how the plane is oriented by default. Not insurmountable, be definitely undocumented in Mach. Add on that you use I & K or J & K instead of I & J when working in one of the other two planes it takes a great deal of experimentation to determine what is going to happen with your code.

Without the help of a third party website that atleast listed all the variables associated with the G-Codes mentioned I would not even have a clue about where to begin experimenting. I would still be watching Mach3 lock up on errors in my code because is wasn't complete. Not even because my math was wrong.

While I don't wish to antagonize you, I wish to point out that whether you thought I was too dumb to look at the code definitions documented in Mach or whether you thought that was a useful answer neither was really the case.

This summary of G-Codes on the Stevensen Engineers website was very useful and helped to atleast document the various G-Codes and applicable variables more thoroughly. It is not on the Mach Support site anywhere that I can find, and it certainly is not included with any documentation I received with the licensed software.

It is probably the best single reference I found for G-code definitions, variables, and some things you can do wrong in coding. It is not 100% complete, but it is the best single on-line reference I have found for Mach compatible coding. Without it I would have been more than just frustrated with your pointing out the code definitions to me.

• posted

The version of the Mach3 doc I was looking at has a pretty decent explanation of the G02/G03 command (section 10, G and M code reference, in rev beta 7.57-a2 doc), it's two forms and the parameters. The best thing to do of course is to fiddle with it running just the toolpath simulation until you understand it.

It's the same as the XY plane, your looking down at it from the positive side of the rotation axis. Again, fiddling with it in the toolpath simulation helps.

The doc has nearly two pages of detail on G02/G03 and it's forms and variables, as well as a full page on the coordinate system complete with a chart listing all the letters and their meaning.

I'm not sure which version of the Mach3 doc you have, perhaps a section was omitted. Certainly the version that I printed out has a 33 page G and M code reference section with plenty of detail.

You might drop Art a message on the machsupport forum about the docs. I haven't looked at the newest docs so I'm not sure if they lost the G and M code reference section or not, but it was certainly there in earlier versions.

I just looked on my system and I have a copy of the Mach3 docs that has the section 10 G and M code reference section. Check your Mach doc (it's the user guide, not the install guide) and see if you have the reference section. If not grab my copy here:

• posted

Here's an on-line reference to G-codes with sample code snippets:

>>

• posted

I am looking at it now. I've only skimmed the few codes I already been trying to figured out to see if it makes sense, and its awesome. Its getting added to my favorites and I may even print it out to go along with the stack of references I keep on my machine bench. Wow!

• posted

SNIP

Hey Mike,

Neat stuff. Likewise, I've "bookmarked it".

I do think that there is a typo under the heading:

=============================================

Other Codes

sub Order of Execution Table

sub sub Order Item

11 Set Active Plane ( G17, G18, G18 )

I believe this last should be

11 Set Active Plane ( G17, G18, G19 )

=============================================

Further along it is correctly shown in the next sub table under

============================================

Modal Groups Table

sub The Modal Groups for G-Codes are

sub sub * group 2 = { G17, G18, G19 } plane selection

============================================

I only comment on this as this was part of the critical question in the OP's query.

Take care.

Brian Lawson, Bothwell, Ontario.

• posted

I'm assuming this is a mill. Look at G17, G18, G19. I think it is called plane select. The examples for G2/3 G12/13 will work, just use the right axis letters.

Wes

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