Help with G-Code Arc & Radius

Lukasz00 · Feb 28, 2021

Hi everyone
Currently I am programming Mazak machines
but I was assigned a new machine.
Where I use G-codes
I have a problem with rays, arcs.
I made the first example myself using g2 / g3 / R

In the second example, I am supposed to use I, J
I am looking for some materials but they are hard to understand for me.

Does anyone have any material on using I, J for arcs and radius

Please write some code for this drawing
Use the I, J functions maybe then on this example I can understand how the commands work

Regards,

HuFlungDung · Feb 28, 2021

Looks like you can handle sine and cosine ok. So I and J are the coordinates for the arc center.

Booze Daily · Feb 28, 2021

I and J are the distance and direction from the start of the arc to the center of the arc.

Delw · Feb 28, 2021

Lukasz00 said:
Hi everyone
Currently I am programming Mazak machines
but I was assigned a new machine.
Where I use G-codes
I have a problem with rays, arcs.
I made the first example myself using g2 / g3 / R

View attachment 315198
View attachment 315199

In the second example, I am supposed to use I, J
I am looking for some materials but they are hard to understand for me.

Does anyone have any material on using I, J for arcs and radius

View attachment 315200

Please write some code for this drawing
Use the I, J functions maybe then on this example I can understand how the commands work

Regards,

do a search online for a hass programing manual its very good for explaing how to use g codes

13engines · Feb 28, 2021

Booze Daily said:
I and J are the distance and direction, with sign, from the start of the arc to the center of the arc.

Just making a near perfect explanation of I and J a bit more perfect-er. :-)

To throw in a small bit of "G-code Arcs For Dummies" speak.

Distance, meaning INCREMENTAL distance

and

SIGN, meaning use - if needed.

Sometimes spelling out the obvious makes the obvious more obvious when first learning something.

CORONA VIRUS · Mar 1, 2021

What I tell people is to download HAAS manuals. They are free on their website for mill and lathes. Haas does a really nice job of going into depth to show you how it works. Great pictures are in there.

EmGo · Mar 1, 2021

Booze Daily said:
I and J are the distance and direction from the start of the arc to the center of the arc.

Just because he didn't say which control .... I've had Is, Js and Ks that were from the arc center to the current position, or from current position to arc center, and even the coordinates of the arc center itself. And sometimes signed and sometimes unsigned.

It is (generally) the distance, but you have to look at the manual for the particular control to be totally accurate.

LockNut · Mar 3, 2021

EmanuelGoldstein said:
Just because he didn't say which control .... I've had Is, Js and Ks that were from the arc center to the current position, or from current position to arc center, and even the coordinates of the arc center itself. And sometimes signed and sometimes unsigned.

It is (generally) the distance, but you have to look at the manual for the particular control to be totally accurate.

On a Fanuc, a parameter controls whether it's from arc center to start of radius or start of radius to arc center. This control may be the same, using a parameter to control this.

Paul

13engines · Mar 3, 2021

EmanuelGoldstein said:
Just because he didn't say which control .... I've had Is, Js and Ks that were from the arc center to the current position, or from current position to arc center, and even the coordinates of the arc center itself. And sometimes signed and sometimes unsigned.

It is (generally) the distance, but you have to look at the manual for the particular control to be totally accurate.

LockNut said:
On a Fanuc, a parameter controls whether it's from arc center to start of radius or start of radius to arc center. This control may be the same, using a parameter to control this.

Paul

To both of these I'll just quote Johnny Carson... "I did not know that!"

But I just searched thru Fanuc OMC, 18C and 18iA parameter manuals using every possible term I could think of, and did not find a parameter that allows selection of arc calling criteria. Please share... I'm interested.

While I'm here... I have yet to try this, but I read somewhere that if you fully and properly call an arc move designed for a plane other then say your standard G17 X-Y plain, (I-K/J-K etc) that the control will successfully execute in the desired plane, regardless of the current plane selected. To those in the know... fantasy land or what? Sounds legit to me. This brings up the idea of a potential parameter that would either set an alarm over this or let it go. Hmmm...

angelw · Mar 4, 2021

LockNut said:
On a Fanuc, a parameter controls whether it's from arc center to start of radius or start of radius to arc center. This control may be the same, using a parameter to control this.

Paul

Hello Paul,
I've been working with and repairing Fanuc Controlled machines for a long time and I'm not aware of such a parameter.

There are quite a few controls that specify the arc center as an absolute position, but Fanuc isn't in that camp either.

Regards,

Bill

metalmadness · Mar 4, 2021

never seen a machine control use arcs that are absolute positions but i suppose anything is possible! Seems like there is alot more math involved to know the abs position which means there is more room for finger banging the codes wrong.

EmGo · Mar 4, 2021

metalmadness said:
never seen a machine control use arcs that are absolute positions but i suppose anything is possible!

Was either the Actrion or the Westinghouse, can't remember ...

Seems like there is alot more math involved to know the abs position which means there is more room for finger banging the codes wrong.

Same. Wasn't really the absolute position, in terms of machine absolute position, was the position of the center of the arc in terms of the current program. Not any harder than distance-to or distance-from.

angelw · Mar 4, 2021

metalmadness said:
never seen a machine control use arcs that are absolute positions but i suppose anything is possible! Seems like there is alot more math involved to know the abs position which means there is more room for finger banging the codes wrong.

At Motion Control software level, arcs are typically specified in terms of Absolute Arc Centre coordinates, Start Point coordinates and the included angle of the arc from start to finish. On that basis, there would be less math involved if the centre coordinates are specified.

Regards,

Bill

Delw · Mar 4, 2021

EmanuelGoldstein said:
Was either the Actrion or the Westinghouse, can't remember ...

Same. Wasn't really the absolute position, in terms of machine absolute position, was the position of the center of the arc in terms of the current program. Not any harder than distance-to or distance-from.

Another control that did that from the early years was General Numric

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