[Geo Girl]

Hi Gang,

confused, i can machine radii on my emco's no problem, but I have a machine with a fanuc oimb controller and i cannot make work.

its a simple profile. I even used mastercam to create a program and its the same i was trying to use, but it doesn't work.

its a 1/2 ball. 1.968 dia material. radius starts at xozo and its a rad of .984 and the end point is x1.968 Z-.984. can't be simpler.

it should be written
G00 X0 Z0
G03 X1.968 Z-.984 R.984 (i've tried I-.984 or K-.984 or i.984 or k.984) The radius (if works) ends up at too small a diameter.

please help

[littlerob]

Hi Gang,

confused, i can machine radii on my emco's no problem, but I have a machine with a fanuc oimb controller and i cannot make work.

its a simple profile. I even used mastercam to create a program and its the same i was trying to use, but it doesn't work.

its a 1/2 ball. 1.968 dia material. radius starts at xozo and its a rad of .984 and the end point is x1.968 Z-.984. can't be simpler.

It can always be simpler, IMO

it should be written
G00 X0 Z0
G03 X1.968 Z-.984 R.984 (i've tried I-.984 or K-.984 or i.984 or k.984) The radius (if works) ends up at too small a diameter.

please help

If the radius is coming out too small with those same numbers in the code, I would guess that a G42 (cutter comp right) is active, and has the wrong value in the offset page. IE if you are programming from M.C. with a .0156 R tool, with comp. at the computer, and the G42 is active at the control, with a .0312 Radius in the offset page, it'll come out smaller. It needs to be cancelled(G40). Other than that it should work

Robert

[Geo Girl]

thanks for the reply.

i made sure the cutter comp is off and ran it again. the tool radius is set at .020 so thats fine. still the same problem. I'm sure i'm doing something wrong.

the program i ran is
G03 x1.969 Z-.984 I0.0 K-.984 (the OD ends up at aprox .984 dia)

if I run it with
G03 x1.969 Z-.984 I0.0 K-1.968 the OD is aprox 1.703

and both look egg shaped.

heeelpppp!!!! please

[sinha_nsit]

Is this a lathe or a milling machine?

[Geo Girl]

Lathe

[CNCRim]

thanks for the reply.

i made sure the cutter comp is off and ran it again. the tool radius is set at .020 so thats fine. still the same problem. I'm sure i'm doing something wrong.

the program i ran is
G03 x1.969 Z-.984 I0.0 K-.984 (the OD ends up at aprox .984 dia)

if I run it with
G03 x1.969 Z-.984 I0.0 K-1.968 the OD is aprox 1.703

and both look egg shaped.

heeelpppp!!!! please

Egg shape cause by angle change..... program it for center of the tool that way tool will tangent to the surface.

[Geo Girl]

But its also not turning it to the correct dia, not even close.
How would you write a radii program?

[CNCRim]

Post the program on here since it's lathe.

[CNCRim]

But its also not turning it to the correct dia, not even close.
How would you write a radii program?

I have a feeling you program is not right and second thing is the ball endmill you put in the machine is not parallel to the axis that is cutting that's why it 's small.

[sinha_nsit]

G00 X0 Z0;
G03 X1.968 Z-.984 R.984 ;
should work provided you have diameter programming on your machine.
With radius programming, it should be
G03 X.984 Z-.984 R.984;
You can choose between diameter/radius programming with a parameter.

[dcoupar]

Sounds like maybe you're not accounting for the virtual tip?

Try the attached code.

[ImanCarrot]

Hang on a sec...

Assuming your cutting clockwise surely you should set X0 Z0 at the vertex of your sphere? you should then go from X 0.984, Z 0.984 to X0, Z0. That's the way I would do it.

No need to machine right over the vertex.

If the resulting "sphere" is "M" shaped your tool is not to centre, if it's an inverted "V" shape, like a cone, your tool's past centre- jog your X0 accordingly. You can make a steel gauge by cutting a concave radius into a flat piece if steel, place it over the sphere and look for the profile (like using a steel rule to check a flat).

I do this regularly except to a very high accuracy and use a Talysurf to check the form of the sphere.

[Geo Girl]

This is on a DMTG TruTurn bed lathe with an indexing tool block, so I am turning the radius clockwise.

i dont believe its a cutter comp issue. the tool moves too far out of scope to be a cutter comp problem.

i have a call in to DMTG, we will see how long it takes to get an answer.

G00 X0 Z0;
G03 X1.968 Z-.984 R.984 ;
does not work, it machines an big egg shape to a dia of .984. and doubleing it does not work either.

keep the ideas coming!

[CNCRim]

Dcoupor attached pix show why it's egg shape and that's what i'm tried to tell you. Look at post #11.

Why don't you post the whole program on here, so we can take a look at it.

[sinha_nsit]

Possibly your program is using radius compensation with wrong tip direction (tool tip number).

[Geo Girl]

i'm so confused....

my program

T0202
G00 X0 Z0
G03 X1.969 Z-.984 R1.234 F.02
G00 X3.0 Z5.0

Running this program.. the tool moves to xo zo but the moves away from the part making a big radius then comes back to cut a little bit of the part.

i tried the post below from the JPG and it also moves away from the part and comes around in a big radius and then around the and just touches the surface of the part at the z-. basically doesnt touch the part. I am test cutting on plastic

[littlerob]

i'm so confused....

my program

T0202
G00 X0 Z0
G03 X1.969 Z-.984 R1.234 F.02
G00 X3.0 Z5.0

Running this program.. the tool moves to xo zo but the moves away from the part making a big radius then comes back to cut a little bit of the part.

i tried the post below from the JPG and it also moves away from the part and comes around in a big radius and then around the and just touches the surface of the part at the z-. basically doesnt touch the part. I am test cutting on plastic

If in fact that is all there is in the program, than the answer to your original question is yes there is something wrong with your machine.

But I am thinking there is more to the code than that ; IE home position, spindle speed, Absolute positioning, or Incremental, an M1 maybe, more I am sure.

Also I am guessing that it is in a canned cycle which is not posted. Post the entire program and let us look at it. There isn't any reason the tool should move away from the part based on what you have posted.

[dcoupar]

i'm so confused....

my program

T0202
G00 X0 Z0
G03 X1.969 Z-.984 R1.234 F.02
G00 X3.0 Z5.0

Running this program.. the tool moves to xo zo but the moves away from the part making a big radius then comes back to cut a little bit of the part.

i tried the post below from the JPG and it also moves away from the part and comes around in a big radius and then around the and just touches the surface of the part at the z-. basically doesnt touch the part. I am test cutting on plastic

Be sure you don't have an R- (minus) in the G03 block. That would cause the machine to interpolate the arc > 180 degrees.

[neilw20]

Please give us a drawing.
1. We need to see what your finished part should look like.
2. We need to know the tool nose radius and shape.
3. How did you set tool zero position?
4. Are we doing the tool compensation or is the machine?
Much easier (IMHO) if you use IK. Then we don't need to worry about -R confusion.

[sinha_nsit]

G03 X1.969 Z-.984 R1.234 F.02

Change to
G03 X1.968 Z-.984 R0.984 F.02
and see what happens.