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CNC Lathe Wont finish cutting radius

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snippycarpenter

Plastic
Joined
Jun 14, 2017
Hello fellow machinists out there. so just recently i have noticed that the Okuma Genos L300m Lathe i use will not fully cut a radius. This is a new issue that just started about a week ago. I have done everything i can think of. it just seems as the radius' are coming out sharp but i know they are completly finished because i put layout fluid on the face of the part and the diameter of the part and wait till i dust it off so i know when everything will be tangent. any help would be great cause this is a big issue since i am in the Tool and Die buisness
 
snippycarpenter said:
Hello fellow machinists out there. so just recently i have noticed that the Okuma Genos L300m Lathe i use will not fully cut a radius. This is a new issue that just started about a week ago. I have done everything i can think of. it just seems as the radius' are coming out sharp but i know they are completly finished because i put layout fluid on the face of the part and the diameter of the part and wait till i dust it off so i know when everything will be tangent. any help would be great cause this is a big issue since i am in the Tool and Die buisness
Click to expand...

Hello snippycarpenter,
It will help the Forum members give you an answer if you Post the Program Code, the Tool Nose Radius of the turning tool being used and the size of the Radius being cut.

Regards,

Bill
 
I'm a little confused also as to what you are saying.

I'm *guessing* that when you roll your radius from the face onto your turned diameter,
its not smooth? Your only getting say 80 degrees of radius wrap and then a sharp corner
onto the turned diameter?

I'm going to assume your code is good, and toss out a few things.

What happens if you take your finish pass the opposite direction?

Something funky going on with your backlash settings?

Are you using some weird insert? Maybe a wiper that doesn't have a consistent nose radius.
 
Hey Bob your right about the code being fine and no the insert im using is a romay corp CNGA432T7 Insert with a .031 radius. we have used these inserts for the last five years and have never had this issue its something that just started randomly. Now a couple factors im having thinking it could be is 1.) i just updated my Esprit software to the 2017 version but i dont see how that could affect the radius not being a full radius since the code is fine. also my night shift kid decided to through a piece of the magnetic chuck that we use and break one of my boring bars. so i thought something in the machine could be off but i checked to make sure the turret wasnt tilted and i have reset every tool multiple times to make sure everything was all set. and what do you mean by trying my finish pass in the opposite direction like having my feature go the opposite way?
 
snippycarpenter said:
Hello fellow machinists out there. so just recently i have noticed that the Okuma Genos L300m Lathe i use will not fully cut a radius
Click to expand...

hy :) thats an old problem with Okumas that does not cut radius :)

snippycarpenter said:
i put layout fluid
Click to expand...

use a marker :)

also, the fact that the marker / fluid is gone means that probably a continuos cut occured :)

a continuous cut may not be among a good toolpath : thus, i am saying that you should not even have used that fluid :)

quick idea 4 you : create a list of comanded_cnc_points and check if the machine follows them :)

comanded_cnc_points are not necesarly program_points, but displayed coordinates ... kindly !
 
deadlykitten said:
quick idea 4 you : create a list of comanded_cnc_points and check if the machine follows them :)

comanded_cnc_points are not necesarly program_points, but displayed coordinates ... kindly !
Click to expand...

... after that consider to reduce feed when axis go syncro on short distances, like chamfers or conection radius :)
 
snippycarpenter said:
also my night shift kid decided to through a piece of the magnetic chuck that we use and break one of my boring bars. so i thought something in the machine could be off but i checked to
Click to expand...

... you may dissalign a turret 5 degrres and still have no problem when turning, especially OD :)
 
Hmmm... A picture might be worth 1000 words on this one.

Does it do the same thing when you cut a convex radius, as a concave radius?

This sounds like a G41/G42 issue almost. Have you put this part on a comparator to ensure the radius is in fact, .350"?

You said you were programming with CAM. If the G41/G42 gets mixed up, or wrongly applied, the machine should still cut an *almost* radius smoothly, but the radii that's cut will be off.

Just a thought...
 
can i assume the crash happened and then this started? if so odds favor something is wrong with the machine, if not.
do you have the tool described correctly , which way it is pointing? have you tried a different part with a radius?
 
G41/G42 is sometimes tricky. The CAM postprocessor may not be spitting a perfect code to exactly suit your control. If you post relevant parts of the code as well as a picture of what you are getting, then it might be easy to pin-point the problem. Bill has already said this. Insufficient information wastes time of too many people who genuinely want to help you.
 
and what do you mean by trying my finish pass in the opposite direction like having my feature go the opposite way?
Click to expand...

Same part, same features.. Just try your finish pass going Z+ from headstock and then down to the face.. Though
a CNMG in a normal orientation might not be the best for that, I'd want at least a Dxxx, maybe a Vxxx if its already
in the turret.

Is this machine a slant bed??
 
IME, the vast majority of issues like this are program errors. Either in the numbers or invoking/canceling TNR. As advised in post #2, post your code and other data lest the "shots in the dark" type answers continue.
 
I don't want to ask stupid questions but sometimes the obvious things get over looked. You have the right radius value and tool "code" in your offsets right? Or if you are not using cutter compensation at the control then double check your tool geometry in esprit.? Updating the software may have changed those values I guess.
 
R-method is not very accurate for 180 deg arcs.
And, a complete circle cannot be made in a single command, using R-method.
However, this method is error-tolerant, unless the radius is too small. In the centre method, the centre specification must be correct within a defined tolerance.
 
N0010 G00 X100. Z50.
G50 S625
G96 G95 S450 F.0033 T010101 M03 M09 M41
X5.3765 Z.1
G01 Z0
G01 X5.5765
G03 X6.339 Z-.3813 I0 K-.3813
G01 Z-.4813
X6.539
G97 S181 M09
G00 X100. Z50.
G00 X100. Z50. M05 M09
M02

Here is the code of the .350 radius it looks like everything checks out. i had the radius put on our cmm machine and its the correct radius just not right tangency points i have triple checked my tool geometry to make sure everything was correct because we dont use the machines radius comp. and everything is good there.
 
snippycarpenter said:
N0010 G00 X100. Z50.
G50 S625
G96 G95 S450 F.0033 T010101 M03 M09 M41
X5.3765 Z.1
G01 Z0
G01 X5.5765
G03 X6.339 Z-.3813 I0 K-.3813
G01 Z-.4813
X6.539
G97 S181 M09
G00 X100. Z50.
G00 X100. Z50. M05 M09
M02

Here is the code of the .350 radius it looks like everything checks out. i had the radius put on our cmm machine and its the correct radius just not right tangency points i have triple checked my tool geometry to make sure everything was correct because we dont use the machines radius comp. and everything is good there.
Click to expand...

Hello snippycarpenter,
Your code is correct, so I don't get it that "you are a victim of the CAM software".

Even if your tool geometry and or offsets were set incorrectly, the radius should still be tangent to the Z0.0 and X6.339 elements. The only thing that could cause a problem with your program as is, is if the radius of the tool being used wasn't actually 1/32"; but then it would still start and finish tangent with your start and finish elements, only the resulting radius would be wrong.

Your program coordinates are correct for a 0.0313" radius tool (1/32 rounded to 4 decimal places), so are actually more correct than if a 0.031 radius had been specified in your CAM system and as you're not using Tool Rad Comp by the control, then any Tool Radius you may have registered in the control is irrelevant.

Given the above, I would start looking for issues with the machine itself. However, given also the approach direction of your tool to the radius being cut, Backlash would seem to be an unlikely cause.

Regards,

Bill
 
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