Help measuring a large radius with probe in Haas

Mathias · Mar 28, 2017

I am trying to do a inspection of a 47.25" radius on a few parts that I have machined and the only way I could come up with is to use the Renishaw probe that I have in my Haas VF-11. I do not have an inspection package, but I am using the "Probe Y Minus" routine and probing multiple points along the radius. I then take those points and plot them into Mastercam and draw an arc on 3 points in order to get the radius.

My concern is, since I am not probing the Y-axis against a perpendicular surface, that I am getting a false reading that is not consistent along the radius due to the relationship between the Y movement and the angle in which the part is on the probe. My question is, is there a way I can plot the diameter of the probe stylus and somehow figure the error that the I am getting?

HuFlungDung · Mar 28, 2017

Can you run two different probe routines? Take the Y data that you gathered in your first series, and use those Y points as data points along which you then probe the part in X. This should give you some sort of an idea of how good those points are, in how well the pairs match up. I'd give more credibility to the trigger coordinates where the approach angle of the probe to the surface is between 90 and 45 degrees.

Why would the radius be incorrect if you just machined it on that machine? Do you suspect the part has sprung when released from clamping?

Another way to plot your results is to probe several points and from each of those points, draw a circle with the 47.25" radius. You'll end up with a bunch of overlapping arcs, and you can then place a point where every and any pair intersect. If they all intersect at the same point, then the part is perfect. If you've got some variance as to where the arc center lies, then that would represent some sort of distortion has occurred. Still, the fix would be to reclamp it without adding more distortion and remachine it.

deljr15 · Mar 28, 2017

I believe you are looking for a vector probing cycle.

If your trying to just check one you could G31 at a known x to the hit in y. mark down the coords and do it again at a different x, followed by a 3rd. Then use the 3 coords to calculate the radius and add the prob stylus radius. This method does introduce the trigger error of the probe if that is a issue for you.

Another method is to hit Y- then Y+ then go to the center and hit X- followed by X+. Now you can go back to Y and have reasonable certainty that your on the center of the arc. If your looking for better accuracy then do it a 3rd time

Larry Dickman · Mar 28, 2017

you say you don't have an inspection package, but you have a Haas that came with the Renishaw probe? Then you should have the inspection plus software installed. As Deljr15 said, you need the vector probing routine. For what you're trying to do, the three point bore might be the easiest. The vector routines are not part of Haas's VQC, so you'll need to program them.

Mathias · Mar 28, 2017

HuFlungDung said:
Can you run two different probe routines? Take the Y data that you gathered in your first series, and use those Y points as data points along which you then probe the part in X. This should give you some sort of an idea of how good those points are, in how well the pairs match up. I'd give more credibility to the trigger coordinates where the approach angle of the probe to the surface is between 90 and 45 degrees.

Why would the radius be incorrect if you just machined it on that machine? Do you suspect the part has sprung when released from clamping?

Another way to plot your results is to probe several points and from each of those points, draw a circle with the 47.25" radius. You'll end up with a bunch of overlapping arcs, and you can then place a point where every and any pair intersect. If they all intersect at the same point, then the part is perfect. If you've got some variance as to where the arc center lies, then that would represent some sort of distortion has occurred. Still, the fix would be to reclamp it without adding more distortion and remachine it.

We waterjetted the part out of 304L stainless and left the part attached with multiple tabs so I could clamp the plate to the mill table and machine the part to the correct thickness without having to add and remove toe clamps. Hindsight 20/20, I should have left material on the outside of the part to mill the part to print after I cut the part out of the plate.

Larry Dickman said:
you say you don't have an inspection package, but you have a Haas that came with the Renishaw probe? Then you should have the inspection plus software installed. As Deljr15 said, you need the vector probing routine. For what you're trying to do, the three point bore might be the easiest. The vector routines are not part of Haas's VQC, so you'll need to program them.

We bought this VF-11 6 years ago and it did not come with the inspection plus software. Even the UMC-750 we just bought this past December didn't come with the inspection plus software which I thought was odd since it is a 5-axis mill and the probing system comes mandatory with the machine. From my understanding, that software is free? I may have to contact HFO or Renishaw and see if we can get these updated. The only probing software that we use is the Haas VQC and I have ne experience in writing probe programs. :confused:

Larry Dickman · Mar 28, 2017

The inspection plus software is part of the probe package, it's just not part of VQC. and Haas doesn't go out of their way to tell you it's there.

Here's a sample 3 point bore routine;

N40
()
()
M06 T40
T1
(PROBE CASTING)
G00 G90 G56 X0 Y0
G43 H40 Z1.
G01 Z0.9 F50.
G65 P9832
G65 P9810 Z0.3 F30.
G65 P9823 A60. B180. C300. D4.S3
G65 P9810 Z2. F60.
G65 P9833

See if it will run on your machine. FYI the first line turns the probe on. 2nd line is a safety approach move, 3rd line it the probe routine, 4th line is a safety retract, 5th line turns the probe off.
A, B, and C arr the angles it will probe at, D is the diameter.

ghost_rider · Mar 28, 2017

here is what you need to read.

Renishaw Inspection Plus for Haas Programming Manual - CNC Manual

Madis Reivik · Mar 29, 2017

I would make a caliper, U-shape, put that on the arc and measure distance between caliper centre and arc.
Then its easy to use CAD and find exact radius.
Probably hard to understand and explain without drawing... I can add that tomorrow

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