Question about Blum Probes

[Guest]

Does anyone have any experience with Blum probes?

 

We seem to be having a repeatability issue and I'm trying to run it down.

 

I probe the datum ring after every toolchange and I am using an 8 point routine to do this. I am also using and 8 point routine to probe an OD boss. Now the macro's themself function fine. The problem I am having is repeatability. I probe a diameter once I get 1 set of numbers. I probe it again I get a slightly different set of numbers. .0003 to .0006 different. This just ain't gonna work I am trying to hold .0005 true position.

 

On the surface it appears that I am having difficulty with thermal expansion. Is there away to deal with this when probing?

 

Or am I just expecting to much from this probe.

 

BTW this machine was just ball bar tested and came in nice and tight.

 

Any suggestions?

[Leon-ZA]

How about if you take a part, any (room temperature) part. And without machining it or anything. Probe it in 8 places, and immediatly probe those exact same places again. Those have to give you a repeatable set of figures.

 

edit to add...

If it does then I don't know what to except adding a temp gauge to the job...

[Guest]

Sometimes yes sometimes no. The variance is minor. .0002/.0003. The problem is when you are trying to hold .0005 true position, that is just too much.

 

I am starting to lean towards a bad probe.

[Leon-ZA]

I'd agree with you there. Without temperature being a factor and your variance is already .0002 - .0003, I'd don't think you'll be able to do what you want to do. To hold .0005 I'd expect "static" repeatability of .0001

[mman10]

Could it be that your probe is gummed up or the battery in the probe, is it old? The Renshaw probe we have is supposed to have a repeatability of .00004 so there is probably other factors.

[HevyMetl]

John,

 

Not to ask a silly question, but what is the positioning repeatablity of your machine? What is the maker of the machine? When it was ballbarred did you have a laser calibration along with it? Have you done a simple backlash test? I don't have a Blum probe, but I do run their laser tool offset setter and have been very pleased with it. It has always checked within tolerance of the machine.

 

Have you used it to test the diameter of the calibration ring to see it yields the same result on a calibrated gauge?

[Guest]

The probe is brand new. We have used it for a few jobs so far, but nothing so tight so the minor variance went unnoticed.

 

Now, we could replaced the battery.

[robk]

No experience with Blum, but we do run Renishaw probes. After a while we like to send them back for recalibration because of repeatability issues. We use ours to hold .0002 tolerances all day long. Once Renishaw recalibrates them, they come back like new.

[Guest]

quote:

---

John,

Not to ask a silly question, but what is the positioning repeatablity of your machine? What is the maker of the machine? When it was ballbarred did you have a laser calibration along with it? Have you done a simple backlash test? I don't have a Blum probe, but I do run their laser tool offset setter and have been very pleased with it. It has always checked within tolerance of the machine.

 

Have you used it to test the diameter of the calibration ring to see it yields the same result on a calibrated gauge?

---

It is a new Mori_Seiki NV-5000 that just hit the floor in January and has not been bumped or crashed yet. The ball bar test showed repeatability and backlash in the millionths on both axis and circularity of .0002 over the 12" test diameter. Squareness of 6.0um/ft.

 

One of the issues I am having is if I check the datum ring location in the morning it is .0005 - .0007 different than after the machine warms up.

 

It checks diameters repeatedly correct it is the locations that are driving me nuts.

[?Mark]

John,

Are you running just one probe cycle or multiple?

R0 in macro will run cycle one time and R1 will run it 3 times and register average of them.

Thats what I use with Renishaw. Average of three measurements, with no problems with regards to repetability...

Hope it helps

Kind regards, Mark

[chris m]

This doesn't answer the question but if you're probing a round feature for location then it doesn't actually matter what size the machine thinks the probe is

 

C

[perfecseal mankato]

John,

I would contact Blum on this issue first.

They could tell you the repeatability and accurracy for your probe.

[Guest]

I have been working thru the reseller. At this point what I am getting is the,

 

"I don't understand why this is happening."

"It shouldn't be."

 

I am about ready to dump this back in my bosses lap since it is not my job to argue with suppliers and I'm about ready to tell them....

 

Repeatability on this model is +/-0.5um which is .00004.

[robk]

quote:

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I have been working thru the reseller

---

Deal directly with Blum web page if at all possible. Not sure how good their tech support is, but it has to be better than than a reseller.

Prior to purchasing Renishaw we looked into Marposs and Blum. I was told to get quotes from those 3 manufacturers. Not sure if they still are, but Standard Systems was a Blum reseller at the time. They had a hard time even returning my phone calls. Glad I didn't go with them, but if memory serves me right I think James Mayette praised Blum in the past (maybe he'll chime in)... Me, I'm glad we went with Renishaw. Excellent service backing a grade A product. Sorry had to rub it in

[Guest CNC Apps Guy 1]

Blum has the ability to comp for thermal growth.

 

So far their stuff seems very good. Still new to them though and want to see the performance over time.

 

Don't get me wrong, but have you checked to make sure the stylus is snug? Runout can cause repeatability issues too.

 

HTH

[HevyMetl]

John,

 

Try asking directly for John Sherick at Blum. He was kind of the lead honcho around there. I believe he used to be an application engineer for Makino, and he has always been able to help me. I have even talked to him while he was at the ball field with his kids. I have Blum's direct number if you are having a hard time getting it, drop me an e-mail and I will send it to you.

[Guest]

quote:

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Runout can cause repeatability issues too.

---

James,

 

Yeah it's tight, 1st thing I checked.

 

What would you consider excessive runout on the stylus?

 

We were told "close but not dead" probe would be able compensate for it. This stylus is indicated within .0006/.0005. I supposed we should go ahead and nail it just to eliminate the varible.

[chris m]

Probe runout is really irrelevant when doing 2-axis probing of round features as long as the stylus doesn't move between calibration and probing your feature. One thing that is important is that the location of your sphere / ring is good so that the machine knows how far from spindle center the center of the ball is.

 

C

[Guest CNC Apps Guy 1]

To me excessive would be .001 or worse. Yours should be close enough I would think.

 

You have exact stop check on? What about Unidirectional positioning?

 

James teh wheels in the head keep on turnin'

[Guest]

Our macros are formatted with a G31 on the touch lines.

 

Unidirectional positioning, Hmmmm. Not sure I've heard of that.

 

 

Well our touch lines in the code look like so

 

G90 G31 X#106 F80.

G91 G00 X#32

G4 P250

G90 G31 X#106 F.5

G4 P250

X#108 = #5061 + #119

 

This is how all our touch lines are formatted. This is how the macros came to us.

 

Are we missing something?

[Guest]

Well here's an update on this probelem we were having.

 

Notice I wrote "were"

 

After alot of and

We finally figures out was was happening.

 

We were suffering from thermal expansion.

 

When we qualifying our probe in the morning when the machine was cold it would repeat for a time, as we requalified everytime it was called into the spindle, it would start to drift.

 

As the machine warmed up, if we reran the datum ring program without verfying the datum ring location(changes after machine warm up) we were adding error into our probe tip offsets caused by the datum ring being in a different location than the set location for the program.

 

Now the only time we requalify our probe is after the tip has been changed. Then we re-indicate the datum ring position and qualify to that location.

 

It has worked well so far.

 

Just bought 2 more of them too.