CMM size and faro arm

[huleo]

We are currently setting up a new facility under AS9100. We have previously been able to avoid some inspection equipment with other methods, but in the direction we are going, a CMM on the floor is likely going to be required by our customers. Whether we 'use' it or not, whatev, but they will want to see that we have one. The space that we want to allocate for the inspection room only has I think 9ft ceilings. Now I have been around small CMMs, but I think we will need to step up a bit, but I know we cannot fit what some shops have, which is like an 8x12ft granite and probably 12ft high. Based on part size at this time, I would say probably roughly a 4x4ft granite table would suit us, but not sure on the Z. We really don't need monster Z travel. I would say 36" would work.

As well, I wanted to ask if any of you guys are in a high end quality dept, are Faro arms becoming more accepted at a method of final inspection, FAI, etc? I know several years ago when I approached this bridge, I did not get positive feedback from customers, but they were still sort of getting proven out I think.

I will say this, we might have to buy a CMM, but I am still looking for acceptable methods for inspection that are more efficient. The Faro is far faster, and many of the parts we do, we are able to prove them out with a digital height station. But if we are talking about using the CMM, it might be prudent to consider the software? All I have seen is quite proprietary and they want to hook you into contracts, etc.??

 

[jccaclimber]

Talking from the customer side, I want to see "suitable gaging". That doesn't necessarily mean CMM, but I've yet to see a case where this is a Faro arm. I recognize that this is heavily colored by the parts I work with, but the conversation almost always falls into this tree of responses:

-Do you have a CMM to check profile?
--Yes
---Is it scanning or manual?
---Manual
----So you aren't really going to use it for a complex profile like this part?
----No, we aren't.
---It's scanning.
----Great, what sort of repeatability do you see if you....longer conversation.

--No, but we have a Faro arm
---Do you think you would pass a gage R&R on any feature with a less than ±0.005" tolerance?
---<Supplier immediately starts to walk back their claim>
----No, it wouldn't.
----Yes, see if you hold your head just right and stick your tongue out while only moving one joint on the arm...
----Can you really measure anything while only moving just one or two of the joints? The wrist counts as a joint.
----No, we can't.
---We pretty much never use it, but we do have it and some customers like to see it.

I've worked at a couple places with them. Last place I was at we had two locations. The other location wanted to borrow ours, which wasn't used much, while theirs went out for annual calibration. I sent it to them on the condition that they never sent it back to us because our guys only misused it for tolerances much tighter than its capability.

Edit, the paperwork minded people (supplier development, purchasing/buyers) seem to love them, as do engineers who have a bad habit of blindly trusting whatever numbers the computer throws at them. The fact that they are still in business selling arms implies there is likely a good application for them, just not one at any of the places I've ever worked.

 

[huleo]

Talking from the customer side, I want to see "suitable gaging". That doesn't necessarily mean CMM, but I've yet to see a case where this is a Faro arm. I recognize that this is heavily colored by the parts I work with, but the conversation almost always falls into this tree of responses:

-Do you have a CMM to check profile?
--Yes
---Is it scanning or manual?
---Manual
----So you aren't really going to use it for a complex profile like this part?
----No, we aren't.
---It's scanning.
----Great, what sort of repeatability do you see if you....longer conversation.

--No, but we have a Faro arm
---Do you think you would pass a gage R&R on any feature with a less than ±0.005" tolerance?
---<Supplier immediately starts to walk back their claim>
----No, it wouldn't.
----Yes, see if you hold your head just right and stick your tongue out while only moving one joint on the arm...
----Can you really measure anything while only moving just one or two of the joints? The wrist counts as a joint.
----No, we can't.
---We pretty much never use it, but we do have it and some customers like to see it.

I've worked at a couple places with them. Last place I was at we had two locations. The other location wanted to borrow ours, which wasn't used much, while theirs went out for annual calibration. I sent it to them on the condition that they never sent it back to us because our guys only misused it for tolerances much tighter than its capability.

Edit, the paperwork minded people (supplier development, purchasing/buyers) seem to love them, as do engineers who have a bad habit of blindly trusting whatever numbers the computer throws at them. The fact that they are still in business selling arms implies there is likely a good application for them, just not one at any of the places I've ever worked.

I appreciate your responses from the customer side!! That is what I wanted to hear! I don't personally know the accuracy of FARO arms but yeah, if +/- .005 is all you can get, that is a joke in our field of work.

I am well known to reach for that height gage for many things. I am unable to check hole diameters, but we have other gages for that. I can check a plane to center of hole, and even distance between holes c to c. It also gives very reliable accuracy to .0002". If we need to get tighter than that, we are currently SOL unless it is something like a bore where we can use air mics.

I think you have confirmed my thoughts that indeed, customers want to see that CMM and more than that, they would like profile capable equipment? I assume you dance in the AS/ISO world? I am not trying to cheat on quality, I am just trying to find better ways than programming a CMM. That is a big ordeal. I know one shop that runs an optical scanner for loose work, flat pattern type stuff. I think it was good to +/-.002 but those parts are all at least +/-.015. Running on new Makinos, only way those parts could really be off is programming or total brain fog.

Could anyone speak to some direction we might look for a machine? There are TONS of them out there, and cheap, but I am sure most are manual, outdated everything, etc. We cannot afford new, but I realize this is not exactly an area you want to skimp on! I recently absorbed some vids on a Zeiss and wondering if the FAI report can be generated right from the software for that extra professional touch. I tend to want to wow my customers. It seems to bring more work. They realize the competence and follow up with other stuff. We just can't throw $250k into something right now.

 

[Dub537h]

Not sure what became of your query, but the Faro arms are good for up to .0005"-.0007" accuracy, which is sufficient for most shops! Especially with the convenience of plopping it down anywhere in the shop to check a part, then generate a report.

 

[jccaclimber]

Not sure what became of your query, but the Faro arms are good for up to .0005"-.0007" accuracy, which is sufficient for most shops! Especially with the convenience of plopping it down anywhere in the shop to check a part, then generate a report.

Bumping a year old thread for a dubious accuracy claim? And my eyechrometer is good to "Up to" spot on perfect. Even Faro specifies that the number you stated applies only to what at the time they deemed "newer" gages and only for single point articulation. So, if you happen to be measuring an object on a perfect arc and have great day, in a temperature controlled space, you could, just maybe, achieve that.

In practice I've not seen a measurement pass gage R&R even near their claimed 0.001" max error through volume.

 

[Dub537h]

Bumping a year old thread for a dubious accuracy claim? And my eyechrometer is good to "Up to" spot on perfect. Even Faro specifies that the number you stated applies only to what at the time they deemed "newer" gages and only for single point articulation. So, if you happen to be measuring an object on a perfect arc and have great day, in a temperature controlled space, you could, just maybe, achieve that.

In practice I've not seen a measurement pass gage R&R even near their claimed 0.001" max error through volume.

I suppose I need a lot more volume to see it then, because I haven't seen worse than .002" repeatability yet for any measurement taken. Not like that's anything impressive anyways, but usually well within the tolerances I work with at my shop.

 

[empower]

Not sure what became of your query, but the Faro arms are good for up to .0005"-.0007" accuracy, which is sufficient for most shops! Especially with the convenience of plopping it down anywhere in the shop to check a part, then generate a report.

VERY vague and misleading statement. the only ones that get into that accuracy range are the small/short arms, which are only useful for little parts.. the longer 6+ft ones are in the +/- .002-003" range.

 

[empower]

I suppose I need a lot more volume to see it then, because I haven't seen worse than .002" repeatability yet for any measurement taken. Not like that's anything impressive anyways, but usually well within the tolerances I work with at my shop.

repeatability is not the same thing as accuracy.

 

[Dub537h]

VERY vague and misleading statement. the only ones that get into that accuracy range are the small/short arms, which are only useful for little parts.. the longer 6+ft ones are in the +/- .002-003" range.

Ah, well we use both and I didnt realize they had different accuracy ranges!

 

[Dub537h]

repeatability is not the same thing as accuracy.

Not for overall accuracy, but it does factor out "roaming" measurements by staying true within the same measurement points (at least in my experience thus-far).

 

[empower]

Not for overall accuracy, but it does factor out "roaming" measurements by staying true within the same measurement points (at least in my experience thus-far).

not really... if your accuracy is lets say .001" and your repeatability is .002", then your overall uncertainty is .003"

 

[EmGo]

not really... if your accuracy is lets say .001" and your repeatability is .002", then your overall uncertainty is .003"

Usually repeatability is quite a bit better than accuracy, so if the repeatability is .002" one could expect an accuracy of around .004 - .005" which would give you an uncertainty of .007-.008" but even that sounds unlikely for a faro arm.

 

[empower]

Usually repeatability is quite a bit better than accuracy, so if the repeatability is .002" one could expect an accuracy of around .004 - .005" which would give you an uncertainty of .007-.008" but even that sounds unlikely for a faro arm.

right, i was just throwing numbers out there.

 

[TwinSpool]

Profile capable depends on your parts. Most parts don't need profiles. You'd have to make that decision based on what you're manufacturing.

Faro arm is probably not the right tool for machined components.