How are hole positions verified on large parts too big for a CMM or Inspection Arm? 1

[Eric Gushiken]

How are hole positions typically verified on large parts where you can't use calipers and micrometers and the part or assembly is too big for a CMM or inspection arm. I know that laser trackers can be used for verifying surface positions. Is there a YouTube video showing the process for inspecting holes that may be located at some distance from the originating surface?

 

[Burunduk]

How big are the parts or assemblies, and how loose are the tolerances? If it's big and loose enough, it's unlikely that a tolerance of position will be used to locate the holes.

 

[drawoh]

Eric Gushiken,

How accurate do you need to be? My tape measure goes to twenty five feet.

--
JHG

 

[Wuzhee]

The crankshaft of the Wartsila RT Flex is measured somehow.
I think there is a whole market for huuuuuuge CMMs and co. for large parts.

 

[Burunduk]

https://youtu.be/BCOefaBGcYc?si=jvq_lDsgAbIplgKI

 

[Eric Gushiken]

I don't have any hard numbers to give but currently (and in the past) I've worked on large weldments that have machined surfaces and holes. Often times with the Engineering team there's debate and resistance to putting GD&T on the drawings because the shop has no way to inspect them. Perhaps I should ask the question differently. With large companies that have standard procedures for receiving fabricated items, usually the drawing is the governing document to determine acceptability. With these type of large companies, does every dimension need to be verified before acceptance?

 

[drawoh]

Eric Gushiken,

If you have a large, inaccurate weldment with clearance holes, you can always enlarge them a bit, allowing sloppier, more easily inspected clearance holes.

--
JHG

 

[3DDave]

Lasers and/or theodolites are typically used for large part inspection.

https://www.qualitydigest.com/static/magazine/sept03/articles/02_article.shtml