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Haas ST-30-Al 10-12 inch OD's +-.0005

stef_sandoval

Plastic
Joined
Dec 3, 2019
Hi, community
Needs some advice on running these similar parts that my company has me running. I'm young and I have experienced setting up mostly small lathe parts, not an expert though. I'm back at my old job and this time I'm expected to run and set up a few production parts that never end. To me there big and more expensive than what I'm used to. Semi-conductor parts for LAM Research. The biggest issue that I and the new crew are having is measuring the large OD's ranging from 10-12 inches. The part is very simple. Face and turn large OD, flip and turn to final length with small OD on the flip side. These parts are somewhat hollow on the inside. We have a caliper, mic, and special gauge made from Dorsey. The caliper is by far the easiest way to measure the part but not precise enough. The mic is hard to handle but every day it gets easier to use. The Dorsey gage is custom and expensive and supposed to be accurate and easy to use. The gage uses a red ruby to make contact on the part and master gage where it's zeroed out and then placed on the part to measure and compare. As the temperature fluctuates inside the shop the gauge has to be frequently zeroed out. The master is the nominal size of my part. Gage says it has an error of .0001. The problem is from what I've been told that parts change size depending on the temperature. The shop has good AC and it gets up to 74 degrees inside. Been running my parts at -.0002 on gauge since this seems to be the sweet spot in order for the CMM in a temperature control room to give me a nominal OD size. It varies but is very close to nominal. On my third inspection of the day, I sent my part to QC with the same reading with a gauge reading -.0002 but my part was .0006 on the high side, .0001 out of spec. I don't understand how the part can grow when the gage is saying the part is good and I've been running similar offsets. Tomorrow I will find out if the part was really out of spec. This is not the first time we have had these issues with QC even though we have an expensive custom OD gauge. Any advice.
 

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MaxPrairie

Hot Rolled
Joined
Jul 9, 2015
What is the ID of the part? How many hits is the CMM taking to give a diameter reading? The lathe could be forcing the ring out of round even a couple tenths and giving you those different readings. If that is the case either lower the chuck pressure or get a set of pie jaws. Take measurements at different angles on the diameter in and out of the machine and see if everything matches. Mark where the jaws are and see if you can tell where they were by measuring out of the machine. Mic should be able to measure the OD fine as well. Make sure you are accounting for ano if they get any, but my guess is probably not if they need electrical conductivity.
 

stef_sandoval

Plastic
Joined
Dec 3, 2019
What is the ID of the part? How many hits is the CMM taking to give a diameter reading? The lathe could be forcing the ring out of round even a couple tenths and giving you those different readings. If that is the case either lower the chuck pressure or get a set of pie jaws. Take measurements at different angles on the diameter in and out of the machine and see if everything matches. Mark where the jaws are and see if you can tell where they were by measuring out of the machine. Mic should be able to measure the OD fine as well. Make sure you are accounting for ano if they get any, but my guess is probably not if they need electrical conductivity.
I'll try an take censored pics tomorrow but when I say hollow it looks like a solid aluminum piece part but it's been brazed and roughed out before it gets to me so I don't see brazed anymore.
 

MaxPrairie

Hot Rolled
Joined
Jul 9, 2015
I'll try an take censored pics tomorrow but when I say hollow it looks like a solid aluminum piece part but it's been brazed and roughed out before it gets to me so I don't see brazed anymore.
No need to take a picture. You don’t want to piss your customer or employer off.
 








 
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