GRR for troque driver.
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- This topic has 15 replies, 5 voices, and was last updated 13 years, 7 months ago by
Robert Kluttz.
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September 1, 2008 at 6:45 am #50855
Hi,
Good morning/afternoon. I had six manual type torque drivers and one torque checker, customer requested me to perform variable GR&R and it should be at 0.3 or below, could someone help how to do it? Thank you very much for kind help.
Best regards
Wilson (Sept.1,2008)(Mon.)0September 2, 2008 at 2:02 am #175362
Michael MeadParticipant@Michael-MeadInclude @Michael-Mead in your post and this person will
be notified via email.Hello Wilson, this seems to be a common topic here. I suggest you go to “search by keyword” in the upper right corner and enter “GR&R” and “Torque”. I just did it and found 13 threads.
Good luck,0September 2, 2008 at 9:49 am #175372We just did one and used 5 torque wrenches of the same nominal value, 3 operators, and 3 replicates. In the GRR platform, substitute “torque wrench” for “part”. Our wrenches have a +/- 6% tolerance so we translated this to in-lbs and plugged this in as the upper minus lower in Minitab. Our R&R / Tol was horrendous. We did a what-if, and used a wider tolerance based on drawing requirements for the screws we are torquing. Even using this tolerance, the R&R/Tol was real bad. We have a new torque analyzer on order.
0September 2, 2008 at 6:22 pm #175385
Robert KluttzMember@Robert-KluttzInclude @Robert-Kluttz in your post and this person will
be notified via email.Are you doing a GR&R just because someone asked you, or are you actually trying to solve a production problem?
You can do a fantastic GR&R and still not know why you’re getting loose terminations. Torque drivers are only one small contributor to termination integrity. So I’d take a step back and figure out what you’re trying to accomplish – do you want a kappa score or do you want a root cause of why you’re getting loose terminations? If it’s the latter, a 8D problem-solving exercise would be more beneficial than a GR&R.0September 4, 2008 at 1:20 am #175437Hi Michael.
Good morning and thanks for the information. Have a great day.
best regards
wilson0September 5, 2008 at 9:37 am #175494Hi Robert,
Yes you are correct, I’m doing this just because customer ask us to do so. we had nearly 500 pieces of manual type driver (brands name as ‘mountz’) and we picked 6 and select 3 operators to perform GR&R in excel spreadsheet format and observe the result is not good, I got P/total tolerance ratio as 0.8 and P/total SD as 1. I knew that if I would like to see both at 0.3 or less, I should have part-to-part variation in a very distinct or obvious stage while for the rest should have less distinct. Anyway may I know whetehr you have any successful example and story about the GR&R which can be shared. Thank you.
best regards
wilson0September 25, 2008 at 3:32 pm #176138
Robert KluttzMember@Robert-KluttzInclude @Robert-Kluttz in your post and this person will
be notified via email.A few questions;
How did you verify the resultant torque from each of the 3 operators?
What was the range of torque values that you have them tighten to?
How did you select the 6 tools & 3 operators?
I would set it up as follows;
Select ten torque values representative of the range used in your shop (if you torque from 1 – 10 in lbs, use 1, 2, 3, 4, 5, 6…… 10). Select 3 operators and 3 tools. Using a desktop torque tester, have each operator use each tool (twice) to tighten to each of the ten settings. record the actual values from the torque tester.
With this method, most of your variation should be part-part. If it’s not, then I’d bet that you’d have some operator variation (applied torque would vary by how fast torque is applied, where on the shaft the driver is held, environmental conditions, etc). If you’re seeing a lot of operator variation, I’d recommend refresher training followed by a repeat of the GR&R0September 25, 2008 at 4:07 pm #176142
TaylorParticipant@Chad-VaderInclude @Chad-Vader in your post and this person will
be notified via email.Wilson
Just a word to the wise, from my experience torque is a Destructive test and replicates will inflate the Repeatability0September 25, 2008 at 5:13 pm #176148
Robert KluttzMember@Robert-KluttzInclude @Robert-Kluttz in your post and this person will
be notified via email.Its only destructive if you’re using actual fasteners and mating surfaces. Using a desktop torque tester allows you to avoid that.
0September 25, 2008 at 6:47 pm #176149
TaylorParticipant@Chad-VaderInclude @Chad-Vader in your post and this person will
be notified via email.I dont disagree, but thats not what the Poster is doing, he specifically stated pulling 6 samples from a 500 part lot
0September 25, 2008 at 6:52 pm #176150
Robert KluttzMember@Robert-KluttzInclude @Robert-Kluttz in your post and this person will
be notified via email.I may be wrong, but I believe the “500” reference was to the number of torque drivers being used on the floor rather than the number of fasteners. Mountz is a brand of drivers.
0September 25, 2008 at 8:01 pm #176152
TaylorParticipant@Chad-VaderInclude @Chad-Vader in your post and this person will
be notified via email.ok, seems silly to perform R&R on just 6 units out of 500 then. From a customer stand point I would be more interested in a Change out/PM schedule and/or calibration/performance test plan rather than a random R&R.
0September 26, 2008 at 1:53 am #176156Hi Chad,
Yes, we have 500 units of the torque. I do agree with you point that we should be more focus on calibration and PM schedule rather than random R&R. Thanks for your response.
best regards
wilson0September 26, 2008 at 1:55 am #176157Hi Robert,
Yes, 500 is refer to number of torque use in the production area.
regards
wilson0September 26, 2008 at 5:08 am #176162the GRR applies to the measurement system. (the torque analyzer).
It is not intended to assess the capabilities of the torque wrenches.
is the customer interested in how well you torque things, or how well you measure torque?0September 26, 2008 at 1:14 pm #176166
Robert KluttzMember@Robert-KluttzInclude @Robert-Kluttz in your post and this person will
be notified via email.In this case, the torque analyzer would be the prime standard.
The Mountz torque drivers are pre-set to the desired value (5 in-lbs for example). The operator would apply the driver to the torque checker and turn in the tightening direction until the driver clicks. The difference between specified torque (5 in-lbs) and actual torque (the reading on the torque checker) would equal the sum of the variation contributed by the tool, the operator and the process.
So it would most certainly assess the capability of the torque driver (as well as the operator and the process).0 -
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