GD&T Datums, Reference Frames, & Part Immobilization | 3-2-1, 4-1-1, 4-2-0 | Actual Mating Envelopes
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- čas přidán 13. 07. 2024
- LECTURE 02
MEEN 426 - GD&T Playlist:
• MEEN 426: Intro to Geo...
This lecture was recorded on March 31, 2020. All retainable rights are claimed by Michael Swanbom.
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Man, I hope your students appreciate how absolutely concise and applicable all your videos are: GD&T along with actual manufacturing principles? Outstanding! As GD&T has evolved along with manufacturing, many machinists have remained sloppy or even used these methods to deliver junk. Aerospace (I''m now retired) is trying to move to reduced dimension drawings. The idea being to put a general callout to something like "produce the part using best shop practices to PoM 0.005" of the theoretical 3D CAD model." The intent is to free up the machinist and inspectors to only inspect the noted areas (truly critical dimensions, bearing and dowel pin locations, etc).
Any CNC made in the last 30 years can hold those tolerances without trying. At trade shows, Haas runs demo parts and hands them out all day long. Dimensions are all obvious numbers and parallel, repeatable, etc. Instead of similar quality, our internal machine shops would deliver things like two coaxial bearing bores more than 0.030" misaligned and not even on parallel axes (why they removed it from the machine between holes remains a mystery). Or another where a pattern of two dowels and a retaining screw, repeated four times, in a single line for twelve holes total. They managed to get one of the three-hole sets off by more than 0.020". No clue how. It could have met print with a knee mill and vise. Could have probably done it with a drill press, layout fluid and a punch. Despite rows of Haas CNCs, they not only made them but, QA bought them and tried to deliver them. Since engineers weren't supposed to have measuring tools, I was reduced to installing the dowels, laying them flat on a vise jaw and showing how a company badge could easily pass under some of them. Crickets.
Being GDTP certified professional, I must say this is the most detailed explanation on DRF. Your way of explaining is excellent sir. Thanks a lot for this video. You make GD&T easy to learn.
Thanks, I'm happy that you see some value in it! Thanks for the positive review, and thanks for watching!
Over the years, I've studied numerous video compilations devoted to GD&T but always gravitate back to the TheBom_PE series. Anyone interested in learning GD&T from scratch should watch this video series in order and read Chapter 20 on GD&T in Shigley's Mechanical Engineering Design. I cannot think of a more thorough and comprehensive starting point.
Such an amazing explanation of GD&T. I think watching these 4 video is sufficient to have a good understanding of the subject matter. Thank you professor.
Exceptional clarity. Order of presentation is very well thought out.
What a marvelous explanation! Thanks, professor!
Excellent lesson! Loved the way you explained it. Thank you very much.
Structural analyser and designer Sweden here. This is the best video regarding GDT I have found! Very good clearifications and comments. Thanks alot sir!
Greetings to Sweden! I come from a Swedish heritage and it's good to hear from you! Thanks for the positive review, and thanks for watching!
Your style is very deliberate which is effective in explaining the concepts. Thank you.
I'm glad it is helpful! Thanks for watching!
Wow. I'm in my second semester of technical college and this lecture is both enlightening and a relief. Thank you.
I'm glad it helped! Thank you for watching!
Wonderful Lectures ! Thanks.
Really great salute to you, for sharing your knowledge, Thank you very much. I really learn lots of thing which was new for me.
As always ,a fantastic lecture dear professor. Thanks for your great explanations.
As always, thank you for your encouragement! All the best to you!
For the explanation for 4-2-0 alignment, I believe the secondary datum locks the axial translation and the axial rotation instead of vertical translation
Great lecture, greetings from Guadalajara, Mexico!
Thank you! Greetings to you down there in Mexico!
Very good explanation of DRFs. thank you. Have to watch the other videos too.
Excellent lesson! This really helped me with programming the CMM at work.
I'm glad you found it useful! Thanks for watching!
@@TheBomPE Can you please make a lesson on bench inspection with GD&T?
Great explanation 👌
Wow ! Thanks sir for such an amazing explanation. I am getting to learn a lot from every one of your videos.
You are most welcome, thanks for the encouragement!
This video really helped me, thank you!
I'm glad it helped! Thanks for watching!
Cool, was always curious about why we had the diamond like pins. 50:38.
thanks sir you are the best, hope we 'l see more from you soon.
I will be posting another video in the next few days, thank you for your patience! In the meantime, here are some of my other playlists in case you haven't seen them yet and might be interested:
ENGR122 (Statics & Engr Econ Intros): czcams.com/play/PL1IHA35xY5H52IKu6TVfFW-BDqAt_aZyg.html
ENGR220 (Statics & Mech of Mat): czcams.com/play/PL1IHA35xY5H5sjfjibqn_XFFxk3-pFiaX.html
MEMT203 (Dynamics): czcams.com/play/PL1IHA35xY5H6G64khh8fcNkjVJDGMqrHo.html
MEEN361 (Adv. Mech of Mat): czcams.com/play/PL1IHA35xY5H5AJpRrM2lkF7Qu2WnbQLvS.html
MEEN462 (Machine Design): czcams.com/play/PL1IHA35xY5H5KqySx6n09jaJLUukbvJvB.html
(MEEN 361 & 462 are taught from Shigley's Mechanical Engineering Design)
Thank you for watching!
Amazing 👏
Thanks! Glad you enjoyed it!
Thank you for sharing this lecture, so helpful. Do you have a lecture about the parts inspection, if yes, please upload, appreciate
Thank you professor , this was very informative video
I'm glad you found it useful! Thanks for watching!
After a long time I am not sleeping during lectures! Even as a practicing engineer, I find these lectures really helpful! may be you could do some videos on tolerance stack up using GD and T using drawings that are Y14.5 based!
YESSSSSSSSSSSSSSS! stack up analysis videos would be awesome!
我正在听你的课。
Thank you From Saudi Arabia
You are welcome! Thanks for watching!
Thank you very much. very much helpful
Glad you found it useful! Thanks for watching!
sir i have a question regarding datums, assume that on one part i have a hole on the top face of the part which is 0.1 mm positional tolerance with respect to datum A, B then C( assume these datums are planar on very basic rectangular block and ordering of datums are important) on the feature control frame. This means that when this hole is inspected first datum A is constrained from 3 point contact, then B from 2 point contact, then C from 1 point. I also have another hole on the same part which is placed on the left face or right face which is again 0.1 mm positional tolerance but this time with respect to datum B A then C on the feature control frame (ordering is important). This time time same datum B which is used for first hole is used to locate second hole but 3 point of contact is done on that datum. Then datum A for 2 point contact and for C 1 point contact. So same part and same drawing but according to my datum ordering, datum A can be used for 3 point of contact or 2 point of contact in inspection. Is my understanding true? if it is wrong pls help me understanding it. Thx for videos.
Question, I have some confusion at my work with fellow engineers. If you have a part with a flat surface as datum A, a cylindrical hole as datum B and another flat edge as datum C. To properly align the part for CMM inspection do you 1. Rotate the part until it makes contact with the theoretical datum C or 2. rotate the part until the surface of datum C is parallel with the theoretical datum C? Thanks
I would say you will need to make the contact with datum C. You can not really make them parallel because the edge feature itself is not a perfect line
Thank you for the education
question when using an insert do I use MMC for hole?
Good stuff
Thanks! I'm glad you liked it!
Thanks
I'm glad you liked it! Here are some of my other playlists in case you haven't seen them yet and might be interested:
ENGR122 (Statics & Engr Econ Intros): czcams.com/play/PL1IHA35xY5H52IKu6TVfFW-BDqAt_aZyg.html
ENGR220 (Statics & Mech of Mat): czcams.com/play/PL1IHA35xY5H5sjfjibqn_XFFxk3-pFiaX.html
MEMT203 (Dynamics): czcams.com/play/PL1IHA35xY5H6G64khh8fcNkjVJDGMqrHo.html
MEEN361 (Adv. Mech of Mat): czcams.com/play/PL1IHA35xY5H5AJpRrM2lkF7Qu2WnbQLvS.html
MEEN462 (Machine Design): czcams.com/play/PL1IHA35xY5H5KqySx6n09jaJLUukbvJvB.html
(MEEN 361 & 462 are taught from Shigley's Mechanical Engineering Design)
Thanks for watching!
I understand the 3 2 1 rule, but how does a designer determine whether to call out A/B/C, A/C/B or C/B/A, etc? I have problem deciding which datum feature goes into secondary and which goes into tertiary spots. In your first example, why did you put B in the 2nd spot, why not C? Or why not use B as the primary datum and A as secondary?
I would say the rule of thumb to have a proper alignment is rigidity. This makes your alignment more repeatable. So, base on the nature of your datum features, you might want to use ABC or CBA. Also, it depends on which feature is more important to you
Excelent explanation; where do you teach?
I teach at Louisiana Tech University. Thanks for watching!
Is it ISO, the standard that you use? what is the number of this ISO standard?
Where it is important to talk about standards, I'm basing my comments on my understanding of ASME Y14.5. My point with the course though, is to first help students (many with very limited understanding of manufacturing) understand why some kind of GD&T system is important, them learn some principles and practices on the implementation of these systems.
Tq
You're welcome! Glad you liked it!
We need more lectures sir
Please
I've got one almost ready to record! Be looking for it early next week! I'm glad they are helpful!
Hi 50+-0.1= how calculate tolerance?
Will there be a 3rd lecture?
I'm planning on recording the 3rd lecture in the series tomorrow. It will be about Rule #1 of GD&T & position control. Check back soon!
@@TheBomPE please do more on GD & T including topics like virtual condition
sir u r from which university? i frequently refer your videos for machine design.
I teach at Louisiana Tech University. I'm glad you are finding my lectures useful! Thanks for watching!