A very good explanation. I'm enjoying the content. My only comment is that manufacturing engineers ( methods dept and Inspection ) can interpret a GDT drawing but I'd say many machinists won't be able to as in many cases it doesn't suit their machine workholding situation or knowledge of other features being at MMC or LMC or even other part sizes. But the definition of part feature importance as defined by drawing must be specified I totally agree; therefore to assist the manufacture there needs to be other manufacturing information such as a route card or job sheet with alternative information specified and tailored towards the intended manufacturing method. I'm beginning to appreciate GDT more but the drawing part definition of a functional assembly fit, doesn't help the maker from a vice face and corner location. There needs to be intermediary unambiguous information to exactly suit the method of manufacture on that particular machine.
Right, a functional design drawing does not replace the manufacturing plan or work instructions for how to make it. Geometric tolerancing on the design drawing only states the functional requirements for the final product. This may have an influence on how the part is made, but it does not state the method of manufacturing or sequence. However, geometric tolerancing could also exist on the manufacturing level to document "in-production" checks to manage process control.
@@GeoTolPro Thanks for this - perhaps this aspect can have a greater emphasis in the videos. I have noted that it's rarely mentioned - for sure you have talked about work Instructions etc but I REALLY WORRY THAT MACHINISTS are really losing sleep over GD&T and how to interpret / apply it. How to tie it all up to their jig, fixtures and vice setups must be a nightmare very often.
If the profile symbol is in both the upper and lower segment, it is not called composite. Any datum features referenced in the back of the feature control frame constrain the tolerance zone in translation and rotation. The lower segment must have less constraints than the upper (maybe only A). This allows the tolerance zone to translate/rotate in the unconstrained directions.
Why don't you have a C datum in your example? If you did, could you repeat the A-B-C in the lower to fully control the orientation of the lower control?
Thank you, I missed that datum B was in 2 plcs. IF you had a hole and slot as the B and C datums, could you repeat the A-B-C in the lower portion of the composite? Could it be appropriate? I only see examples repeating A and B and they are always parts that resemble blocks. I work with sheet metal parts or molded plastic parts with complex shapes where the datums aren't always square to the part.
Yes, in that case all 3 datum features A|B|C could be referenced in the lower frame of the composite. It looks funny, but it works because the lower frame only constrains rotational degrees of freedom. Your datum feature C is stopping rotation.
@@GeoTolProGreat. Thank you. Can you site any reference material for this three datum situation? I use this frequently and have constant debates about this specific issue because of the lack of applicable examples in ASME Y14.5-Y.
Figure 10-43 and 10-44 in ASME Y14.5-2018. If people have problems with all three datum features references listed in both segments, then its a good indicator that they don't understand the rules of composite position or composite profile.
A very good explanation. I'm enjoying the content. My only comment is that manufacturing engineers ( methods dept and Inspection ) can interpret a GDT drawing but I'd say many machinists won't be able to as in many cases it doesn't suit their machine workholding situation or knowledge of other features being at MMC or LMC or even other part sizes. But the definition of part feature importance as defined by drawing must be specified I totally agree; therefore to assist the manufacture there needs to be other manufacturing information such as a route card or job sheet with alternative information specified and tailored towards the intended manufacturing method.
I'm beginning to appreciate GDT more but the drawing part definition of a functional assembly fit, doesn't help the maker from a vice face and corner location. There needs to be intermediary unambiguous information to exactly suit the method of manufacture on that particular machine.
Right, a functional design drawing does not replace the manufacturing plan or work instructions for how to make it. Geometric tolerancing on the design drawing only states the functional requirements for the final product. This may have an influence on how the part is made, but it does not state the method of manufacturing or sequence. However, geometric tolerancing could also exist on the manufacturing level to document "in-production" checks to manage process control.
@@GeoTolPro Thanks for this - perhaps this aspect can have a greater emphasis in the videos. I have noted that it's rarely mentioned - for sure you have talked about work Instructions etc but I REALLY WORRY THAT MACHINISTS are really losing sleep over GD&T and how to interpret / apply it. How to tie it all up to their jig, fixtures and vice setups must be a nightmare very often.
Can you explain composite tolerance with profile symbol in both upper and lower segments
If the profile symbol is in both the upper and lower segment, it is not called composite. Any datum features referenced in the back of the feature control frame constrain the tolerance zone in translation and rotation. The lower segment must have less constraints than the upper (maybe only A). This allows the tolerance zone to translate/rotate in the unconstrained directions.
Why don't you have a C datum in your example? If you did, could you repeat the A-B-C in the lower to fully control the orientation of the lower control?
Datum feature B in this example is both holes, which constrain the final 3 degrees of freedom. Datum features A|B fully constrain the part.
Thank you, I missed that datum B was in 2 plcs. IF you had a hole and slot as the B and C datums, could you repeat the A-B-C in the lower portion of the composite? Could it be appropriate? I only see examples repeating A and B and they are always parts that resemble blocks. I work with sheet metal parts or molded plastic parts with complex shapes where the datums aren't always square to the part.
Yes, in that case all 3 datum features A|B|C could be referenced in the lower frame of the composite. It looks funny, but it works because the lower frame only constrains rotational degrees of freedom. Your datum feature C is stopping rotation.
@@GeoTolProGreat. Thank you. Can you site any reference material for this three datum situation? I use this frequently and have constant debates about this specific issue because of the lack of applicable examples in ASME Y14.5-Y.
Figure 10-43 and 10-44 in ASME Y14.5-2018. If people have problems with all three datum features references listed in both segments, then its a good indicator that they don't understand the rules of composite position or composite profile.
with just A and B datums shown, how is rotation about datum B axis constrained? I am new to GD&T so sorry if it's obvious
Datum feature B is two holes. The 2X creates a pattern and also stops rotation. The datum reference frame is balanced between the two.
Perfect Thank you. Your videos are fantastic@@GeoTolPro
Great
dint understand :(
不懂