towards the design examination of machines

[snaroz]

Hi, I wanted to ask you something. very often I am asked to draw a reducer in section and to quote one of the tree that compose it with geometric tolerances, dimensional, indications on the surface state etc. my question is this: on the lengths and diameters of the various pieces that form the tree I have to apply dimensional tolerances? in the exercises I have carried out I have never applied dimensional tolerances to the quotas indicating the length of a tree piece; With regard to diameters, dimensional tolerances I prescribed only to those on which something had to be mounted, for example bearings.
I wanted to know if that was correct. I then have another question: if I quote the length of a piece of tree by prescribing for example a diameter of 20 mm (without adding dimensional tolerances), am I requiring that the piece once out of the workshop has exactly this diameter?
Thank you!

 

[Fulvio Romano]

in theory all tolerances must be specified. if there is no tolerance on the quota will be the general ones of the table, possibly reported in the cartiglio.

a diameter "exactly" of 20mm has no physical meaning.

 

[MBT]

read what is written herehttp://www.cad3d.it/forum1/showthread.php?37870-concetto-di-tolleranza&p=316471#post316471ask "that the piece has exactly this diameter" is technically absurd and impossible

when in a drawing there is a quota without tolerance, it means that it is subject to general tolerances of processing, which must be specified in some way on the drawing (usually referred, direct or indirect, to en 22768).

 

[snaroz]

Hello, according to you 2 hours to make freehand 4 exercises of which the first is a projection+quota of a simple object, the second exercise is the design in section of a threaded link between two plates with antisvitation system, the third is the design in section of a reducer and the 4 drawing and quotation with geometric tolerance of the gear shaft or a toothed wheel, is not a little bit short?
I have just performed a "do it yourself" simulation of the exam and to do everything without touching the book and watching nothing (forbidden to the exam) I took little less than 2 hours, but without rechecking anything or taking breaks. What do you think?

 

[snaroz]

I wanted to tell you that I finally supported the drawing exam successfully! ! !

 

[Fulvio Romano]

I wanted to tell you that I finally supported the drawing exam successfully! ! !

:wink:

 

[snaroz]

:wink:

and what I passed the exam!

 

[Fulvio Romano]

and what I passed the exam!

but "supered" is a range from 18 to 30...

 

[snaroz]

but "supered" is a range from 18 to 30...

Well, for me the vote is a senseless parameter and not to be taken into account, since it is generated by too many factors, among which obviously there is preparation but also luck, c**o of the moment etc.
Anyway, I got 21!

and I do not say this only because this 21 is closer to 18 than to 30. last year I took 26 to physics 1, but I have no problem saying that a year ago of physics I did not know a bat. same thing with analysis 1, backed 2 years ago and to which I took 25, where I think they overestimated me, since I would have failed. as you see, the vote says everything and nothing at the same time. reasoning in terms of vote is stupid, and they would be abolished.

 

[Fulvio Romano]

Well, for me the vote is a senseless parameter and not to be taken into account, since it is generated by too many factors, among which obviously there is preparation but also luck, c**o of the moment etc.
Anyway, I got 21!

and I do not say this only because this 21 is closer to 18 than to 30. last year I took 26 to physics 1, but I have no problem saying that a year ago of physics I did not know a bat. same thing with analysis 1, backed 2 years ago and to which I took 25, where I think they overestimated me, since I would have failed. as you see, the vote says everything and nothing at the same time. reasoning in terms of vote is stupid, and they would be abolished.

I disagree with that. As you say, around each vote there is a "noise" that can make it vary even sensibly according to different factors. It is also true, however, that this "noise" is generally on average nothing, and therefore the average of all grades of all exams is actually a correct parameter to evaluate the preparation of a student, future engineer. You think?

As you see, you took 21 and maybe you thought you deserved more, but when you took 25 you thought you were worth less, averagely the athenaeus knows what you're worth, right? :smile:

 

[snaroz]

Well yes, this is true though it is also true that one can have more luck than bad luck or vice versa and be overrated/underrated. However, as far as I am concerned, my goal more than to take notes and mark the questions that prof. does at the exam is to understand things deep, because I think that is what really matters. I prefer to spend time questioning me about the seemingly more trivial but actually deep issues, rather than learning only what the prof demands and aspiring at 30. because in my opinion it is this introspective study that creates the difference between the figure of the technician (mechanical, hydraulic, electrician, pompista etc...) and the engineer. Hello!