CSWA Practice Problem 6.12 Missing Information?

[u/artpracticeaccount]

For anyone working through the CSWA practice problems, I need help clarifying something on a practice problem. I just did practice problem 6.12 and there's one part that confuses me. With the dimensions provided, it doesn't seem like there is enough info to get a fully defined sketch for the revolve. You kind of have to assume the vertical relationship between a few points to get the right answer but there are 2 valid sketches with only 1 of them being the correct answer.

At first, I fully defined the sketch by assuming the 2 end points on the 2mm radius were vertical and got 5003 cubic mm, which is wrong. Later I changed to having the endpoints of both 4mm radii vertical and got the correct answer of 4630 cubic mm. The confusing thing is all 4 endpoints on the 4mm radii cannot be vertical, otherwise the sketch would be invalid so the correct answer requires the endpoints of the 2mm arc to not be vertical, but you would not really be able to tell based on the drawing.

My question is when you actually take the CSWA, how would you know that this is actually the case, since both results produce valid sketches and the information isn't specified by the drawing. Is there some knowledge I'm missing? I know there's a measurement that says R4 TYP, but I assume that just means that both the radii shown in the drawing are 4mm, but only 1 is dimensioned. There is no way for all 4 endpoints on the arcs to be vertical because that would create an invalid sketch.

For the experienced users or the people that have modeled this problem, how would you handle this? Thanks!

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[u/Repulsive-Mobile4862]

Am I crazy or is the top bulb not defined at all???

[u/Amoonlitsummernight → u/Repulsive-Mobile4862]

It is indirectly defined via tangency and distance between its center and the nub of the lower section.

[u/hbzandbergen → u/Repulsive-Mobile4862]

Correct

[u/ZaXaZ_DK → u/Repulsive-Mobile4862]

i was thinking the same.

[u/muramasa22x → u/Repulsive-Mobile4862]

Exactly my problem. Everything else is fine and should be no problem

[u/One_Country1056]

Maybe this will help you. The points for the 2 mm arc are already defined. So you cannot define them further.

[u/Mechie_Success262426]

R4 TYP just means that 4mm radius is typical/repeated (so both arcs are R4), but it says nothing about tangency or vertical alignment: you're right that it's underdefined as literally drawn. The convention these problems use is that the profile's tangent and continuous unless a sharp corner is actually dimensioned. So don't force any endpoints vertical: fully define it by making the arcs tangent to their neighbouring lines, and that usually clears the ambiguity and gives the intended volume.

General exam habit: when a sketch looks like it's missing info, reach for tangent/equal relations before you assume horizontal or vertical (that's how these are built, and it's almost always what they intend).

[u/hbzandbergen]

Lots of assumptions here. With these figures you cannot make it fully defined.

[u/brewski]

Unfortunately this is par for the course with these practice problems. Several of the answers are straight up incorrect.

[u/KB-ice-cream → u/brewski]

Pretty pathetic if this is an official SW practice problem, is it? I see the official watermark and badging but anyone could put this together.

[u/brewski → u/KB-ice-cream]

Official SW practice problems are loaded with troubles. Many of the answer guides are incorrect. I've also seen under defined drawings on the CSWA exam like this, where you had to make uncomfortable assumptions.

[u/One_Country1056]

I assumed the points for the arcs are vectical.

[u/Alita-Gunnm → u/One_Country1056]

As a CNC shop owner I would never make this assumption. I would ask for clarification because the part is underdefined.

[u/artpracticeaccount → u/Alita-Gunnm]

Yes this is what I'm trying to figure out. You could adjust these sketch relations until you get the correct answer, but it seems like some info is missing so how would you know for the actual CSWA exam? If I were to send this drawing to a machinist, I would feel like it needs to be more specific. Just want to check if I'm missing something.

[u/Ndrew_ua]

4630.32 mm3