IS this question too hard?

[L Hanft]

This is a question on a bonus exam? Can you solve it? Do you think it is too hard?

 

Assume HSS tool is used to cut a steel cylinder with an allowable cutting speed of 360 sfm, doc of 0.2 in and a feed rate of 8 ipm. The horsepower specific of the steel is 0.60 hp/cu in/min and the lathe has a 10 hp motor.

 

What is the spindle speed?

What is the feed rate in in/revolution?

What is the material removal rate?

What are the diameters of the cylinder before and after the cut?

 

Any takers?

[L Hanft]

Forgot to add.... many students are complaining...."it's too hard, too little information.

[Harryman]

What is the class?

[L Hanft]

This is intro to manufacturing.... mechanical engineering and industrial systems manufacturing engineering students. This is a 200 level course.

[Scott Bond]

quote:

---

What are the diameters of the cylinder before and after the cut?

---

I am not able to answer this without the size of "HSS tool "and for me where it starts.

[Harryman]

Not too hard.

 

If I answer correctly, do I get a degree? Or just one more reason to people that put me down for not having one?

[L Hanft]

Sorry Scott, that's all the information you get. Harryman..... you got it? Show me the numbers and the degree is in the mail.

[Fig sign]

Aniway it is kinda silly academic type of question far, far from the real life.

 

It makes me sick -ick .

 

Iskander teh do your math alone ,man !

[Harryman]

Not yet... Trying to get some real work done between checks on forum.

 

May I suggest that folks email answers to Larry to keep the challenge open for others?

 

[ 10-23-2003, 10:21 AM: Message edited by: Harryman ]

[L Hanft]

Good idea email me your answer. Yea, yea it is an acedemic bs question, but I'm trying to make them think. Not an easy thing to do everyone wants the easy way out..... maybe they will start to see the relationships between tool, work piece, machine..... sometimes there just aren't any easy answers.

 

email- [email protected]

 

(Iowa State University Mechanical Engineering)

[steve f]

For extra bonus marks add:

 

How many inches will the tool travel under these conditions before turning into smoking ball off molten hss?

 

 

steve

[Harryman]

quote:

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How many inches will the tool travel under these conditions before turning into smoking ball off molten hss

---

Yup. That would be real world experience thinking.

 

An alternate ending is that college boy has no idea what such a cut will do when he's got that 30" long bar supported by a dead center, properly greased of course, in a #2 centerdrill hole.

[CAM-mando]

quote:

---

What are the diameters of the cylinder before and after the cut?

---

Not enough data to answer this unless you are asking the student to provide the D1/D2 numbers in which case it would seem you should ask for length as well.

[L Hanft]

I hire work study students to empty the broken tool buckets.......

[jbel]

How does this sound?

 

Spindle Speed (RPM):

 

12(in/ft) * 360 (ft/min)

------------------------

Pi * Cylinder Dia. (in)

 

1375.2

= -------------------- (Rev/Min)

CD (cylinder dia)

 

 

Feed Rate (in/rev):

 

8 (in/min)

-------------------- =

1375.2/(CD)(rev/min)

 

 

= 0.0058*(CD) (in/rev)

 

MRR:

 

10 HP

----------------------

0.60 (hp * min / in^3)

 

= 16.67 (in^3 / min)

 

 

Dia before and after:

 

(boy this is getting long

 

How about 0.4 in less than the start??

[jbel]

And one less lathe tool.

[Keith Graydon]

just run it till the chips turn blue

[Bullines]

quote:

---

Good idea email me your answer. Yea, yea it is an acedemic bs question, but I'm trying to make them think. Not an easy thing to do everyone wants the easy way out..... maybe they will start to see the relationships between tool, work piece, machine..... sometimes there just aren't any easy answers.

---

+1

 

A well-designed post-secondary curriculum will teach the students how to think to solve any given problem that may arise and not to rely soley on precedent.

[jbel]

quote:

---

A well-designed post-secondary curriculum will teach the students how to think to solve any given problem that may arise and not to rely soley on precedent.

---

Just because college boy knows how to solve a problem doesn't mean he still wont try to rely on precedent and find the 'easy' way out.

 

Besides isn't that what engineers do? Design a product with the least number of new and unproven features, therefore herlping to assure reliability.

[Bullines]

quote:

---

Just because college boy knows how to solve a problem doesn't mean he still wont try to rely on precedent and find the 'easy' way out.

---

Note that I said "...will teach the students how to think to solve any given problem that may arise and not to rely soley on precedent.". That implies that BOTH problem solving skills AND precedence is used; NOT one OR the other. Call me Johnny Boolean today

[chris m]

May I ask when in the world anyone in this trade would need to answer that question?

 

Mostly people come to me and say "here's a print; need the parts tomorrow" they don't say "here is an obscure variety of parameters; can you give me some more?"

 

Just an observation

 

C

[Müřlıń®]

quote:

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May I ask when in the world anyone in this trade would need to answer that question?

---

+ 1

 

I have been machining for 30 years and never figured a chip load, sfm, ect one time......

 

I take that back....

Once in a post here everyone figured up how fast they used a fly cutter or sumpthin.

 

 

Murlin teh hold your thumb up and have your tounge stuck just right at corner of mouth

[Fig sign]

I studied machining in university.

 

But I rely mostly on my experience ,intuition and indications from the tools manufactures.

 

I said that this guestion is purely academic .

If it not hurts anybody I may also say that it is

completly scholastic ,like medieaval prob about how many devils can be placed at the neadle`s edge .

[jbel]

chris m,

 

quote:

---

Yea, yea it is an acedemic bs question, but I'm trying to make them think. Not an easy thing to do everyone wants the easy way out..... maybe they will start to see the relationships between tool, work piece, machine..... sometimes there just aren't any easy answers.

 

email- [email protected]

 

(Iowa State University Mechanical Engineering)

 

---

That being said...

 

Who in the world relates horse power specific for steel to anything?????

 

This is exactly where book smarts and real life diverge from each other.

 

While this may in some way prove that there sometimes aren't any easy answers, it also instills in college boy the misguided perception that horsepower specific for steel matters to someone, somewhere, besides some college prof.

[jbel]

No hard feelings, Lhanft