Machining cycle time

rishi07

Please help me to calculate theoratical machining cycle time for the below mentioned operations:

1. Hobbing
2. Shaping
3. Shaving

I need variious calculations involed in determining the theoratical cycle time.
Please refer any website, if it can help me.

Thanks,
Rishi

ank_gl

dude you can find the required formulas in the text, or they can also be derived. they are pretty easy, i dunno where my stupid handbook is:((

FredGarvin

Cycle times are going to be highly dependent on each particular part being machined at that time. What depth of cut? What length of cut? How many total operations?

I would recommend that you go to your school's library and start looking for manufacturing engineering books. Sometimes you have to crack a book open. Websites don't do it all.

TVP45

Any of these operations will be a function of feed speed and depth of cut, and those will be determined by the machine, the desired finish, the cutter shape and material, and the material. Ideally, you need about a two year apprenticeship in a machine shop to understand the questions, but you could start with The American Machinist's Handbook (which is out of print) or, alternatively, Machinery's Handbook.

rishi07

thanks for your replies,
i knew that these terms require various input parameters to calculate the time.
But can't we still freeze all those parameters like depth of cut etc. to make a general
empirical formulae, in which putting all inputs will give a relevant theoratical time.

I've starting googling in manufacturing handbooks for different formulaes and cutting forces required to calculate time. Please help me in with the referance of some books, if someone have some good literature in soft stage.

Regards,

RiShI

TVP45

Your question suggests you're new to machining, yet asks for "rules of thumb" that a senior manufacturing engineer might use. Is this just an exercise for a class or are you trying to do take-offs from prints?

ank_gl

arent they just the emperical formulas in text anyways??
you put in all the inputs and get the machining time

TVP45

So, there are some empirical formulas out there and very senior manufacturing engineers use those as a starting point for setting up processes and estimating costs. Note that this would be practical only for high volume production, not for one-offs. Usually, there will be a pilot production run during which bugs will be worked out and a time-motion study done to calibrate the actual machining time.

Low volume stuff is usually done by a skilled estimator or machinist who uses the time of a previously machined similar piece as the basis for the estimate.

If you are in school (and I swear to the heavens that some schools now teach engineering without ever putting students into a shop), you may learn theoretical estimates. If you are in that boat, I suggest you get the ASM books for the metals you are interested in.

ank_gl

yes, i am in school, but my school is good enough to put me in workshops for first 5 of my eight semester

that is exactly what i meant, the empirical formula ARE used as a starting point and then it will be modified with various variable inputs, as some factors depend on the human part, so that part has to be optimized

rishi07

well...to start with....i've some literature on simple turning as well as milling...
but i precisely mentioned to calculate times for hobbing, shaping and shaving operations.

mohsinkhalid

Cycle times are going to be highly dependent on each particular part being machined at that time. What depth of cut? What length of cut? How many total operations?

I would recommend that you go to your school's library and start looking for manufacturing engineering books. Sometimes you have to crack a book open. Websites don't do it all.