Metal Removal Rate - Sawing

Oops... forgot blade thickness as a variable as well.

What sort of saw are you 'using'? a cold saw, machine hacksaw, band saw, cut off or diamond saw?

you might find you want to consider accuracy and quality of cut too as these can vary quite a bit depending on things such as material hardness, saw blade tooth design etc.

And there are Electric Arc Saws---where a toothless disc causes metal to melt and fly.May be any hardness metal/alloy.

Your making it too hard when it's not. It's really easy. You need to know cut per tooth, usually around .004" for most steels, .010" per tooth for a broach, but your using a saw, so use .006" per tooth, then you need the length of cut, how long, then feed per inch.... Poof... done! next question please?

Thanks for all your input. My ultimate intention is to be able to solve for a varying feed rate in order to maintain a constant metal removal rate as the blade travels through the tube.

Once the tooth design and blade surface feet per revolution are established that will provide a quality cut, I'd like to have a spreadsheet that I could plug in my blade diameter/number of teeth and tube OD and wall and it would graph for me what my feed rate curve should be.

Anyway, thanks again for your input.

<My ultimate intention is to be able to solve for a varying feed rate in order to maintain a constant metal removal rate as the blade travels through the tube.>

Simple!

At start you will have to accept Zero rate of removal!

Suddenly you go into one vertical wall and hence Maximum rate of metal removal .

As you go into the midsection of pipe you are removing metal at fairly constant* rate. Depending on wall thickness * could be small or large.

Then you meet far wall and remove heavily.

Then suddenly Zero at finish.

You have NOWto continue running the bandsaw--because you have to come out.

So unless you a have some kind of sophisticated ,Variable,automatized Table/job infeed possibility, where you merely dial in OD/ID and UTS of material-- and sit back, you can not get a constant rate of metal removal!

I'm the type of person that wants to find simple ways of calculating things. I like to avoid intelectual work.

When I read your statment it makes me think of Fourier and Laplace transforms. The thought of that makes me cringe!!

If this was my experiment, I would set up some test pieces of various diameters and wall thicknesses, and time how long each one takes. Graph your results and then you should be able to predict certain trends from there with other samples.

You could also measure the amp draw on the saw, that would translate to horsepower.

Metal Removel Rate = Time to remove metal.

<of Fourier and Laplace transforms. The thought of that makes me cringe!!>

Don't worry to much about these pseudo Math Guys who drop names and try to scare you. 99% of these are quite innocent. They can't tell a bolt from a screw.

Ultimately COMMON SENSE wins.

As they say :" Common Sense is not very common"

Do a search on the internet for "saw speed and feed calculators". There are several sites with calculators and the mathmatical formulas that pertain to them. I think this info. would also be avaliable in the Machinist hand book.

I agree with muku's post above!How are you going to imput this acceleration curve into your machine?It would be a complex curve and require extensive mathmatical equations to solve.I can only imagine the curve in my head, it would be something along the lines of this:

#1.The speed of the saw would increase at a constant rate until you broke through the first wall(solid area) because the chord length of cut and the dia. of the circle increases.

#2.Next as you enter the I.D.(hollow area) portion of the tube your speed would decrease very slowly as the chord length you are cutting decreases down to the middle or true diameter of circle.

#3.Then when you enter the far wall (solid area) of the tube, here your speed would spike. Then decrease at a steady rate opposite of #1

You're right, it is going to be complex; that's why I came here and posed the question. Plus, it's not a band saw operation but a radial saw operation so you actually have compound arc lengths. If it was just a band saw blade going through a tube, even I could figure that one out.

I had two options going into this:

Pressure (i.e. DPR card, pressure transducers, tempasonics, etc.)

Programmable (i.e. precalculated feed rate curve dumped into the blade actuation device)

I like the last one because it's cut 'n dry and less parts; well, that is if I can figure out the math.

Anyway, I appreciate all the responses... keep 'em coming if you'd like.

Laby guy has 1/2 the solution

Your making it too hard when it's not. It's really easy. You need to know cut per tooth, usually around .004" for most steels, .010" per tooth for a broach, but your using a saw, so use .006" per tooth, then you need the length of cut, how long, then feed per inch.... Poof... done! next question please?

Now just figure the changing area & pressure / tooth

A round or straight blade are not different, unless you're talking about abrasives which change in diameter

For a continuous blade it is a linear function. For a reciprocating blade it is a simple matter becausev the blade only cuts as it pushes forward. Same a a hand held hack saw. So the waste is only produced for half the stroke rate. If it is a big problem either use copressed air to clear the cut or if cutting big blocks of metal a liquid to keep the blade clean. There is no need to spread sheet it.