Milling machine tutorial - cutter selection, speeds and feeds, coolant, high speed machining----make money online

hey everyone this will be a short

tutorial on cutter selection and speeds

and feeds for vertical milling machines

specifically CNC milling but a lot of

this would apply to manual machines as

well so today we're going to make this

little part it really doesn't matter you

know it isn't this doesn't do anything

useful I mean it does kind of mate

together sort of but it's not important

the reason that I chose these two small

pieces is because one has sort of an

outside feature and one has sort of an

inside feature but when we get into the

cutter selections and things it's it

this stuff applies to almost any kind of

part that has similar features so let's

start with this one this is a very

simple pocket it's got a flat bottom and

is straight walls all the way from the

bottom to the top so this is a about as

basic as it gets for a milling machine

task so the first question is how do you

choose a cutter like if you're given

this as the requirement

you know replicate this in an aluminum

using a milling machine how do you get

started so there's all kinds of

different cutters to choose from and the

thing to always keep in mind is that you

want to use the largest diameter cutter

that you can that will produce the

correct geometry in here so for example

if we used a really large diameter

cutter like this this isn't going to

work because I don't know if you can see

that the cutter diameter is actually

bigger than the diameter than the radius

you know that that's at the edge of the

pocket here so if we tried to cut that

with this cutter you'd end up with too

big of a radius there and as it turns

out I made this part so that it would

work well with a 3/8 inch diameter

milling cutter which is this size here

in more complex parts you'll have inside

corners and things that may be

impossible to cut the proper radius for

example if you have an inside square cut

that has a radius of 0 essentially so

that's impossible to cut with a milling

machine in this configuration and the

best that you can do is use a small

diameter cutter and get as close to zero

as you can however

as you might imagine using a really

small diameter cutter is a pain in the

butt because they break easily so this

is why Hugh who is your machinists and

mechanical engineer is complaining about

small internal radius cuts if you want

to make this little corner in here

really sharp that means you need to use

a really small cutter and then you have

all these problems so for today we have

a pretty gentle a pretty easy cut and we

can use a 3/8 diameter tool to get the

job done second you want to choose a

cutter that's not unnecessarily long so

this feature is only about a half inch

deep the pockets only a half inch deep

and it would be very very stupid to use

a cutter this long because all of this

distance all this distance on the on the

cutter can flex probably the single most

important thing when setting up

machining operation is the total

rigidity if your whole setup so you

might have a super powerful machine you

know with tons of steel and a really

tight clamping setup but if you put a

long cutter in a tool holder like this

and try to do the work like this you're

going to have a bad finish and the

reason is that the cutter itself is just

going to wobble around too much so I

chose a 3/8 diameter end mill and it's

it's relatively short so the cut is

going to you know there's not as a you

this is probably only about an inch long

or 3/4 inch long cutting area end mill

so we know the diameter and the length

of the cutter that we're going to use to

make this pocket how do we choose the

cutter material and coatings you've

probably heard a lot about you know

carbide tooling or high speed steel

tooling or stuff like that and for Home

shops and hobbyists and prototype shops

high speed steel tooling is fine the

main reason that production shops like

carbide tooling is that you can go a lot

faster so if time is an issue for you

and it is for most job shops you

basically want to be able to run as

quickly as you can and get that part out

the door as soon as possible but for

hobbyists the the only you know downside

is that you have to go a little bit

slower with high speed steel

aluminum even that is not too much of an

issue unless you've got one heck of a

machine in your garage but we'll talk

about that later also you've probably

seen a lot of coatings on tools so these

gold colored tools are titanium nitride

coated and it's it's always high speed

steel under here although I've heard of

carbide tools that are even coated now

and the coating is supposed to increase

the life of the of the cutter the idea

is that the titanium nitride coating is

harder than the high speed steel

material under it and when you're

cutting through something it actually

contacts the titanium nitride coating

however in my experience the coatings

are kind of a waste of time nowadays

there's probably five or six different

common coatings you can get titanium

carbo nitride titanium aluminum nitride

aluminum titanium nitride I don't know

and so there's tons and tons of coatings

but for cutting aluminum and plastics

you generally do not want a coating I

think Zarko Neum nitride is considered

okay for aluminum but you generally just

want a really sharp tool for soft things

like aluminum and plastic so if that's

mostly what you're going to be milling

high speed steel uncoated is perfectly

fine as you can see most of my tooling

is just high speed steel uncoated okay

so now we know to machine this pocket

feature we're going to use an uncoated

high speed steel tool and it's going to

be only as long as necessary and the

diameter is small enough to make these

features come out correctly I should add

that the high speed steel tooling is is

cheaper than the carbide which is of

course why you'd want to use it

otherwise if money is no object sure use

carbide but there's probably some

reasons why you wouldn't anyway a

carbide is more brittle so if your setup

is a little wobbly carbide tooling is

more likely to chip off but anyway

that's that's kind of another story so

we talked about that later so you've got

the cutter set that the cutter chosen

and set up like this now I get to figure

out how fast to spin this and how

quickly to push it through the work and

also how deep it should plunge into the

work for every pass

and those are sort of the main cutting

parameters that you'll be putting into a

cam a computer-aided manufacturing

software or if your programming is

manually in G code what you'd actually

be entering directly so since we have

the cutter material selected its

uncoated high speed steel and we have

the stock material chosen it's it's a

given in this equation it's just

aluminum 6061 we can figure out how fast

we want to spin the cutter in the mill

because the spindle speed depends only

on the material of the cutter and the

material of the work you'd want to vary

it a little bit depending if you're if

you're having like a vibration or a

clamping issue but generally it's just a

material property and the way that we

figure this out is actually empirically

and you can look it up on a speeds and

feeds chart the thing that actually

determines what this number is

is the amount of pressure developed

right at the cutting edge so if you know

imagine you're holding a knife and

you're going to push the knife through

metal the tip of the knife is the only

thing that's actually doing the cutting

the rest of the knife is there just to

support the edge and the edge is so

small I mean it's so fine that the

pressure and temperature right at that

cutting edge is extremely high I mean

it's it's high and worse than that you

can't really use coolant to cool it down

so everything that we're talking about

here is is not dependent on cool anger

or how much flood cooling or mist

cooling or whatever the cutting speed

the spindle speed is limited by the

material selection itself so if you take

a high speed cutter and you start going

too fast that's basically like pushing a

knife so hard through your material that

the edge is going to fall apart because

it's experiencing too much temperature

and pressure so one thing we can do is

use tungsten carbide tooling which is

actually a composite it's particles of

tungsten carbide bound together in a

matrix and very often the matrix is

cobalt metal so the tungsten carbide

particles are extremely hard but the

matrix cobalt is relatively softer so

there's all kinds of different

formulations you can have

different particle sizes of tungsten

carbide and different ratios of matrix

to particle and all that sort of stuff

and that's why some manufacturers are

better at making carbide tooling than

others in any case it's pretty

interesting to notice that the limiting

thing and all machining operations is

typically the material of the tool we

can always build a bigger milling

machine that's got a more powerful motor

but the limiting factor is the tool

itself it doesn't really pay to make a

machine more and more and more powerful

because they were actually limited sort

of by the the physics of the material

properties of the tooling so we've got

our high speed steel tool here and we

consult the Putsch art this is for high

speed steel in non ferrous materials so

aluminium and down here it says

aluminium alloys 6061 and then for high

speed steel it says 450 to 650 sfm that

surface feet per minute this is a pretty

horrible set of units here but I've

noticed even like shops that deal in

metric units still use sfm surface feet

per minute to describe cutting

parameters in any case what that means

is at between 450 and 650 is a good

range for high speed steel cutters for

that moving edge is going through the

aluminum at about 500 feet per minute so

since this is a rotating cutter what we

have to do is convert that surface feet

per minute which is a linear speed into

a rotational speed so the formula is rpm

equal surface feet per minute times 12

to get inches per minute divided by pi

times the tool diameter to get our p.m.

so we're dividing by the circumference

of the tool and then all comes out the

diameters in inches so for our example

here we've got a lot of times sometimes

machinists will approximate this by rpm

equals s FM times 4 over the tool

diameter since you PI is close to 3 and

the ranges that we're talking about are

pretty big I mean this isn't an exact

science the reason that all these

numbers are ranges is because your alloy

might be slightly different your tool

might be slightly dull

the moon might be in the wrong phase I

mean there's kind of a lot of different

things that that go into machining and

it's I'd say machining is about 80%

science and 20% art or maybe even less

and so there's a lot of things that go

into it that are not hard and fast so

this comes out to be five thousand

ninety five rpm which is actually beyond

the top speed of my milling machine so

we're going to say that the RPM is going

to be 3800 which is a good comfortable

speed for my machine it's okay to go

slower what this is telling you is the

maximum surface feed per minute we can

always turn the tool more slowly and

then adjust the other cutting parameters

to match but you can't go faster than

this without breaking down the edge of

the tool prematurely this is sort of a

speed limit on on how fast you can spin

the tool in that material if this were

plastic we could go much faster because

plastic it doesn't present the same

amount of cutting force that aluminum

does okay so now we know the cutter

diameter the material this thing the

speed next we get to figure out how fast

we actually want to push the cutter

through the material so we've got this

spinning cutter here and it's engaged

into the stock and we're going to push

it in a in a linear direction through

the material we go back to our chart

here and it says for a tool diameter of

3/8 of an inch if we're going to cut a

slot meaning that the cutter is

completely surrounded by the stock

material and we're going to be moving in

a straight line so generally if you're

going to be making a pocket there's

going to be some slotting going on

because you're starting off with a flat

surface and you've got to push the

cutter down into it and then start

moving there's more advanced tool paths

that sort of make this easier but for

standard for standard operations and for

doing this on a manual mill for sure

you're going to be slot cutting so this

says for a slot 3/8 inch tool diameter

in aluminum the chip load which is the

new term is 3.8

thousandths of an inch so put that down

the chip load describes how much

material is removed for every for every

tooth on the cutter as it's going

through the material so if this thing's

spinning and it's being pushed through

the material every time the cutter tooth

comes around cuts away some of the

material and this is you know three

point eight thousandths of an inch

that's how thick the chip is that's how

much this thing advances for every tooth

and that number is determined by the

tooling by the tool manufacturer I mean

in theory you could go super fat and you

can go incredibly fast but what limits

you is that the tool eventually breaks

so if you try to go too fast in the

linear direction sort of regardless of

how quick you're spinning the tool

eventually you'll put enough force on it

where it will snap off or it will just

dull you know one thing that might seem

a little counterintuitive is that you

actually shouldn't go slower than this

in the case of determining the RPM that

we want to spin the cutter that's kind

of a maximum and we can always go more

slowly if we want but in the case of the

chip load you generally don't want to go

too far below the manufacturers

recommendation and this is seems kind of

strange but what will happen is if

you're not taking a big enough chip like

if this cutter is moving along and

you're just sort of rubbing the surface

like you're not digging into it enough

to actually cut off a good chunk of

metal what will happen is the material

will try to burnish the edge so instead

of slicing off a piece the edge of the

material won't get cut it will actually

just kind of rub along the front surface

of the cutter and what that does is it

just it just dulls your cutter and you'd

be surprised how quickly you can dull a

cutter by not pushing it hard enough and

again it seems weird like if you're

having a vibration issue or the the work

isn't clamped down well enough your

instinct is to back off on the feed rate

which might help the vibration issue but

it will also cause a lot of premature

cutter wear so try to stick to this and

we'll talk about ways of reducing

vibration without

without wimping out on the chip load so

some modern cam software's can take the

chip load and just calculate all this

stuff automatically for you but I'll

show you how to do it for the old the

old-fashioned way if your cam software

won't okay and the formula is the feed

rate is the speed and RPM times the chip

load times the number of cutters or the

number of edges on your cutter so this

is a two flute end middle so it has two

cutting edges and we come up with twenty

eight point nine inches per minute I

should say when we were choosing cutters

how do you choose how many flutes you

have so for example this is a for flute

end mill and this is a two flute end

mill when you're cutting slots it's

generally a good idea to go with a two

flute and the reason is that all those

chips that you're creating down in the

slot have an easier time getting out if

you use a two flute cutter because

there's just less volume of cutters kind

of in the way the downside is that you

can't go as fast so you can see from

this formula just by adding another set

of of flutes to the cutter you can go

twice as fast and feed rate so the

trade-off is I mean it depends sort of

on your part geometry if you're doing

like a deep pocket and this is this is a

a relatively good aspect ratio pocket

you really want to have some chip

clearance to get those chips out as

we'll see you later also another thing

to be aware of is some cutters cannot go

straight down into material so this one

has cutting edges that go all the way to

the center and this one does as well but

some cutters like this one obviously you

can't plunge that down and to work

because there's nothing there's nothing

there in the middle so this this cutter

can't go straight down it actually has

to approach from the side either at an

angle or in a helix or maybe it doesn't

even cut in the middle at all okay so

we've got the cutter speed 3800 rpm we

plug that into this equation and we got

twenty eight point nine inches per

minute so these are the speeds and feeds

that you might have heard about these is

there to define your cut

the last number to figure out is how

deep to put the cutter down into the

material so this pocket is about a half

inch deep we could if we want to just go

all the way in into one in one pass and

cut it out the problem with that is that

the cutter might snap off so imagine in

the extreme I mean let's say you had a

cutter like this you really can't put

all that cutter down into material at

once and cut off because it would just

snap your cutter so a good rule of thumb

when you're doing a slot is to not

plunge more than half the diameter of

the cutter so in this case the cutter is

3/8 of an inch or 0.375 of an inch so it

would be good not to plunge more than

half of that per cut so what we'll do is

go in half or 3/16 of an inch and then

you know let the chips clear basically

and then drop another 3/16 until you get

down to the final depth now if we were

to just do that over and over again so

we start off at 3/16 deep do a cut

another 3/16 down do another cut and all

the way to the bottom what we'd have

with are a bunch of stair steps on the

wall of our of our cut there inevitably

what will happen is the cutter will have

some slight forces on it as it's you

know pushing through the material and

those slight forces will make something

deflect either the cutter itself is

going to deflect or the whole milling

machine is going to move a small amount

and our surface finish is not going to

be the greatest so what we do for almost

almost all machining operations you

would do roughing cuts first and then a

finishing cut to get a good finish and

to get ringgit to final dimension so

what we'll do is do these 3/16

stair-step cuts that purposefully cut

this a little bit undersized and then

we'll come back and put them into the

cutter all the way down to the bottom of

the of the feature and then cut it to

the final dimension and that last cut

will only involve removing maybe 5 or 10

thousandths of an inch of material all

the way around so it will be much less

cutting load on the cutter and they'll

be less deflection and you'll get a

better finish and a more accurate more

precise cut so a word

coolant and cutting fluids generally

some materials just work a whole lot

better with coolant than others so

aluminum definitely is a material that

benefits from having coolant either a

mist coolant or a flood coolant the

problem with cutting aluminum is that

it's just so soft and squishy that the

chips aren't very good at blowing away

and taking the heat with them instead

the chips will stick to your cutter or

stick to the work itself and transfer

all that heat back into the work and the

cutter and eventually you end up with

sort of a global heating situation this

is different from the the heating at the

cutting edge that causes us to choose

between high speed steel and carbide

this global heating issue is sort of a

macroscale thing in the end the cutting

edge is sort of a microscale problem if

you don't have coolant of any kind

pretty much your only option is to turn

down the cutting speed and then you have

to put the new rpm value back into the

feed equation and step that down as well

so that your chip load stays constant

and this will work pretty well you

actually can't just keep turning it down

until you catch up with whatever cooling

you have even an air-blast is better

than nothing at all another thing to

mention is the direction that we're

going to push the cutter if it's not

cutting a slot so let's say the cutter

this this represents the cutter like

this on the edge of a piece of material

if the cutter is spinning clockwise when

viewed from the top we have the option

of either making the cutter go this way

around the object or the other way so in

other words does the cutter drive into

its rotation or drive away from it when

it's driving into the rotation basically

it's trying to chop the stuff that's

coming toward it like this that's called

climb milling and when the cutter is

rotating like that and on older mills I

mean like you know very old the first

milling machines this generally wouldn't

work very well because there was so much

free play in the mechanics of the mill

that if you tried to push the cutter in

that direction the tooth would grab the

material and yank the carriage forward

on the mill and then I would you know

bumps the thing forward you'd end up

with

app here and as you keep turning the

crank to feed more material and it would

grab another chunk and chatter quite

badly so they would tend to go the other

direction which for a long time or still

is called conventional milling where the

cutter is going this way but the work is

going this way so in this case the chip

starts off small as its as the cutter is

going this way and it gets thicker as it

comes out the other side this is

conventional milling and this is climb

milling where the chip starts off thick

and becomes thin generally all modern

machine operations would use climb

milling because you get slightly better

surface finish and FreePlay on modern

machines really an issue because they

all use ball screws now here's a

question that comes up fairly often this

this chart is very helpful but it only

goes down to a tool diameter of a

quarter inch so what happens if you're

using like a tiny little end of null

like this how do you figure out what the

chip load is and everything a good rule

of thumb is to divide the diameter of

the cutter by 150 to get a conservative

chip load for the other side of this

project there isn't really an internal

feature so what should our cutter

diameter be now the answer is that you

should use the biggest diameter that you

comfortably can so you know generally

getting larger than 3/4 of an inch is

pretty uncommon for you know smallish

machines especially ones that you might

have in your garage a half-inch is a

good size at least for the kind of mill

that I have which is an old bridge board

artooie three and a half inch in this

case is enough to clean this off in one

shot so you know this this piece started

off as a rectangular prism and we can

come in here like this and basically in

one pass get rid of all the material

there you might have heard the phrase

high speed machining thrown around a bit

I think the phrase is a lot like web 2.0

or it means so many different things to

different people that it's it's almost

kind of meaningless at this point

there's a couple common threads though I

mean obviously high speed so you're

spinning the tool a lot faster than you

would in

conventional machining so for example if

you're using carbide tooling here's the

chart for solid carbide in non-ferrous

materials under sfm they say 800 to max

which basically means go as fast as your

machine can handle so if you're using

carbide tooling especially and your

machine has a top speed of 10,000 rpm go

for it

spin the thing as fast as you absolutely

can use lots of cooling and basically

just go for it people realize that

there's no reason to hold back

especially if the tooling is cheaper

than your time who cares if it you know

has 75 percent life if you're going you

know three hundred percent faster or

more another technique that's common in

high speed machining is if you did want

to clear away a lot of material if you

keep doing these small cuts like let's

say we were going to do this clearing

this away with with a tool like this we

could take a little step you know twenty

percent of the depth and cut around and

then another step twenty percent down

and cut around and all the way down to

the bottom the problem with that is

think about what happens to the cutter

you're repeatedly only using the bottom

10% of your cutter so as you're you know

using just that teeny little bit the

upper 90 or 80 percent of your cutter

cutter never actually sees metal at all

until the finishing cut so obviously

that's wasteful so high speed machining

says that you should use a very deep

plunge but don't go too far in in the

width veer cut so this doesn't really

apply to slotting because you don't

really have much choice but if you're

coming in from the outside you can

choose how far in from the outside of

the material you want how big of a bite

you want to take from the side so a high

speed machinist would tend to try to use

as much of the cutter depth as you can

and then just take as much off laterally

as your machine can handle and when I

say machine can handle I mean the

fixture mostly so if you have a very

rigid setup and your machine is powerful

enough you can really remove material

very quickly using this technique hence

the you know the high-speed other people

will say you know high speed machining

just refers to any spindle over 10000

rpm er or whatever but it means a lot of

different things so I guess I'll end by

saying that rigidity is really by far

the most important thing in any

machining operation

you know the coating of your bid or the

exact number of flutes or this two that

are all totally totally not important

compared to how rigid your setup is you

always want to use the shortest cutter

possible the largest diameter possible

and always have your work clamped as

securely as possible

anything that extends out from the bias

or makes it a longer path is going to be

damaging to you and if you're choosing

milling machines it's it's far

worthwhile to get the most rigid machine

you can even if it's I mean I would

almost say it'd be better to have a

rigid manual machine than a flimsy CNC

but I mean it kind of depends on what

sort of materials are cutting you might

think oh well if I'm cutting small

things then rigidity doesn't matter as

much but you might be wrong and the

reason is that if you're using tiny

little end mills like this if your

machine flexes a small amount the cutter

is going to break so you know if you're

using a quarter-inch cutter or bigger

you're going to have a little bit more

flexibility in terms of how much your

machine can flex already Hart but if

you're using this little guy you guys to

get no second chances so if you're

cutting even in aluminum or something

and your machine is wobbling a little

bit it will eventually ruin the cutter

okay well I hope that was at least

somewhat helpful I know it's kind of a

brain dump and maybe not the most

structured thing ever but let me know if

you guys have more questions about that

and maybe I'll do another more directed

lesson if there's one topic in

particular that seems useful okay see

you next time byeTop Search Keyword : online earning, , make money online, earn money online, online earning, online earning sites, make money online free, online money income, earn money online free, money online, best way to earn money online, online income site, money earning websites, best online earning sites, easiest way to earn money online, earn money payment bkash, online money income site