[scottgeorgeson]

Hi guys,
Well I can confirm that just having a go comes with a huge price tag.
I am about 5 cutters down and lost as to what to do next.. And yes I am new at this, but loving it.

I am trying to cut some letters out of 3mm corten steel.

I have a high speed spindle that stops when i set it below 5000 RPM ( First 2 bits..) Stopped spinning while gantry was moving SNAP!!

I am using a 6 mill plunge end mill 2 flute Cutting the full 3mm thickness in one pass.

I tried 12,000 rpm at 1mm - 5mm per second. Worked great for about 2 minutes, then bit glowed bright red, some sparks and it broke off welding itself to the steel. ( 2 More Bits Down. )

So any thoughts please anyone, other than yes I dont know what I am doing.

I have read that maybe I should be running faster up around 18,000 RPM with a feed rate of 20 -30 mm per second..

[pippin88]

What machine (photos please).

Full thickness may be rather ambitious. Routers are not really the correct tool.

You need to go and look up some surface speed numbers. 12,000 rpm at 60mm per min will definitely burn cutters.

[RCaffin]

Ah, the smell of glowing cutters on alloy steel ...

Sounds to me as though you are way, way off in feed and speed! So, first check
Cutting Speed and Feed Rate Calculations
for some idea of what Surface Speed you should be cutting at, and what sort of chip loading. You will have to do the calculations. They may not suit your spindle at all.

Very very rough guesses, subject to all sorts of corrections: a spin of 1500 RPM and a feed of 30 mm/min might be suitable, with with a coated 6 mm carbide cutter and an air blast for cooling and chip evacuation, and a depth of cut per pass of 0.5 mm. I could be out by a factor of 2 very easily. Full depth of 3 mm will invariably be far too exciting unitil you are a lot more experienced. Trying to use a cheap Chinese carbide cutter will probably not be great joy for more than 1 minute. (Many of them are not rated for steel at all.)

12krpm - whee! Good for friction welding maybe. 1-5 mm/second (60-300 mm/min) - probably snap the cutter off anyhow as far too fast.

If you have access to a lathe, try facing off a bit of the steel with a common carbide lathe tool - that will give you some idea of surface speed and chip load.

Cheers
Roger

[scottgeorgeson]

Thanks Guys
I have been reading about HSC High Speed Cutting - however that seems to suggest fast spindle and speeds are quite doable.. just not sure what I am missing..?

[RCaffin]

High Speed Machining ... yes, but.
You will need rather expensive cutters, a heavy (rigid) machine, and a very good idea of what surface cutting speed and chip loading will work. You will also need fair bit of spindle power. Finally, you will also need either high pressure coolant or a good air blast system with a matched pulsed misting.

Yes, you can drive a Ferrari at 300 kph down a race track (or an Italian autobahn), but you had better know what you are doing.

Cheers
Roger

[scottgeorgeson]

Hi Roger can you reccomend a good web page on HSC, I have read many, but they dont ever talk about type of cutter and cooling. I have a lube pump on my machine and a 24000 rpm spindle.. it certainly has no problem power wise. it is a big machine 1.5mtrs x 3 mtrs. with a water table.

[RCaffin]

> a good web page on HSC
Um - not off the top of my head. It is not really Home Shop stuff, although I imagine some have played with it.
You would need to search through mags like Modern Machine Shop & Machine Design, and then look for 'white papers' from some of the more $$ CNC vendors.
Chuckle - alternately, Google and YouTube might help.

> a big machine 1.5mtrs x 3 mtrs. with a water table.
The water table sounds like either a water jet machine or a laser machine? I can't think what else it could be, with a water table that size.
I gather however it has been modified with a spindle and a lube pump? Odd. Unless what you are calling the water table is actually the sump tray for the coolant system? It does sound like a router rather than a mill, but I have no idea what you have.

Thing is, without even seeing it, I would hazard a guess that at that size it is unlikely to be suitable for High Speed Machining. Unless of course it cost about $400k or more.

EDIT: actually, the water table might be of some use. In many HSM jobs the chips coming off are almost incandescent. I've made glowing chips, but not that bright!

Sorry
Cheers
Roger Caffin

[daniellyall]

you need to add more info on your machine picks, specks so on look up Carbide End Mills, Thread Mills, Thread Gages, Drills, Solid Carbide Thread Mills they have the type of info you need free

[victorofga]

glowing chips... seco , sandvik and other tool makers has videos showing chips almost melting.. BUT....
they made those videos not on a router..

on a conventional machine, you wouldn't use more than 1500 rpm with a carbide bit....

on cnc virtually you can use the 10000 even...

with hsm milling, you go down to depth, then pending on machine rigidity you can make very deep passes...

instead I would try suggest how you find your feed and speeds, and of course the proper tool, heres a couple of video,.. they show everything..

https://www.youtube.com/watch?v=OXnbnxb4iyw

https://www.youtube.com/watch?v=Z-_z...&nohtml5=False

https://www.youtube.com/watch?v=NZJC...&nohtml5=False

https://www.youtube.com/watch?v=jL5jpoP3QCg

[FastFarmer]

Thanks Guys
I have been reading about HSC High Speed Cutting - however that seems to suggest fast spindle and speeds are quite doable.. just not sure what I am missing..?

Guessing is just stupid. There are only two things that matter - Chip load per tooth for the required material and tool deflection.

Understand these two things and then calculate the maximum speed or feed (I always keep one fixed and vary the other) for your machine with consideration given its rigidity, accuracy, and power.

[Beefy]

Corten steel got its name from "corrosion" and "tensile", so it's supposed to be a higher tensile steel than your basic stuff.

The first thing that surprised me is when you said your spindle cuts out at less than 5000 rpm. I'd say you need less speed not more. There's a set of really crap chinese drills (up to 1 inch) I bought about 20 years ago. They don't stand up to much without chipping and blunting. What keeps them alive continuously is slower speed and plenty coolant (flooding the cutting area). But even better quality cutting tools have their limit.

If you are welding your bits at 12,000 rpm, my guess is you'll vapourise them at 18,000 rpm or have a great fireworks display. You could try flood cooling your bit and see if that will allow your bits to survive above 5000 rpm, but make sure they are truly flooded with no interruption to the submersion of the cutting part of the tool. Of course you'll need a recirculating cooling system set up to recapture the expensive coolant.

[hanermo]

Power is lacking.
Rigidity is very much lacking.
(For your settings, vs milling machine for HSM).

For high speed milling, on a 1.5x3 m table, its 12.000 kg, and 25-40 kW spindle power, on ISO50 tapers.

You CAN almost certainly do high speed milling.

You probably need a 3-4 mm cutter, about 2-3 flute not 6.
Single pass possibly ok 3 mm corten.
End mill for corten.
Maybe 8000 rpm or so.
Chip load approx 0.02 mm per tooth.
8000 rpm / 60 secs * 0.02 * 2 teeth == 5.2 mm / sec.

This is 1/3 of what you were trying (75% rpm x 50% flutes).
See hsmadvisor.

Hi Roger can you reccomend a good web page on HSC, I have read many, but they dont ever talk about type of cutter and cooling. I have a lube pump on my machine and a 24000 rpm spindle.. it certainly has no problem power wise. it is a big machine 1.5mtrs x 3 mtrs. with a water table.

[InMesh]

I have machined a lot of steel in my time but never at that speed I gotta take my hat of to you for effort .