Iron machining - What kind of Iron / settings / endmills?


(RaXor) #1

Hey,

Has anyone ever tried machining Cast iron with the Nomad ?
If yes, what kind of settings ? And what kind of Iron ?

I believe it’ll be pretty much the same as steel, so rather take it slow, and do you need coolant or oil ?

Reason that I would do iron instead of steel or aluminium is the price.

I’m very new to the CNC world and even mechanics in general, so any advise is really usefull when it comes to Iron machining!

Thanks!


#2

Not tried it, but I don’t think that you will have much success here. Just not enough torque. Additionally, most CI is MESSY. And the dust eats machinery.

If you try it, no liquid coolants. They increase the mess and form a slurry that eats tooling. Makes a decent lapping paste, though. On the lathe, shaper, and full size mill, I use a suction line at the work point to get the dust, and only when needed, an air nozzle for cooling. For the purposes of edged tool machining, CI is brittle and self lubricating.

Even with HEPA dust collection and a mask, you will probably have black snot for days.


(William Adams) #3

Rather than cast iron, most folks just use mild steel where cast iron would have been used in the past — is there a reason mild steel is not an option here? We do have feeds and speeds for some steel alloys — so long as you select one with good machining characteristics it should be workable, albeit slow, with low material removal rate and tooling engagement.


(RaXor) #4

Well, I’m still considering with which materials I want to go for a simple custom made object in series.

The material shouldn’t bend or warp below 300°C for a short time, aluminum seemed to be the best, but the price of the material makes it less interesting. Iron Cast seemed the cheapest option, I wasn’t aware about mild steel, I’ll take a look thanks!

Oh, also isn’t mild steel usually coated with some toxic chemicals ? The material should be safe and not emit smoke or be hazardous when heated at 280-300°C for short amount of time. Apart from that I don’t have any other precise requirements.


#5

A little more information about what you are making might help.

Low carbon steel with minimal alloy elements is referred to as mild steel. It refers to the common grades used for structural and manufacturing purposes when no special properties are needed. In the US and Canada, this is sold as hot rolled structural shapes, plate, and bar, often to the A36 spec, which is loose on the alloy but specific about mechanical properties such as tensile strength. Hot roll has the black scale coating. It comes of with a wire wheel or a grinder, and machines off.

There is also cold rolled, such as 1010 and 1018, where the designation refers to a particular alloy (in these cases, iron with 0.10% and iron with 0.18% carbon by mass, respectively, and very low limits on all other elements). This is seen as rounds and square/rectangular bars. It is usually coated with an oil film left over from the rolling process, and the film helps prevent the stock from rusting. I cleans off with solvent.

These steels machine ok and, in the US, are less expensive than any other metal. Cast iron stock is not cheap and not real available.

AVOID any steel material listed as free machining or ‘easy to machine’ if you are concerned about toxic materials. These will contain either lead or high sulfur, or both, to improve machinability. Second hand materials-- old shaft stock, for example-- is often leaded. In the US, the leaded grades often, but don’t always, have an ‘L’ in the designation, such as 12L15 (a common free machining steel, with a dash of manganese for strength. Pure joy in the lathe, when it can be used)

Clean steel should not smoke. Coatings on it will.

At 300C, many aluminum grades will have degraded properties. Some ‘red’ and ‘yellow’ metals (bronzes, brasses, other copper based alloys) may have better properties in that temp range, and many machine well, but there are toxicity issues both in food contact and at elevated temperature (some contain lead and copper oxides are real bad news, which is why copper cookware MUST be coated with tin, and recoated if the coating is damaged)


(RaXor) #6

I can tell that the product woudn’t be heated at more than 280°C.
The heating woudn’t occur for more than a few minutes, and it would always be cooled off before another heating occurs.

Oh cool, interesting informations, thanks.

Last, I’m not sure what you mean by degrated properties, but as long as it doesn’t bend, warp, break and generate toxicity issues, aluminum looks good for the usage, could you confirm it could withstand for the usage I described above ?


(mikep) #7

The only coatings you should find on mild steel (assuming it’s new material) is oil/grease, and the dirt it collects. Strip it off with acetone/degreaser.

You may be thinking of galvanized steel, which is zinc coated - the zinc protects it from corrosion. There are important safety issues with welding/machining this, but galvanized material can just be avoided most of the time.


(Chris) #8

Any mild steel with a very low carbon or nickle content will cut. Very painful and slow. Around .005 steep and bellow 2-3ipm speed with a 2 flute .125 cutter. HSS is your best bet just start very slow. If the carbide cutter gets chatty it will break. If you loose speed on the spindle the machine will stop. It’s a major pain. But it’s all just math.
If cost is an issue look at brass or bronze even copper. They cut like butter on the nomad.
For alu I run a low volume mist coolant system. Put a pan under your table on the bottom of the machine. You will need to clean a lot more and an air compressor is a must. You can find low volume mister coolant systems on Amazon cheep. I’ve engraved on mild steel and ss with a 70° v cutter witch came out good. You just have to give it a trial and error. In my case more error than trial.
Hope that helps.


(Phil Gorsuch) #9

If you do give cast iron a go please let us all know how it turns out! Inquiring minds all!

Anecdotally if you are working on the actual cast part where it touches the mold I have read that its best to remove this outer skin part first (using an angle grinder or such) as there can be bits of casting mold or sand in the skin which can be very hard on tooling.

Best of luck!


#10

Definitely remove the ‘skin’ on cast iron. I didn’t even think to mention this. Even the continuous cast stock has a hard skin, but not as bad as mold cast. That skin eats tooling, but is brittle, so getting underneath it lifts it right off. The Nomad doesn’t have the power to do that, so, if trying I, do be sure to take off the surface first. By hand with a file (hard on files), or with a grinder.


(RaXor) #11

I thought about the cooling system, but I’m inside an appartment and I can’t make too much noise, well, it’s well isolated here but even for myself having an air compressor is difficult.

I was taking a look at the air compressor that the airbrush guys uses and the quietest one are rated at 40db, I think that would do it really.

However, about the mist cooling system, I’m unsure if it’s safe to run it inside an appartment, the air vent isn’t that great. What do you think about that ?

For the other, sorry I don’t plan on trying cast iron, I’m inside an appartment so I’ll avoid any hazardous materials.


(Chris) #12

The mist system will remove 95% of any gases and cool the cutter and lessen chip welding. That’s why most of the newer high end mills are using it. But it dose make a mess. Worst material to cut for your health is Alu and carbide. Minus BC you should never cut that on a mill. I ran edm wire and sinkers for years and the stuff that the filters pulled out of both metals were deadly.

If you are worried about gases get a nidec blower fan and a tube with a window kit for a air conditioner exhaust kit. 30/50$ Hole saw the side for the intake and duct it out the window. 12v wall plug. Can’t be any worse than 3d printers. As a point of reference. If you are creating gasses while cutting. You need to look at your chip rate vs bite vs cutting speed in your settings for the endmill.

If you run fusion 360 you can calculate how much material is bit off per flute to rotation. Never exceed 50% of the flute depth. Or you well be RE-cutting your own tailing. Aka a crappy cut. The mist helps flushing and will allow you to cut faster.

With the nomad you are handy capped and have to give up feed speed for a stable cut. But ripping on the other hand is all a balance of spindle speed vs feed rate and how much face aka depth, the torq the machine can handle. And how much you can flush. Air works with lite material but fluid works better with heavy. It’s all a balance.


(RaXor) #13

I guess all kind of milling is pretty bad for the health, it all comes to having the right equipments to makes it as safe as possible.

I got mixed up with the mist cooling system, I thought at first it was something just refreshing the air sent by the air compressor, but yeah those liquid coolant system makes a real mess, I woudn’t run it inside the nomad without a proper enclosure.

Dry milling will be the way to go, feed isn’t really a priority anyway.