Steel mold for rubber

Hi guys

Yes, it’s steel :slight_smile:

The “secret” is to using wd40 as coolant, relative high rpm (18000-25000 depend on bit) and small feedrate (100/120/200 mm/min depend on bit)

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Do not try to milling steel without a lubricant (wd40 as i had used):

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Very cool! I think you’re the first to cut a mold on a MPCNC, certainly a metal one. So do you put some rubber in and clamp the crap out of it to fill it?


Chip evacuation is definitely important, the steel cutting I’ve done so far has been dry with air blast and worked OK but lube would help.

Not yet. The ring on the picture is example which i had used to design the mold.

For aluminium alloy dry milling works ok. But for steel without lubrication ball end bit became vibrate and steppers lost steps

Maybe the ball mill is a different story, I haven’t tried that. My tool got a little beat up but I had pretty good luck running dry with a 1/8" 2fl. If you could get all those little mounds of chips out of there I’m sure that would help! Nice work, in any case.

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I had used vacuum cleaner when milled aluminium. And the most actual problem is to make dust shoe.

For steel i think is better to use good flow of flood. But there is another problem - to build something on the table to collect liquid

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Look into mist/air blast, it’s the most practical/effective option we have unless you want to build on a waterproof base/have enclosure/electronics protection/etc…

I started with just a dust shoe on aluminum, works OK but you have to be really careful slotting/pocketing deep materials. I had to rake stuff out constantly when thru-pocketing 3/8". Air blast handles it easily.

Real flood coolant (enough to clear chips in slots/pockets) is just not worth it on a MPCNC IMO. What you have in that video is just little mounds of chips sitting in your cut, I’m sure a lot is getting re-cut. Mist will get you some cooling/lubrication and much much better chip evacuation.

What kind of tool are you using? Looks coated.


I already bought this thing when had collected parts for mpcnc,

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but i haven’t compressor yet. Good one like Metabo 1500W 220L/min 50L costs here about $180. May be i will buy it


And i agree that anyway for steel this jet must not be used in dry mode, but in mist mode mixing air flow with some lubricant. Surface of 3 short slots that i milled with dry tool looks terrible, and i think lifetime of the bit will be much shorter without lubrication

More steel! This is too cool. I hope it works for you, molds are tough.

silicone oil is best to take out rubber products from moulds.