High feed milling question
I have been watching videos on companies touting their high feed indexable end mills. They cut at blazing fast speeds and the chips come out blue. After all that, I started wondering how long the inserts could last being used like that?
I remember when I stopped using the bottom 20% of my solid end mills and started using as much of the side as possible which really increased my tool life. It would seem in the case of this high feed milling strategy, the end mills only take up to a .040 DOC with as much as a 100% width and then they take a huge chip load to get back the metal removal rate.
Unless there is something special about the inserts used or the geometry, I don't see how it would be practical to run a mill with its cutters like that. Perhaps I can see it being done for slotting or something like that. The only other thing I could see being a possible advantage is a supposed change in loading vectors where the tool deflection is split into a couple of components and some of that gets translated up the shaft of the cutter to reduce chatter with a tool that has long stick out for deep pockets or something.
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Re: High feed milling question
I think it depends on the machine, tool holder, the material, and the cutter geometry. The big tooling manufacturers spend a lot of resources developing the geometry and insert chemistry for various applications. But unless you have a high HP and very rigid machine, you really can't take advantage of the full capability of most modern cutters. The HSM tool paths help maximize the MRR for a given cutter.
Jim Dawson
Sandy, Oregon, USA
Re: High feed milling question
Hi,
I have often looked on in amazment at those videos too.
A friend of mine has a major shareholding in a company that specialies in tool manufacture with CNC machines. I visited the factory
and he had his long-time foreman/workshop manager show me around.
I posed the same question to him when I was watching a CNC lathe peeling off blue swarf like it was going out of fashion.
He described it this way: the design of the insert is such that when the chip leaves the workpiece it takes the majority of the heat with it.
Second point is that yes you could make the same insert last much longer by a less aggressive toolpath, but the it would take longer.
His concern is not how to make the tool last as much as it is to make the machine (and operator) as profitable as possible, and that means
agressive toolpaths run flat-stick.
He has a guy doing nothing else but fitting new inserts to the various toolholders and measuring tool-offsets. An operator might rock up to this guy
with a worn or broken shell-mill say and he would be handed a new mill, ready with fresh inserts and the numeric tool offset data is transmitted
over a data link direct to the machine for which it was going to be used. Fantastic!
The little room in which this guy worked had one complete wall, like a book shelf that held tens if not hundreds of thousands of inserts.
As he said, he pays 30 operators at something like $6000 a day, why would he not spend $100-$200-$300 a day or whatever to keep these
operators machines working as fast and as profitably as possible?
It all made sense as he explained it to me.....but I stil find it hard to put myself in that mindset. I use 0.5mm endmills for making circuit
boards, made by Tycom Kyocera, and they work out to about $4.50USD each including shipping. I usually get 8-10 hours cutting from them before
the cut quality degrades. The main reason I use them in the first place is the cut quality, it superior to an engraving tool. If I let the tool run too long
the advantage for which I paid does not materialize. Yet I still have to force myself to replace the tool before the cut degradation takes place!
It is exactly that mindset that I lack.....that is consider a tool to be a consumable item.
Craig
Re: High feed milling question
Hi Jake and others - MMR is huge these days and we are at "peak hogging" to borrow a phrase. Large companies are swinging towards printing now so CNC machines will become finishing machines vs roughing and finishing machines. The rough part will be printed then transferred to a cnc or some companies now have printers/mills in one so its printed and milled along the way, then finished in the same machine. I was looking at some printed titanium 6-4 specs the other day and they were better then the wrought specs... Steel and many steel alloys are now available for 3D printing as well. Peter
Re: High feed milling question
HiOriginally Posted by peteeng
The key to using High Feed Mills are the usual suspects - Rigidity of the machine, the size of the cutter (we usually use around a 2 1/2" diameter), step over (approx 1 1/2" with 2 1/2"), speed & feed and turning down engagement velocity to 50% and to cut dry. We machine 304 & 316 stainless & our inserts will last around 2-3 hours per edge with a 0.40" depth of cut at 400 R.P.M. at a feed of 0.070 - 0.080" per tooth.
Good luck if you go down this road for weight removal, it's worthwhile spending the time.
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