How fast a spindle speed can you really use?

[leeputman]

Question for the experts,

If you had to justify the cost of a high speed spindle for a one time purchase,(let's say for the next 10 years) how fast would you want to go?

back ground:


I know, my lead sounds a little snobby but this is why: I am about to purchase a new VMC for the shop. This may be my only chance to get what I need. My shop supports a grad school environment. We do everything from put things a mile under the ice to flying parts into Jupiter. I need to be prepared for as much as possilbe. While we will always have the capability to send jobs out, I want to provide as much service to my employer as humanly possible.

Outside sources are encouraging me to move from my original TOOL ROOM type CNC mill to consideration of a fully automatic enclosed VMC.

Currently a Haas Super Mini Mill is under consideration. Seems like the most expensive upgrade is always the high speed spindle. My work requirements are as follows:

I primarily work in aluminum, either 6061 or 2024/ 2022. From a tooling stand point and working in 3D CAD/CAM how fast of a spindle speed will I really be able to use?

The shop has in the past made parts out of titanium and magnesium and copper.

You can see why I want to hear from the experts in cutting tool design. Opinions are great but I need justification for spending money. Using CAT40 tool holders and exotic cutting tools (no more then 3/4" I imagine), how fast of a spindle speed could I ever even use?

See, I never know what will come in the future. For the next 3 years I may be making parts where 4,000 rpm is fine. I may have some very small holes to drill in the time frame where I need the high speeds.

When a high profile job comes to me, and my abilities continue to improve (a serious goal of mine) it will be easy easy to buy a high tech tool $200-$500 cutting tool. But I cannot later decide to buy a 15,000 RPM spindle. Maybe this question is better suited for a tool and die maker.

How fast have you ever used?

Could you have worked around it?

If you think the highest speed possible is necessary, would you go with through tool cooling options?

Thanks a bunch, if you need to talk to me, a phone call would be welcome. Email me and I will give you the number.

Lee

[PinMan]

I do a lot of protype work as well as production. I design, setup, and run a lot of different applications on our VMCs.
I primarily work with all types of Stainless and Aluminum.
I haven't gone over 10k ever.

The only time I have seen machines go over 10k is in micro milling.

[leeputman]

Thank you , that is valuable information. It is what I am looking for.

[dertsap]

for cutting aluminum the sky is the limit , the higher end cutters large or small have geometries that are designed for high material removal rates at high speeds , the only thing that would cause any trouble would be a lack of coolant which could cause a meltdown if the tool isn't getting enough coolant or the chips aren't being properly removed , one thing to look into getting is high pressure through spindle coolant , this way you can use er or tg type collets and you can be assured that you have coolant always on the tool and the chips are being properly removed
time is money , you can run at 4000rpm comfortably slow or 15,000 and knock your cycle time by almost 75%

[ckirchen]

But I cannot later decide to buy a 15,000 RPM spindle.

You can always buy a CAT40 spindle speeder. They have electric, air, and gearbox versions. NSK (http://www.nskamericacorp.com/) makes electric and air versions and Big Kaiser (http://bigkaiser.com/images/tooling/profitg.jpg) make air and gearbox versions. There are more companies out there, but these are off the top of my head.

Personaly, I have gone to 35,000 rpm. It was with a Ø1/32 end mill in an aluminum mold; I was cutting deep ribs into the core insert. Without the spindle speed, the cutters still work fine, but you have to decrease the feedrate to match.

The maximum tool shank diameter on spindle speeders is typically Ø1/4", so if you need 15,000 rpm for a tool larger than that, get it with the machine.

Chris Kirchen

[PinMan]

time is money , you can run at 4000rpm comfortably slow or 15,000 and knock your cycle time by almost 75%

While I agree with this, this is a production frame of view. Which is perfectly fine. If you are knocking out 5,000 parts of something, then by all means, cycle time is extremely important. But, if you are like me and run usually 20-30 parts, the setup takes longer than the machining.

I guess it depends on what types of runs you are doing. You are looking for justification to spend the extra money for a spindle upgrade (which are usually $$$). For large runs where the cycle time is going to be a major factor, then the spondle upgrade might be worth it. In my opinion, the extra money for small runs arent justified.

[dertsap]

Pinman I was only responding Lee's question , to each his own if you can justify running at slower speeds then thats fine , I'm not going to try to convince you or anyone else otherwise .
but honestly with production or jobbing I feel it doesnt matter how many parts a guy is running why wait ? Lee is talking about cutting for aerospace and deep sea both which i am familiar with and I know that there can be enormous amounts of cutting happening on these types of parts and when 10 parts take hrs or days to run high speed in my opinion is a necessity

[CNC Viking]

Hi Lee,

For a real shop, I think that you should look for at least XYZ 800mm (or maybe even 1000mm if you are putting a 4:th axis at one end) x 400mm x 500mm, ATC, 4:th axis (or maybe even 5:th) if you see a future need. Starting with a 40 taper is a must for sturdiness! If such a machine is available with a 10 000 rpm spindle as "standard", I would consider that fairly OK and go for the other features instead.

my 2 cents...

/Peter

[underthetire]

3d milling requires a lot of RPM, and a machine than can handle it ( acceleration, deceleration, block processing speed etc.) Don't just assume because a high speed spindle is offered by a lower end company that it will net you the same results as a higher end machine. It might be ok for drilling and straight line machining though.

[beege]

I'd love to have 15,000+, but I'd have to consider the tools and balance. Over a certain speed, you'd have to consider a balancing rig, to minimize the vibration you're going to get I've never run over 10,000 myself, but I've heard/read about the balancing issue) Aluminum? As fast as you can get!

[Geof]

I'd love to have 15,000+, but I'd have to consider the tools and balance. Over a certain speed, you'd have to consider a balancing rig, to minimize the vibration you're going to get I've never run over 10,000 myself, but I've heard/read about the balancing issue) Aluminum? As fast as you can get!

This is a very important point, maybe the most important point. When you crunch the numbers for cutting aluminum with carbide it is easy to come up with speeds up around 20,000 rpm or higher. The faster the cutter goes the faster the part is made and if you are machining complex shape with CAM programs you want to go really really fast so you can take a small stepover and get a good finish.

There is a problem, however, once you go above 10,000 rpm balanced tooling becomes important, once you go above 15,000 rpm balanced tooling becomes essential; it is all related to that nasty little relationship between centrifugal force and omega squared.

So if you are going to be really careful and make sure you always balance your tools go for 15,000 rpm or higher, but remember that if you slip up sometime and stick an unbalanced tool in the spindle you are likely to need a new spindle. Sticking with 10,000 rpm is a good compromise, you can remove metal fast, get good finishes on aluminum and if you stick in an unbalanced tool the machines drones a lot so you know you have been sloppy, but you don't destroy the spindle bearings.

Maybe I am biased because I own so many of them but I think a Haas SuperMiniMill is a good choice. If you can squeeze the extra money get a VF2 with a 10k spindle they are much more rigid than the SuperMini.

[mc-motorsports]

I would check with your cutting tool manufacture. You know what tools your using, check the reccomended feeds and speeds, if they are 10K and under, I would get a 10K spindle. If they can reccomend up to 15K, go for it, but realize that high speed spindles are more expensive to repair, and don't last as long as a lower speed spindle.

A 6K steel bearing CAT-40 spindle will last A LOT longer and quite possibly survive a mistake or two (crash) vs. a 24K HSK63 spindle will require service within 6000 hours, expected to live between 2000 and 4000 hours for high speed milling use, but also won't accept more than a gentle "nudge" as far as making a mistake.

I've personally rebuilt 80K spindles, HSK-32 tooling. The company I worked for was developing a 100K spindle when I left a couple of years ago. I'm sure they are out by now, and I'm sure you need linear servo's to get the feed to accomodate the feed rates that those spindles can do.

One thing is for sure, a lot of small shops who buy "high speed" milling machines and don't really realize the trade off's that come with it, they SCREAM when they get the repair bills.

High speed spindles are mainly used by major production manufacturing companies and mold shops. With a high speed spindle, you don't want to do a lot of set-ups. You'll need to dry run every set-up and program to scan for possible mistakes, mistakes will become even more costly with the high speed ceramic bearings.

If your running major production days on end, especially in aluminum, YES! If your making molds, especially a mold for the trunk of a car or something along the lines of HUGE, YES! Job shops? Probably not. Short run? Nope. It could quite possibly end up costing you more money in the long run... But you can make a lot of money with the right jobs and a high speed machine too.