max RPM

[wtf ? really ?]

I have been machining for about 12 yrs. i currently set up and program YCM and HAAS mills. The shop i work at curently does a lot of small work( using 1/32 em's in a2) and aluminum cutting. I was recently told not to program the machines to the max RPM (YCM is 10k and HAAS is 12k) due to spindle wear. Has anyone EVER heard of this being a problem? i was under the impression that these machines were capable of running all day at these rpms.

[fizzissist]

Belts wear out disproportionately faster, as do bearings as spindle speed increases towards the max.

Don't know what the actual numbers are, but I know a 15,000rpm spindle will last a lot longer run at 12,000rpm than at the full 15. Even longer at 10,000.

The belt on our 10,000rpm mill is almost 8yrs old, and looks new. I usually keep it down to 8000, but mostly run at 5000 and lower. Service guys tell me that machines run at max will go through belts in 6-8 months.

A friend of mine reports that by dialing his machines back to 80% of max spindle speed is rebuilding his spindles less frequently, such that the loss in productivity is more than offset by the decrease in machine downtime and spindle costs. Again, numbers, I don't have 'em.

If you've got a big enough operation to justify keeping a spare spindle cartridge on hand, that'll at least soften the downtime issue.

[gpcoe]

In theory if your chip load is constant you should have similar wear regardless of RPM. It'll take longer to wear out, but the job will be on your table longer too. This doesn't fully account for heat differences but if you're holding back to 10k rpm from 12k There probably isn't much difference as long as the coolant is circulating. If your haas has a 12k spindle it probably means it's a direct drive unit and therefore has no belts other than the encoder. Can't comment on the YCM other than to say belts are cheap if that's what you're worried about. Call the manufacturer and see what they say about it. Maybe the people you work for are being overly conservative. Keep in mind to, that if you're using 1/32 EM's at 12k your surface footage is around 90-100 which may or may not be optimal for what you're doing as it is. The place I work at we have a lot of VF-ss machines and they run all day at 12k on endmills up to and over 1/2 inch, unless we're working with stainless or something. The biggest problem we've had is the motor bearings. The spindles themselves have been fine. The bearings cost around $40 a piece for a top and bottom, but we have our own maintenance team that tackles them so maintenance cost is minimal. Downtime is around a day and a half. But we're production so cycle time is kinda critical. I'd say run 'em all the way up as long as spindle load isn't always at 100% you'll be fine. But they're not your machines so really it's up to them what they're comfortable with.

Greg

[wtf ? really ?]

neither of the machines r belt driven. i also realize that i cannot acheive optimum sfm even at 12K. But it stands to reason that closer is better. I understand that the machines r not mine, but im trying to do my job in an effective manner ant increace production and profits NOT decrease.

[gpcoe]

I guess just try to remember who's profits they really are. It's not you keeping them down. If they won't listen to reason then they're the ones missing out. I didn't really catch what kind of work you're doing. Is this production, prototyping? That could play a big role with their decision. To me, if it's capable of 12k it better be capable of it all the time or the manufacturer should be very explicative of the limits at such speed. Most of the ratings I've seen are say 15-30 min at 100% load and say 5-10 min at 150-200%.

[wtf ? really ?]

it is mainly short production runs and prototyping. I rarley am over 50% on the load meter for longer than 1 min at a time. most of it barley reads cause it is such small work. not micro-machining but close. microchip testing equipt. mainly

[Donkey Hotey]

Well, it seems to me that if you guys are doing that much work with small endmills in aluminum, that you should probably consider a CAT40 air spindle for the small cutter(s). They're relatively inexpensive and with the air coupling, they still work with the tool changer.

[Pondo]

I've had my Minimill for over 3 years and I have run it @6K max rpm on every part I've made. I cut aluminum and do engraving with 1/32 BNEM's and smaller tips, but I run @6K for all tools up to 1/2".
I've cut graphite on a VF-3 for 3 months while our Makino was down. 7500 max rpm 16-20 hours a day for just over 3 months straight with no problems.
You do need to keep the coolant flowing thru the head though, that's what cools the spindle.
We use HSM techniques - high speed, high chipload, low DOC - and our machines last and run accurately. In our other plant they run high DOC, more standard techniques and their mills are focked. They push to the load meter but run low RPM compared to us. We do molds, they do castings and contract machining. To me, if I had to choose between high spindle speed or high spindle load, I'd say high speed does no harm comparatively.

[daleman]

we have 3 haas super mini mills and they tend to run between 8,000 and 10,000 revs all day long never had a problem with spindle wear yet they are all 3 to 4 yrs old .
and machine small to med size alu components for the electronics industry all day long that would be 10hrs a day 5 days a week.

[Cmailco]

By the time you machine all your parts at 20% reduced capacity (for those tools that need it) vs replacing an item that should be replaced every 5 years (spindle bearings) under normal wear conditions, you could have bought 10 sets of bearings. Not to mention, the machine wear and maintenance is deductible. I fail to see any logic in this argument, though it seems to be a popular one.

Machine bearing life due to 20% more rpm is negligible in the scheme of things. It costs MORE not to use the full capacity of the machine. The enemy of spindle bearings is vibration and chatter, not rpm.