[gpcoe]

We have 9 SS machines where I work. I'm curious how hard people are pushing these machines. We do mostly aluminum work with some stainless and the occasional small inconel or titanium job. On some of our aluminum jobs where we have a lot of 3D roughing we'll push them harder than some might think is acceptable but I'm not all that convinced it's inappropriate. In particular one job uses a 1/2 inch 3 flt roughing carbide tool 12000 rpm full slot at approximately .1 axial depth of cut at 600 ipm. Initial perimeter roughing is approximately .5 axial deep and .2 radial depth at 800 ipm. With fresh coolant there's no shrieking of the tool at any point. Certain points around the perimeter will reach 130% spindle load momentarily and during the rest at 600 ipm it typically doesn't exceed 50-60%. The machine sounds fairly smooth. The cut sounds typical of the tool at slower feedrates, but louder because of the high feed rate. In other words, nothing seems to be overworked including the axis loads.

To be fair, during the 600 ipm cycle it propably doesn't get up that fast because of the cornering, etc. However during the 800 ipm cycle I'm sure it achieves at least most of the speed there.

What are others doing with these machines? With a top feedrate of 833 ipm how many of you are pushing them this far? The spindle's designed to run at 12k rpm and that's where ours spend most of their time. What are your opinions/typical use of these machines. It should be noted that these are production machines in a job shop.

I ask this because the machine that is running this job currently, just went down last week because the spindle motor bearings sh*t the bed. Now some are up in arms suggesting that this job is the cause. We've had other motors fail in the exact same way including machines that never get pushed that hard. Seems to maybe be a typical failure for this motor. The spindle is perfectly fine, in fact the machine went down this past Friday and the motor was pulled, bearings replaced, reinstalled and the machine was back up running this morning. The axis are still accurate (the parts are good at least). I would expect to see spindle damage or axis damage from hard running like this before motor failure.

Thanks

Greg

[Talisman]

Well how old is the machine in question? How many cutting hours?

Being into racing, I have to rebuild my tranny and engine (1000 hp) every year, because I push them to the limit and get as much as I can out of them.

I look at our machine tools the same way. I've had spindles go out on machines that weren't really being pushed, and I've had them go out on machines that I'm pushing the limit on. I think its to be expected and its just part of the biz.

It comes down to dollars and cents. How much money is that machine making your now? If you back it down 20-50%, now how much is it making? And how does the couple grand to replace the spindle bearings compare to the machine's profitability?

[Pondo]

You are not pushing the mill too hard at all. You can run them at 100% spindle load continuously with no problems. You will snap the 1/2" mill long before you would damage the spindle.
We rough 4140PH and H-13 with a 2" button mill for long periods. I adjust the feed to hold the loadmeter to 90-110% during the vast majority of the cycle. (In a VF-4).
The high feedrate is not the hard part for the machine, it's the starting and stopping. It has nothing to do with the spindle though.
And it's freakin' aluminum - as long as it don't melt you'll be fine.

[gpcoe]

Thanks for the replies. There has been no spindle or axis damage to any of our machines as of yet as far as premature wear goes. The spindle motor bearings are what have failed for us on several machines. Since the motor is completely un-coupled from the actual cutting there's pretty much no chance of it being the result of cutting forces. The machines are all still very accurate as far as I'm concerned so I don't think there's anything going on. It's kind of annoying every time this job or any other high feed job is running, others think that it's beating on the machine. Of course when the machine goes down during those jobs it doesn't help this any. Typical comment "well it runs at 12k rpm all day what do you expect to happen". I expect haas to put a disclaimer saying that it can only run at 12k for so and so period of time if it can't handle running at that speed. Is it just me or is it hard for the majority to accept that these machines are designed to do this task? These aren't my machines and I don't even program them (yet), but every time I set one of these jobs up, I wait for the comments, "wow, that's running beating the snot out of it, huh?". "No, it's running like it should be. Just cause it's not a Mori-Seiki (our horizontals) doesn't mean it can't work hard."

Rant off

Greg

[gpcoe]

The machines are about 5 years old btw.

[HuFlungDung]

Rolling bearings have a finite life of some many revolutions, if they are loaded at the manufacturer's rated load. The faster you run 'em, the sooner they die. I don't suppose they put anything special for bearings in those motors, and I am not sure if these motors are running at 12,000 or is there an overdrive gear involved.

Anyways, I'd be thinking about trying some super precision bearings in the motor if you want to run them at that speed on a continuous basis. Most electric motor bearings are C3 clearance which is loose, but maybe Haas uses something better? A super precision bearing might run cooler because the controlled ball diameter will cause less skidding and more balls are likely to share the load. If you have to regularly rebuild the motors for this reason, it might be worth checking into and trying upgrading one as an experiment.

[Pondo]

If it's a 12K spindle it should run @12K all day IMHO.
I had a VF-3 W/15K spindle that ran 12-16 hours a day @15K cutting small slots in aluminum plates for 3 years solid (Automotive tranny plates)
I currently have a Minimill W/6K spindle that I run 95%+ of the time at 6K milling aluminum. It's just finishing up a 2.5 hour cycle now. Normally the cycles are 30-60 minutes and all tools except drills and taps are run @6K.
The only thing that needs to be watched when running @ top RPM for long periods in a Haas is that the coolant keeps flowing. To keep the aluminum from melting, yes, but also because it flows thru the head and cools the spindle. If the coolant runs low or the screen filter gets clogged, the spindle gets hot - there is no spindle chiller like on some machines.
I ran graphite for a while once when our Makino electrode mill was down and had to rig a hose around and back to the tank so we could keep the coolant on and not overheat the spindle. Same with running some plastics that just absorb coolant.

[cygnus x-1]

These aren't my machines and I don't even program them (yet), but every time I set one of these jobs up, I wait for the comments, "wow, that's running beating the snot out of it, huh?".

That's the wrong way to look at it. The machine is a tool used to make money, so the only thing that matters is return on investment. If you get a greater return by running Haas machines and having to replace the motor bearings every 6 months, than you would by running a Mori and never having to replace the bearings, then you go with Haas. The machine doesn't have feelings and doesn't care how hard it has to work. It will work until it wears out and that's that.

Load it up and let it rip.

C|