MiniMill purchase?

[scbeer]

I'm looking at buying a standard MiniMill. I've read the posts here and the only recurring problem seems to be spindle drive belt tension. Is there any other gremlins that I should be aware of?
I will mostly be cutting aluminum(6061) with 3/8" hihelix end mills. I do plan to run a 3" indexable insert shellmill for light skin cuts.
I also plan on buying a three phase mill and use a phase converter to run it on single phase(home) power. Is there a major down side to this?
I belive the 3 phase would draw less power(ie. less electrical expense), although there is a loss in power going to the machine thru the converter?
My day job is programing/running 40 and 50 tapper mills and I know I'll have to get use to the low horse power in a minimill compared to the larger machines I usually run, but is what I'm planning to do the way to go?
I've never run a Haas before but have never heard anthing bad about them.

[Geof]

The standard MiniMill can be operated from 240V single phase 40 amp so if you are getting this you do not need a phase converter. The spindle is limited to 7.5 hp maximum on single phase. I am not sure how prevalent the drive belt problem is; I have two standard MiniMills and three Super MiniMills ranging from 2001 to 2004 and have so far not had any belt problems.

One thing you might want to consider is the raised Z axis option. This lifts the Z axis 4 inches but does not change the Z travel. The standard MiniMill has the Z travel too close to the table and as soon as you put a vise on you have lost 2 or 3 inches.

[Ken_Shea]

scbeer,
For the money it seems the Haas is a very solid choice, great controllers, most are very happy with them. I was thinking the Mini-Mill was a direct Drive so there may not be any belts, but I do not know for sure.

Do yourself a favor and get a Rotary Phase converter, or you can build one quite easily, I tried the static type, even purchased hi-quality units but they do not compare to a commercial rotary phase converter, or even the home brew type.

EDIT:
Geof is correct, if the converter is for the MiniMill you will not need it, the Haas run great off 240V single phase, at least the TM and Mini series, not sure on the larger units..

Ken

[Geof]

Ken; The MiniMills are belt drive. I think some Haas catalogues describe them as direct drive but what they mean is no gearbox; or at least that is my interpretation.

[Ken_Shea]

They are two speed arn't they Geof?

[mikeh78]

i have a minimill with single phase set-up. this machine is great. I have been taking .100 deep cut with 1/2 inch endmill over 1/2 the cutter diameter with less than 25% spindle load. It has pleanty of horse power for what I throw at it. I do not believe you will be disappointed with this machine.

[Geof]

Originally Posted by Ken_Shea They are two speed arn't they Geof?

I am not quite sure what you mean Ken. The useful speed range for a MiniMill is around 300 rpm to 6000 rpm with a variable frequency drive; Haas call it a vector drive. Below 300rpm it is easy to stall the spindle.

[Ken_Shea]

Geof, That was a bit confusing, I was meaning is do they have a high and low range?
From your post I am presuming they do not.

Being able to Stall it easily below 300RPM does not sound typical.

They have the same motor / vector drive as the TM series as I understand it and they do not stall easily, do you think it might be due to the higher RPM and the required gear ratio to obtain it?

[Geof]

I do confusing really well; both myself and other people. I should clarify the stalling; we use a 1/8" wide by 4" diameter slitting saw to cut a deep groove on a part we make and have stalled the spindle with these. I guess easy was a bit misleading.

[scbeer]

Thanks for all the feedback. I have a couple of more questions.

1)If the minimill and the Tool Room mill use the same same servos and spindle why does the minimill have a better positioning and repeatability rating?
I've just seen the new TM-1P and really like the larger work envelope compared to the minimill. With the enclosure and 6000rpm spindle speed it looks like a better deal(for me anyway). I can live with the slower rapid rates.

2)I'm planning on operating which ever mill I get at home. While single phase would be a no brainer, I've always been under the assumption that running a 3 phase machine with a phase converter would result in a lower electrical bill. Anyone runing a mini or TM at home? What kind of an increase do you see in your electrical bill?

Once again thanks to all of you for the help.

[timlkallam]

Hello Scbeer i was looking also for a cnc mini mill last july Something that would fit throught my basement door and operate under a 97 inch ceiling height .I also looked at the hass mini mill. I didn't like the hass because it had such small travels
after you mount a vise you have very little z space. And I never
could get an exact answer about the horsepower and it only weights 3500 lbs.But what really turned me away from hass is they charge you a fortune for evey option ridged tap ,coolant pump, memory ,spindle orintation, A plexiglass top costs $400
its crazy.
So I looked at the sharp mini mill it weighted much more than the hass 5500 lbs. It has ALOT more travel , It comes with ALL Fanuc motors and drives, box ways .And best of all it comes with All options included in the price .ridged tap ,coolant pump, ,spindle orintation, and more . What i liked best was the sales man said he would have rigers but it in my shop and have the tec come out and give me a day of training with it for $35000 and pay him when i am satisfied. Here are some pics.

[scbeer]

Wow, thanks Tim. I did not know about the sharp minimill, I'll give then a look. Since I already run a variety of FANUC controllers at my day job it would be less of a learning curve.
Are you running the mill on single phase power?