Re: [CAD_CAM_EDM_DRO] Re: Comments on this new CNC

John,

Thanks a lot for the info and I know you have a lot of experience with this
type of machine particularly the Super X3.

If you will excuse my ignorance, may I pick your mind and ask the following
questions:


A) Ball Screw

1) I have no experience whatsoever with Chinese made ball screw and nuts and
I really do not know how good they are. This particular mill's ball screw
indicates a C5 accuracy so it should mean it is a ground ball screw, is that
correct?

2) I know Taiwanese companies like Hiwin and Abba have a comparatively
better quality ball screw and should not be far behind Japanese, American,
or European companies. Have you any good experience with Chinese made ones
so far?


B) Spindle Motor/Drive combination

1) As you have said, with a speed range of 100 - 3500 rpm, the torque will
not be there for the lower rev.
2) Aside from going for a pulley/belt reduction or a dual belt pulley
arrangement, do you think there is any mod a DIYer can make?
3) Or, as you said, we should simple accept this as a fact of life for
DIYers that we can not have our cake and eat it too?
4) In other words, is it worth having such 100 - 3500 rpm range and live
with the prospect of taking tiny cuts?
5) Are there any small size CNC mill of the same size range that can do
better?

Kind regards,

WT

----- Original Message -----
From: John Stevenson
To: CAD_CAM_EDM_DRO@...
Sent: Saturday, March 31, 2007 5:13 PM
Subject: [CAD_CAM_EDM_DRO] Re: Comments on this new CNC

> Hi, all.
>
> I have recently received the following picture from a friend in China of a
> new
> Milling Machine about to be introduce in the market 2nd half of this year:
>
> http://i152.photobucket.com/albums/s172/CNCQuest/KX3-NU-Forum-2.jpg
>
> This is supposed to be a milling machine installed with 3-axis stepper
> motors,
> ball screws, variable speed spindle motor, limit/home switches, oil
> lubrication
> line/pump, and J7325/ISO50 milling chuck ready to be converted to a CNC
> milling
> machine with end-user provided CNC control system.
>
> The end-user will just have to install stepper drivers and
> hardware/software
> controller to turn this milling machine into a CNC milling machine.
>
> Can I have your comments whether this will be a good choice to turn it
> into a
> CNC milling machine?
>
> TIA!
>
> Regards,
>
> WT

Looks like a genericmachine that's produced over there but two things I'm
concerened about given I have seen some of the various machine siliar to
this and parts.
One is the ball screws, so far unless we are talking new suppiers their
cheap ballscrews leasve a lot to be desired.
I have seen some with more play than a decent acme screw, this may be
latering but it's hard to judge from a picture.

Secondly and more important is the motor / drive combination.
In an effort to cut costs this is single belt driven from a 1,000W motor
with a variable speed board, the earlier ones were DC, later ones 3 phase AC
and cheap invertor or VFD.
They give a speed range of 100 to 3,000 and it's not possible to get WORKING
speeds over this range.
What happens is you get no torque down the range where you need the torque
for large slow running cutters.
Sorry just a fact of life.
Only way to hget tourque at lower revs is to gear down by gears or belts to
increase torque or do like the big boys do fit 30 HP motors because they
know when throttled back they will have a
useable 10 HP for the cutter.

The Super X3 has this same drive on it and it's crap. It can't drive a large
cutter at the speeds the cutter requires so you either have to go faster and
burn the cutter out or take tiny cuts so as not to stall.

Unfortunatly this is were marketing and costing takes over from practical
experiance.

John S.