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From: i9577699 <i9577699@wsunix.wsu.edu>
Subject: Re: cyberlab cnc fiasco 
In-Reply-To: <D31n4E.Axy@armory.com> 
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Date: Sun, 29 Jan 1995 09:58:41 GMT
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On Fri, 27 Jan 1995, Richard Steven Walz wrote:

> In article <3g6lrn$cpv@synapse.bms.com>, David Allen  <Allen@bms.com> wrote:
> >ok, I give up.  I bought a tabletop cnc system from u.s. cyberlab because
> >it was cheap, and boy is it cheap.  after re-drilling over half the 
> >mounting holes in order to align the components and substituting my
> >own connectors because the supplied ones wouldn't, it's still giving me
> >problems.  may someone out there can help.
> >
> >the problem seems to be the mounting hole in one of the threaded 
> >shafts.  the system drives a mounting block, containing a nut, via a 
> >threaded shaft which is turned by a stepper motor.  the motor shaft 
> >is inserted into an axial hole in the threaded shaft and held in place 
> >with a set screw.  the motor is mounted on the face near the shaft 
> >with the opposite end floating free.  the mechanical connection 
> >and alignment between the motor and drive shafts is solid, which may 
> >be causing the problem.  when driving the platform and it's in the 
> >middle of the threaded rod, the free end of the motor wobbles, the 
> >platform raises and lowers about 1/16", and the drive noise from 
> >the motor seems to vary in direct relation to the rotary position 
> >of the threaded shaft.  at either end of travel, the motor occasionally
> >binds and loses position.  it's almost like the hole in the threaded rod
> >was drilled non-parallel to the axis and the system is trying to 
> >torque the block around (like I feel I've been).  
> >
> >aside from having the drive rods re-milled (which would double the cost
> >of the system) is there a good way to connect the shafts to permit some 
> >sort of axial compliance.  I've thought about a universal joint of some
> >type but can't find one the right size in either Berg or Small Parts.
> >any suggestions?
> >da
> ---------------------------------------------
> We got screwed over by them too! Same symptoms and flaws. You WILL have to
> have your ACME screws rebored and decent couplings mated for them to the
> steppers. The steppers are fairly good, but the rest of the construction
> sucks! It's aluminum, when it NEEDS to be steel! And the guide rods are NOT
> the nice super hardened rods but stinking low temper drill rod polished!
> You'll have to replace THAT too! Throw away the box aluminum members and
> have aluminum I-beam replace it as well, and bolt it down good! And you'll
> have to have steel end assemblies machined as well. And the polmer-fiber
> blocks that ride the threads is a joke. I recommend replacing it with any
> other ACME rod nut assembly instead. Good luck, you'll need it! And people,
> QUIT buying US Cyberlabs' CRAP! They DON'T know what they are doing at ALL!
> -Steve Walz   rstevew@armory.com
> 
> 
> 
I couldn't agree with you more, this stuff, isn't worth the money to blow 
it up, but a quick note from personal experience, if you are going to 
spend the time to re-work the whole thing, leave one end of the acme 
shaft free floating, if you plan to machine hardend stuff, it will save 
hours of headaches.

	-ken

