Re: Stepper for Homier (mini-mill) and other questions

Wow, you newbies put a LOT in one post.


For the Mini-mill, I would see how others have done it. It's not
high precision out of the box, but precision is what you add as you
modify.

The mini-mill has a design that makes the head somewhat less rigid
than most other styles. The upright can flex under heavy loads in
the Y movement and can possibly move under heavy X axis movement.

Also, I think this machine is under the bar for ball screws.
(Comments welcome) The reason is that on big mills, the tradeoff is
a large motor overcomming the effency loss of the leadscrew as well
as keeping the price low for the stepper and the fact that stepppers
have a ceiling in power.

The big thing is anti-backlash to eleminate any marks in the part
when cutting and associated errors. You should be able to remove the
backlash on the ACME screws. And if the screws are accurate over
the length, accuracy would not be improved.

- - -
If you sell TurboCAD/CAM then you already have a software package.

and you are correct, the parallel port control is a replacement for
dedicated add-in controller cards like Allen Bradley.

The benefit is ultra low cost, the down side is that the limit is 8
axis for most programs.

So the G-code controls the stepper controller (Gecko?) and that
contorls the stepper. you need to add a power supply and some limit
switches. all pretty simple.

Dave

--- In CAD_CAM_EDM_DRO@y..., "Andrew Werby" <drewid@a...> wrote:
> Message: 18
> Date: Mon, 14 Oct 2002 15:11:03 -0400
> From: "Terry D Palmer" <tdp_130@b...>
> Subject: Stepper for Homier and other questions
>
> I have recently joined this group, and have been following the
discussions
> and have a couple of questions that I'm sure this group can answer.
>
> I'm thinking of trying to automate a Homier mini-mill. I am
wondering what
> is the "standard" stepper used to automate this mill and what might
be a
> good source for those motors ? I've seen the dicussion on feed
rates, etc,
> but assume that there are probably several Homiers already
automated.
>
> Also, what is typically done for the Z axis feed ? I have seen
some mods
> with an acme screw.
>
> Is it necessary or wise to go to ball feeds on the X and Y axis
(and Z) ?
>
> [It may not be absolutely necessary, but it will save a lot of
problems.]
>
> I think my approach is to assemble the modules rather than buy a
> pre-packaged kit. I have been looking at the Gecko drives. I am
just
> starting to look at ths software, Turbocnc, Dolphin, Vector, etc,
etc. One
> feature that I think would be nice is to be able to work from
AutoCad
> drawings. Certainly the price for Turbocnc ( $20 ?) would make it
easy to
> get started.
>
> [There's TurboCNC ($20 controller shareware) and TurboCADCAM (an
entirely
> unrelated drawing and 2.5d G-code package which I sell for $450). I
mention
> it because the rest of the items on your list are CAD or CADCAM
programs.
> Other control programs, beside TurboCNC, are CNC Pro, Master5,
DeskWin and
> EMC. These just tell the computer how to execute G-code programs,
but don't
> let you produce drawings or models (like a CAD program) or G-code
(like a
> CAM program).]
>
> I'm not sure if I have the whole picture. One of the above software
> packages runs on the PC that outputs (parallel port ?) to the 3
Gecko's that
> drive the steppers.
>
> [Right- one of the control programs like TurboCNC. These replace the
> proprietary controls and built-in computers (think Centroid,
AllenBradley,
> DeltaTau, Fadal) that used to be the only way to run machine
tools. ]
>
> A power supply runs the Gecko / Steppers. Is that all, or am I
missing
> something ?
>
> Terry
> Northwest PA
>
> [There's a lot more assorted stuff you'll need to put a control box
> together, but that's essentially the way it works. Depending on the
step and
> direction signals they get from the PC and the control system that's
> running, the Geckos send power to the motors in a series of
pulses, each
> equivalent to some portion of a step, depending on how your system's
> configured. At least that's how I understand it- and I'm sure there
will be
> someone to step in if I've got it wrong...]
>
> Andrew Werby
> www.computersculpture.com