Re: Digest Number 12

"Dan Mauch" <dmauch@...> wrote:

The big problem with maxnc is the max size of the tool path file is limited
to ~250K bytes and the limitations in the config file for backlash.

[The filesize limitation hasn't been true of MaxNC's software for over a
year. Their newer software (MaxL) supports unlimited file sizes, as well
as 4 axes. If you have an older version, you should get the upgrade. Newer
versions of the mill (the MaxNC 15, for instance) include "zero-backlash"
screws as standard hardware; they are available as options for the less
expensive models. Are you saying there's no backlash compensation in the
software? ]

Andrew Werby

Tom Kulaga <tkulaga@...> wrote:

>Subject: Re: Digitizing arm - CMM
>
>James P Crombie wrote:

>>I am a machinist with lots of available machines to work with and
>>own a copy of Rhinocad. Aside from the mechanical part of the
>>arm you are going to need an interface box that can convert the
>>signals of the 4-6 encoders and either store the points for
>>export to rhino or have a little program that will introduce the
>>points to rhino as they are taken. There are several little
>>programs that people have designed for Rhino like the calculator
>>add-on Rhinolator. It can generate a group of random points and
>>then send them to Rhino and make a surface from them. With the I/O
>>toolkit available for Rhino I guess that a knowledgeable person
>>could make up the interface program( but that not me :-)
>
>The interface is covered, don't worry about that. I was interested
>in something else you said though. Is it possible in import a series
>of points into Rhino and have them assembled into a solid?

[I've never had any luck with that myself, although I hesitate to say
anything's not possible with a program as versatile as Rhino. But I haven't
tried the "Rhinolater" approach outlined above either. (I do have a link to
it from my page at www.computersculpture.com , under Rhino Links- it is
freely downloadable.) There is a program called Geomagic Wrap which
specializes in this function- fitting surfaces to pointclouds- but even the
"lite" version costs around $1500. ]

If so,

>could you pass along the file format info? Gathering the points is
>easy enough, but I was concerned about what to do with them when I
>was done. If I can just store them into a text file, we're in
>business. Well, after I slap together an arm to experiment with, and
>write the software, and buy the parts for a 6-axis encoder board,
>and... and... :)
>
>-Tom Kulaga

[If you have a digitizing arm, it's no problem to enter points into Rhino
directly, one by one. But you'd need to do something tricky (like maybe
write a macro) in order to feed it a whole bunch at once. Also, Rhino is
oriented towards building surfaces from splines, not points, so connecting
the points in parallel rows would be a necessary first step.]

Andrew Werby

From: john@... (John Stevenson) wrote:
Subject: Re: What does everybody use...



Mines easy its called checkbook CNC not as interesting as a project but I
needed
to get up and running quick as I work with mine.

I have a Beaver CNC, like a manual Bridgeport only bigger that had an old
Posidata controller on when I bought it from a college, worked but tape reader
broken, limited to 999 lines of code and MDI input.

[I just got a big old CNC mill that sounds a lot like this one, with the
same file-size limitation, although it can currently be programmed in
G-code, and I'm looking at converting it to a modern controller setup that
will run unlimited file-sizes. Mine is a "RAMCO", purpose-built for CNC,
with servos on 3 axes and ball-screws. (After pricing out the conversion
of my old Bridgeport, I realized that starting with something closer to
what I wanted was going to save a lot of time and money.)]

We bought the Ahha card plus an opto isolator card that's available here in the
UK and fitted it into a PC.

[What's an "opto isolator card"? Do I need one too, if I'm powering servos
instead of steppers?]

The isolator card then plugs direct into the stepper controller on the posidata
controller.
This meant that we kept the bottom half of the cabinet and scrapped the top
half
with screen and keyboard etc.
We then made a sheet metal housing to accept a 12" monitor and keyboard on the
side of the beaver.

[I'm planning to keep the existing servo amplifiers, but gut out the rest
of the control hardware like John mentions. I'll probably hook it to an old
486 running DOS. (I'm not sure I'm ready for Linux). Is the Aha system
going to work for me, or should I be prepared for major problems and
expense? I've also been checking out Flashcut as an alternative. Has
anybody used this one for a mill retrofit? ]

As I say all cheque book engineering and possibly not in the theme of this
group
but the conversion took a weekend and paid for itself with a month.


Regards,
John Stevenson
Nottingham, England

[That sounds good to me, much as I like to tinker around...]

Andrew Werby

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com