Re: Machine Options in CAM Software ?

Thanks Jerry, it did help clarify a few things although I can't say I
completely understand it all. The learning curve on all the issues
involved is pretty steep, but I love learning! So far, I am plannig
on using the Gecko's. I did think the Gecko's recieved their signals
straight from the parralel port. The part I'm having problems with
is understanding the link between the CAM software which generates
the G code and toolpath info and the Gecko drives. I'm assuming now
that the CAM software like VisualMill doesn't interface with the
Gecko's. The G code file generated by the CAM is read by a NC
program like Turbocnc and then sent to the Gecko's ? Thanks again,
this group is pretty cool.

Mark

--- In CAD_CAM_EDM_DRO@y..., Jerry Kimberlin <kimberln@a...> wrote:
> natchamp_87 wrote:
> >
> > While I'm waiting to buy my mill for the retrofit project I have
been
> > playing around with different software for the CAD and CAM part.
Why
> > do the different CAM softwares ask for what type (Fidal, Faunc,
etc)
> > of machine? I thought G code was somewhat universal for CNC? Is
it
> > because not all machines use all G codes?
> > Also, is the G code converted into step and directions signals in
the
> > NC software? Thanks for any clarifications!
>
> Mark, a year ago more or less I asked the same question by
> wondering what a post processor was. I got some good answers,
> but nothing definitive from the development types. Everyone
> seems to try to answer this question starting from a drawing on
> Autocad or what you do once you have a DXF file drawing of a part
> to be machined. However, I think the question should be answered
> from the other direction.
>
> You have a motor - stepper or whatever.
>
> You will need a driver for the motor, for example a Gecko 320
> which will take pulses to drive that motor in one direction or
> the other to accomplish forward or backward movement of the axis
> in question. The Gecko drives get their logic sense from the
> parallel port of the computer and their power from an auxillary
> power supply, whose maximum voltage and amperage should be
> selected based on the motors you want to use. Since the Gecko's
> can drive your motors either forward or backward and accept
> pulses at certain rates, you need a program that outputs to your
> parallel port to tell them what to do.
>
> It seems to me that Fadal, Fanuc, Haas, Bridgeport, etc., all use
> different motor drivers. In those motor drivers there is circuit
> controlled by a group of transistors, whether in a microprocessor
> or as discrete silicon. Somewhere in there is a read-only-memory
> chip that gets in the way of things, taking what it is given and
> sending out the direction and number of steps the motor should
> turn. In the case of the Geckos which don't have a ROM to govern
> things, the number of steps and the direction is controlled by a
> program in your computer.
>
> As a consequence, you don't need a post processor to use the
> Geckos. You do need a post processor to use some of the
> commercial stuff because they do not adnere to any standard,
> letting a translator ROM, which is propriatary, get in the way of
> a straight through signal path. Some commercial stuff does take
> G-code, but doesn't let it pass straight thru, necessitating
> translation thru a post processor program, which sometimes costs
> thousands of bucks.
>
> So far as I understand, you can bypass a lot of this by using EMC
> which should output the proper logic signals to the motor
> drivers, bypassing the need for a post processor program that has
> to be interfaced between your motor drivers and the DXF file
> outlining your part. All you need to do is customize the EMC
> program a little and this customization is based on the
> dimensions of the pitch of your table screws and whether they are
> left hand or right hand.
>
> Now....I have tried from what I understand. Anyone who has both
> definitive hardware experience, please tell me what I have said
> that is FOS. Somewhere along the line someone has to spoon feed
> the newbie on this list and after a year of listening to all the
> stuff, I know no more about post processors than I did ten years
> ago - except that I need one and I'm not sure that is the case
> unless I have a commercial machine. Why do I need a post
> processor if I am building an amateur CNC machine.
>
> Thanks to all,
>
> JerryK