Re: [CAD_CAM_EDM_DRO] Machine Options in CAM Software ?

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