Re: [CAD_CAM_EDM_DRO] Re: PC based CNC system architecture

Wally K wrote:

> Thanks Matt, You are starting to clear things up for me.

Good!

> Could you tell me what the motherboard consists of. Is it a passive
> backplane or does it have smarts on it.

Basically a passive backplane. There is one ttl chip on it for signal
conditioning purposes, but that's it.

> On the proposed 4 axis stepper card you are working on. Can you put
> more than 1 card in the motherbord.

Yes, 8 cards for a total of 32 motors. Quite an impressive machine,
difficult to program too..

> Also on the proposed stepper card why does this ignore the digital
> I/O issue all together.

Because there aren't any I/O bits to turn the spindle on or read the
home switches, etc. That would involves a different card.

> First, header connectors do not pull apart that easily. But it would
> depend on board size. Second, how in the world would anything unplug
> inside of a control cabinet.

OK, maybe you're right about that...

> There is no reason to put connectors that unplug on the axis cards.
> Once the cards are in place why would you want to unwire them.
>
> Connectors that are external to the box can be of use but not inside.

Well, everything I've ever built, I've had to take apart sooner or
later. Suppose something goes wrong with a board out in the field,
someone will have to pull it out and replace it and they may want to
swap boards around to isolate their problems. I've worked on a lot of
cnc machines (doing repairs) and most are really difficult to work on. A
common example would be replacing the bridge rectifier modules on an
older Bridgeport mill. You have to take a bunch of stuff loose before
you can even SEE them!

> My point is, depending on card size and layout you do not need
> expensive backplane connectors and removable external connectors or a
> card cage.

The daughter card size is about 4" x 6".

> By the way. Is your layout etched in stone and are you getting
> boards made yet.

Some boards are made already, although once things are proven out,
repackaging the basic technology to fit particular applications would be
possible. For example, a single board configuration with a fixed set of
features adequate for most 4 axis or less machines might be an
arrangement that better suited the folks participating in this
discussion.

> I would like to say with the cost and miscellaneous construction
> issues aside that it sounds like you are making a very nice control.

It will be especially nice if I can sell some of them!

Matt