Mesa 7i96 system planning-How Supported is Supported?

Ok, so it seems that while the 7I96 has everything I need, it does not have an analog spindle signal-but it does have a spindle encoder input. I'm trying to figure out how to do spindle indexing and ensure I have the hardware needed to do rigid tapping, as the parts I would like to be capable of all have significant numbers of small diameter drilled and tapped holes (1/4-20 and smaller...down to 2-56!)

Ideally peck tapping would be great, but I can live without that. Either way, I'm looking for a solution to the 800W rigid-tapping capable spindle.

Using an as-yet-unrealized Modbus RS485 port to control a VFD would probably work, but I am wary of saying "Yep That's the Plan" until I can find an example of a modbus controlled VFD that can be indexed and synchronized. I don't know that it's impossible, but I don't know that it isn't crappy at best, either.

Any thoughts?

Well, it's not an 800W spindle, but I found a BIG 4-brush Permanant-Magnet motor with a 16mm hollow spindle-it's a Minertia low-inertia motor. 20V at 20A rating, so that's 400W. The other motor on hand is a 2-brush motor that is much smaller, but runs at 90V.

The big motor has a 16mm spindle protruding on both ends, so it would be very easy to add an encoder to the motor shaft, however I really need spindle position, so I think the spindle needs the encoder, and the belt drive won't be a contributor to spindle position error.

However, the 7I96 only does step/direction control. How can I get a PWM signal out of this card? Is there a step/dir to PWM/Dir signal converter out there?

The 7I96 can do PWM/DIR, both on its step/dir pins or on the expansion connector.

For PWM --> analog VFD interfaces you could add one of the inexpensive ebay "Mach 5 Axis BOBs" and use the 7i96_5abob_d.bit firmware. Beware that the cheap EBAY BOBs do not isolate the analog out so are not suitable for common SCR drives like the KBIC series

If you want a single PWM/DIR output from the last stepgen channel you can use the 7i96d_1pwm.bit firmware

That solves the issue then. I ordered a 7i96 today, when it shows up I'll have the PC built to run the system, and start building the motion control enclosure.

PWM/Direction drivers are very inexpensive and since the encoder is handled on the 7i96, the driver doesn't have to be smart. Next on the list of aquisitions is a properly setup encoder to go on the spindle.

Alright, I've got the 7I96, I am building my PC station now, and I am working out the axis of motion I need to control. It seems to have the most rigid setup possible I will want to put my Z-axis rails on the two pillars, instead of on a plate back-to-back with the Y-axis rails.

So, X-axis has a single 20mm ballscrew, and is set on a pair of 36" long 25mm rails, with four 25mm medium preload blocks, for a net of a 26" X-axis.

Y axis (on the bridge) has a single 20mm ballscrew, and is set on a pair of 26" long 25mm rails, with 4 medium preload blocks, for a net of 16" of Y-axis.

Z axis (on the two vertical pillars) has two 20mm ballscrews, and is set on a pair of 20" long rails (one rail each pillar), with 4 medium preload blocks, for a net of 10" of Z-axis

The bridge will run up and down on the pillars, and the pillars will be connected across the top and bolted to the base that is the X-axis. I guess I could run four rails on the Z-axis, one rail on each the front and back, and still run 4 blocks, that would give me 15 inches of Z axis travel, and I think it would be just as stable.

The machine will be made of epoxy granite around steel embedments, so plates embedded in the base will house the rails, the stepper and ballscrew mounting plates, and the pillar mounting plates-this will all be machined at work on the big grinder. (after epoxy is set I'll blanchard grind the base.

More tomorrow.

Every mill has that problem, movable Z or not. Just a matter of workholding and fixturing to get around it.

I'm a bit biased though, I work with horizontal mills and lathes at work because our other machinists don't like them.

I do see the issue your talking about, and it is totally in the cards to have a quill that is manually settable for depth. Just haven't figured how I want to do it yet.

So, I've been blessed with a 10 dollar 1kW yaskawa AC servomotor for the spindle motor for this machine, and so I don't really have to run the 400W 4-pole DC motor I've got. (Which is good, and bad...)

Now, I have to find a "dumb" servo drive to run it, since Yaskawa says they don't make anything to deal with this motor anymore, and buying one of the original drives (20+ years old) is insane.

Is the Mesa 8i20 a good candidate for driving a 1KW AC servo with an 8192ppr incremental encoder? Furthermore, has anyone used it in conjuction with the 7i96?