One G-Rex, multiple machines (though not at once!)

[youngjim]

Hi everyone, I have a question about using a G-Rex to a typical home CNC environment. How feasible is it to have multiple machines (a lathe and a mill, to start) with dedicated Geckodrives, but have it set up so a single G-Rex could be connected to one machine or the other?

From my inexperienced vantage point, it appears to me that the Geckodrives are tuned for each motor, but the GRex has no definite relation like that. Have I got this right?

Barring any major obstacles, I figure connecting to one machine or the other would mean perhaps 8-10 multipin connectors, two per axis (so that signal and power lines can be separated and better shielded), and extras for coolant pump, enclosure switches, etc. I think the simplicity, reliability, and ability to add a second GRex (budget permitting) would outweigh the need to swap connectors.

Scheming aside, how well would this work? Any flat-out showstoppers?

Jim

[ger21]

What are you going to control the G100 with? If Mach3, then the Smoothstepper would be a better choice than the G100.

[youngjim]

I confess to being in lust with OneCNC XR3. I figure I might as well spend the money once, rather than twice. It is likely overkill, but it does do some pretty amazing things.

Jim

[ger21]

OnceCNC is CAM software, it doesn't control your machine. I believe that mach3 is the only software available capable of controlling a machine via the G100, unless you right your own software. The problem is that Mach3 development for the G100 stopped a few years ago without being 100% completed.

[Crevice Reamer]

Keling has the Smooth Stepper:

http://kelinginc.net/BreakoutBoards.html

CR.

[asuratman]

Hello,
I read in meahmate forum, but I forget the thread. Somebody download new g100 driver and new mach3, so that he can run 2 servo motors in one axis simultaneously.

[youngjim]

So let me see if I have this straight:

To play to their strengths, it is more or less a choice between:

A. CAD s/w of choice -> Mach3 -> Smoothstepper -> Geckodrives -> Steppers -> Leadscrews + something else for I/O, or

B. CAD c/w -> OneCNC -> something like Mach3? -> G-Rex -> Geckodrives -> Servos -> Ballscrews.

The first is simple, cheaper, and proven; the second being notably more expensive, but possibly faster and more feature-rich? I'd rather ask questions now than end up buying the right stuff the second time rather than the first.

I can tolerate the idea of finding an XP license somewhere; I use Linux (64-bit Ubuntu 8.10) on both of my computers, although I've used XP extensively. So the software platform isn't a restriction for me. I don't mind fabricating power supplies, wiring etc either. I guess I just need a little guidance into what works together the best.

Thank you for all the replies already, and I'd appreciate any further insight you could offer.

Jim

[Crevice Reamer]

I don't see any reason for you to use EITHER a G100 or a Smooth Stepper. Unless you are planning to run more than 4 Axes, or do not HAVE a parallel port on your computer.

A pair of ordinary Break out boards should do. You could then simply run the parallel cable from your computer to a DB-25 A-B switch. From that would exit TWO parallel cables, one to the mill and one to the lathe. That would allow switching the COMPUTER from one machine to another. Mach3 would run different profiles for the mill and lathe.

What size mill and lathe are you thinking of? You might even be able to use a G540 for each.

CR.

[ger21]

Originally Posted by youngjim So let me see if I have this straight: To play to their strengths, it is more or less a choice between: A. CAD s/w of choice -> Mach3 -> Smoothstepper -> Geckodrives -> Steppers -> Leadscrews + something else for I/O, or B. CAD c/w -> OneCNC -> something like Mach3? -> G-Rex -> Geckodrives -> Servos -> Ballscrews. The first is simple, cheaper, and proven; the second being notably more expensive, but possibly faster and more feature-rich?

Not really a choice just between A and B. There are an infinite number of combinations to choose from.

As was mentioned, you may not need either a G100 or a Smoothstepper. Most recent PC's (with a parallel port, or at least a PCI parallel port card) can run Mach3 just fine. You can also use EMC under linux with a parallel port.

Why did you want to use the G100 anyway?

As for your original question, if you use a parallel port, a $5 printer switch box would let you use one PC to run two machines. (Not at the same time of course).

[youngjim]

Right now I want a G0602 lathe, and probably an X3-pattern mill, although getting either out here in the boonies will be a challenge, no doubt. I should explain a little bit of my thinking about the electronics:

The idea with a G-Rex, servos, and ballscrews was to go for (ethernet rather than parallel port) performance and expandability to a 4th and eventually 5th axis for the mill, and an ATC or live tooling for the lathe. Maybe even a drive servo for the spindle for turning polygons...

If was to go with steppers and leadscrews, the machine would be slower, but it would be substantially cheaper. If I did that then I'd simply build a PC for each of them, they're dirt-cheap these days. I know I could mix and match (servos for leadscrews, etc.) but I'd prefer to either spend the money on a balanced set of high-performance parts, or on a set of lower-cost parts rather than end up with an inefficient hodgepodge.

I read a thread in the yahoo gecko group to the effect that the G-Rex won't be developed any further. If this is the case then making a part looks like this, I think:

Some manner of CAD app (possibly T-Flex) eventually,
OneCNC for basic CAD and CAM (eventually, and before I bother with T-Flex),
Mach3,
Possibly a Smoothstepper to get away from parallel port timing limitations (worth it?),
Drives,
Motors,
Leadscrews/Ballscrews.

My overall intention is here is to gain the capability to make useful parts. I enjoy the idea of putting things (i.e. the retrofit kit) together myself, and I am inspired by all the mods and special tools people have come up with, but at the end of the day I want a reliable means of going from an idea to a part. I don't mind spending the time and money to get the right parts, but I want to start from a properly tuned machine and work out from there.

For instance, if I have the choice between lead and ballscrews, then I'd get ballscrews; might as well make it the best it can be the first time. Ditto the servos, if it is a matter of choosing from Gecko's catalog. After that, Mach3 is good (and cheap) enough that I don't have to think about that one, although I won't buy it until I try EMC2.

So I think I'm getting closer to a plan that looks like this:

Get the mill & lathe first, probably at the same time if I have to drive a day and a half each way to get them. Then a basically useful set of workholding tools, cutters, measuring tools, etc. After that, start on the CNC parts. I'm ok with buying a kit (CNCFusion's for instance) because any money I'd save in buying parts individually I'd burn up probably twice over on shipping and fees. (!)

I've got some time to plan this properly, and I know enough to know that I don't know nearly enough yet!

Jim

[ger21]

With all the money you'll be spending, it makes no sense not to have 2 PC's. Especially when there are hundreds of capable used PC's on Ebay for $100 or less.

[Crevice Reamer]

Stepper or servo:

http://geckodrive.com/support.aspx?n=516022

X3 mill in Canada:

http://cnczone.com/forums/showthread...271#post596271

CR.