Thought this might be worth a new thread since the micRo really isn't restricted to milling.

With the shipment of the kits nearing, I've been going through the motors I have on hand (an 18V cordless drill motors looks the most promising of what I have, but RPMs I doubt would suffice) and looking at what I can find online. As far as specs go I'm not sure what I should be looking for. Material wise, I'm planning on a good deal of UHMW, Delrin, and Aluminum, probably acrylic - but still not sure on the machinablity of it might be a bit more advanced.

Size wise OD should be 2 inches at most according to the micro thread.

(1) When putting together a setup, what kind of weight should we be looking at for a ball park? Total weight on the Y/Z axis(axises/axia) [FAIL: I can't spell] -- ok, how much total weight are we talking about for the gantry to support?

(2) Voltage/Amperage - If I remember right the motor controller had the umph needed to handle the spindle as well. Correct? So, that would be what? 18vdc?

(3) RPMs - Does the EMC2 setup control RPM? Or do we set that up manually? I've been researching what I can, and looks like you really need to dial it in for some materials, too fast and the plastics could melt and bye bye bit, too slow and the shavings get crazy and can get hard to manage - not to mention feed rates have to then slow down.

(4) Torque - Highest torque we kind find for the RPM range we need?

(5) Shaft - We need high tolerances, so we want a good platform to hold the tooling and little runout. What at the common sizes for the tool holders that we'd be talking about?

(6) Gearing - I'm sure some planetary gear setups could be sourced. Or even a pulley setup. Is that something out of the question for something like this or would that be reasonable to get the desired RPMS? Seems a belt would allow the tool to slip where it may other wise break, but then could present a lot of shear force on the gantry if not stopped.

I'm pretty much a complete noob to this. I can do electronics. I can do most any tool work by hand. I can program like no ones business. So, I'm using this to get into putting it all together and using my micro to build parts for some robotics projects I've been wanting to do and some dirt bike parts. So, I've got the desire and means to make this happen, just missing on some details.

Can I guess from the wiring that these are 3 phase motors?

What application are they intended for originally? Miniature, powerful, high speed synchro motors? Is someone making tiny electric black helicopters?

Best go get my tinfoil hat...

Unlikely, based upon their size. Variable reluctance (no permanent magnets inside) stepper motors usually have 3 windings (but sometimes 4).

For a good overview on the various types of stepper motors, go to http://en.wikipedia.org/wiki/Stepper_motor. Be sure to follow all the links at the bottom of the page.

-Brian

I don't think those pictured motors are steppers. The wires coming out of them are huge, there's only 3 (don't steppers only have 4,5,6, or 8 wires?), and brainchild was suggesting to use them for the spindle of the micRo. From all accounts I've seen steppers make poor spindles (they loose torque as speed increases, they vibrate, they're expensive, and there's little reason to have the capacity to "step").

Those are BLDC "*reluctance digital syncro" motors used in high-end R/C...so yes, miniature black helicopters. They are about as related to steppers as Oprah is to Jonah.

The leftward one is my current favorite. Hirudin's sharp eye caught the massive leads, and maybe even the fireproof sheathed wire needed for the big amps this motor can pull. A hitherto undisclosed bonus: The PWM speed control: EMC2's HAL can be programmed to run the spindle at nearly any speed ranging from ~1 to 50,000 RPM. This makes jobs like milling/drilling a PCB way easier. It also means programs can be made to adapt the spindle speed to local measured conditions, allowing your spindle to 'tip-toe' through the delicate, melty or resonant areas.

*(analog reluctance feedback for tachometry paired with PWM speed/torque control...you know, like an elevator motor)

And the big question .... how much would one of those bad boys set me back?

Oh, they're not that different; you're still energizing coils in a sequence. Of course, the mechanism of how you energize the coils varies substantially between them. I guess it depends upon how you look at them. If you approach it from a control perspective, then yes, they have little in common, but from a mechanical perspective, they're similar (energizing coils in a sequence).

-Brian

Exactly, I'm glad you noticed. Both are AC syncro motors, but you'll never position a reluctance motor without an encoder, and if you encode it, who needs reluctance?

That said, the Oprah-Jonah analogy was meant as a humerous quip; both whale and Oprah may be large (not so different), but only whale eats Jonah (big difference, sorry Oprah!)

(Actually, is Oprah even fat anymore? I haven't seen TV in years)

Would something like this work well as a spindle?

A50 Brushless Electric Motor

Good question...so good I began the micRo thread with it! That said, you posted an 'outrunner' which is open to contaminate.

<rant>Someone posted about a Kress 1050 FME Milling motor from Germany, but I can't find the post because the forum search page won't return me a link to the actual post, only a useless link to the head of the topic. I think it's in the micro topic somewhere.</rant>

Anyway. I contacted the company to get a quote for this motor and wanted to share it with everyone.

They said they can ship to the US and it would be 101,50 Euros + freight. That comes out to 160,38015 U.S. dollars + freight. The 1050 FME comes with a 8mm clamping jaw and 43mm (approx 1" 11/16) mounting flange and they sell both US and Metric collet inserts. The two US size collets are 1/8" and 1/4".

http://www.kress-elektrik.com/en/products/...p?categorie=767

Kurt

If for some stupid reason it gives you one of those 1-post pages you may be able to switch the display mode from "Outline" to "Standard" (the option is on the top-right of the screen)...
Click to view attachment

Whoa, I just saw your Outrunner video over on your Video Blog (which up until tonight I didn't know about).

That thing is scary indeed! Looks amazingly smooth too... I can't wait to see a video of the bigger one...* Actually, I really can't wait to see what you come up with for the RoGR

*After watching the beginning again (with my speakers turned on at the beginning this time) it sounds like the little (purple people eater) one is actually better than the red one.

So... Brain, How does this Kress motor look? You've been researching for some time now. You certainly have a greater knowledge base than I. Is this motor looking like a good option? 32,000 rpm free running is not 125,000, but does that really matter? Is the $160 + shipping (whatever that is) in the neighborhood. Are you finding significant advantages in price/performance in the motors you are considering?

Dave

Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke

Just saw an ebay posting for a Kress 1050 FME. The bids are up to $308 + $57 shipping from England. Something does'nt seem right.

Dave

Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke

You got it. The purple motor is the beastie. Those extra windings make a huge difference. I've already got RoGR's spindle. A big router with 1/2" collet.




The Kress is better for a machine about 1/2 way between micRo and RoGR. For micRo, I am set on the reluctance syncro. It is just right, and is technically superior in function thanks to its dedicated speed control which I can dynamically control with EMC2 using PWM. Nothing can best the power to weight, or usable RPM range. Depending on the outcome of this week's tests, I believe the micRo spindle will go on sale at ≤$100.

Actually when I finally got a quote for UPS shipping from them, it was equal to 130% the cost of the motor itself!! 135,00 euros... uhh OUCH. Making the total cost in dollars like $400+ (I forget the precise conversion). Anyway that's a no go unless one of their other shipping methods is less expensive. I noticed that their UPS shipment is "Freight Forwarded" through another provider, so maybe it's just a case of having to pass through too many hands to get here, and each one wanting their slice of the dollar pie. I'm guessing that if I really wanted one I could find a way to get it here for cheaper, maybe through a friend in Germany or something.

For right now I'm waiting to see how the big brain creates a collet/tool-holder for what is basically an RC car motor. I'm rather fussy on my opinions of what this should look like. I won't settle for just set screws, but I can't wait to take a see what he thinks up.

Kurt

What no grub-screw collet? I was going to use hot-glue and duct-tape...

I'm certain you have something fantastic planned, I'm just dying to see what it is, even if it's just scribbled on a piece of paper.