I can update this first post with updates as new suggestions come.

Does this Kress 530 FM fit the micRo, or is it too large?


Nominal rated input 530 Watt
No-load speed 29.000 1/min.
Collet 8 mm
Clamping collar Ø 43 mm
Tool weight 1,3 kg

It looks like it's almost 3 inches wide (and 9.5 inches tall), IIRC the micro Y carriage is 2 inches wide... or maybe it's 2.5 inches. One way or another it's probably just about as big (physically) as would fit on the micRo. That 8mm collet would be nice though!

As someone who has never seen a micRo in person, I think it's probably a little too big.

You see the clamping collar is 43 mm, so it looks as if the motor housing is about 75mm in diameter. That is about 3 inches. So it would fit right?

I assume the micRo won't have a problem with the weight (just under three pounds)?

I've been wondering about using a pneumatic motor, as it'll be smaller in size, less vibrations(if fastened correctly) and a lot easier to regulate the speed(air flow) and torque(pressure). Perhaps an idea?

Sounds expensive... Not sure but it sounds to me that you need a large air compressor then.

Oops, I meant to post this earlier, but I guess I forgotted (got sidetracked).

I think a pneumatic motor sounds like a good idea. It actually seems familiar, I wonder if they're already used on CNC machines. IIRC pneumatic motors can be very high speed which would be perfect for the micro.

Do they have much torque? I know impact wrenches have a ton of torque, but can they have constant torque?

Regarding an air compressor I imagine you probably don't need too much, you just need one that can run constantly or one that can refill your tank quickly (high SFPM).

The torque should be constant at a given air flow, as the only variable is the pressure. Higher flows will give a lower pressure, thus less torque, but nothing too dramatic . It all depends on the quality of the compressor. You can get away with a cheap compressor, you just need set the pressure a bit higher if you want to use high speeds, to compensate for the pressure drop.

I know they use both pneumatics and hydraulics on some cnc-machines. (Of course, many also use something even smarter, which is an induction motor with frequency regulation).

Eg. say a motor with a displacement volume of about 15 cm^3/rev, and I would like 10 000rpm. That gives an airflow of ca. 150L/min. I've not calculated in any losses, so you should perhaps multiply it by 1.2 or more. With, say, a pressure of 6 bar, it'll give a torque of 1.43Nm, and the power will be 1.5kW.

I'm surprised the torque is that high!

If I did the right conversions 150L/min is ~5.5 FPM (I wonder what that is in SFPM?) and 6 bar is ~90 PSI. Those are fairly run of the mill specs by the looks of it. Is the typical compressor capable of running for hours at a time?

Sure, but 150l/min means that a 24l compressor with 2hp will have to run continuously. They cant do that for long. Then you want a screw compressor like the ones they use at spray shops, but you will have to pay twice of what a gold package micRo costs for a really cheap one. So then what is the point.

I would like to find spindle motors that are affordable compared to the price of the micRo, and as an alternative to the flexible shaft spindle that lumenlab sells.

What is the size of the z axis block?

Having a micRo down stairs in my basement at the moment. I can go measure if you really need it precise. But the Z-blocks are not wider than 2.5" (the stepper motors in the picture are about 42.3mm on a side if that helps scale things). The actual blocks are maybe an inch wide. I think that in the first picture would be too large. In part on the size of the casing and that you'd end up with a lot of weight hanging out quite a way from the actual Z-axis (there is a lip, combined with the casing on that spindle I think it would cause problems).

I've got one of the flex shaft grinders like will be coming from China and I think it will suit just fine. It does possibly have a torque deficiency, but that's yet to be tested as I don't have any mounts yet.

That spindle in the first post would probably be excellent for a mid sized Rogr (2x2 anyone?), but I think for the micro your best alternative would be a dremal sized rotary tool.

By the way...anyone thinking about a pneumatic spindle how about this? $13, rig it up for always on with a regulator. 3 CFM and a 1/4" collet.

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=36572

Huge!



Torque = speed and feed, ultimately. A robot is patiently precise; opposite of most humans. A robot will take a precise cut repeatedly, no matter how small. Consider that the Kress is pushing 530w for an 8mm mill, and the flex shaft spindle (China) is pushing 250w for a 4mm mill; they are ~the same torque-wise (actually China has more power/tool_d; presumably...I've yet to test it).

the units not to big if you can get a flexshaft for it then the size of the motor part doesn't really matter anymore just as long as you dont bind it those flex shaft wind up

I have a Rotozip with a flex shaft I might try.

Click to view attachmentClick to view attachment

There was some talk about using a rc brushless engine with tool collet earlier. Sounds like a good idea. Anyone still looking at this alternative?