Brushless DC CNC Spindle

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Re: Brushless DC CNC Spindle

Postby Enraged » Mon Feb 20, 2012 5:38 pm

Are the DWGs for this available?
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Re: Brushless DC CNC Spindle

Postby bdring » Mon Feb 20, 2012 7:19 pm

I can publish the step files. I'll need to load that project up when I get a chance.
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Re: Brushless DC CNC Spindle

Postby Enraged » Mon Feb 20, 2012 7:31 pm

thanks! should be a nice improvement over the dremel spindle on a Shapeoko
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Step File

Postby bdring » Tue Feb 21, 2012 4:02 am

STEP Attached
Attachments
spindle_asm.zip
(375.84 KiB) Downloaded 469 times
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Re: Brushless DC CNC Spindle

Postby edward.ford » Wed Feb 22, 2012 6:14 pm

I see now that I'm the holdup on this! Here are a few pictures I took with my phone a couple months back. I'm hoping again to get this mounted up to my test rig in the *very* near future, and report back regarding it's status and performance.

It's a water cooled motor, so there was a little more to it than just bolting it onto the machine. I ended up buying a water pump for a fish tank ($12) and an empty plastic paint can from the LHS ($5) to use as my reservoir. I then drilled three holes in the top of the paint can - Power, return, and supply. Then grommetted the holes to be safe. Dropping 120v AC into a bucket of water was a little scary to begin with. The last thing I wanted was to fray the cable and end up zapping both my machine and myself!

The biggest challenge with this thing is the wire management! Between the water cooler lines, the extra power supply for the motor itself, the ESC wires and the arduino, it's a top notch rats nest! You can see in one of the pictures that I have the ESC mounted to the side of the UHMW (haphazardly) which IMO will be the best place to store it. If I remember correctly, the wires coming from the ESC cannot be modified in length, else the motor will not act properly. Why that is, I don't know. I'm sure someone here knows why....

I have a mount designed to easily bolt it to a piece of makerslide, I'll combine that with Bart's step file and post it for download.

rc_spindle_1.jpg

rc_spindle_2.jpg
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Re: Brushless DC CNC Spindle

Postby Enraged » Thu Feb 23, 2012 7:46 pm

How are you controlling the spindle? Bart says in his post that he used an Arduino to send the signal to the speed controller. Can we use the same Arduino that is controlling the Shapeoko to control this as well? If so, any details on wiring?
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Re: Brushless DC CNC Spindle

Postby edward.ford » Thu Feb 23, 2012 8:54 pm

Yes, the spindle is controlled via an arduino. I believe the sketch is from somewhere on the intrawebs. I'll try and hunt it down.

As far as sharing the arduino: Unlikely. Because the arduino used to control shapeoko has a custom firmware (grbl), simply "combining" the programs isn't really feasible. However, if you're willing to hack around with the grbl source, it might very well be in the cards. For me, it's worth spending an extra $20-$30 on a second arduino. You'll also need a POT

I think another question is: could EMC2 somehow control the spindle speed? I think that would be a much simpler integration, but I don't know what exactly would be required to make that happen.
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Re: Brushless DC CNC Spindle

Postby bdring » Thu Feb 23, 2012 9:06 pm

The motor is powered by a standard RC Motor controller and takes a signal like a hobby servo. That is a 1ms-2ms pulse on a roughly 20Hz rate for full scale. You can program the controller to either have full scale one direction or half is forward and half is forward. A simple pot will not control the speed.

The Arduino can easily control this. Like Edward said this requires a little hacking of the GRBL code. I think it is worth it because it is a nice single Arduino solution where G Code could handle the whole thing.

Another slightly easier method would be to use a fixed speed generated by a 555 circuit on simple controller and use the Arduino/GRBL enable it.
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Re: Brushless DC CNC Spindle

Postby Enraged » Thu Feb 23, 2012 10:57 pm

I was looking at the schematics for the Arduino shield and the Pololu-compatible relay driver earlier, and it got me thinking at an interesting option would be designing a Pololu-compatible board with a circuit to drive this motor controller. Then all you would need is an output from the Arduino to turn on the spindle via the circuit board, but control the speed with a pot mounted to the circuit board.
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Re: Brushless DC CNC Spindle

Postby edward.ford » Fri Feb 24, 2012 6:20 pm

I think on a simplified level the pololu compatible driver (PCD?) could turn on the spindle. But, If I remember correctly, the arduino uses the servo library to control the ESC. There is a certain "arm" sequence that needs to happen in order to start controlling the motor through the ESC which grbl couldn't handle without modification. The POT is actually controlling the spindle through the software. It's not physically adjusting the voltage, just changing the pulses to the ESC.

So, it seems that you would need a second arduino to carry the servo library and perform the subsiquent arm sequences and interface with the POT.

I've assembled a second shapeoko for testing purposes and am hoping to have a little time tonight to mount this spindle to the test rig and see what I can come up with. If all goes well I should have a video in the next couple of days!

I think once the spindle is mouted again and doing some work, and everyone gets a look at the setup it'll be easier to know what the next step should be.
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