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Old Apr 23, 2010, 02:29 AM
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Thanks Steve and Ken

Casting the aluminium wasnt that big a deal. It was fun and interesting and something I had wanted to try for some time. A lot of people here on RC-Groups have that: "I wonder if it would be possible to..." approach to things. Just like yourself, Steve, building a CNC router without having any experience in that particular area. Nice build by the way Ive been following it from the beginning.

Ken, I use Mach3 to control my CNC router, but the spindle is just controlled with a cheap ESC and a servo tester. Works like a charm. Ill mount the servo tester above the spindle and can control the speed of the spindle just by turning the knob. I know it is possible to integrate speed contol into mach3, but for me its just as easy to turn the knob.

This weekend Im going to test the spindle with different cutters and material.

- Michael Hammer
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Old Apr 23, 2010, 10:44 AM
Team of ONE....or...Team Me
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Reno, Nevada
Joined Oct 2006
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Michael,
I have to say that I would have never thought of a brushless motor for the spindle.
Now if you could take the signal from Mach 3 for the spindle control and convert that signal to DC for the motor then you could really take advantage of that control wintin Mach 3. Spindle control and a tool changer would make the whole maching process much easier, someday.
Right now I have a huge Sears variable speed router on my DIY JGRO machine. It gets the job done but it is additional weight to push and pull around.
Now as far as casting metals, that is an area I have been meaning to try. I picked up an LPG burner at a garage sale a few years ago in thoughts of using is it in the smelting process. I better get busy so many things I still want to do and so little time left.
Thanks for sharing,
DT
Thomas
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Old Apr 23, 2010, 11:39 AM
Slipping the Surly Bonds
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Attica, MI
Joined Dec 2006
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Michael,

I am using Mach3 also, and would like to be able to use the signal from the software to start the spindle as Thomas has said. I have the relay for turning on the power to spindle, but wonder how one might energize the brushless esc with the speed preset.

Ken
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Old Apr 25, 2010, 12:34 PM
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Sterling Heights, Michigan, United States
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Michael thanks for the spindle design. I'll have to build one. Here is my DIY design; I wanted it as simple as possible while using mostly parts from the hardware store.
http://www.rcgroups.com/forums/showt...83#post7469041 It’s fairly accurate.
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Old Apr 26, 2010, 09:03 AM
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Thank you for your comments.

The idea of using a brushless motor for a spindle is not new, but all the designs Ive seen so far has all used a coupling or a belt gear. My design is very simple and pretty straight forward. Im NOT a great machinist but I did manage to get the spindle to run very smooth with a minimum of effort.

I tested the spindle with a 12V PC power supply this weekend and the results were very incouraging. I let the machine mill some blue foam for more than an hour and the spindle was barely warm. Of course I need to mill some wood to test it, but right now I have this foam fuselage job that I need to finish. I also want to double the voltage to increase rpm.

Funny thing is that the new spindle is so quiet that the stepper motors and the tool are now the primary source of noise. With the Dremel you couldnt hear the stepper motors at all

Im sure its pretty simple to make an interface between Mach3 and the ESC, but I have absolutely no idea how. Electronics are not my forte. Maybe a post in the DIY electronics forum could shed some light over the problem. Right now Im quite happy with the "Turn a Knob" system. I try to keep my CNC machine simple, because its primary function is to help me build model planes.

Kfong, nice CNC router. I like the system with the two aluminium profiles on top of each other. What kind of spindle are you using.

DeadTom, go for the aluminium casting. Its fun. Plenty of time left...

- Michael Hammer
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Old Apr 26, 2010, 12:59 PM
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Michael, the spindle is a 20volt DC brush motor originally taken from an old printed circuit board cutter. The good thing about it is the 1/8” bearing spindle that came with it. I can only use 1/8” bits though. It doesn’t have much torque but is good for wood and plastic parts. Perfect for RC stuff, which is what the mill was designed for. Cutting foam is a breeze for the mill. I have cut 1/2" plywood, but with several passes to keep the motor from getting loaded. What still surprises me is how accurate the cuts are. The design was something I came up with and ran with it, not expecting much precision, but I'm able to keep cuts within .01 tolerances. The only issue is the wood table, it's not quite as flat as I like, but acceptable since the alternative would have been an aluminum frame for better flatness.
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Old Apr 30, 2010, 07:01 PM
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ebay link for collets went dead!

Looks like there are only ER20 Collets remaining at the ebay store. I have ordered that set and will adapt it to the spindle style discussed. Looks like some aluminum smelting is in my future!
OOPS! The link in the Proxxon 70 Thread still gets to a relisted set of the ER 11 collet system. Now I won't have to find as much scrap aluminum to melt!
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Old May 04, 2010, 12:06 AM
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Spindle dimentions?

It appears that the 25mm section is about 30mm long and the 70mm section about 20mm long, is this about right? I am eager to try a quieter solution. Thanks for posting this informative thread!
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Old May 04, 2010, 02:13 AM
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Hi mlmcquiggjr

Im glad you find this thread usefull

The dimensions of the aluminium bearing block was dictated by my "old" Dremel mount. I cant recommend mounting 22mm bearings in a 25mm aluminium tube. It will most likely crack when you press the bearings in. When the dremel mount is firmly tightend around the 25mm bearing block this risk of cracking is gone, but none the less I would recommend a beefier bearing block and a different way of mounting the spindle to the z-axis.

The length of the bearing block is not critical. Just make it a little bit shorter than the collet chuck + the motor. The excess part of the shaft will protrude out the back of the motor.

This weekend I tried cutting different materials like plywood, balsa and carbon fiber. All went well and Im quite impressed by the spindle. Even after an hour of plywood cutting the spindle wasnt particularly hot. The windings could easily be touched and there was no nasty smell of melting varnish.

At one point Mach3 made a mistake (well, I gave Mach3 the wrong info ) and tried to exit through 18mm plywood at full rapid speed and a cutter with only 10 mm cutting length. The spindle and the x-axis stalled and I thought I had damaged the spindle and fried the ESC. But I was surprised to find that the overload protection of the PC power supply had shut down the power and saved the ESC.

I still need to test the spindle with more volts and see how hot it gets...

Good luck with your spindle, mlmcquiggjr.

- Michael Hammer
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Old May 06, 2010, 08:23 AM
Charged up and buzzing
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Quote:
Originally Posted by michaelghammer View Post
I still need to test the spindle with more volts and see how hot it gets...
In that case the HK surplus parts become handy and you can just screw on a cut down prop with the prop adapter.

Would also help extracting the dust from the milling table ...
(by evenly spreading it in the room)

P.S. this thread has encurraged me to try the BLDC spindle.
I don't have a lathe but the single piece bearing holder wouldn't being to expensive to make by a CNC shop.

My idea would be to use a more massive 44mm diameter holder that would fit into the regular tool holder for the typical (non-Dremel) grinder.
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Old May 07, 2010, 02:19 AM
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Quote:
In that case the HK surplus parts become handy and you can just screw on a cut down prop with the prop adapter.
Vampire67, that is an excellent idea!!!

So without further ado I cut down an old Graupner 8x6 prop to 70mm in diameter and mounted it with the very nice prop adapter that came with the motor. The prop adapter is designed to be mounted directly on the motor bell which is perfect. Because the motor spins in a clockwise direction seen from behind the spindle, the prop spins in the "wrong" direction and sucks air away from the motor. This works well with the design of the end of the motor bell, which also sucks air from the motor.

I ran the spindle with a 25V power supply and boy did it go Im guessing 20-22000 rpm. The cut down prop sucks a lot of air from the spindle. It also makes quite a lot more noise. The windings of the motor get hot after some minutes but the rest of the spindle stays cool.

As it is now, the prop sucks air both from the inside and outside of the motor. If I could limit the prop to suck all the air through the motor, the windings would be cooled a lot more. So the obvious next step (if youre used to working with model aeroplanes ) would be to make a shroud that fits the outside diameter of the motor and then gets bigger where the prop is. Or I could cut the prop down to the same size as the motor and make the duct the same size as the motor.

Good luck with your BLDC spindle, Vampire67 and feel free to post any progress in this thread. The 44mm bearing block sounds like a good idea.

- Michael Hammer
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Old May 07, 2010, 05:44 AM
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Quote:
Originally Posted by michaelghammer View Post
So the obvious next step (if youre used to working with model aeroplanes ) would be to make a shroud that fits the outside diameter of the motor and then gets bigger where the prop is. Or I could cut the prop down to the same size as the motor and make the duct the same size as the motor.
How about making a simple cardboard tube or using 0,6mm ply and roll a tube with the diameter to slide onto your bearing holder.
Cut the prop a few mm shorter than the tube inside and drill some venting holes just above were the tube meets the bearing holder.
Would also being a nice protection for the rotating parts.
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Old May 07, 2010, 06:37 AM
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Quote:
How about making a simple cardboard tube or using 0,6mm ply and roll a tube with the diameter to slide onto your bearing holder.
I was planning to do just that. But instead of a rolled tube I plan to make a duct from slices of pink foam cut with the CNC Router, stacked and glued together. This way I can make a duct that slides over the bearing block, fits tightly around the motor and has a shape that fits the z-axis.

- Michael Hammer
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Old May 07, 2010, 01:46 PM
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Did you have to turn down the shaft of the ER11 collet holder to fit in the BL motor?
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Old May 07, 2010, 11:36 PM
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I believe the answer is NOPE !

The collet shaft is 8mm. The motor shaft 8mm.
How about cutting down a pusher prop and ditching the shroud idea.
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