Spindle Idea

[MechanoMan]

Wow I didn't see this thread before...

I was working on the idea for a tougher, lighter "Dremel" tool, OR a milling spindle.

So far I've run into two notable problems: one, these BLDC motors are almost all designed for low voltages. It's hard to get a supply that provides like 40A @ 12v, and the wiring gauge required is awkward. PWM to reduce the power from a higher voltage source doesn't work well with higher ratios (big technical electrical thing there).

Two, for the Dremel-type handtool, getting low runout is a problem. There are no "shaft extenders" or machinist-type collets systems in this size that I could find. First off Dremel's collet system is horribly misdesigned on multiple fronts; it's not a matter of machining accuracy. Runout is BAD even for hand use. I found Proxxon collets WERE much better designed (3-jaw not 4, hardened steel, and long/deep chamfers), however, as of yet I'm still unable to make a low-runout spindle.

The primary problem seems to be that the collet's orientation is set by the nut. The nut is of course placed by threads, which can orient all over the place. I thought the Proxxon collets were different, but once I got the first attempt of a motor shaft off the lathe, I saw they were not. Also creating threads with a die was clearly an inaccurate process- sure, it tightened nicely. But the center of the threads, this the nut, thus the collet, thus the tool are macroscopically NOT coaxial with the shaft. Several degrees off. Want to get a lathe threading kit here.

I had considered getting a Dremel/Wecheer handpiece (normally used with a flex cable) and simply thrown a BLDC motor on back. However, this didn't give me the design flexibility to make the form I ultimately wanted, although I may do it anyways just to get something working.

Note this- the smaller the bearing, the easier it is to get high RPM.

Also check out BLDC boat motors. SOME HAVE WATER JACKETS! And/or you can get water-cooling jackets for them.

[Sea Shadow]

First off, hello everyone. I've been a long time lurker and finally decided to register on the forums. I have built a 3D printer (a RepRap) and now have the CNC bug. I'm trying to hobble together a PCB mill using junk parts (just to make it a challenge) and I stumbled across this thread. I'm going to be using an RC brushless motor for my setup. Now that the introductions are over, on to the topic at hand.

Originally Posted by MechanoMan So far I've run into two notable problems: one, these BLDC motors are almost all designed for low voltages. It's hard to get a supply that provides like 40A @ 12v, and the wiring gauge required is awkward. PWM to reduce the power from a higher voltage source doesn't work well with higher ratios (big technical electrical thing there).

Here is a thought, why not use a computer power supply? A lot of the high end computer power supplies are capable of supplying such amperages. Most of them have active PFC and are designed around extended periods of use. It is a trivial matter to jumper them on. All you need is a paper clip and a junk hard drive to partially load the 5v and 12v rails while the main motor is off.

Here is an example of one that can supply 60A on the 12v rail for ~$100

[MechanoMan]

The supply may be rated @ 60A, but you'd need like 6ga wire to carry the current, unless it's got high-temp silicone insulation, in which case the wire's still gonna get really hot. That's some REALLY thick wire for a hand tool or moving-spindle. Simply interfacing it with the ESC PCB- or getting PCB traces which can realistically handle that current- is problematic.

6A @ 120v is much, much more practical, but I can't find readily available cheap, powerful BLDC with that kv rating. There ARE ones which are designed for more like 24v, which is a better idea. Half the current.

But here's what I may want to do. The Taig has that headstock with the T-slot on the sides, right?

Well, for milling aluminum, I could use the regular head. When doing PCB engraving, or whatever that requires high speed/low torque and only light side loading, pull the bit out of the Taig collet, bolt a light high-speed spindle on the side, and spin away at 30K-40k rpm or whatever I need.

At first I thought that meant my workbox would be shorter, but actually no, it's just offset. With a matrix workplate, you'd just side the workplate over a bit to place the work area under the spindle. It's all still there!

[atwooddon]

agreed, trying to get necessary watts from 12V would result in a lot of current. 24-30V would give us a much better range of options. BLDC motors are also rated in kV (rpm per volt unloaded) so you would also want to pick a motor with a kV and voltage range that would correspond to our desire milling rpms.

My competition motors pull a max of 75A at 38V (2850 watts) and I only use 12ga silicone shielded wires from the battery to the ESC (controller). The wires from the battery (10S lipo) are barely warm under load. The wires from the ESC to the motor are 14-16ga but they are only carrying 1/3 the load at any given time.

Don

[MechanoMan]

I started another thread for BLDC calcs and detailed, but necessary, reasoning behind this-and-that:
http://www.cnczone.com/forums/diy-cn...s_spindle.html

[MechanoMan]

delete

[bboymanuel]

Im getting ready to build a CNC Router but my question is Is there a spindle that will support Drilling and Tapping? And is there is specific spindle I can use with a specific collet set? Please help me. Or any info would help me. THANKS!

[asuratman]

LMS Spindle Cartridge...? A little while ago I was searching the Little Machine Shop site for "Spindle" and found this combination in their "Replacement Parts --> 3503 CNC Mills (KX3)" section.

Somebody here have tried LMS spindle. What is the use of the gear?

[D3Spindles]

Have you selected a spindle yet?

[Cha4NCam]

which might do the trick for you.

[Paciente8159]

Hi there.
I've build an CNC for milling PCB. I've made a spindle with a RC motor + ESC and an ER11 collet shank, by replacing the motor's shaft directly with the ER shank.
For PCB miling this works fine, little to no strenght will be required from the motor/bearings.
But now I would like to be able to mill alluminium blocks (maybe to generate my next CNC) and I need a much stronger Spindle.

My ideia was to pull this off with an other RC motor (a 2Kw), an ER16 collet shank and some gearing system to reduce speed and gain torque.

As any one experienced with those cheap ebay timing pulleys and belts (5$-10$ each) (will they hold the torque required?)

Thank's in advanced.

[JRoque]

Hi and welcome to the forum. I haven't done much CNCing lately so wait for others to comment as they'll like have a better suggestion.

If your aluminum cutting will be casual, or perhaps you want to just build a better CNC machine, I would strap a wood router to your exiting machine. It will be the easiest and most economical path as long as it's a temporary one.

I've seen Chinese watercooled spindles on eBay that come complete with VFD controller and everything for a couple 100 dollars.

JR